The first three patches are identical to: https://www.redhat.com/archives/libguestfs/2018-January/msg00079.html "[PATCH nbdkit v2 0/3] Refactor plugin_* functions into a backend" The rest of the patches add filters using the new filter API previously described here: https://www.redhat.com/archives/libguestfs/2018-January/msg00073.html This needs a lot more testing -- and tests -- and I also want to write a couple of more complicated filters to prove the point that the API allows different plugin methods to be called from a single filter method. However the two included filters (delay and offset) do appear to work well. Rich.
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 1/9] plugins: Move locking to a new file.
Mostly code motion.
---
src/Makefile.am | 1 +
src/connections.c | 14 +++----
src/internal.h | 14 ++++---
src/locks.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
src/plugins.c | 77 +++++-------------------------------
5 files changed, 142 insertions(+), 79 deletions(-)
diff --git a/src/Makefile.am b/src/Makefile.am
index 12b9043..1f05eab 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -40,6 +40,7 @@ nbdkit_SOURCES = \
crypto.c \
errors.c \
internal.h \
+ locks.c \
main.c \
plugins.c \
protocol.h \
diff --git a/src/connections.c b/src/connections.c
index 111a810..74bb8e4 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -211,7 +211,7 @@ _handle_single_connection (int sockin, int sockout)
int nworkers = threads ? threads : DEFAULT_PARALLEL_REQUESTS;
pthread_t *workers = NULL;
- if (!plugin_is_parallel() || nworkers == 1)
+ if (plugin_thread_model () < NBDKIT_THREAD_MODEL_PARALLEL || nworkers ==
1)
nworkers = 0;
conn = new_connection (sockin, sockout, nworkers);
if (!conn)
@@ -287,9 +287,9 @@ handle_single_connection (int sockin, int sockout)
{
int r;
- plugin_lock_connection ();
+ lock_connection ();
r = _handle_single_connection (sockin, sockout);
- plugin_unlock_connection ();
+ unlock_connection ();
return r;
}
@@ -740,12 +740,12 @@ negotiate_handshake (struct connection *conn)
{
int r;
- plugin_lock_request (conn);
+ lock_request (conn);
if (!newstyle)
r = _negotiate_handshake_oldstyle (conn);
else
r = _negotiate_handshake_newstyle (conn);
- plugin_unlock_request (conn);
+ unlock_request (conn);
return r;
}
@@ -1057,9 +1057,9 @@ recv_request_send_reply (struct connection *conn)
error = ESHUTDOWN;
}
else {
- plugin_lock_request (conn);
+ lock_request (conn);
error = handle_request (conn, cmd, flags, offset, count, buf);
- plugin_unlock_request (conn);
+ unlock_request (conn);
}
/* Send the reply packet. */
diff --git a/src/internal.h b/src/internal.h
index 73bc09e..068204b 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -144,17 +144,13 @@ extern int crypto_negotiate_tls (struct connection *conn,
int sockin, int sockou
/* plugins.c */
extern void plugin_register (const char *_filename, void *_dl, struct
nbdkit_plugin *(*plugin_init) (void));
extern void plugin_cleanup (void);
+extern int plugin_thread_model (void);
extern const char *plugin_name (void);
extern void plugin_usage (void);
extern const char *plugin_version (void);
extern void plugin_dump_fields (void);
extern void plugin_config (const char *key, const char *value);
extern void plugin_config_complete (void);
-extern void plugin_lock_connection (void);
-extern void plugin_unlock_connection (void);
-extern void plugin_lock_request (struct connection *conn);
-extern void plugin_unlock_request (struct connection *conn);
-extern bool plugin_is_parallel (void);
extern int plugin_errno_is_preserved (void);
extern int plugin_open (struct connection *conn, int readonly);
extern void plugin_close (struct connection *conn);
@@ -169,6 +165,14 @@ extern int plugin_flush (struct connection *conn);
extern int plugin_trim (struct connection *conn, uint32_t count, uint64_t
offset);
extern int plugin_zero (struct connection *conn, uint32_t count, uint64_t
offset, int may_trim);
+/* locks.c */
+extern void lock_connection (void);
+extern void unlock_connection (void);
+extern void lock_request (struct connection *conn);
+extern void unlock_request (struct connection *conn);
+extern void lock_unload (void);
+extern void unlock_unload (void);
+
/* sockets.c */
extern int *bind_unix_socket (size_t *);
extern int *bind_tcpip_socket (size_t *);
diff --git a/src/locks.c b/src/locks.c
new file mode 100644
index 0000000..6021356
--- /dev/null
+++ b/src/locks.c
@@ -0,0 +1,115 @@
+/* nbdkit
+ * Copyright (C) 2013-2018 Red Hat Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "internal.h"
+
+static pthread_mutex_t connection_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_mutex_t all_requests_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_rwlock_t unload_prevention_lock = PTHREAD_RWLOCK_INITIALIZER;
+
+void
+lock_connection (void)
+{
+ int thread_model = plugin_thread_model ();
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
+ debug ("acquire connection lock");
+ pthread_mutex_lock (&connection_lock);
+ }
+}
+
+void
+unlock_connection (void)
+{
+ int thread_model = plugin_thread_model ();
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
+ debug ("release connection lock");
+ pthread_mutex_unlock (&connection_lock);
+ }
+}
+
+void
+lock_request (struct connection *conn)
+{
+ int thread_model = plugin_thread_model ();
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
+ debug ("acquire global request lock");
+ pthread_mutex_lock (&all_requests_lock);
+ }
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS) {
+ debug ("acquire per-connection request lock");
+ pthread_mutex_lock (connection_get_request_lock (conn));
+ }
+
+ debug ("acquire unload prevention lock");
+ pthread_rwlock_rdlock (&unload_prevention_lock);
+}
+
+void
+unlock_request (struct connection *conn)
+{
+ int thread_model = plugin_thread_model ();
+
+ debug ("release unload prevention lock");
+ pthread_rwlock_unlock (&unload_prevention_lock);
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS) {
+ debug ("release per-connection request lock");
+ pthread_mutex_unlock (connection_get_request_lock (conn));
+ }
+
+ if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
+ debug ("release global request lock");
+ pthread_mutex_unlock (&all_requests_lock);
+ }
+}
+
+void
+lock_unload (void)
+{
+ pthread_rwlock_wrlock (&unload_prevention_lock);
+}
+
+void
+unlock_unload (void)
+{
+ pthread_rwlock_unlock (&unload_prevention_lock);
+}
diff --git a/src/plugins.c b/src/plugins.c
index 9b5d2d5..b7ab43d 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -46,10 +46,6 @@
#include "nbdkit-plugin.h"
#include "internal.h"
-static pthread_mutex_t connection_lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_mutex_t all_requests_lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_rwlock_t unload_prevention_lock = PTHREAD_RWLOCK_INITIALIZER;
-
/* Maximum read or write request that we will handle. */
#define MAX_REQUEST_SIZE (64 * 1024 * 1024)
@@ -165,7 +161,7 @@ plugin_cleanup (void)
/* Acquiring this lock prevents any plugin callbacks from running
* simultaneously.
*/
- pthread_rwlock_wrlock (&unload_prevention_lock);
+ lock_unload ();
debug ("%s: unload", filename);
if (plugin.unload)
@@ -176,10 +172,18 @@ plugin_cleanup (void)
free (filename);
filename = NULL;
- pthread_rwlock_unlock (&unload_prevention_lock);
+ unlock_unload ();
}
}
+int
+plugin_thread_model (void)
+{
+ assert (dl);
+
+ return plugin._thread_model;
+}
+
const char *
plugin_name (void)
{
@@ -312,67 +316,6 @@ plugin_config_complete (void)
exit (EXIT_FAILURE);
}
-/* Handle the thread model. */
-void
-plugin_lock_connection (void)
-{
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
- debug ("%s: acquire connection lock", filename);
- pthread_mutex_lock (&connection_lock);
- }
-}
-
-void
-plugin_unlock_connection (void)
-{
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
- debug ("%s: release connection lock", filename);
- pthread_mutex_unlock (&connection_lock);
- }
-}
-
-void
-plugin_lock_request (struct connection *conn)
-{
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
- debug ("acquire global request lock");
- pthread_mutex_lock (&all_requests_lock);
- }
-
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS) {
- debug ("acquire per-connection request lock");
- pthread_mutex_lock (connection_get_request_lock (conn));
- }
-
- debug ("acquire unload prevention lock");
- pthread_rwlock_rdlock (&unload_prevention_lock);
-}
-
-void
-plugin_unlock_request (struct connection *conn)
-{
- debug ("release unload prevention lock");
- pthread_rwlock_unlock (&unload_prevention_lock);
-
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_REQUESTS) {
- debug ("release per-connection request lock");
- pthread_mutex_unlock (connection_get_request_lock (conn));
- }
-
- if (plugin._thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
- debug ("release global request lock");
- pthread_mutex_unlock (&all_requests_lock);
- }
-}
-
-bool
-plugin_is_parallel (void)
-{
- assert (dl);
-
- return plugin._thread_model >= NBDKIT_THREAD_MODEL_PARALLEL;
-}
-
int
plugin_errno_is_preserved (void)
{
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 2/9] Refactor plugin_* functions into a backend struct.
Introduce the concept of a backend. Currently the only type of
backend is a plugin, and there can only be one of them. Instead of
calling functions like ‘plugin_pwrite’ you call the backend method
‘backend->pwrite (backend, ...)’.
The change is largely mechanical. I was able to remove ‘assert (dl)’
statements throughout since we can now prove they will never be
called.
Note this does not lift the restriction of one plugin per server, and
it can *never* do that because plugins can use global variables.
---
src/connections.c | 40 +++--
src/internal.h | 55 +++---
src/locks.c | 8 +-
src/main.c | 31 ++--
src/plugins.c | 529 ++++++++++++++++++++++++++++++------------------------
5 files changed, 368 insertions(+), 295 deletions(-)
diff --git a/src/connections.c b/src/connections.c
index 74bb8e4..921a5b2 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -211,16 +211,17 @@ _handle_single_connection (int sockin, int sockout)
int nworkers = threads ? threads : DEFAULT_PARALLEL_REQUESTS;
pthread_t *workers = NULL;
- if (plugin_thread_model () < NBDKIT_THREAD_MODEL_PARALLEL || nworkers ==
1)
+ if (backend->thread_model (backend) < NBDKIT_THREAD_MODEL_PARALLEL ||
+ nworkers == 1)
nworkers = 0;
conn = new_connection (sockin, sockout, nworkers);
if (!conn)
goto done;
- if (plugin_open (conn, readonly) == -1)
+ if (backend->open (backend, conn, readonly) == -1)
goto done;
- threadlocal_set_name (plugin_name ());
+ threadlocal_set_name (backend->name (backend));
/* Handshake. */
if (negotiate_handshake (conn) == -1)
@@ -251,7 +252,8 @@ _handle_single_connection (int sockin, int sockout)
set_status (conn, -1);
goto wait;
}
- if (asprintf (&worker->name, "%s.%d", plugin_name (),
nworkers) < 0) {
+ if (asprintf (&worker->name,
+ "%s.%d", backend->name (backend), nworkers)
< 0) {
perror ("asprintf");
set_status (conn, -1);
free (worker);
@@ -340,7 +342,7 @@ free_connection (struct connection *conn)
*/
if (!quit) {
if (conn->handle)
- plugin_close (conn);
+ backend->close (backend, conn);
}
free (conn);
@@ -352,7 +354,7 @@ compute_eflags (struct connection *conn, uint16_t *flags)
uint16_t eflags = NBD_FLAG_HAS_FLAGS;
int fl;
- fl = plugin_can_write (conn);
+ fl = backend->can_write (backend, conn);
if (fl == -1)
return -1;
if (readonly || !fl) {
@@ -363,7 +365,7 @@ compute_eflags (struct connection *conn, uint16_t *flags)
eflags |= NBD_FLAG_SEND_WRITE_ZEROES;
}
- fl = plugin_can_flush (conn);
+ fl = backend->can_flush (backend, conn);
if (fl == -1)
return -1;
if (fl) {
@@ -371,7 +373,7 @@ compute_eflags (struct connection *conn, uint16_t *flags)
conn->can_flush = 1;
}
- fl = plugin_is_rotational (conn);
+ fl = backend->is_rotational (backend, conn);
if (fl == -1)
return -1;
if (fl) {
@@ -379,7 +381,7 @@ compute_eflags (struct connection *conn, uint16_t *flags)
conn->is_rotational = 1;
}
- fl = plugin_can_trim (conn);
+ fl = backend->can_trim (backend, conn);
if (fl == -1)
return -1;
if (fl) {
@@ -407,7 +409,7 @@ _negotiate_handshake_oldstyle (struct connection *conn)
return -1;
}
- r = plugin_get_size (conn);
+ r = backend->get_size (backend, conn);
if (r == -1)
return -1;
if (r < 0) {
@@ -703,7 +705,7 @@ _negotiate_handshake_newstyle (struct connection *conn)
return -1;
/* Finish the newstyle handshake. */
- r = plugin_get_size (conn);
+ r = backend->get_size (backend, conn);
if (r == -1)
return -1;
if (r < 0) {
@@ -848,7 +850,7 @@ get_error (struct connection *conn)
{
int ret = threadlocal_get_error ();
- if (!ret && plugin_errno_is_preserved ())
+ if (!ret && backend->errno_is_preserved (backend))
ret = errno;
return ret ? ret : EIO;
}
@@ -881,28 +883,28 @@ handle_request (struct connection *conn,
switch (cmd) {
case NBD_CMD_READ:
- if (plugin_pread (conn, buf, count, offset) == -1)
+ if (backend->pread (backend, conn, buf, count, offset) == -1)
return get_error (conn);
break;
case NBD_CMD_WRITE:
- if (plugin_pwrite (conn, buf, count, offset) == -1)
+ if (backend->pwrite (backend, conn, buf, count, offset) == -1)
return get_error (conn);
break;
case NBD_CMD_FLUSH:
- if (plugin_flush (conn) == -1)
+ if (backend->flush (backend, conn) == -1)
return get_error (conn);
break;
case NBD_CMD_TRIM:
- if (plugin_trim (conn, count, offset) == -1)
+ if (backend->trim (backend, conn, count, offset) == -1)
return get_error (conn);
break;
case NBD_CMD_WRITE_ZEROES:
- if (plugin_zero (conn, count, offset,
- !(flags & NBD_CMD_FLAG_NO_HOLE)) == -1)
+ if (backend->zero (backend, conn, count, offset,
+ !(flags & NBD_CMD_FLAG_NO_HOLE)) == -1)
return get_error (conn);
break;
@@ -910,7 +912,7 @@ handle_request (struct connection *conn,
abort ();
}
- if (flush_after_command && plugin_flush (conn) == -1)
+ if (flush_after_command && backend->flush (backend, conn) == -1)
return get_error (conn);
return 0;
diff --git a/src/internal.h b/src/internal.h
index 068204b..9c4993d 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -35,6 +35,7 @@
#define NBDKIT_INTERNAL_H
#include <stdbool.h>
+#include <stddef.h>
#include <stdarg.h>
#include <sys/socket.h>
#include <pthread.h>
@@ -91,6 +92,11 @@
# endif
#endif
+#define container_of(ptr, type, member) ({ \
+ const typeof (((type *) 0)->member) *__mptr = (ptr); \
+ (type *) ((char *) __mptr - offsetof(type, member)); \
+ })
+
/* main.c */
extern const char *exportname;
extern const char *ipaddr;
@@ -108,6 +114,8 @@ extern int threads;
extern volatile int quit;
extern int quit_fd;
+extern struct backend *backend;
+
/* cleanup.c */
extern void cleanup_free (void *ptr);
#define CLEANUP_FREE __attribute__((cleanup (cleanup_free)))
@@ -142,28 +150,31 @@ extern int crypto_negotiate_tls (struct connection *conn,
int sockin, int sockou
#define debug nbdkit_debug
/* plugins.c */
-extern void plugin_register (const char *_filename, void *_dl, struct
nbdkit_plugin *(*plugin_init) (void));
-extern void plugin_cleanup (void);
-extern int plugin_thread_model (void);
-extern const char *plugin_name (void);
-extern void plugin_usage (void);
-extern const char *plugin_version (void);
-extern void plugin_dump_fields (void);
-extern void plugin_config (const char *key, const char *value);
-extern void plugin_config_complete (void);
-extern int plugin_errno_is_preserved (void);
-extern int plugin_open (struct connection *conn, int readonly);
-extern void plugin_close (struct connection *conn);
-extern int64_t plugin_get_size (struct connection *conn);
-extern int plugin_can_write (struct connection *conn);
-extern int plugin_can_flush (struct connection *conn);
-extern int plugin_is_rotational (struct connection *conn);
-extern int plugin_can_trim (struct connection *conn);
-extern int plugin_pread (struct connection *conn, void *buf, uint32_t count,
uint64_t offset);
-extern int plugin_pwrite (struct connection *conn, void *buf, uint32_t count,
uint64_t offset);
-extern int plugin_flush (struct connection *conn);
-extern int plugin_trim (struct connection *conn, uint32_t count, uint64_t
offset);
-extern int plugin_zero (struct connection *conn, uint32_t count, uint64_t
offset, int may_trim);
+struct backend {
+ void (*free) (struct backend *);
+ int (*thread_model) (struct backend *);
+ const char *(*name) (struct backend *);
+ void (*usage) (struct backend *);
+ const char *(*version) (struct backend *);
+ void (*dump_fields) (struct backend *);
+ void (*config) (struct backend *, const char *key, const char *value);
+ void (*config_complete) (struct backend *);
+ int (*errno_is_preserved) (struct backend *);
+ int (*open) (struct backend *, struct connection *conn, int readonly);
+ void (*close) (struct backend *, struct connection *conn);
+ int64_t (*get_size) (struct backend *, struct connection *conn);
+ int (*can_write) (struct backend *, struct connection *conn);
+ int (*can_flush) (struct backend *, struct connection *conn);
+ int (*is_rotational) (struct backend *, struct connection *conn);
+ int (*can_trim) (struct backend *, struct connection *conn);
+ int (*pread) (struct backend *, struct connection *conn, void *buf, uint32_t
count, uint64_t offset);
+ int (*pwrite) (struct backend *, struct connection *conn, void *buf, uint32_t
count, uint64_t offset);
+ int (*flush) (struct backend *, struct connection *conn);
+ int (*trim) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset);
+ int (*zero) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset, int may_trim);
+};
+
+extern struct backend *plugin_register (const char *_filename, void *_dl,
struct nbdkit_plugin *(*plugin_init) (void));
/* locks.c */
extern void lock_connection (void);
diff --git a/src/locks.c b/src/locks.c
index 6021356..62b2dd0 100644
--- a/src/locks.c
+++ b/src/locks.c
@@ -45,7 +45,7 @@ static pthread_rwlock_t unload_prevention_lock =
PTHREAD_RWLOCK_INITIALIZER;
void
lock_connection (void)
{
- int thread_model = plugin_thread_model ();
+ int thread_model = backend->thread_model (backend);
if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
debug ("acquire connection lock");
@@ -56,7 +56,7 @@ lock_connection (void)
void
unlock_connection (void)
{
- int thread_model = plugin_thread_model ();
+ int thread_model = backend->thread_model (backend);
if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS) {
debug ("release connection lock");
@@ -67,7 +67,7 @@ unlock_connection (void)
void
lock_request (struct connection *conn)
{
- int thread_model = plugin_thread_model ();
+ int thread_model = backend->thread_model (backend);
if (thread_model <= NBDKIT_THREAD_MODEL_SERIALIZE_ALL_REQUESTS) {
debug ("acquire global request lock");
@@ -86,7 +86,7 @@ lock_request (struct connection *conn)
void
unlock_request (struct connection *conn)
{
- int thread_model = plugin_thread_model ();
+ int thread_model = backend->thread_model (backend);
debug ("release unload prevention lock");
pthread_rwlock_unlock (&unload_prevention_lock);
diff --git a/src/main.c b/src/main.c
index 4eca859..b3e6bad 100644
--- a/src/main.c
+++ b/src/main.c
@@ -64,7 +64,7 @@
static int is_short_name (const char *);
static char *make_random_fifo (void);
-static void open_plugin_so (const char *filename, int short_name);
+static struct backend *open_plugin_so (const char *filename, int short_name);
static void start_serving (void);
static void set_up_signals (void);
static void run_command (void);
@@ -103,6 +103,9 @@ volatile int quit;
int quit_fd;
static int write_quit_fd;
+/* The currently loaded plugin. */
+struct backend *backend;
+
static char *random_fifo_dir = NULL;
static char *random_fifo = NULL;
@@ -493,12 +496,12 @@ main (int argc, char *argv[])
}
}
- open_plugin_so (filename, short_name);
+ backend = open_plugin_so (filename, short_name);
if (help) {
usage ();
printf ("\n%s:\n\n", filename);
- plugin_usage ();
+ backend->usage (backend);
exit (EXIT_SUCCESS);
}
@@ -506,8 +509,8 @@ main (int argc, char *argv[])
const char *v;
display_version ();
- printf ("%s", plugin_name ());
- if ((v = plugin_version ()) != NULL)
+ printf ("%s", backend->name (backend));
+ if ((v = backend->version (backend)) != NULL)
printf (" %s", v);
printf ("\n");
exit (EXIT_SUCCESS);
@@ -518,7 +521,7 @@ main (int argc, char *argv[])
* we assume it is 'script=...'.
*/
if (optind < argc && (p = strchr (argv[optind], '=')) ==
NULL) {
- plugin_config ("script", argv[optind]);
+ backend->config (backend, "script", argv[optind]);
++optind;
}
@@ -528,14 +531,14 @@ main (int argc, char *argv[])
* script=... parameter (and do not wait for config_complete).
*/
if (dump_plugin) {
- plugin_dump_fields ();
+ backend->dump_fields (backend);
exit (EXIT_SUCCESS);
}
while (optind < argc) {
if ((p = strchr (argv[optind], '=')) != NULL) {
*p = '\0';
- plugin_config (argv[optind], p+1);
+ backend->config (backend, argv[optind], p+1);
++optind;
}
else {
@@ -546,11 +549,12 @@ main (int argc, char *argv[])
}
}
- plugin_config_complete ();
+ backend->config_complete (backend);
start_serving ();
- plugin_cleanup ();
+ backend->free (backend);
+ backend = NULL;
free (unixsocket);
free (pidfile);
@@ -609,9 +613,10 @@ make_random_fifo (void)
return unixsocket;
}
-static void
+static struct backend *
open_plugin_so (const char *name, int short_name)
{
+ struct backend *ret;
char *filename = (char *) name;
int free_filename = 0;
void *dl;
@@ -647,10 +652,12 @@ open_plugin_so (const char *name, int short_name)
}
/* Register the plugin. */
- plugin_register (filename, dl, plugin_init);
+ ret = plugin_register (filename, dl, plugin_init);
if (free_filename)
free (filename);
+
+ return ret;
}
static void
diff --git a/src/plugins.c b/src/plugins.c
index b7ab43d..b687849 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -49,192 +49,100 @@
/* Maximum read or write request that we will handle. */
#define MAX_REQUEST_SIZE (64 * 1024 * 1024)
-/* Currently the server can only load one plugin (see TODO). Hence we
- * can just use globals to store these.
+/* We extend the generic backend struct with extra fields relating
+ * to this plugin.
*/
-static char *filename;
-static void *dl;
-static struct nbdkit_plugin plugin;
-
-void
-plugin_register (const char *_filename,
- void *_dl, struct nbdkit_plugin *(*plugin_init) (void))
+struct backend_plugin {
+ struct backend backend;
+ char *filename;
+ void *dl;
+ struct nbdkit_plugin plugin;
+};
+
+static void
+plugin_free (struct backend *b)
{
- const struct nbdkit_plugin *_plugin;
- size_t i, len, size;
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- filename = strdup (_filename);
- if (filename == NULL) {
- perror ("strdup");
- exit (EXIT_FAILURE);
- }
- dl = _dl;
-
- debug ("registering %s", filename);
-
- /* Call the initialization function which returns the address of the
- * plugin's own 'struct nbdkit_plugin'.
+ /* Acquiring this lock prevents any plugin callbacks from running
+ * simultaneously.
*/
- _plugin = plugin_init ();
- if (!_plugin) {
- fprintf (stderr, "%s: %s: plugin registration function failed\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
+ lock_unload ();
- /* Check for incompatible future versions. */
- if (_plugin->_api_version != 1) {
- fprintf (stderr, "%s: %s: plugin is incompatible with this version of
nbdkit (_api_version = %d)\n",
- program_name, filename, _plugin->_api_version);
- exit (EXIT_FAILURE);
- }
+ debug ("%s: unload", p->filename);
+ if (p->plugin.unload)
+ p->plugin.unload ();
- /* Since the plugin might be much older than the current version of
- * nbdkit, only copy up to the self-declared _struct_size of the
- * plugin and zero out the rest. If the plugin is much newer then
- * we'll only call the "old" fields.
- */
- size = sizeof plugin; /* our struct */
- memset (&plugin, 0, size);
- if (size > _plugin->_struct_size)
- size = _plugin->_struct_size;
- memcpy (&plugin, _plugin, size);
+ dlclose (p->dl);
+ free (p->filename);
- /* Check for the minimum fields which must exist in the
- * plugin struct.
- */
- if (plugin.name == NULL) {
- fprintf (stderr, "%s: %s: plugin must have a .name field\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
- if (plugin.open == NULL) {
- fprintf (stderr, "%s: %s: plugin must have a .open callback\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
- if (plugin.get_size == NULL) {
- fprintf (stderr, "%s: %s: plugin must have a .get_size
callback\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
- if (plugin.pread == NULL) {
- fprintf (stderr, "%s: %s: plugin must have a .pread callback\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
-
- len = strlen (plugin.name);
- if (len == 0) {
- fprintf (stderr, "%s: %s: plugin.name field must not be empty\n",
- program_name, filename);
- exit (EXIT_FAILURE);
- }
- for (i = 0; i < len; ++i) {
- if (!((plugin.name[i] >= '0' && plugin.name[i] <=
'9') ||
- (plugin.name[i] >= 'a' && plugin.name[i] <=
'z') ||
- (plugin.name[i] >= 'A' && plugin.name[i] <=
'Z'))) {
- fprintf (stderr, "%s: %s: plugin.name ('%s') field must
contain only ASCII alphanumeric characters\n",
- program_name, filename, plugin.name);
- exit (EXIT_FAILURE);
- }
- }
- /* Copy the module's name into local storage, so that plugin.name
- * survives past unload. */
- if (!(plugin.name = strdup (plugin.name))) {
- perror ("strdup");
- exit (EXIT_FAILURE);
- }
+ unlock_unload ();
- debug ("registered %s (name %s)", filename, plugin.name);
-
- /* Call the on-load callback if it exists. */
- debug ("%s: load", filename);
- if (plugin.load)
- plugin.load ();
-}
-
-void
-plugin_cleanup (void)
-{
- if (dl) {
- /* Acquiring this lock prevents any plugin callbacks from running
- * simultaneously.
- */
- lock_unload ();
-
- debug ("%s: unload", filename);
- if (plugin.unload)
- plugin.unload ();
-
- dlclose (dl);
- dl = NULL;
- free (filename);
- filename = NULL;
-
- unlock_unload ();
- }
+ free (p);
}
-int
-plugin_thread_model (void)
+static int
+plugin_thread_model (struct backend *b)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- return plugin._thread_model;
+ return p->plugin._thread_model;
}
-const char *
-plugin_name (void)
+static const char *
+plugin_name (struct backend *b)
{
- return plugin.name;
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
+ return p->plugin.name;
}
-void
-plugin_usage (void)
+static void
+plugin_usage (struct backend *b)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- printf ("%s", plugin.name);
- if (plugin.longname)
- printf (" (%s)", plugin.longname);
+ printf ("%s", p->plugin.name);
+ if (p->plugin.longname)
+ printf (" (%s)", p->plugin.longname);
printf ("\n");
- if (plugin.description) {
+ if (p->plugin.description) {
printf ("\n");
- printf ("%s\n", plugin.description);
+ printf ("%s\n", p->plugin.description);
}
- if (plugin.config_help) {
+ if (p->plugin.config_help) {
printf ("\n");
- printf ("%s\n", plugin.config_help);
+ printf ("%s\n", p->plugin.config_help);
}
}
-const char *
-plugin_version (void)
+static const char *
+plugin_version (struct backend *b)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- return plugin.version;
+ return p->plugin.version;
}
/* This implements the --dump-plugin option. */
-void
-plugin_dump_fields (void)
+static void
+plugin_dump_fields (struct backend *b)
{
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
char *path;
- path = nbdkit_absolute_path (filename);
+ path = nbdkit_absolute_path (p->filename);
printf ("path=%s\n", path);
free (path);
- printf ("name=%s\n", plugin.name);
- if (plugin.version)
- printf ("version=%s\n", plugin.version);
+ printf ("name=%s\n", p->plugin.name);
+ if (p->plugin.version)
+ printf ("version=%s\n", p->plugin.version);
- printf ("api_version=%d\n", plugin._api_version);
- printf ("struct_size=%" PRIu64 "\n",
plugin._struct_size);
+ printf ("api_version=%d\n", p->plugin._api_version);
+ printf ("struct_size=%" PRIu64 "\n",
p->plugin._struct_size);
printf ("thread_model=");
- switch (plugin._thread_model) {
+ switch (p->plugin._thread_model) {
case NBDKIT_THREAD_MODEL_SERIALIZE_CONNECTIONS:
printf ("serialize_connections");
break;
@@ -248,13 +156,13 @@ plugin_dump_fields (void)
printf ("parallel");
break;
default:
- printf ("%d # unknown thread model!", plugin._thread_model);
+ printf ("%d # unknown thread model!",
p->plugin._thread_model);
break;
}
printf ("\n");
- printf ("errno_is_preserved=%d\n", plugin.errno_is_preserved);
+ printf ("errno_is_preserved=%d\n",
p->plugin.errno_is_preserved);
-#define HAS(field) if (plugin.field) printf ("has_%s=1\n", #field)
+#define HAS(field) if (p->plugin.field) printf ("has_%s=1\n",
#field)
HAS (longname);
HAS (description);
HAS (load);
@@ -278,64 +186,64 @@ plugin_dump_fields (void)
#undef HAS
/* Custom fields. */
- if (plugin.dump_plugin)
- plugin.dump_plugin ();
+ if (p->plugin.dump_plugin)
+ p->plugin.dump_plugin ();
}
-void
-plugin_config (const char *key, const char *value)
+static void
+plugin_config (struct backend *b, const char *key, const char *value)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
debug ("%s: config key=%s, value=%s",
- filename, key, value);
+ p->filename, key, value);
- if (plugin.config == NULL) {
+ if (p->plugin.config == NULL) {
fprintf (stderr, "%s: %s: this plugin does not need command line
configuration\n"
"Try using: %s --help %s\n",
- program_name, filename,
- program_name, filename);
+ program_name, p->filename,
+ program_name, p->filename);
exit (EXIT_FAILURE);
}
- if (plugin.config (key, value) == -1)
+ if (p->plugin.config (key, value) == -1)
exit (EXIT_FAILURE);
}
-void
-plugin_config_complete (void)
+static void
+plugin_config_complete (struct backend *b)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- debug ("%s: config_complete", filename);
+ debug ("%s: config_complete", p->filename);
- if (!plugin.config_complete)
+ if (!p->plugin.config_complete)
return;
- if (plugin.config_complete () == -1)
+ if (p->plugin.config_complete () == -1)
exit (EXIT_FAILURE);
}
-int
-plugin_errno_is_preserved (void)
+static int
+plugin_errno_is_preserved (struct backend *b)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- return plugin.errno_is_preserved;
+ return p->plugin.errno_is_preserved;
}
-int
-plugin_open (struct connection *conn, int readonly)
+static int
+plugin_open (struct backend *b, struct connection *conn, int readonly)
{
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
void *handle;
- assert (dl);
assert (connection_get_handle (conn) == NULL);
- assert (plugin.open != NULL);
+ assert (p->plugin.open != NULL);
- debug ("%s: open readonly=%d", filename, readonly);
+ debug ("%s: open readonly=%d", p->filename, readonly);
- handle = plugin.open (readonly);
+ handle = p->plugin.open (readonly);
if (!handle)
return -1;
@@ -343,179 +251,192 @@ plugin_open (struct connection *conn, int readonly)
return 0;
}
-void
-plugin_close (struct connection *conn)
+static void
+plugin_close (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("close");
- if (plugin.close)
- plugin.close (connection_get_handle (conn));
+ if (p->plugin.close)
+ p->plugin.close (connection_get_handle (conn));
connection_set_handle (conn, NULL);
}
-int64_t
-plugin_get_size (struct connection *conn)
+static int64_t
+plugin_get_size (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
- assert (plugin.get_size != NULL);
+ assert (p->plugin.get_size != NULL);
debug ("get_size");
- return plugin.get_size (connection_get_handle (conn));
+ return p->plugin.get_size (connection_get_handle (conn));
}
-int
-plugin_can_write (struct connection *conn)
+static int
+plugin_can_write (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("can_write");
- if (plugin.can_write)
- return plugin.can_write (connection_get_handle (conn));
+ if (p->plugin.can_write)
+ return p->plugin.can_write (connection_get_handle (conn));
else
- return plugin.pwrite != NULL;
+ return p->plugin.pwrite != NULL;
}
-int
-plugin_can_flush (struct connection *conn)
+static int
+plugin_can_flush (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("can_flush");
- if (plugin.can_flush)
- return plugin.can_flush (connection_get_handle (conn));
+ if (p->plugin.can_flush)
+ return p->plugin.can_flush (connection_get_handle (conn));
else
- return plugin.flush != NULL;
+ return p->plugin.flush != NULL;
}
-int
-plugin_is_rotational (struct connection *conn)
+static int
+plugin_is_rotational (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("is_rotational");
- if (plugin.is_rotational)
- return plugin.is_rotational (connection_get_handle (conn));
+ if (p->plugin.is_rotational)
+ return p->plugin.is_rotational (connection_get_handle (conn));
else
return 0; /* assume false */
}
-int
-plugin_can_trim (struct connection *conn)
+static int
+plugin_can_trim (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("can_trim");
- if (plugin.can_trim)
- return plugin.can_trim (connection_get_handle (conn));
+ if (p->plugin.can_trim)
+ return p->plugin.can_trim (connection_get_handle (conn));
else
- return plugin.trim != NULL;
+ return p->plugin.trim != NULL;
}
-int
-plugin_pread (struct connection *conn,
+static int
+plugin_pread (struct backend *b, struct connection *conn,
void *buf, uint32_t count, uint64_t offset)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
- assert (plugin.pread != NULL);
+ assert (p->plugin.pread != NULL);
debug ("pread count=%" PRIu32 " offset=%" PRIu64, count,
offset);
- return plugin.pread (connection_get_handle (conn), buf, count, offset);
+ return p->plugin.pread (connection_get_handle (conn), buf, count, offset);
}
-int
-plugin_pwrite (struct connection *conn,
+static int
+plugin_pwrite (struct backend *b, struct connection *conn,
void *buf, uint32_t count, uint64_t offset)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("pwrite count=%" PRIu32 " offset=%" PRIu64, count,
offset);
- if (plugin.pwrite != NULL)
- return plugin.pwrite (connection_get_handle (conn), buf, count, offset);
+ if (p->plugin.pwrite != NULL)
+ return p->plugin.pwrite (connection_get_handle (conn), buf, count,
offset);
else {
errno = EROFS;
return -1;
}
}
-int
-plugin_flush (struct connection *conn)
+static int
+plugin_flush (struct backend *b, struct connection *conn)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("flush");
- if (plugin.flush != NULL)
- return plugin.flush (connection_get_handle (conn));
+ if (p->plugin.flush != NULL)
+ return p->plugin.flush (connection_get_handle (conn));
else {
errno = EINVAL;
return -1;
}
}
-int
-plugin_trim (struct connection *conn, uint32_t count, uint64_t offset)
+static int
+plugin_trim (struct backend *b, struct connection *conn,
+ uint32_t count, uint64_t offset)
{
- assert (dl);
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
assert (connection_get_handle (conn));
debug ("trim count=%" PRIu32 " offset=%" PRIu64, count,
offset);
- if (plugin.trim != NULL)
- return plugin.trim (connection_get_handle (conn), count, offset);
+ if (p->plugin.trim != NULL)
+ return p->plugin.trim (connection_get_handle (conn), count, offset);
else {
errno = EINVAL;
return -1;
}
}
-int
-plugin_zero (struct connection *conn,
+static int
+plugin_zero (struct backend *b, struct connection *conn,
uint32_t count, uint64_t offset, int may_trim)
{
- assert (dl);
- assert (connection_get_handle (conn));
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
char *buf;
uint32_t limit;
int result;
int err = 0;
+ assert (connection_get_handle (conn));
+
debug ("zero count=%" PRIu32 " offset=%" PRIu64 "
may_trim=%d",
count, offset, may_trim);
if (!count)
return 0;
- if (plugin.zero) {
+ if (p->plugin.zero) {
errno = 0;
- result = plugin.zero (connection_get_handle (conn), count, offset,
may_trim);
+ result = p->plugin.zero (connection_get_handle (conn),
+ count, offset, may_trim);
if (result == -1) {
err = threadlocal_get_error ();
- if (!err && plugin_errno_is_preserved ())
+ if (!err && plugin_errno_is_preserved (b))
err = errno;
}
if (result == 0 || err != EOPNOTSUPP)
return result;
}
- assert (plugin.pwrite);
+ assert (p->plugin.pwrite);
threadlocal_set_error (0);
limit = count < MAX_REQUEST_SIZE ? count : MAX_REQUEST_SIZE;
buf = calloc (limit, 1);
@@ -525,7 +446,8 @@ plugin_zero (struct connection *conn,
}
while (count) {
- result = plugin.pwrite (connection_get_handle (conn), buf, limit, offset);
+ result = p->plugin.pwrite (connection_get_handle (conn),
+ buf, limit, offset);
if (result < 0)
break;
count -= limit;
@@ -538,3 +460,134 @@ plugin_zero (struct connection *conn,
errno = err;
return result;
}
+
+static struct backend plugin_functions = {
+ .free = plugin_free,
+ .thread_model = plugin_thread_model,
+ .name = plugin_name,
+ .usage = plugin_usage,
+ .version = plugin_version,
+ .dump_fields = plugin_dump_fields,
+ .config = plugin_config,
+ .config_complete = plugin_config_complete,
+ .errno_is_preserved = plugin_errno_is_preserved,
+ .open = plugin_open,
+ .close = plugin_close,
+ .get_size = plugin_get_size,
+ .can_write = plugin_can_write,
+ .can_flush = plugin_can_flush,
+ .is_rotational = plugin_is_rotational,
+ .can_trim = plugin_can_trim,
+ .pread = plugin_pread,
+ .pwrite = plugin_pwrite,
+ .flush = plugin_flush,
+ .trim = plugin_trim,
+ .zero = plugin_zero,
+};
+
+/* Register and load a plugin. */
+struct backend *
+plugin_register (const char *filename,
+ void *dl, struct nbdkit_plugin *(*plugin_init) (void))
+{
+ struct backend_plugin *p;
+ const struct nbdkit_plugin *plugin;
+ size_t i, len, size;
+
+ p = malloc (sizeof *p);
+ if (p == NULL) {
+ out_of_memory:
+ perror ("strdup");
+ exit (EXIT_FAILURE);
+ }
+
+ p->backend = plugin_functions;
+ p->filename = strdup (filename);
+ if (p->filename == NULL) goto out_of_memory;
+ p->dl = dl;
+
+ debug ("registering %s", p->filename);
+
+ /* Call the initialization function which returns the address of the
+ * plugin's own 'struct nbdkit_plugin'.
+ */
+ plugin = plugin_init ();
+ if (!plugin) {
+ fprintf (stderr, "%s: %s: plugin registration function failed\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+
+ /* Check for incompatible future versions. */
+ if (plugin->_api_version != 1) {
+ fprintf (stderr, "%s: %s: plugin is incompatible with this version of
nbdkit (_api_version = %d)\n",
+ program_name, p->filename, plugin->_api_version);
+ exit (EXIT_FAILURE);
+ }
+
+ /* Since the plugin might be much older than the current version of
+ * nbdkit, only copy up to the self-declared _struct_size of the
+ * plugin and zero out the rest. If the plugin is much newer then
+ * we'll only call the "old" fields.
+ */
+ size = sizeof p->plugin; /* our struct */
+ memset (&p->plugin, 0, size);
+ if (size > plugin->_struct_size)
+ size = plugin->_struct_size;
+ memcpy (&p->plugin, plugin, size);
+
+ /* Check for the minimum fields which must exist in the
+ * plugin struct.
+ */
+ if (p->plugin.name == NULL) {
+ fprintf (stderr, "%s: %s: plugin must have a .name field\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+ if (p->plugin.open == NULL) {
+ fprintf (stderr, "%s: %s: plugin must have a .open callback\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+ if (p->plugin.get_size == NULL) {
+ fprintf (stderr, "%s: %s: plugin must have a .get_size
callback\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+ if (p->plugin.pread == NULL) {
+ fprintf (stderr, "%s: %s: plugin must have a .pread callback\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+
+ len = strlen (p->plugin.name);
+ if (len == 0) {
+ fprintf (stderr, "%s: %s: plugin.name field must not be empty\n",
+ program_name, p->filename);
+ exit (EXIT_FAILURE);
+ }
+ for (i = 0; i < len; ++i) {
+ if (!((p->plugin.name[i] >= '0' &&
p->plugin.name[i] <= '9') ||
+ (p->plugin.name[i] >= 'a' &&
p->plugin.name[i] <= 'z') ||
+ (p->plugin.name[i] >= 'A' &&
p->plugin.name[i] <= 'Z'))) {
+ fprintf (stderr, "%s: %s: plugin.name ('%s') field must
contain only ASCII alphanumeric characters\n",
+ program_name, p->filename, p->plugin.name);
+ exit (EXIT_FAILURE);
+ }
+ }
+ /* Copy the module's name into local storage, so that plugin.name
+ * survives past unload. */
+ if (!(p->plugin.name = strdup (p->plugin.name))) {
+ perror ("strdup");
+ exit (EXIT_FAILURE);
+ }
+
+ debug ("registered %s (name %s)", p->filename,
p->plugin.name);
+
+ /* Call the on-load callback if it exists. */
+ debug ("%s: load", p->filename);
+ if (p->plugin.load)
+ p->plugin.load ();
+
+ return (struct backend *) p;
+}
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 3/9] Fix const-correctness of backend pwrite method.
---
src/internal.h | 2 +-
src/plugins.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/internal.h b/src/internal.h
index 9c4993d..c4ee51b 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -168,7 +168,7 @@ struct backend {
int (*is_rotational) (struct backend *, struct connection *conn);
int (*can_trim) (struct backend *, struct connection *conn);
int (*pread) (struct backend *, struct connection *conn, void *buf, uint32_t
count, uint64_t offset);
- int (*pwrite) (struct backend *, struct connection *conn, void *buf, uint32_t
count, uint64_t offset);
+ int (*pwrite) (struct backend *, struct connection *conn, const void *buf,
uint32_t count, uint64_t offset);
int (*flush) (struct backend *, struct connection *conn);
int (*trim) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset);
int (*zero) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset, int may_trim);
diff --git a/src/plugins.c b/src/plugins.c
index b687849..6a2ef66 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -355,7 +355,7 @@ plugin_pread (struct backend *b, struct connection *conn,
static int
plugin_pwrite (struct backend *b, struct connection *conn,
- void *buf, uint32_t count, uint64_t offset)
+ const void *buf, uint32_t count, uint64_t offset)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 4/9] backend: Add a .plugin_name method.
This returns the plugin name, which for plugins is the same as the
ordinary .name method (but for filters will be different).
---
src/connections.c | 4 ++--
src/internal.h | 1 +
src/plugins.c | 1 +
3 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/connections.c b/src/connections.c
index 921a5b2..e1ac543 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -221,7 +221,7 @@ _handle_single_connection (int sockin, int sockout)
if (backend->open (backend, conn, readonly) == -1)
goto done;
- threadlocal_set_name (backend->name (backend));
+ threadlocal_set_name (backend->plugin_name (backend));
/* Handshake. */
if (negotiate_handshake (conn) == -1)
@@ -253,7 +253,7 @@ _handle_single_connection (int sockin, int sockout)
goto wait;
}
if (asprintf (&worker->name,
- "%s.%d", backend->name (backend), nworkers)
< 0) {
+ "%s.%d", backend->plugin_name (backend),
nworkers) < 0) {
perror ("asprintf");
set_status (conn, -1);
free (worker);
diff --git a/src/internal.h b/src/internal.h
index c4ee51b..dc26665 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -154,6 +154,7 @@ struct backend {
void (*free) (struct backend *);
int (*thread_model) (struct backend *);
const char *(*name) (struct backend *);
+ const char *(*plugin_name) (struct backend *);
void (*usage) (struct backend *);
const char *(*version) (struct backend *);
void (*dump_fields) (struct backend *);
diff --git a/src/plugins.c b/src/plugins.c
index 6a2ef66..f0fe864 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -465,6 +465,7 @@ static struct backend plugin_functions = {
.free = plugin_free,
.thread_model = plugin_thread_model,
.name = plugin_name,
+ .plugin_name = plugin_name,
.usage = plugin_usage,
.version = plugin_version,
.dump_fields = plugin_dump_fields,
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 5/9] connections: Allow multiple handles to be stored in the connection object.
Previously only one handle could be stored, but we will need to store
multiple handles when we have filters.
The plugin handle is defined as index 0. Filters will use indices > 0.
---
src/connections.c | 37 ++++++++++++++++++++++++++++++-------
src/internal.h | 4 ++--
src/plugins.c | 53 +++++++++++++++++++++++++++--------------------------
3 files changed, 59 insertions(+), 35 deletions(-)
diff --git a/src/connections.c b/src/connections.c
index e1ac543..51a9772 100644
--- a/src/connections.c
+++ b/src/connections.c
@@ -69,10 +69,12 @@ struct connection {
pthread_mutex_t write_lock;
pthread_mutex_t status_lock;
int status; /* 1 for more I/O with client, 0 for shutdown, -1 on error */
- void *handle;
void *crypto_session;
int nworkers;
+ void **handles;
+ size_t nr_handles;
+
uint64_t exportsize;
int readonly;
int can_flush;
@@ -100,16 +102,37 @@ static void raw_close (struct connection *);
/* Accessors for public fields in the connection structure.
* Everything else is private to this file.
*/
-void
-connection_set_handle (struct connection *conn, void *handle)
+int
+connection_set_handle (struct connection *conn, size_t i, void *handle)
{
- conn->handle = handle;
+ size_t j;
+
+ if (i < conn->nr_handles)
+ conn->handles[i] = handle;
+ else {
+ j = conn->nr_handles;
+ conn->nr_handles = i+1;
+ conn->handles = realloc (conn->handles,
+ conn->nr_handles * sizeof (void *));
+ if (conn->handles == NULL) {
+ perror ("realloc");
+ conn->nr_handles = 0;
+ return -1;
+ }
+ for (; j < i; ++j)
+ conn->handles[j] = NULL;
+ conn->handles[i] = handle;
+ }
+ return 0;
}
void *
-connection_get_handle (struct connection *conn)
+connection_get_handle (struct connection *conn, size_t i)
{
- return conn->handle;
+ if (i < conn->nr_handles)
+ return conn->handles[i];
+ else
+ return NULL;
}
pthread_mutex_t *
@@ -341,7 +364,7 @@ free_connection (struct connection *conn)
* callback should always be called.
*/
if (!quit) {
- if (conn->handle)
+ if (conn->nr_handles > 0 && conn->handles[0])
backend->close (backend, conn);
}
diff --git a/src/internal.h b/src/internal.h
index dc26665..5a68d59 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -131,8 +131,8 @@ typedef int (*connection_recv_function) (struct connection
*, void *buf, size_t
typedef int (*connection_send_function) (struct connection *, const void *buf,
size_t len);
typedef void (*connection_close_function) (struct connection *);
extern int handle_single_connection (int sockin, int sockout);
-extern void connection_set_handle (struct connection *conn, void *handle);
-extern void *connection_get_handle (struct connection *conn);
+extern int connection_set_handle (struct connection *conn, size_t i, void
*handle);
+extern void *connection_get_handle (struct connection *conn, size_t i);
extern pthread_mutex_t *connection_get_request_lock (struct connection *conn);
extern void connection_set_crypto_session (struct connection *conn, void
*session);
extern void *connection_get_crypto_session (struct connection *conn);
diff --git a/src/plugins.c b/src/plugins.c
index f0fe864..e732587 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -238,7 +238,7 @@ plugin_open (struct backend *b, struct connection *conn, int
readonly)
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
void *handle;
- assert (connection_get_handle (conn) == NULL);
+ assert (connection_get_handle (conn, 0) == NULL);
assert (p->plugin.open != NULL);
debug ("%s: open readonly=%d", p->filename, readonly);
@@ -247,7 +247,7 @@ plugin_open (struct backend *b, struct connection *conn, int
readonly)
if (!handle)
return -1;
- connection_set_handle (conn, handle);
+ connection_set_handle (conn, 0, handle);
return 0;
}
@@ -256,14 +256,14 @@ plugin_close (struct backend *b, struct connection *conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("close");
if (p->plugin.close)
- p->plugin.close (connection_get_handle (conn));
+ p->plugin.close (connection_get_handle (conn, 0));
- connection_set_handle (conn, NULL);
+ connection_set_handle (conn, 0, NULL);
}
static int64_t
@@ -271,12 +271,12 @@ plugin_get_size (struct backend *b, struct connection
*conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
assert (p->plugin.get_size != NULL);
debug ("get_size");
- return p->plugin.get_size (connection_get_handle (conn));
+ return p->plugin.get_size (connection_get_handle (conn, 0));
}
static int
@@ -284,12 +284,12 @@ plugin_can_write (struct backend *b, struct connection
*conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("can_write");
if (p->plugin.can_write)
- return p->plugin.can_write (connection_get_handle (conn));
+ return p->plugin.can_write (connection_get_handle (conn, 0));
else
return p->plugin.pwrite != NULL;
}
@@ -299,12 +299,12 @@ plugin_can_flush (struct backend *b, struct connection
*conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("can_flush");
if (p->plugin.can_flush)
- return p->plugin.can_flush (connection_get_handle (conn));
+ return p->plugin.can_flush (connection_get_handle (conn, 0));
else
return p->plugin.flush != NULL;
}
@@ -314,12 +314,12 @@ plugin_is_rotational (struct backend *b, struct connection
*conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("is_rotational");
if (p->plugin.is_rotational)
- return p->plugin.is_rotational (connection_get_handle (conn));
+ return p->plugin.is_rotational (connection_get_handle (conn, 0));
else
return 0; /* assume false */
}
@@ -329,12 +329,12 @@ plugin_can_trim (struct backend *b, struct connection
*conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("can_trim");
if (p->plugin.can_trim)
- return p->plugin.can_trim (connection_get_handle (conn));
+ return p->plugin.can_trim (connection_get_handle (conn, 0));
else
return p->plugin.trim != NULL;
}
@@ -345,12 +345,12 @@ plugin_pread (struct backend *b, struct connection *conn,
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
assert (p->plugin.pread != NULL);
debug ("pread count=%" PRIu32 " offset=%" PRIu64, count,
offset);
- return p->plugin.pread (connection_get_handle (conn), buf, count, offset);
+ return p->plugin.pread (connection_get_handle (conn, 0), buf, count,
offset);
}
static int
@@ -359,12 +359,13 @@ plugin_pwrite (struct backend *b, struct connection *conn,
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("pwrite count=%" PRIu32 " offset=%" PRIu64, count,
offset);
if (p->plugin.pwrite != NULL)
- return p->plugin.pwrite (connection_get_handle (conn), buf, count,
offset);
+ return p->plugin.pwrite (connection_get_handle (conn, 0),
+ buf, count, offset);
else {
errno = EROFS;
return -1;
@@ -376,12 +377,12 @@ plugin_flush (struct backend *b, struct connection *conn)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("flush");
if (p->plugin.flush != NULL)
- return p->plugin.flush (connection_get_handle (conn));
+ return p->plugin.flush (connection_get_handle (conn, 0));
else {
errno = EINVAL;
return -1;
@@ -394,12 +395,12 @@ plugin_trim (struct backend *b, struct connection *conn,
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("trim count=%" PRIu32 " offset=%" PRIu64, count,
offset);
if (p->plugin.trim != NULL)
- return p->plugin.trim (connection_get_handle (conn), count, offset);
+ return p->plugin.trim (connection_get_handle (conn, 0), count, offset);
else {
errno = EINVAL;
return -1;
@@ -416,7 +417,7 @@ plugin_zero (struct backend *b, struct connection *conn,
int result;
int err = 0;
- assert (connection_get_handle (conn));
+ assert (connection_get_handle (conn, 0));
debug ("zero count=%" PRIu32 " offset=%" PRIu64 "
may_trim=%d",
count, offset, may_trim);
@@ -425,7 +426,7 @@ plugin_zero (struct backend *b, struct connection *conn,
return 0;
if (p->plugin.zero) {
errno = 0;
- result = p->plugin.zero (connection_get_handle (conn),
+ result = p->plugin.zero (connection_get_handle (conn, 0),
count, offset, may_trim);
if (result == -1) {
err = threadlocal_get_error ();
@@ -446,7 +447,7 @@ plugin_zero (struct backend *b, struct connection *conn,
}
while (count) {
- result = p->plugin.pwrite (connection_get_handle (conn),
+ result = p->plugin.pwrite (connection_get_handle (conn, 0),
buf, limit, offset);
if (result < 0)
break;
--
2.15.1
Filters can be placed in front of plugins to modify their behaviour.
This commit introduces the <nbdkit-filter.h> header file, the manual
page, the ‘filterdir’ directory (like ‘plugindir’), and the ‘filters/’
source directory which will contain both example and real filters.
---
Makefile.am | 2 +-
TODO | 17 +-
configure.ac | 3 +-
docs/Makefile.am | 9 +-
docs/nbdkit-filter.pod | 477 ++++++++++++++++++++++++++++++++++++++++++++++++
docs/nbdkit-plugin.pod | 3 +-
docs/nbdkit.pod | 3 +-
filters/Makefile.am | 33 ++++
include/Makefile.am | 4 +-
include/nbdkit-filter.h | 144 +++++++++++++++
include/nbdkit-plugin.h | 2 +
src/Makefile.am | 5 +-
src/main.c | 1 +
src/nbdkit.pc.in | 1 +
14 files changed, 682 insertions(+), 22 deletions(-)
diff --git a/Makefile.am b/Makefile.am
index f3c88b0..9c5b4c3 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -49,7 +49,7 @@ SUBDIRS = \
src
if HAVE_PLUGINS
-SUBDIRS += plugins
+SUBDIRS += plugins filters
endif
SUBDIRS += tests
diff --git a/TODO b/TODO
index 0c027e2..0955db7 100644
--- a/TODO
+++ b/TODO
@@ -34,10 +34,8 @@ nbdkit there is no compelling reason unless the result is
better than
qemu-nbd. For the majority of users it would be better if they were
directed to qemu-nbd for these use cases.
-Filters
--------
-
-It should be possible to layer filters over plugins to do things like:
+Suggestions for filters
+-----------------------
* adding artificial delays (see wdelay/rdelay options in the file
plugin)
@@ -50,17 +48,6 @@ It should be possible to layer filters over plugins to do
things like:
* export a single partition (like qemu-nbd -P)
-A possible syntax would be:
-
- nbdkit --filter=delay [--filter=...] file file=foo wdelay=10
-
-The filter(s) intercept all plugin calls and can either return, return
-an error, or pass the call down to the next layer in the stack (and
-eventually to the plugin). By intercepting the .config call the
-filter can process its own parameters from the command line (wdelay=10
-in the example above), and by intercepting the .pread, .pwrite methods
-the filter could inject the delaying behaviour.
-
Composing nbdkit
----------------
diff --git a/configure.ac b/configure.ac
index a2950f6..7032614 100644
--- a/configure.ac
+++ b/configure.ac
@@ -181,7 +181,7 @@ AS_IF([test "x$POD2MAN" != "xno"],[
AM_CONDITIONAL([HAVE_POD2MAN], [test "x$POD2MAN" != "xno"])
AC_ARG_ENABLE([plugins],
- [AS_HELP_STRING([--disable-plugins], [disable all bundled plugins])])
+ [AS_HELP_STRING([--disable-plugins], [disable all bundled plugins and
filters])])
AM_CONDITIONAL([HAVE_PLUGINS], [test "x$enable_plugins" !=
"xno"])
dnl Check for Perl, for embedding in the perl plugin.
@@ -512,6 +512,7 @@ AC_CONFIG_FILES([Makefile
plugins/tar/Makefile
plugins/vddk/Makefile
plugins/xz/Makefile
+ filters/Makefile
src/Makefile
src/nbdkit.pc
tests/Makefile])
diff --git a/docs/Makefile.am b/docs/Makefile.am
index 323f48d..d2330fb 100644
--- a/docs/Makefile.am
+++ b/docs/Makefile.am
@@ -33,6 +33,7 @@
EXTRA_DIST = \
nbdkit.pod \
nbdkit-plugin.pod
+ nbdkit-filter.pod
CLEANFILES = *~
@@ -40,7 +41,8 @@ if HAVE_POD2MAN
man_MANS = \
nbdkit.1 \
- nbdkit-plugin.3
+ nbdkit-plugin.3 \
+ nbdkit-filter.3
CLEANFILES += $(man_MANS)
nbdkit.1: nbdkit.pod
@@ -53,4 +55,9 @@ nbdkit-plugin.3: nbdkit-plugin.pod
if grep 'POD ERROR' $@.t; then rm $@.t; exit 1; fi && \
mv $@.t $@
+nbdkit-filter.3: nbdkit-filter.pod
+ $(POD2MAN) $(POD2MAN_ARGS) --section=3 --name=nbdkit-filter $< $@.t
&& \
+ if grep 'POD ERROR' $@.t; then rm $@.t; exit 1; fi && \
+ mv $@.t $@
+
endif
diff --git a/docs/nbdkit-filter.pod b/docs/nbdkit-filter.pod
new file mode 100644
index 0000000..81f0079
--- /dev/null
+++ b/docs/nbdkit-filter.pod
@@ -0,0 +1,477 @@
+=encoding utf8
+
+=head1 NAME
+
+nbdkit-filter - How to write nbdkit filters
+
+=head1 SYNOPSIS
+
+ #include <nbdkit-filter.h>
+
+ static int
+ myfilter_config (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value)
+ {
+ if (strcmp (key, "myparameter") == 0) {
+ // ...
+ return 0;
+ }
+ else {
+ // pass through to next filter or plugin
+ return next (nxdata, key, value);
+ }
+ }
+
+ static struct nbdkit_filter filter = {
+ .name = "filter",
+ .config = myfilter_config,
+ /* etc */
+ };
+
+ NBDKIT_REGISTER_FILTER(filter)
+
+When this has been compiled to a shared library, do:
+
+ nbdkit [--args ...] --filter=./myfilter.so plugin [key=value ...]
+
+When debugging, use the I<-fv> options:
+
+ nbdkit -fv --filter=./myfilter.so plugin [key=value ...]
+
+=head1 DESCRIPTION
+
+One or more nbdkit filters can be placed in front of an nbdkit plugin
+to modify the behaviour of the plugin. This manual page describes how
+to create an nbdkit filter.
+
+Filters can be used for example to limit requests to an offset/limit,
+add copy-on-write support, or inject delays or errors (for testing).
+
+Different filters can be stacked:
+
+ NBD ┌─────────┐ ┌─────────┐ ┌────────┐
+ client ───▶│ filter1 │───▶│ filter2 │── ─ ─ ──▶│ plugin │
+ request └─────────┘ └─────────┘ └────────┘
+
+Each filter intercepts plugin functions (see L<nbdkit-plugin(3)>) and
+can call the next filter or plugin in the chain, modifying parameters,
+calling before the filter function, in the middle or after. Filters
+may even short-cut the chain. As an example, to process its own
+parameters the filter can intercept the C<.config> method:
+
+ static int
+ myfilter_config (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value)
+ {
+ if (strcmp (key, "myparameter") == 0) {
+ // ...
+ // here you would handle this key, value
+ // ...
+ return 0;
+ }
+ else {
+ // pass through to next filter or plugin
+ return next (nxdata, key, value);
+ }
+ }
+
+ static struct nbdkit_filter filter = {
+ // ...
+ .config = myfilter_config,
+ // ...
+ };
+
+The call to C<next (nxdata, ...)> calls the C<.config> method of
the
+next filter or plugin in the chain. In the example above any
+instances of C<myparameter=...> on the command line would not be seen
+by the plugin.
+
+To see example filters, take a look at the source of nbdkit, in the
+C<filters> directory.
+
+Filters must be written in C and must be fully thread safe.
+
+=head1 C<nbdkit-filter.h>
+
+All filters should start by including this header file:
+
+ #include <nbdkit-filter.h>
+
+=head1 C<struct nbdkit_filter>
+
+All filters must define and register one C<struct nbdkit_filter>,
+which contains the name of the filter and pointers to plugin methods
+that the filter wants to intercept.
+
+ static struct nbdkit_filter filter = {
+ .name = "filter",
+ .longname = "My Filter",
+ .description = "This is my great filter for nbdkit",
+ .config = myfilter_config,
+ /* etc */
+ };
+
+ NBDKIT_REGISTER_FILTER(filter)
+
+The C<.name> field is the name of the filter. This is the only field
+which is required.
+
+=head1 NEXT PLUGIN
+
+F<nbdkit-filter.h> defines two function types
(C<nbdkit_next_config>,
+C<nbdkit_next_config_complete>) and a structure called C<struct
+nbdkit_next>. These abstract the next plugin or filter in the chain.
+There is also an opaque pointer C<nxdata> which must be passed along
+when calling these functions.
+
+The filter’s C<.config> and C<.config_complete> methods may only
call
+the next C<.config> or C<.config_complete> method in the chain
+(optionally).
+
+The filter’s C<.open> and C<.close> methods are called when a new
+connection is opened or an old connection closed, and these have no
+C<next> parameter because they cannot be short-circuited.
+
+The filter’s other methods like C<.get_size>, C<.pread> etc ―
always
+called in the context of a connection ― are passed a pointer to
+C<struct nbdkit_next> which contains a subset of the plugin methods
+that can be called during a connection. It is possible for a filter
+to issue (for example) extra read calls in response to a single
+C<.pwrite> call.
+
+You can modify parameters when you call the C<next> function. However
+be careful when modifying strings because for some methods
+(eg. C<.config>) the plugin may save the string pointer that you pass
+along. So you may have to ensure that the string is not freed for the
+lifetime of the server.
+
+Note that if your filter registers a callback but in that callback it
+doesn't call the C<next> function then the corresponding method in
the
+plugin will never be called.
+
+=head1 CALLBACKS
+
+C<struct nbdkit_filter> has some static fields describing the filter
+and optional callback functions which can be used to intercept plugin
+methods.
+
+=head2 C<.name>
+
+ const char *name;
+
+This field (a string) is required, and B<must> contain only ASCII
+alphanumeric characters and be unique amongst all filters.
+
+=head2 C<.version>
+
+ const char *version;
+
+Filters may optionally set a version string which is displayed in help
+and debugging output.
+
+=head2 C<.longname>
+
+ const char *longname;
+
+An optional free text name of the filter. This field is used in error
+messages.
+
+=head2 C<.description>
+
+ const char *description;
+
+An optional multi-line description of the filter.
+
+=head2 C<.load>
+
+ void load (void);
+
+This is called once just after the filter is loaded into memory. You
+can use this to perform any global initialization needed by the
+filter.
+
+=head2 C<.unload>
+
+ void unload (void);
+
+This may be called once just before the filter is unloaded from
+memory. Note that it's not guaranteed that C<.unload> will always be
+called (eg. the server might be killed or segfault), so you should try
+to make the filter as robust as possible by not requiring cleanup.
+See also L<nbdkit-plugin(3)/SHUTDOWN>.
+
+=head2 C<.config>
+
+ int (*config) (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value);
+
+This intercepts the plugin C<.config> method and can be used by the
+filter to parse its own command line parameters. You should try to
+make sure that command line parameter keys that the filter uses do not
+conflict with ones that could be used by a plugin.
+
+If there is an error, C<.config> should call C<nbdkit_error> with
an
+error message and return C<-1>.
+
+=head2 C<.config_complete>
+
+ int (*config_complete) (nbdkit_next_config_complete *next, void *nxdata);
+
+This intercepts the plugin C<.config_complete> method and can be used
+to ensure that all parameters needed by the filter were supplied on
+the command line.
+
+If there is an error, C<.config_complete> should call
C<nbdkit_error>
+with an error message and return C<-1>.
+
+=head2 C<.config_help>
+
+ const char *config_help;
+
+This optional multi-line help message should summarize any
+C<key=value> parameters that it takes. It does I<not> need to
repeat
+what already appears in C<.description>.
+
+If the filter doesn't take any config parameters you should probably
+omit this.
+
+=head2 C<.open>
+
+ void * (*open) (int readonly);
+
+This is called when a new client connection is opened and can be used
+to allocate any per-connection data structures needed by the filter.
+The handle (which is not the same as the plugin handle) is passed back
+to other filter callbacks and could be freed in the C<.close>
+callback.
+
+Note that the handle is completely opaque to nbdkit, but it must not
+be NULL.
+
+If there is an error, C<.open> should call C<nbdkit_error> with an
+error message and return C<NULL>.
+
+=head2 C<.close>
+
+ void (*close) (void *handle);
+
+This is called when the client closes the connection. It should clean
+up any per-connection resources used by the filter.
+
+=head2 C<.get_size>
+
+ int64_t (*get_size) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+
+This intercepts the plugin C<.get_size> method and can be used to read
+or modify the apparent size of the block device that the NBD client
+will see.
+
+The returned size must be E<ge> 0. If there is an error,
C<.get_size>
+should call C<nbdkit_error> with an error message and return C<-1>.
+
+=head2 C<.can_write>
+
+=head2 C<.can_flush>
+
+=head2 C<.is_rotational>
+
+=head2 C<.can_trim>
+
+ int (*can_write) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+ int (*can_flush) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+ int (*is_rotational) (struct nbdkit_next *next,
+ void *nxdata,
+ void *handle);
+ int (*can_trim) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+
+These intercept the corresponding plugin methods.
+
+If there is an error, the callback should call C<nbdkit_error> with an
+error message and return C<-1>.
+
+=head2 C<.pread>
+
+ int (*pread) (struct nbdkit_next *next, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offset);
+
+This intercepts the plugin C<.pread> method and can be used to read or
+modify data read by the plugin.
+
+If there is an error (including a short read which couldn't be
+recovered from), C<.pread> should call C<nbdkit_error> with an
error
+message B<and> set C<errno>, then return C<-1>.
+
+=head2 C<.pwrite>
+
+ int (*pwrite) (struct nbdkit_next *next, void *nxdata,
+ void *handle,
+ const void *buf, uint32_t count, uint64_t offset);
+
+This intercepts the plugin C<.pwrite> method and can be used to modify
+data written by the plugin.
+
+If there is an error (including a short write which couldn't be
+recovered from), C<.pwrite> should call C<nbdkit_error> with an
error
+message B<and> set C<errno>, then return C<-1>.
+
+=head2 C<.flush>
+
+ int (*flush) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+
+This intercepts the plugin C<.flush> method and can be used to modify
+flush requests.
+
+If there is an error, C<.flush> should call C<nbdkit_error> with an
+error message B<and> set C<errno>, then return C<-1>.
+
+=head2 C<.trim>
+
+ int (*trim) (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset);
+
+This intercepts the plugin C<.trim> method and can be used to modify
+trim requests.
+
+If there is an error, C<.trim> should call C<nbdkit_error> with an
+error message B<and> set C<errno>, then return C<-1>.
+
+=head2 C<.zero>
+
+ int (*zero) (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset, int may_trim);
+
+This intercepts the plugin C<.zero> method and can be used to modify
+zero requests.
+
+If there is an error, C<.zero> should call C<nbdkit_error> with an
+error message B<and> set C<errno>, then return C<-1>.
+
+=head1 THREADS
+
+Because filters can be mixed and used with any plugin and thus any
+threading model supported by L<nbdkit-plugin(3)>, filters must be
+thread safe. They must be able to handle concurrent requests even on
+the same handle.
+
+Filters may have to use pthread primitives like mutexes to achieve
+this.
+
+=head1 DEBUGGING
+
+Run the server with I<-f> and I<-v> options so it doesn't fork
and you
+can see debugging information:
+
+ nbdkit -fv --filter=./myfilter.so plugin [key=value [key=value [...]]]
+
+To print debugging information from within the filter, call
+C<nbdkit_debug>, which has the following prototype and works like
+L<printf(3)>:
+
+ void nbdkit_debug (const char *fs, ...);
+ void nbdkit_vdebug (const char *fs, va_list args);
+
+For convenience, C<nbdkit_debug> preserves the value of C<errno>.
+Note that C<nbdkit_debug> only prints things when the server is in
+verbose mode (I<-v> option).
+
+=head1 INSTALLING THE FILTER
+
+The filter is a C<*.so> file and possibly a manual page. You can of
+course install the filter C<*.so> file wherever you want, and users
+will be able to use it by running:
+
+ nbdkit --filter=/path/to/filter.so plugin [args]
+
+However B<if> the shared library has a name of the form
+C<nbdkit-I<name>-filter.so> B<and if> the library is
installed in the
+C<$filterdir> directory, then users can be run it by only typing:
+
+ nbdkit --filter=name plugin [args]
+
+The location of the C<$filterdir> directory is set when nbdkit is
+compiled and can be found by doing:
+
+ nbdkit --dump-config
+
+If using the pkg-config/pkgconf system then you can also find the
+filter directory at compile time by doing:
+
+ pkgconf nbdkit --variable=filterdir
+
+=head1 PKG-CONFIG/PKGCONF
+
+nbdkit provides a pkg-config/pkgconf file called C<nbdkit.pc> which
+should be installed on the correct path when the nbdkit development
+environment is installed. You can use this in autoconf
+F<configure.ac> scripts to test for the development environment:
+
+ PKG_CHECK_MODULES([NBDKIT], [nbdkit >= 1.2.3])
+
+The above will fail unless nbdkit E<ge> 1.2.3 and the header file is
+installed, and will set C<NBDKIT_CFLAGS> and C<NBDKIT_LIBS>
+appropriately for compiling filters.
+
+You can also run pkg-config/pkgconf directly, for example:
+
+ if ! pkgconf nbdkit --exists; then
+ echo "you must install the nbdkit development environment"
+ exit 1
+ fi
+
+=head1 SEE ALSO
+
+L<nbdkit(1)>,
+L<nbdkit-plugin(1)>.
+
+=head1 AUTHORS
+
+Richard W.M. Jones
+
+=head1 COPYRIGHT
+
+Copyright (C) 2013-2018 Red Hat Inc.
+
+=head1 LICENSE
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+=over 4
+
+=item *
+
+Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+
+=item *
+
+Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+=item *
+
+Neither the name of Red Hat nor the names of its contributors may be
+used to endorse or promote products derived from this software without
+specific prior written permission.
+
+=back
+
+THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS''
AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod
index 9abf75f..3cafc42 100644
--- a/docs/nbdkit-plugin.pod
+++ b/docs/nbdkit-plugin.pod
@@ -692,6 +692,7 @@ and then users will be able to run it like this:
=head1 SEE ALSO
L<nbdkit(1)>,
+L<nbdkit-filter(3)>,
L<nbdkit-example1-plugin(1)>,
L<nbdkit-example2-plugin(1)>,
L<nbdkit-example3-plugin(1)>,
@@ -711,7 +712,7 @@ Pino Toscano
=head1 COPYRIGHT
-Copyright (C) 2013-2017 Red Hat Inc.
+Copyright (C) 2013-2018 Red Hat Inc.
=head1 LICENSE
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index 1687ac9..3b37db8 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -856,6 +856,7 @@ L</SOCKET ACTIVATION>.
Other nbdkit manual pages:
L<nbdkit-plugin(3)>,
+L<nbdkit-filter(3)>,
L<nbdkit-curl-plugin(1)>,
L<nbdkit-example1-plugin(1)>,
L<nbdkit-example2-plugin(1)>,
@@ -895,7 +896,7 @@ Pino Toscano
=head1 COPYRIGHT
-Copyright (C) 2013-2017 Red Hat Inc.
+Copyright (C) 2013-2018 Red Hat Inc.
=head1 LICENSE
diff --git a/filters/Makefile.am b/filters/Makefile.am
new file mode 100644
index 0000000..ed1580b
--- /dev/null
+++ b/filters/Makefile.am
@@ -0,0 +1,33 @@
+# nbdkit
+# Copyright (C) 2013-2018 Red Hat Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+#SUBDIRS diff --git a/include/Makefile.am b/include/Makefile.am
index 7d54215..deccc6b 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -30,4 +30,6 @@
# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
-include_HEADERS = nbdkit-plugin.h
+include_HEADERS = \
+ nbdkit-plugin.h \
+ nbdkit-filter.h
diff --git a/include/nbdkit-filter.h b/include/nbdkit-filter.h
new file mode 100644
index 0000000..8c49b5e
--- /dev/null
+++ b/include/nbdkit-filter.h
@@ -0,0 +1,144 @@
+/* nbdkit
+ * Copyright (C) 2013-2017 Red Hat Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/* See nbdkit-filter(3) for documentation and how to write a filter. */
+
+#ifndef NBDKIT_FILTER_H
+#define NBDKIT_FILTER_H
+
+/* This header also defines some useful functions like nbdkit_debug
+ * and nbdkit_parse_size which are appropriate for filters to use.
+ */
+#include <nbdkit-plugin.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define NBDKIT_FILTER_API_VERSION 1
+
+typedef int nbdkit_next_config (void *nxdata,
+ const char *key, const char *value);
+typedef int nbdkit_next_config_complete (void *nxdata);
+
+struct nbdkit_next {
+ int64_t (*get_size) (void *nxdata);
+
+ int (*can_write) (void *nxdata);
+ int (*can_flush) (void *nxdata);
+ int (*is_rotational) (void *nxdata);
+ int (*can_trim) (void *nxdata);
+
+ int (*pread) (void *nxdata, void *buf, uint32_t count, uint64_t offset);
+ int (*pwrite) (void *nxdata,
+ const void *buf, uint32_t count, uint64_t offset);
+ int (*flush) (void *nxdata);
+ int (*trim) (void *nxdata, uint32_t count, uint64_t offset);
+ int (*zero) (void *nxdata, uint32_t count, uint64_t offset, int may_trim);
+};
+
+struct nbdkit_filter {
+ /* Do not set these fields directly; use NBDKIT_REGISTER_FILTER.
+ * They exist so that we can support filters compiled against
+ * one version of the header with a runtime compiled against a
+ * different version with more (or fewer) fields.
+ */
+ uint64_t _struct_size;
+ int _api_version;
+
+ /* New fields will only be added at the end of the struct. */
+ const char *name;
+ const char *longname;
+ const char *version;
+ const char *description;
+
+ void (*load) (void);
+ void (*unload) (void);
+
+ int (*config) (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value);
+ int (*config_complete) (nbdkit_next_config_complete *next, void *nxdata);
+ const char *config_help;
+
+ void * (*open) (int readonly);
+ void (*close) (void *handle);
+
+ int64_t (*get_size) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+
+ int (*can_write) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+ int (*can_flush) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+ int (*is_rotational) (struct nbdkit_next *next,
+ void *nxdata,
+ void *handle);
+ int (*can_trim) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+
+ int (*pread) (struct nbdkit_next *next, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offset);
+ int (*pwrite) (struct nbdkit_next *next, void *nxdata,
+ void *handle,
+ const void *buf, uint32_t count, uint64_t offset);
+ int (*flush) (struct nbdkit_next *next, void *nxdata,
+ void *handle);
+ int (*trim) (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset);
+ int (*zero) (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset, int may_trim);
+};
+
+#ifndef NBDKIT_CXX_LANG_C
+#ifdef __cplusplus
+#define NBDKIT_CXX_LANG_C extern "C"
+#else
+#define NBDKIT_CXX_LANG_C /* nothing */
+#endif
+#endif
+
+#define NBDKIT_REGISTER_FILTER(filter) \
+ NBDKIT_CXX_LANG_C \
+ struct nbdkit_filter * \
+ filter_init (void) \
+ { \
+ (filter)._struct_size = sizeof (filter); \
+ (filter)._api_version = NBDKIT_API_VERSION; \
+ return &(filter); \
+ }
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NBDKIT_FILTER_H */
diff --git a/include/nbdkit-plugin.h b/include/nbdkit-plugin.h
index 2ec3b15..13541e5 100644
--- a/include/nbdkit-plugin.h
+++ b/include/nbdkit-plugin.h
@@ -111,11 +111,13 @@ extern char *nbdkit_absolute_path (const char *path);
extern int64_t nbdkit_parse_size (const char *str);
extern int nbdkit_read_password (const char *value, char **password);
+#ifndef NBDKIT_CXX_LANG_C
#ifdef __cplusplus
#define NBDKIT_CXX_LANG_C extern "C"
#else
#define NBDKIT_CXX_LANG_C /* nothing */
#endif
+#endif
#define NBDKIT_REGISTER_PLUGIN(plugin) \
NBDKIT_CXX_LANG_C \
diff --git a/src/Makefile.am b/src/Makefile.am
index 1f05eab..6033fe5 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -31,6 +31,7 @@
# SUCH DAMAGE.
plugindir = $(libdir)/nbdkit/plugins
+filterdir = $(libdir)/nbdkit/filters
sbin_PROGRAMS = nbdkit
@@ -47,13 +48,15 @@ nbdkit_SOURCES = \
sockets.c \
threadlocal.c \
utils.c \
- $(top_srcdir)/include/nbdkit-plugin.h
+ $(top_srcdir)/include/nbdkit-plugin.h \
+ $(top_srcdir)/include/nbdkit-filter.h
nbdkit_CPPFLAGS = \
-Dbindir=\"$(bindir)\" \
-Dlibdir=\"$(libdir)\" \
-Dmandir=\"$(mandir)\" \
-Dplugindir=\"$(plugindir)\" \
+ -Dfilterdir=\"$(filterdir)\" \
-Dsbindir=\"$(sbindir)\" \
-Dsysconfdir=\"$(sysconfdir)\" \
-I$(top_srcdir)/include
diff --git a/src/main.c b/src/main.c
index b3e6bad..4790c46 100644
--- a/src/main.c
+++ b/src/main.c
@@ -179,6 +179,7 @@ dump_config (void)
printf ("%s=%s\n", "mandir", mandir);
printf ("%s=%s\n", "name", PACKAGE_NAME);
printf ("%s=%s\n", "plugindir", plugindir);
+ printf ("%s=%s\n", "filterdir", filterdir);
printf ("%s=%s\n", "root_tls_certificates_dir",
root_tls_certificates_dir);
printf ("%s=%s\n", "sbindir", sbindir);
#ifdef HAVE_LIBSELINUX
diff --git a/src/nbdkit.pc.in b/src/nbdkit.pc.in
index cbb301d..fe8f511 100644
--- a/src/nbdkit.pc.in
+++ b/src/nbdkit.pc.in
@@ -3,6 +3,7 @@ exec_prefix=@exec_prefix@
libdir=@libdir@
includedir=@includedir@
plugindir=@libdir@/nbdkit/plugins
+filterdir=@libdir@/nbdkit/filters
Name: @PACKAGE_NAME@
Version: @PACKAGE_VERSION@
--
2.15.1
Also implements the --filters parameter.
---
docs/nbdkit.pod | 21 +-
nbdkit.in | 17 +-
src/Makefile.am | 1 +
src/filters.c | 606 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
src/internal.h | 23 ++-
src/main.c | 114 +++++++++--
src/plugins.c | 11 +-
7 files changed, 772 insertions(+), 21 deletions(-)
diff --git a/docs/nbdkit.pod b/docs/nbdkit.pod
index 3b37db8..636eedc 100644
--- a/docs/nbdkit.pod
+++ b/docs/nbdkit.pod
@@ -7,7 +7,7 @@ nbdkit - A toolkit for creating NBD servers
=head1 SYNOPSIS
nbdkit [-e EXPORTNAME] [--exit-with-parent] [-f]
- [-g GROUP] [-i IPADDR]
+ [--filter=FILTER ...] [-g GROUP] [-i IPADDR]
[--newstyle] [--oldstyle] [-P PIDFILE] [-p PORT] [-r]
[--run CMD] [-s] [--selinux-label LABEL] [-t THREADS]
[--tls=off|on|require] [--tls-certificates /path/to/certificates]
@@ -119,6 +119,13 @@ not allowed with the oldstyle protocol.
I<Don't> fork into the background.
+=item B<--filter> FILTER
+
+Add a filter before the plugin. This option may be given one or more
+times to stack filters in front of the plugin. They are processed in
+the order they appear on the command line. See L</FILTERS> and
+L<nbdkit-filter(3)>.
+
=item B<-g> GROUP
=item B<--group> GROUP
@@ -354,6 +361,18 @@ languages. The file should be executable. For example:
(see L<nbdkit-perl-plugin(3)> for a full example).
+=head1 FILTERS
+
+One or more filters can be placed in front of an nbdkit plugin to
+modify the behaviour of the plugin, using the I<--filter> parameter.
+Filters can be used for example to limit requests to an offset/limit,
+add copy-on-write support, or inject delays or errors (for testing).
+
+Several existing filters are available in the C<$filterdir>. Use
+C<nbdkit --dump-config> to find the directory name.
+
+How to write filters is described in L<nbdkit-filter(3)>.
+
=head1 SOCKET ACTIVATION
nbdkit supports socket activation (sometimes called systemd socket
diff --git a/nbdkit.in b/nbdkit.in
index 20bc9c0..d4fe4e0 100644
--- a/nbdkit.in
+++ b/nbdkit.in
@@ -1,7 +1,7 @@
#!/bin/bash -
# @configure_input@
-# Copyright (C) 2017 Red Hat Inc.
+# Copyright (C) 2017-2018 Red Hat Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
@@ -79,6 +79,21 @@ while [ $# -gt 0 ]; do
shift
;;
+ # Filters can be rewritten if purely alphanumeric.
+ --filter)
+ args[$i]="--filter"
+ ((++i))
+ if [[ "$2" =~ ^[a-zA-Z0-9]+$ ]]; then
+ if [ -x "$b/filters/$2/.libs/nbdkit-$2-filter.so" ];
then
+
args[$i]="$b/filters/$2/.libs/nbdkit-$2-filter.so"
+ else
+ args[$i]="$2"
+ fi
+ fi
+ ((++i))
+ shift 2
+ ;;
+
# Anything else can be rewritten if it's purely alphanumeric,
# but there is only one module name so only rewrite once.
*)
diff --git a/src/Makefile.am b/src/Makefile.am
index 6033fe5..ae16fde 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -40,6 +40,7 @@ nbdkit_SOURCES = \
connections.c \
crypto.c \
errors.c \
+ filters.c \
internal.h \
locks.c \
main.c \
diff --git a/src/filters.c b/src/filters.c
new file mode 100644
index 0000000..675aedc
--- /dev/null
+++ b/src/filters.c
@@ -0,0 +1,606 @@
+/* nbdkit
+ * Copyright (C) 2013-2018 Red Hat Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <inttypes.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <dlfcn.h>
+
+#include "nbdkit-filter.h"
+#include "internal.h"
+
+/* We extend the generic backend struct with extra fields relating
+ * to this filter.
+ */
+struct backend_filter {
+ struct backend backend;
+ char *filename;
+ void *dl;
+ struct nbdkit_filter filter;
+};
+
+/* Note this frees the whole chain. */
+static void
+filter_free (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ f->backend.next->free (f->backend.next);
+
+ /* Acquiring this lock prevents any filter callbacks from running
+ * simultaneously.
+ */
+ lock_unload ();
+
+ debug ("%s: unload", f->filename);
+ if (f->filter.unload)
+ f->filter.unload ();
+
+ dlclose (f->dl);
+ free (f->filename);
+
+ unlock_unload ();
+
+ free (f);
+}
+
+/* These are actually passing through to the final plugin, hence
+ * the function names.
+ */
+static int
+plugin_thread_model (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ return f->backend.next->thread_model (f->backend.next);
+}
+
+static int
+plugin_errno_is_preserved (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ return f->backend.next->errno_is_preserved (f->backend.next);
+}
+
+static const char *
+plugin_name (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ return f->backend.next->name (f->backend.next);
+}
+
+static const char *
+filter_name (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ return f->filter.name;
+}
+
+static const char *
+filter_version (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ return f->filter.version;
+}
+
+static void
+filter_usage (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ printf ("filter: %s", f->filter.name);
+ if (f->filter.longname)
+ printf (" (%s)", f->filter.longname);
+ printf ("\n");
+ printf ("(%s)", f->filename);
+ if (f->filter.description) {
+ printf ("\n");
+ printf ("%s\n", f->filter.description);
+ }
+ if (f->filter.config_help) {
+ printf ("\n");
+ printf ("%s\n", f->filter.config_help);
+ }
+}
+
+static void
+filter_dump_fields (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ f->backend.next->dump_fields (f->backend.next);
+}
+
+static int
+next_config (void *nxdata, const char *key, const char *value)
+{
+ struct backend *b = nxdata;
+ b->config (b, key, value);
+ return 0;
+}
+
+static void
+filter_config (struct backend *b, const char *key, const char *value)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ debug ("%s: config key=%s, value=%s",
+ f->filename, key, value);
+
+ if (f->filter.config) {
+ if (f->filter.config (next_config, f->backend.next, key, value) ==
-1)
+ exit (EXIT_FAILURE);
+ }
+ else
+ f->backend.next->config (f->backend.next, key, value);
+}
+
+static int
+next_config_complete (void *nxdata)
+{
+ struct backend *b = nxdata;
+ b->config_complete (b);
+ return 0;
+}
+
+static void
+filter_config_complete (struct backend *b)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+
+ debug ("%s: config_complete", f->filename);
+
+ if (f->filter.config_complete) {
+ if (f->filter.config_complete (next_config_complete, f->backend.next)
== -1)
+ exit (EXIT_FAILURE);
+ }
+ else
+ f->backend.next->config_complete (f->backend.next);
+}
+
+static int
+filter_open (struct backend *b, struct connection *conn, int readonly)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = NULL;
+
+ debug ("%s: open readonly=%d", f->filename, readonly);
+
+ if (f->filter.open) {
+ handle = f->filter.open (readonly);
+ if (handle == NULL)
+ return -1;
+ }
+ connection_set_handle (conn, f->backend.i, handle);
+ return f->backend.next->open (f->backend.next, conn, readonly);
+}
+
+static void
+filter_close (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+
+ debug ("close");
+
+ if (f->filter.close)
+ f->filter.close (handle);
+ f->backend.next->close (f->backend.next, conn);
+}
+
+/* The next_functions structure contains pointers to backend
+ * functions. However because these functions are all expecting a
+ * backend and a connection, we cannot call them directly, but must
+ * write some next_* functions that unpack the two parameters from a
+ * single ‘void *nxdata’ struct pointer (‘b_conn’).
+ */
+
+/* Literally a backend + a connection pointer. This is the
+ * implementation if ‘void *nxdata’ in the filter API.
+ */
+struct b_conn {
+ struct backend *b;
+ struct connection *conn;
+};
+
+static int64_t
+next_get_size (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->get_size (b_conn->b, b_conn->conn);
+}
+
+static int
+next_can_write (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->can_write (b_conn->b, b_conn->conn);
+}
+
+static int
+next_can_flush (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->can_flush (b_conn->b, b_conn->conn);
+}
+
+static int
+next_is_rotational (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->is_rotational (b_conn->b, b_conn->conn);
+}
+
+static int
+next_can_trim (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->can_trim (b_conn->b, b_conn->conn);
+}
+
+static int
+next_pread (void *nxdata, void *buf, uint32_t count, uint64_t offset)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->pread (b_conn->b, b_conn->conn, buf, count,
offset);
+}
+
+static int
+next_pwrite (void *nxdata, const void *buf, uint32_t count, uint64_t offset)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->pwrite (b_conn->b, b_conn->conn, buf, count,
offset);
+}
+
+static int
+next_flush (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->flush (b_conn->b, b_conn->conn);
+}
+
+static int
+next_trim (void *nxdata, uint32_t count, uint64_t offset)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->trim (b_conn->b, b_conn->conn, count, offset);
+}
+
+static int
+next_zero (void *nxdata, uint32_t count, uint64_t offset, int may_trim)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->zero (b_conn->b, b_conn->conn, count, offset,
may_trim);
+}
+
+static struct nbdkit_next next_functions = {
+ .get_size = next_get_size,
+ .can_write = next_can_write,
+ .can_flush = next_can_flush,
+ .is_rotational = next_is_rotational,
+ .can_trim = next_can_trim,
+ .pread = next_pread,
+ .pwrite = next_pwrite,
+ .flush = next_flush,
+ .trim = next_trim,
+ .zero = next_zero,
+};
+
+static int64_t
+filter_get_size (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("get_size");
+
+ if (f->filter.get_size)
+ return f->filter.get_size (&next_functions, &nxdata, handle);
+ else
+ return f->backend.next->get_size (f->backend.next, conn);
+}
+
+static int
+filter_can_write (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("can_write");
+
+ if (f->filter.can_write)
+ return f->filter.can_write (&next_functions, &nxdata, handle);
+ else
+ return f->backend.next->can_write (f->backend.next, conn);
+}
+
+static int
+filter_can_flush (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("can_flush");
+
+ if (f->filter.can_flush)
+ return f->filter.can_flush (&next_functions, &nxdata, handle);
+ else
+ return f->backend.next->can_flush (f->backend.next, conn);
+}
+
+static int
+filter_is_rotational (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("is_rotational");
+
+ if (f->filter.is_rotational)
+ return f->filter.is_rotational (&next_functions, &nxdata,
handle);
+ else
+ return f->backend.next->is_rotational (f->backend.next, conn);
+}
+
+static int
+filter_can_trim (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("can_trim");
+
+ if (f->filter.can_trim)
+ return f->filter.can_trim (&next_functions, &nxdata, handle);
+ else
+ return f->backend.next->can_trim (f->backend.next, conn);
+}
+
+static int
+filter_pread (struct backend *b, struct connection *conn,
+ void *buf, uint32_t count, uint64_t offset)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("pread count=%" PRIu32 " offset=%" PRIu64, count,
offset);
+
+ if (f->filter.pread)
+ return f->filter.pread (&next_functions, &nxdata, handle,
+ buf, count, offset);
+ else
+ return f->backend.next->pread (f->backend.next, conn,
+ buf, count, offset);
+}
+
+static int
+filter_pwrite (struct backend *b, struct connection *conn,
+ const void *buf, uint32_t count, uint64_t offset)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("pwrite count=%" PRIu32 " offset=%" PRIu64, count,
offset);
+
+ if (f->filter.pwrite)
+ return f->filter.pwrite (&next_functions, &nxdata, handle,
+ buf, count, offset);
+ else
+ return f->backend.next->pwrite (f->backend.next, conn,
+ buf, count, offset);
+}
+
+static int
+filter_flush (struct backend *b, struct connection *conn)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("flush");
+
+ if (f->filter.flush)
+ return f->filter.flush (&next_functions, &nxdata, handle);
+ else
+ return f->backend.next->flush (f->backend.next, conn);
+}
+
+static int
+filter_trim (struct backend *b, struct connection *conn,
+ uint32_t count, uint64_t offset)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("trim count=%" PRIu32 " offset=%" PRIu64, count,
offset);
+
+ if (f->filter.trim)
+ return f->filter.trim (&next_functions, &nxdata, handle, count,
offset);
+ else
+ return f->backend.next->trim (f->backend.next, conn, count,
offset);
+}
+
+static int
+filter_zero (struct backend *b, struct connection *conn,
+ uint32_t count, uint64_t offset, int may_trim)
+{
+ struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ void *handle = connection_get_handle (conn, f->backend.i);
+ struct b_conn nxdata = { .b = f->backend.next, .conn = conn };
+
+ debug ("zero count=%" PRIu32 " offset=%" PRIu64 "
may_trim=%d",
+ count, offset, may_trim);
+
+ if (f->filter.zero)
+ return f->filter.zero (&next_functions, &nxdata, handle,
+ count, offset, may_trim);
+ else
+ return f->backend.next->zero (f->backend.next, conn,
+ count, offset, may_trim);
+}
+
+static struct backend filter_functions = {
+ .free = filter_free,
+ .thread_model = plugin_thread_model,
+ .name = filter_name,
+ .plugin_name = plugin_name,
+ .usage = filter_usage,
+ .version = filter_version,
+ .dump_fields = filter_dump_fields,
+ .config = filter_config,
+ .config_complete = filter_config_complete,
+ .errno_is_preserved = plugin_errno_is_preserved,
+ .open = filter_open,
+ .close = filter_close,
+ .get_size = filter_get_size,
+ .can_write = filter_can_write,
+ .can_flush = filter_can_flush,
+ .is_rotational = filter_is_rotational,
+ .can_trim = filter_can_trim,
+ .pread = filter_pread,
+ .pwrite = filter_pwrite,
+ .flush = filter_flush,
+ .trim = filter_trim,
+ .zero = filter_zero,
+};
+
+/* Register and load a filter. */
+struct backend *
+filter_register (struct backend *next, size_t index, const char *filename,
+ void *dl, struct nbdkit_filter *(*filter_init) (void))
+{
+ struct backend_filter *f;
+ const struct nbdkit_filter *filter;
+ size_t i, len, size;
+
+ f = calloc (1, sizeof *f);
+ if (f == NULL) {
+ out_of_memory:
+ perror ("strdup");
+ exit (EXIT_FAILURE);
+ }
+
+ f->backend = filter_functions;
+ f->backend.next = next;
+ f->backend.i = index;
+ f->filename = strdup (filename);
+ if (f->filename == NULL) goto out_of_memory;
+ f->dl = dl;
+
+ debug ("registering filter %s", f->filename);
+
+ /* Call the initialization function which returns the address of the
+ * filter's own 'struct nbdkit_filter'.
+ */
+ filter = filter_init ();
+ if (!filter) {
+ fprintf (stderr, "%s: %s: filter registration function failed\n",
+ program_name, f->filename);
+ exit (EXIT_FAILURE);
+ }
+
+ /* Check for incompatible future versions. */
+ if (filter->_api_version != 1) {
+ fprintf (stderr, "%s: %s: filter is incompatible with this version of
nbdkit (_api_version = %d)\n",
+ program_name, f->filename, filter->_api_version);
+ exit (EXIT_FAILURE);
+ }
+
+ /* Since the filter might be much older than the current version of
+ * nbdkit, only copy up to the self-declared _struct_size of the
+ * filter and zero out the rest. If the filter is much newer then
+ * we'll only call the "old" fields.
+ */
+ size = sizeof f->filter; /* our struct */
+ memset (&f->filter, 0, size);
+ if (size > filter->_struct_size)
+ size = filter->_struct_size;
+ memcpy (&f->filter, filter, size);
+
+ /* Only filter.name is required. */
+ if (f->filter.name == NULL) {
+ fprintf (stderr, "%s: %s: filter must have a .name field\n",
+ program_name, f->filename);
+ exit (EXIT_FAILURE);
+ }
+
+ len = strlen (f->filter.name);
+ if (len == 0) {
+ fprintf (stderr, "%s: %s: filter.name field must not be empty\n",
+ program_name, f->filename);
+ exit (EXIT_FAILURE);
+ }
+ for (i = 0; i < len; ++i) {
+ if (!((f->filter.name[i] >= '0' &&
f->filter.name[i] <= '9') ||
+ (f->filter.name[i] >= 'a' &&
f->filter.name[i] <= 'z') ||
+ (f->filter.name[i] >= 'A' &&
f->filter.name[i] <= 'Z'))) {
+ fprintf (stderr, "%s: %s: filter.name ('%s') field must
contain only ASCII alphanumeric characters\n",
+ program_name, f->filename, f->filter.name);
+ exit (EXIT_FAILURE);
+ }
+ }
+ /* Copy the module's name into local storage, so that filter.name
+ * survives past unload. */
+ if (!(f->filter.name = strdup (f->filter.name))) {
+ perror ("strdup");
+ exit (EXIT_FAILURE);
+ }
+
+ debug ("registered filter %s (name %s)", f->filename,
f->filter.name);
+
+ /* Call the on-load callback if it exists. */
+ debug ("%s: load", f->filename);
+ if (f->filter.load)
+ f->filter.load ();
+
+ return (struct backend *) f;
+}
diff --git a/src/internal.h b/src/internal.h
index 5a68d59..291e657 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2017 Red Hat Inc.
+ * Copyright (C) 2013-2018 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -41,6 +41,7 @@
#include <pthread.h>
#include "nbdkit-plugin.h"
+#include "nbdkit-filter.h"
#ifdef __APPLE__
#define UNIX_PATH_MAX 104
@@ -115,6 +116,7 @@ extern volatile int quit;
extern int quit_fd;
extern struct backend *backend;
+#define for_each_backend(b) for (b = backend; b != NULL; b = b->next)
/* cleanup.c */
extern void cleanup_free (void *ptr);
@@ -149,8 +151,19 @@ extern int crypto_negotiate_tls (struct connection *conn,
int sockin, int sockou
/* errors.c */
#define debug nbdkit_debug
-/* plugins.c */
struct backend {
+ /* Next filter or plugin in the chain. This is always NULL for
+ * plugins and never NULL for filters.
+ */
+ struct backend *next;
+
+ /* A unique index used to fetch the handle from the connections
+ * object. The plugin (last in the chain) has index 0, and the
+ * filters have index 1, 2, ... depending how "far" they are from
+ * the plugin.
+ */
+ size_t i;
+
void (*free) (struct backend *);
int (*thread_model) (struct backend *);
const char *(*name) (struct backend *);
@@ -175,7 +188,11 @@ struct backend {
int (*zero) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset, int may_trim);
};
-extern struct backend *plugin_register (const char *_filename, void *_dl,
struct nbdkit_plugin *(*plugin_init) (void));
+/* plugins.c */
+extern struct backend *plugin_register (size_t index, const char *filename,
void *dl, struct nbdkit_plugin *(*plugin_init) (void));
+
+/* filters.c */
+extern struct backend *filter_register (struct backend *next, size_t index,
const char *filename, void *dl, struct nbdkit_filter *(*filter_init) (void));
/* locks.c */
extern void lock_connection (void);
diff --git a/src/main.c b/src/main.c
index 4790c46..38691c9 100644
--- a/src/main.c
+++ b/src/main.c
@@ -64,7 +64,8 @@
static int is_short_name (const char *);
static char *make_random_fifo (void);
-static struct backend *open_plugin_so (const char *filename, int short_name);
+static struct backend *open_plugin_so (size_t i, const char *filename, int
short_name);
+static struct backend *open_filter_so (struct backend *next, size_t i, const
char *filename, int short_name);
static void start_serving (void);
static void set_up_signals (void);
static void run_command (void);
@@ -120,6 +121,7 @@ static const struct option long_options[] = {
{ "export", 1, NULL, 'e' },
{ "export-name",1, NULL, 'e' },
{ "exportname", 1, NULL, 'e' },
+ { "filter", 1, NULL, 0 },
{ "foreground", 0, NULL, 'f' },
{ "no-fork", 0, NULL, 'f' },
{ "group", 1, NULL, 'g' },
@@ -154,7 +156,7 @@ usage (void)
{
printf ("nbdkit [--dump-config] [--dump-plugin]\n"
" [-e EXPORTNAME] [--exit-with-parent] [-f]\n"
- " [-g GROUP] [-i IPADDR]\n"
+ " [--filter=FILTER ...] [-g GROUP] [-i IPADDR]\n"
" [--newstyle] [--oldstyle] [-P PIDFILE] [-p PORT]
[-r]\n"
" [--run CMD] [-s] [--selinux-label LABEL] [-t
THREADS]\n"
" [--tls=off|on|require] [--tls-certificates
/path/to/certificates]\n"
@@ -206,6 +208,11 @@ main (int argc, char *argv[])
int short_name;
const char *filename;
char *p;
+ static struct filter_filename {
+ struct filter_filename *next;
+ const char *filename;
+ } *filter_filenames = NULL;
+ size_t i;
threadlocal_init ();
@@ -245,6 +252,18 @@ main (int argc, char *argv[])
exit (EXIT_FAILURE);
#endif
}
+ else if (strcmp (long_options[option_index].name, "filter") ==
0) {
+ struct filter_filename *t;
+
+ t = malloc (sizeof *t);
+ if (t == NULL) {
+ perror ("malloc");
+ exit (EXIT_FAILURE);
+ }
+ t->next = filter_filenames;
+ t->filename = optarg;
+ filter_filenames = t;
+ }
else if (strcmp (long_options[option_index].name, "run") == 0)
{
if (socket_activation) {
fprintf (stderr, "%s: cannot use socket activation with --run
flag\n",
@@ -497,23 +516,46 @@ main (int argc, char *argv[])
}
}
- backend = open_plugin_so (filename, short_name);
+ /* Open the plugin (first) and then wrap the plugin with the
+ * filters. The filters are wrapped in reverse order that they
+ * appear on the command line so that in the end ‘backend’ points to
+ * the first filter on the command line.
+ */
+ backend = open_plugin_so (0, filename, short_name);
+ i = 1;
+ while (filter_filenames) {
+ struct filter_filename *t = filter_filenames;
+ const char *filename = t->filename;
+ int short_name = is_short_name (filename);
+
+ backend = open_filter_so (backend, i++, filename, short_name);
+
+ filter_filenames = t->next;
+ free (t);
+ }
if (help) {
+ struct backend *b;
+
usage ();
- printf ("\n%s:\n\n", filename);
- backend->usage (backend);
+ for_each_backend (b) {
+ printf ("\n");
+ b->usage (b);
+ }
exit (EXIT_SUCCESS);
}
if (version) {
const char *v;
+ struct backend *b;
display_version ();
- printf ("%s", backend->name (backend));
- if ((v = backend->version (backend)) != NULL)
- printf (" %s", v);
- printf ("\n");
+ for_each_backend (b) {
+ printf ("%s", b->name (b));
+ if ((v = b->version (b)) != NULL)
+ printf (" %s", v);
+ printf ("\n");
+ }
exit (EXIT_SUCCESS);
}
@@ -575,7 +617,7 @@ main (int argc, char *argv[])
exit (EXIT_SUCCESS);
}
-/* Is it a name relative to the plugindir? */
+/* Is it a plugin or filter name relative to the plugindir/filterdir? */
static int
is_short_name (const char *filename)
{
@@ -615,7 +657,7 @@ make_random_fifo (void)
}
static struct backend *
-open_plugin_so (const char *name, int short_name)
+open_plugin_so (size_t i, const char *name, int short_name)
{
struct backend *ret;
char *filename = (char *) name;
@@ -653,7 +695,55 @@ open_plugin_so (const char *name, int short_name)
}
/* Register the plugin. */
- ret = plugin_register (filename, dl, plugin_init);
+ ret = plugin_register (i, filename, dl, plugin_init);
+
+ if (free_filename)
+ free (filename);
+
+ return ret;
+}
+
+static struct backend *
+open_filter_so (struct backend *next, size_t i,
+ const char *name, int short_name)
+{
+ struct backend *ret;
+ char *filename = (char *) name;
+ int free_filename = 0;
+ void *dl;
+ struct nbdkit_filter *(*filter_init) (void);
+ char *error;
+
+ if (short_name) {
+ /* Short names are rewritten relative to the filterdir. */
+ if (asprintf (&filename,
+ "%s/nbdkit-%s-filter.so", filterdir, name) == -1) {
+ perror ("asprintf");
+ exit (EXIT_FAILURE);
+ }
+ free_filename = 1;
+ }
+
+ dl = dlopen (filename, RTLD_NOW|RTLD_GLOBAL);
+ if (dl == NULL) {
+ fprintf (stderr, "%s: %s: %s\n", program_name, filename, dlerror
());
+ exit (EXIT_FAILURE);
+ }
+
+ /* Initialize the filter. See dlopen(3) to understand C weirdness. */
+ dlerror ();
+ *(void **) (&filter_init) = dlsym (dl, "filter_init");
+ if ((error = dlerror ()) != NULL) {
+ fprintf (stderr, "%s: %s: %s\n", program_name, name, error);
+ exit (EXIT_FAILURE);
+ }
+ if (!filter_init) {
+ fprintf (stderr, "%s: %s: invalid filter_init\n", program_name,
name);
+ exit (EXIT_FAILURE);
+ }
+
+ /* Register the filter. */
+ ret = filter_register (next, i, filename, dl, filter_init);
if (free_filename)
free (filename);
diff --git a/src/plugins.c b/src/plugins.c
index e732587..6046320 100644
--- a/src/plugins.c
+++ b/src/plugins.c
@@ -102,10 +102,11 @@ plugin_usage (struct backend *b)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- printf ("%s", p->plugin.name);
+ printf ("plugin: %s", p->plugin.name);
if (p->plugin.longname)
printf (" (%s)", p->plugin.longname);
printf ("\n");
+ printf ("(%s)", p->filename);
if (p->plugin.description) {
printf ("\n");
printf ("%s\n", p->plugin.description);
@@ -489,7 +490,7 @@ static struct backend plugin_functions = {
/* Register and load a plugin. */
struct backend *
-plugin_register (const char *filename,
+plugin_register (size_t index, const char *filename,
void *dl, struct nbdkit_plugin *(*plugin_init) (void))
{
struct backend_plugin *p;
@@ -504,11 +505,13 @@ plugin_register (const char *filename,
}
p->backend = plugin_functions;
+ p->backend.next = NULL;
+ p->backend.i = index;
p->filename = strdup (filename);
if (p->filename == NULL) goto out_of_memory;
p->dl = dl;
- debug ("registering %s", p->filename);
+ debug ("registering plugin %s", p->filename);
/* Call the initialization function which returns the address of the
* plugin's own 'struct nbdkit_plugin'.
@@ -584,7 +587,7 @@ plugin_register (const char *filename,
exit (EXIT_FAILURE);
}
- debug ("registered %s (name %s)", p->filename,
p->plugin.name);
+ debug ("registered plugin %s (name %s)", p->filename,
p->plugin.name);
/* Call the on-load callback if it exists. */
debug ("%s: load", p->filename);
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 8/9] filters: Add nbdkit-offset-filter.
This very basic filter allows you to select an offset and range within
a plugin, for example:
nbdkit --filter=offset file file=foo offset=1M range=100M
which serves the byte range [ 1M .. 101M-1 ] from file ‘foo’.
---
TODO | 2 -
configure.ac | 1 +
filters/Makefile.am | 3 +-
filters/offset/Makefile.am | 62 ++++++++++++++
filters/offset/nbdkit-offset-filter.pod | 99 +++++++++++++++++++++
filters/offset/offset.c | 147 ++++++++++++++++++++++++++++++++
6 files changed, 311 insertions(+), 3 deletions(-)
diff --git a/TODO b/TODO
index 0955db7..8eda0d7 100644
--- a/TODO
+++ b/TODO
@@ -44,8 +44,6 @@ Suggestions for filters
* copy-on-write, a popular feature in other servers
-* export a subset using offset/size
-
* export a single partition (like qemu-nbd -P)
Composing nbdkit
diff --git a/configure.ac b/configure.ac
index 7032614..4892dc4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -513,6 +513,7 @@ AC_CONFIG_FILES([Makefile
plugins/vddk/Makefile
plugins/xz/Makefile
filters/Makefile
+ filters/offset/Makefile
src/Makefile
src/nbdkit.pc
tests/Makefile])
diff --git a/filters/Makefile.am b/filters/Makefile.am
index ed1580b..91fbe6c 100644
--- a/filters/Makefile.am
+++ b/filters/Makefile.am
@@ -30,4 +30,5 @@
# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
-#SUBDIRS +SUBDIRS = \
+ offset
diff --git a/filters/offset/Makefile.am b/filters/offset/Makefile.am
new file mode 100644
index 0000000..f6e253c
--- /dev/null
+++ b/filters/offset/Makefile.am
@@ -0,0 +1,62 @@
+# nbdkit
+# Copyright (C) 2018 Red Hat Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+EXTRA_DIST = nbdkit-offset-filter.pod
+
+CLEANFILES = *~
+
+filterdir = $(libdir)/nbdkit/filters
+
+filter_LTLIBRARIES = nbdkit-offset-filter.la
+
+nbdkit_offset_filter_la_SOURCES = \
+ offset.c \
+ $(top_srcdir)/include/nbdkit-filter.h
+
+nbdkit_offset_filter_la_CPPFLAGS = \
+ -I$(top_srcdir)/include
+nbdkit_offset_filter_la_CFLAGS = \
+ $(WARNINGS_CFLAGS)
+nbdkit_offset_filter_la_LDFLAGS = \
+ -module -avoid-version -shared
+
+if HAVE_POD2MAN
+
+man_MANS = nbdkit-offset-filter.1
+CLEANFILES += $(man_MANS)
+
+nbdkit-offset-filter.1: nbdkit-offset-filter.pod
+ $(POD2MAN) $(POD2MAN_ARGS) --section=1 --name=`basename $@ .1` $< $@.t
&& \
+ if grep 'POD ERROR' $@.t; then rm $@.t; exit 1; fi && \
+ mv $@.t $@
+
+endif
diff --git a/filters/offset/nbdkit-offset-filter.pod
b/filters/offset/nbdkit-offset-filter.pod
new file mode 100644
index 0000000..c7f7bdf
--- /dev/null
+++ b/filters/offset/nbdkit-offset-filter.pod
@@ -0,0 +1,99 @@
+=encoding utf8
+
+=head1 NAME
+
+nbdkit-offset-filter - nbdkit offset filter
+
+=head1 SYNOPSIS
+
+ nbdkit --filter=offset plugin offset=OFFSET range=LENGTH [plugin-args...]
+
+=head1 DESCRIPTION
+
+C<nbdkit-offset-filter> is a filter that limits requests to the byte
+range C<[offset .. range-1]> within another plugin.
+
+=head1 PARAMETERS
+
+=over 4
+
+=item B<offset=OFFSET>
+
+The start offset.
+
+This parameter is required.
+
+=item B<range=LENGTH>
+
+The length of data to serve.
+
+This is optional. If not given then the range is served starting from
+the offset through to the end of the underlying file/device.
+
+=back
+
+Note it is an error if the range parameter is supplied and
+C<offset+range> is larger than the size of data served by the
+underlying plugin.
+
+=head1 EXAMPLE
+
+Using L<nbdkit-file-plugin(1)>, serve the C<100M> length range
+starting from C<1M> through to S<C<101M - 1 byte>> from the
file
+C<disk.img>:
+
+ nbdkit --filter=offset file file=disk.img offset=1M range=100M
+
+=head1 SEE ALSO
+
+L<nbdkit(1)>,
+L<nbdkit-file-plugin(1)>,
+L<nbdkit-filter(3)>.
+
+=head1 AUTHORS
+
+Richard W.M. Jones
+
+=head1 COPYRIGHT
+
+Copyright (C) 2018 Red Hat Inc.
+
+=head1 LICENSE
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+=over 4
+
+=item *
+
+Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+
+=item *
+
+Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+=item *
+
+Neither the name of Red Hat nor the names of its contributors may be
+used to endorse or promote products derived from this software without
+specific prior written permission.
+
+=back
+
+THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS''
AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
diff --git a/filters/offset/offset.c b/filters/offset/offset.c
new file mode 100644
index 0000000..cd0c89b
--- /dev/null
+++ b/filters/offset/offset.c
@@ -0,0 +1,147 @@
+/* nbdkit
+ * Copyright (C) 2018 Red Hat Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <nbdkit-filter.h>
+
+static int64_t offset = -1, range = -1;
+
+/* Called for each key=value passed on the command line. */
+static int
+offset_config (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value)
+{
+ if (strcmp (key, "offset") == 0) {
+ offset = nbdkit_parse_size (value);
+ if (offset == -1)
+ return -1;
+ return 0;
+ }
+ else if (strcmp (key, "range") == 0) {
+ range = nbdkit_parse_size (value);
+ if (range == -1)
+ return -1;
+ return 0;
+ }
+ else
+ return next (nxdata, key, value);
+}
+
+/* Check the user did pass both parameters. */
+static int
+offset_config_complete (nbdkit_next_config_complete *next, void *nxdata)
+{
+ if (offset == -1) {
+ nbdkit_error ("you must supply the offset parameter on the command
line");
+ return -1;
+ }
+
+ return next (nxdata);
+}
+
+#define offset_config_help \
+ "offset=<OFFSET> (required) The start offset to serve.\n"
\
+ "range=<LENGTH> The total size to serve."
+
+/* Get the file size. */
+static int64_t
+offset_get_size (struct nbdkit_next *next, void *nxdata,
+ void *handle)
+{
+ int64_t real_size = next->get_size (nxdata);
+
+ if (range >= 0) {
+ if (offset + range > real_size) {
+ nbdkit_error ("offset + range is larger than the real size of the
underlying file or device");
+ return -1;
+ }
+ return range;
+ }
+ else
+ return real_size - offset;
+}
+
+/* Read data. */
+static int
+offset_pread (struct nbdkit_next *next, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offs)
+{
+ return next->pread (nxdata, buf, count, offs + offset);
+}
+
+/* Write data. */
+static int
+offset_pwrite (struct nbdkit_next *next, void *nxdata,
+ void *handle,
+ const void *buf, uint32_t count, uint64_t offs)
+{
+ return next->pwrite (nxdata, buf, count, offs + offset);
+}
+
+/* Trim data. */
+static int
+offset_trim (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offs)
+{
+ return next->trim (nxdata, count, offs + offset);
+}
+
+/* Zero data. */
+static int
+offset_zero (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offs, int may_trim)
+{
+ return next->zero (nxdata, count, offs + offset, may_trim);
+}
+
+static struct nbdkit_filter filter = {
+ .name = "offset",
+ .longname = "nbdkit offset filter",
+ .version = PACKAGE_VERSION,
+ .config = offset_config,
+ .config_complete = offset_config_complete,
+ .config_help = offset_config_help,
+ .get_size = offset_get_size,
+ .pread = offset_pread,
+ .pwrite = offset_pwrite,
+ .trim = offset_trim,
+ .zero = offset_zero,
+};
+
+NBDKIT_REGISTER_FILTER(filter)
--
2.15.1
Richard W.M. Jones
2018-Jan-17 20:53 UTC
[Libguestfs] [PATCH 9/9] filters: Move rdelay/wdelay from file plugin to new delay filter.
Previously the file plugin supported ‘rdelay’ and ‘wdelay’ parameters
for injecting delays (for testing) into read and write requests. This
moves the functionality to a new delay filter so that it can be used
with any plugin.
---
TODO | 3 -
configure.ac | 1 +
filters/Makefile.am | 1 +
filters/delay/Makefile.am | 62 +++++++++++++
filters/delay/delay.c | 161 ++++++++++++++++++++++++++++++++++
filters/delay/nbdkit-delay-filter.pod | 88 +++++++++++++++++++
plugins/file/file.c | 76 ++--------------
plugins/file/nbdkit-file-plugin.pod | 14 +--
tests/test-parallel-file.sh | 4 +-
tests/test-parallel-nbd.sh | 1 +
10 files changed, 324 insertions(+), 87 deletions(-)
diff --git a/TODO b/TODO
index 8eda0d7..3ec45fd 100644
--- a/TODO
+++ b/TODO
@@ -37,9 +37,6 @@ directed to qemu-nbd for these use cases.
Suggestions for filters
-----------------------
-* adding artificial delays (see wdelay/rdelay options in the file
- plugin)
-
* injecting artificial errors for testing clients
* copy-on-write, a popular feature in other servers
diff --git a/configure.ac b/configure.ac
index 4892dc4..9376a2e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -513,6 +513,7 @@ AC_CONFIG_FILES([Makefile
plugins/vddk/Makefile
plugins/xz/Makefile
filters/Makefile
+ filters/delay/Makefile
filters/offset/Makefile
src/Makefile
src/nbdkit.pc
diff --git a/filters/Makefile.am b/filters/Makefile.am
index 91fbe6c..d4aa6c0 100644
--- a/filters/Makefile.am
+++ b/filters/Makefile.am
@@ -31,4 +31,5 @@
# SUCH DAMAGE.
SUBDIRS = \
+ delay \
offset
diff --git a/filters/delay/Makefile.am b/filters/delay/Makefile.am
new file mode 100644
index 0000000..5b20b69
--- /dev/null
+++ b/filters/delay/Makefile.am
@@ -0,0 +1,62 @@
+# nbdkit
+# Copyright (C) 2018 Red Hat Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+EXTRA_DIST = nbdkit-delay-filter.pod
+
+CLEANFILES = *~
+
+filterdir = $(libdir)/nbdkit/filters
+
+filter_LTLIBRARIES = nbdkit-delay-filter.la
+
+nbdkit_delay_filter_la_SOURCES = \
+ delay.c \
+ $(top_srcdir)/include/nbdkit-filter.h
+
+nbdkit_delay_filter_la_CPPFLAGS = \
+ -I$(top_srcdir)/include
+nbdkit_delay_filter_la_CFLAGS = \
+ $(WARNINGS_CFLAGS)
+nbdkit_delay_filter_la_LDFLAGS = \
+ -module -avoid-version -shared
+
+if HAVE_POD2MAN
+
+man_MANS = nbdkit-delay-filter.1
+CLEANFILES += $(man_MANS)
+
+nbdkit-delay-filter.1: nbdkit-delay-filter.pod
+ $(POD2MAN) $(POD2MAN_ARGS) --section=1 --name=`basename $@ .1` $< $@.t
&& \
+ if grep 'POD ERROR' $@.t; then rm $@.t; exit 1; fi && \
+ mv $@.t $@
+
+endif
diff --git a/filters/delay/delay.c b/filters/delay/delay.c
new file mode 100644
index 0000000..c8d9ef2
--- /dev/null
+++ b/filters/delay/delay.c
@@ -0,0 +1,161 @@
+/* nbdkit
+ * Copyright (C) 2018 Red Hat Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of Red Hat nor the names of its contributors may be
+ * used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS
IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <time.h>
+
+#include <nbdkit-filter.h>
+
+static int rdelayms = 0; /* read delay (milliseconds) */
+static int wdelayms = 0; /* write delay (milliseconds) */
+
+static int
+parse_delay (const char *value)
+{
+ size_t len = strlen (value);
+ int r;
+
+ if (len > 2 && strcmp (&value[len-2], "ms") == 0) {
+ if (sscanf (value, "%d", &r) == 1)
+ return r;
+ else {
+ nbdkit_error ("cannot parse rdelay/wdelay milliseconds parameter:
%s",
+ value);
+ return -1;
+ }
+ }
+ else {
+ if (sscanf (value, "%d", &r) == 1)
+ return r * 1000;
+ else {
+ nbdkit_error ("cannot parse rdelay/wdelay seconds parameter:
%s",
+ value);
+ return -1;
+ }
+ }
+}
+
+static void
+delay (int ms)
+{
+ if (ms > 0) {
+ const struct timespec ts = {
+ .tv_sec = ms / 1000,
+ .tv_nsec = (ms * 1000000) % 1000000000
+ };
+ nanosleep (&ts, NULL);
+ }
+}
+
+static void
+read_delay (void)
+{
+ delay (rdelayms);
+}
+
+static void
+write_delay (void)
+{
+ delay (wdelayms);
+}
+
+/* Called for each key=value passed on the command line. */
+static int
+delay_config (nbdkit_next_config *next, void *nxdata,
+ const char *key, const char *value)
+{
+ if (strcmp (key, "rdelay") == 0) {
+ rdelayms = parse_delay (value);
+ if (rdelayms == -1)
+ return -1;
+ return 0;
+ }
+ else if (strcmp (key, "wdelay") == 0) {
+ wdelayms = parse_delay (value);
+ if (wdelayms == -1)
+ return -1;
+ return 0;
+ }
+ else
+ return next (nxdata, key, value);
+}
+
+#define delay_config_help \
+ "rdelay=<NN>[ms] Read delay in
seconds/milliseconds.\n" \
+ "wdelay=<NN>[ms] Write delay in
seconds/milliseconds." \
+
+/* Read data. */
+static int
+delay_pread (struct nbdkit_next *next, void *nxdata,
+ void *handle, void *buf, uint32_t count, uint64_t offset)
+{
+ read_delay ();
+ return next->pread (nxdata, buf, count, offset);
+}
+
+/* Write data. */
+static int
+delay_pwrite (struct nbdkit_next *next, void *nxdata,
+ void *handle,
+ const void *buf, uint32_t count, uint64_t offset)
+{
+ write_delay ();
+ return next->pwrite (nxdata, buf, count, offset);
+}
+
+/* Zero data. */
+static int
+delay_zero (struct nbdkit_next *next, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset, int may_trim)
+{
+ write_delay ();
+ return next->zero (nxdata, count, offset, may_trim);
+}
+
+static struct nbdkit_filter filter = {
+ .name = "delay",
+ .longname = "nbdkit delay filter",
+ .version = PACKAGE_VERSION,
+ .config = delay_config,
+ .config_help = delay_config_help,
+ .pread = delay_pread,
+ .pwrite = delay_pwrite,
+ .zero = delay_zero,
+};
+
+NBDKIT_REGISTER_FILTER(filter)
diff --git a/filters/delay/nbdkit-delay-filter.pod
b/filters/delay/nbdkit-delay-filter.pod
new file mode 100644
index 0000000..10aba94
--- /dev/null
+++ b/filters/delay/nbdkit-delay-filter.pod
@@ -0,0 +1,88 @@
+=encoding utf8
+
+=head1 NAME
+
+nbdkit-delay-filter - nbdkit delay filter
+
+=head1 SYNOPSIS
+
+ nbdkit --filter=delay plugin rdelay=SECS wdelay=SECS [plugin-args...]
+
+ nbdkit --filter=delay plugin rdelay=<NN>ms wdelay=<NN>ms
[plugin-args...]
+
+=head1 DESCRIPTION
+
+C<nbdkit-delay-filter> is a filter that delays read and write requests
+by some seconds or milliseconds. This is used to simulate a slow or
+remote server, or to test certain kinds of race conditions in Linux.
+
+=head1 PARAMETERS
+
+=over 4
+
+=item B<rdelay=SECS>
+
+=item B<rdelay=E<lt>NNE<gt>ms>
+
+The optional read delay in seconds or milliseconds.
+
+=item B<wdelay=SECS>
+
+=item B<wdelay=E<lt>NNE<gt>ms>
+
+The optional write delay in seconds or milliseconds.
+
+=back
+
+=head1 SEE ALSO
+
+L<nbdkit(1)>,
+L<nbdkit-filter(3)>.
+
+=head1 AUTHORS
+
+Richard W.M. Jones
+
+=head1 COPYRIGHT
+
+Copyright (C) 2018 Red Hat Inc.
+
+=head1 LICENSE
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+=over 4
+
+=item *
+
+Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+
+=item *
+
+Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+=item *
+
+Neither the name of Red Hat nor the names of its contributors may be
+used to endorse or promote products derived from this software without
+specific prior written permission.
+
+=back
+
+THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS''
AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGE.
diff --git a/plugins/file/file.c b/plugins/file/file.c
index 4a91251..1fe4191 100644
--- a/plugins/file/file.c
+++ b/plugins/file/file.c
@@ -40,7 +40,6 @@
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
-#include <time.h>
#include <errno.h>
#include <nbdkit-plugin.h>
@@ -50,8 +49,6 @@
#endif
static char *filename = NULL;
-static int rdelayms = 0; /* read delay (milliseconds) */
-static int wdelayms = 0; /* write delay (milliseconds) */
static void
file_unload (void)
@@ -59,56 +56,6 @@ file_unload (void)
free (filename);
}
-static int
-parse_delay (const char *value)
-{
- size_t len = strlen (value);
- int r;
-
- if (len > 2 && strcmp (&value[len-2], "ms") == 0) {
- if (sscanf (value, "%d", &r) == 1)
- return r;
- else {
- nbdkit_error ("cannot parse rdelay/wdelay milliseconds parameter:
%s",
- value);
- return -1;
- }
- }
- else {
- if (sscanf (value, "%d", &r) == 1)
- return r * 1000;
- else {
- nbdkit_error ("cannot parse rdelay/wdelay seconds parameter:
%s",
- value);
- return -1;
- }
- }
-}
-
-static void
-delay (int ms)
-{
- if (ms > 0) {
- const struct timespec ts = {
- .tv_sec = ms / 1000,
- .tv_nsec = (ms * 1000000) % 1000000000
- };
- nanosleep (&ts, NULL);
- }
-}
-
-static void
-read_delay (void)
-{
- delay (rdelayms);
-}
-
-static void
-write_delay (void)
-{
- delay (wdelayms);
-}
-
/* Called for each key=value passed on the command line. This plugin
* only accepts file=<filename>, which is required.
*/
@@ -122,15 +69,10 @@ file_config (const char *key, const char *value)
if (!filename)
return -1;
}
- else if (strcmp (key, "rdelay") == 0) {
- rdelayms = parse_delay (value);
- if (rdelayms == -1)
- return -1;
- }
- else if (strcmp (key, "wdelay") == 0) {
- wdelayms = parse_delay (value);
- if (wdelayms == -1)
- return -1;
+ else if (strcmp (key, "rdelay") == 0 ||
+ strcmp (key, "wdelay") == 0) {
+ nbdkit_error ("add --filter=delay on the command line");
+ return -1;
}
else {
nbdkit_error ("unknown parameter '%s'", key);
@@ -157,9 +99,7 @@ file_config_complete (void)
}
#define file_config_help \
- "file=<FILENAME> (required) The filename to serve.\n" \
- "rdelay=<NN>[ms] Read delay in
seconds/milliseconds.\n" \
- "wdelay=<NN>[ms] Write delay in
seconds/milliseconds." \
+ "file=<FILENAME> (required) The filename to serve." \
/* The per-connection handle. */
struct handle {
@@ -241,8 +181,6 @@ file_pread (void *handle, void *buf, uint32_t count,
uint64_t offset)
{
struct handle *h = handle;
- read_delay ();
-
while (count > 0) {
ssize_t r = pread (h->fd, buf, count, offset);
if (r == -1) {
@@ -267,8 +205,6 @@ file_pwrite (void *handle, const void *buf, uint32_t count,
uint64_t offset)
{
struct handle *h = handle;
- write_delay ();
-
while (count > 0) {
ssize_t r = pwrite (h->fd, buf, count, offset);
if (r == -1) {
@@ -292,8 +228,6 @@ file_zero (void *handle, uint32_t count, uint64_t offset,
int may_trim)
#endif
int r = -1;
- write_delay ();
-
#ifdef FALLOC_FL_PUNCH_HOLE
if (may_trim) {
r = fallocate (h->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
diff --git a/plugins/file/nbdkit-file-plugin.pod
b/plugins/file/nbdkit-file-plugin.pod
index a2d1e6a..016513a 100644
--- a/plugins/file/nbdkit-file-plugin.pod
+++ b/plugins/file/nbdkit-file-plugin.pod
@@ -31,21 +31,13 @@ This parameter is required.
=item B<rdelay=E<lt>NNE<gt>ms>
-Delay reads for C<SECS> seconds or C<NN> milliseconds.
-This is used to simulate a slow or remote server, or to
-test certain kinds of race conditions in Linux.
-
-The default is no delay.
-
=item B<wdelay=SECS>
=item B<wdelay=E<lt>NNE<gt>ms>
-Delay writes for C<SECS> seconds or C<NN> milliseconds.
-This is used to simulate a slow or remote server, or to
-test certain kinds of race conditions in Linux.
-
-The default is no delay.
+These plugin parameters have been moved to the
+L<nbdkit-delay-filter(1)> filter. Modify the command line to add
+I<--filter=delay> in order to use these parameters.
=back
diff --git a/tests/test-parallel-file.sh b/tests/test-parallel-file.sh
index 79a60ac..b9e5f40 100755
--- a/tests/test-parallel-file.sh
+++ b/tests/test-parallel-file.sh
@@ -49,7 +49,7 @@ $QEMU_IO -f raw -c "aio_write -P 2 1 1" -c
"aio_read -P 1 0 1" -c aio_flush \
trap 'rm -f test-parallel-file.out' 0 1 2 3 15
# With --threads=1, the write should complete first because it was issued first
-nbdkit -v -t 1 -U - file file=file-data wdelay=2 rdelay=1 --run '
+nbdkit -v -t 1 -U - --filter delay file file=file-data wdelay=2 rdelay=1 --run
'
$QEMU_IO -f raw -c "aio_write -P 2 1 1" -c "aio_read -P 1 0
1" -c aio_flush $nbd
' | tee test-parallel-file.out
if test "$(grep '1/1' test-parallel-file.out)" != \
@@ -59,7 +59,7 @@ read 1/1 bytes at offset 0"; then
fi
# With default --threads, the faster read should complete first
-nbdkit -v -U - file file=file-data wdelay=2 rdelay=1 --run '
+nbdkit -v -U - --filter delay file file=file-data wdelay=2 rdelay=1 --run '
$QEMU_IO -f raw -c "aio_write -P 2 1 1" -c "aio_read -P 1 0
1" -c aio_flush $nbd
' | tee test-parallel-file.out
if test "$(grep '1/1' test-parallel-file.out)" != \
diff --git a/tests/test-parallel-nbd.sh b/tests/test-parallel-nbd.sh
index f8e5071..d87573d 100755
--- a/tests/test-parallel-nbd.sh
+++ b/tests/test-parallel-nbd.sh
@@ -54,6 +54,7 @@ trap 'rm -f test-parallel-nbd.out
test-parallel-nbd.sock' 0 1 2 3 15
(
rm -f test-parallel-nbd.sock
nbdkit --exit-with-parent -v -U test-parallel-nbd.sock \
+ --filter delay \
file file=file-data wdelay=2 rdelay=1 &
# With --threads=1, the write should complete first because it was issued first
--
2.15.1
Eric Blake
2018-Jan-17 21:44 UTC
Re: [Libguestfs] [PATCH 5/9] connections: Allow multiple handles to be stored in the connection object.
On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:> Previously only one handle could be stored, but we will need to store > multiple handles when we have filters. > > The plugin handle is defined as index 0. Filters will use indices > 0. > --- > src/connections.c | 37 ++++++++++++++++++++++++++++++------- > src/internal.h | 4 ++-- > src/plugins.c | 53 +++++++++++++++++++++++++++-------------------------- > 3 files changed, 59 insertions(+), 35 deletions(-) >> +int > +connection_set_handle (struct connection *conn, size_t i, void *handle) > { > - conn->handle = handle; > + size_t j; > + > + if (i < conn->nr_handles) > + conn->handles[i] = handle; > + else { > + j = conn->nr_handles; > + conn->nr_handles = i+1; > + conn->handles = realloc (conn->handles, > + conn->nr_handles * sizeof (void *));Growing linearly (adding 1 per realloc) is a quadratic O(n^2) growth algorithm; it won't matter if we don't expect a large number of filters (say anything less than 100), but can get noticeable if we want to allow extremes. A less-intensive algorithm is to grow geometrically (a fixed growth factor, say x1.5 or x2, gives you amortized O(n) - although you have to track the array size independently from the number of slots in the array). At this point, I'm fine keeping the simpler linear realloc, on the grounds that a large number of filters on the command line is unlikely. ACK. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Eric Blake
2018-Jan-17 22:14 UTC
Re: [Libguestfs] [PATCH 4/9] backend: Add a .plugin_name method.
On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:> This returns the plugin name, which for plugins is the same as the > ordinary .name method (but for filters will be different). > ---Just as .name and .plugin_name can differ for filters, should we also have a way to report independent version numbers (via .version) for the filter, compared to the version of the underlying plugin (via .plugin_version)?> +++ b/src/plugins.c > @@ -465,6 +465,7 @@ static struct backend plugin_functions = { > .free = plugin_free, > .thread_model = plugin_thread_model, > .name = plugin_name, > + .plugin_name = plugin_name, > .usage = plugin_usage, > .version = plugin_version, > .dump_fields = plugin_dump_fields, >-- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:> Also implements the --filters parameter. > --- > docs/nbdkit.pod | 21 +- > nbdkit.in | 17 +- > src/Makefile.am | 1 + > src/filters.c | 606 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > src/internal.h | 23 ++- > src/main.c | 114 +++++++++-- > src/plugins.c | 11 +- > 7 files changed, 772 insertions(+), 21 deletions(-) >> +/* The next_functions structure contains pointers to backend > + * functions. However because these functions are all expecting a > + * backend and a connection, we cannot call them directly, but must > + * write some next_* functions that unpack the two parameters from a > + * single ‘void *nxdata’ struct pointer (‘b_conn’). > + */ > + > +/* Literally a backend + a connection pointer. This is the > + * implementation if ‘void *nxdata’ in the filter API.s/if/of/> +++ b/src/main.c > @@ -120,6 +121,7 @@ static const struct option long_options[] = { > { "export", 1, NULL, 'e' }, > { "export-name",1, NULL, 'e' }, > { "exportname", 1, NULL, 'e' }, > + { "filter", 1, NULL, 0 },If you assign a value > 256 to options that only have a long spelling...> @@ -245,6 +252,18 @@ main (int argc, char *argv[]) > exit (EXIT_FAILURE); > #endif > } > + else if (strcmp (long_options[option_index].name, "filter") == 0) {...then you can simply add additional case labels in your switch statement that handle each option, rather than having to make an ever-increasing if chain. That's a separate cleanup, so I'll go ahead and propose it on top of your series (I'm also planning on rebasing my FUA flags on top of your series, since so far it is looking pretty good). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Eric Blake
2018-Jan-17 22:38 UTC
Re: [Libguestfs] [PATCH 9/9] filters: Move rdelay/wdelay from file plugin to new delay filter.
On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:> Previously the file plugin supported ‘rdelay’ and ‘wdelay’ parameters > for injecting delays (for testing) into read and write requests. This > moves the functionality to a new delay filter so that it can be used > with any plugin. > ---> +/* Write data. */ > +static int > +delay_pwrite (struct nbdkit_next *next, void *nxdata, > + void *handle, > + const void *buf, uint32_t count, uint64_t offset) > +{ > + write_delay (); > + return next->pwrite (nxdata, buf, count, offset); > +} > + > +/* Zero data. */ > +static int > +delay_zero (struct nbdkit_next *next, void *nxdata, > + void *handle, uint32_t count, uint64_t offset, int may_trim) > +{ > + write_delay (); > + return next->zero (nxdata, count, offset, may_trim);If next->zero() fails with EOPNOTSUPP, that means we will delay once in trying the underlying command, and again for each iteration of the fallback loop as it calls delay_pwrite(). Is that okay, or do we want to reproduce some fallback logic here and directly call next->pwrite on EOPNOTSUPP so as to only have a single write delay in that case?> +++ b/plugins/file/nbdkit-file-plugin.pod > @@ -31,21 +31,13 @@ This parameter is required. > > =item B<rdelay=E<lt>NNE<gt>ms> > > -Delay reads for C<SECS> seconds or C<NN> milliseconds. > -This is used to simulate a slow or remote server, or to > -test certain kinds of race conditions in Linux. > - > -The default is no delay. > - > =item B<wdelay=SECS> > > =item B<wdelay=E<lt>NNE<gt>ms> > > -Delay writes for C<SECS> seconds or C<NN> milliseconds. > -This is used to simulate a slow or remote server, or to > -test certain kinds of race conditions in Linux. > - > -The default is no delay. > +These plugin parameters have been moved to the > +L<nbdkit-delay-filter(1)> filter. Modify the command line to add > +I<--filter=delay> in order to use these parameters.I guess we don't promise back-comptibility on plugin parameters, but at least you've documented how to fix things (and the testsuite had to follow that advice). -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Eric Blake
2018-Jan-18 03:02 UTC
Re: [Libguestfs] [PATCH 2/9] Refactor plugin_* functions into a backend struct.
On 01/17/2018 02:53 PM, Richard W.M. Jones wrote:> Introduce the concept of a backend. Currently the only type of > backend is a plugin, and there can only be one of them. Instead of > calling functions like ‘plugin_pwrite’ you call the backend method > ‘backend->pwrite (backend, ...)’. > > The change is largely mechanical. I was able to remove ‘assert (dl)’ > statements throughout since we can now prove they will never be > called. > > Note this does not lift the restriction of one plugin per server, and > it can *never* do that because plugins can use global variables. > --- > src/connections.c | 40 +++-- > src/internal.h | 55 +++--- > src/locks.c | 8 +- > src/main.c | 31 ++-- > src/plugins.c | 529 ++++++++++++++++++++++++++++++------------------------ > 5 files changed, 368 insertions(+), 295 deletions(-)Hmmm. I'm wondering if we want a src/backend.c,...> - if (plugin_thread_model () < NBDKIT_THREAD_MODEL_PARALLEL || nworkers == 1) > + if (backend->thread_model (backend) < NBDKIT_THREAD_MODEL_PARALLEL || > + nworkers == 1)...where we'd call backend_thread_model (backend), and backend.c has: int backend_thread_model (struct backend *b) { return b->thread_model (b); } The real reason I ask is because of:> +++ b/src/plugins.c> +static int > +plugin_zero (struct backend *b, struct connection *conn, > uint32_t count, uint64_t offset, int may_trim) > { > - assert (dl); > - assert (connection_get_handle (conn)); > + struct backend_plugin *p = container_of (b, struct backend_plugin, backend); > char *buf; > uint32_t limit; > int result; > int err = 0; > > + assert (connection_get_handle (conn)); > + > debug ("zero count=%" PRIu32 " offset=%" PRIu64 " may_trim=%d", > count, offset, may_trim); > > if (!count) > return 0; > - if (plugin.zero) { > + if (p->plugin.zero) { > errno = 0; > - result = plugin.zero (connection_get_handle (conn), count, offset, may_trim); > + result = p->plugin.zero (connection_get_handle (conn), > + count, offset, may_trim); > if (result == -1) { > err = threadlocal_get_error (); > - if (!err && plugin_errno_is_preserved ()) > + if (!err && plugin_errno_is_preserved (b)) > err = errno; > } > if (result == 0 || err != EOPNOTSUPP) > return result; > } > > - assert (plugin.pwrite); > + assert (p->plugin.pwrite); > threadlocal_set_error (0); > limit = count < MAX_REQUEST_SIZE ? count : MAX_REQUEST_SIZE; > buf = calloc (limit, 1); > @@ -525,7 +446,8 @@ plugin_zero (struct connection *conn, > } > > while (count) { > - result = plugin.pwrite (connection_get_handle (conn), buf, limit, offset); > + result = p->plugin.pwrite (connection_get_handle (conn), > + buf, limit, offset);this fallback. If I leave the EOPNOTSUPP check in plugins.c, then every filter has to duplicate the logic. But with a backend.c, I could do something along these lines (psuedocode, not actually tested): int backend_zero (struct backend *b, struct connection *conn, uint32_t count, uint64_t offset, int may_trim) { try b->zero (b, conn, count, offset, may_trim) if EOPNOTSUPP loop on b->pwrite (b, conn, buf, limit, offset) } coupled with: static int plugin_zero (struct backend *b, struct connection *conn, uint32_t count, uint64_t offset, int may_trim) { if (!p->plugin.zero) { errno = EOPNOTSUPP; return -1; } return p->plugin.zero (connection_get_handle (conn), count, offset, may_trim); } basically, splitting the fallback code that needs to be reusable from the plugin code that just has to call into the actual plugin.so function; this way, filters can also implement .zero to fail with EOPNOTSUPP and trigger the fallback code without having to duplicate things. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Reasonably Related Threads
- [nbdkit PATCH v2 08/13] connections: Allow multiple handles to be stored in the connection object.
- [PATCH nbdkit 2/3] Refactor plugin_* functions into a backend struct.
- [PATCH 2/9] Refactor plugin_* functions into a backend struct.
- [PATCH nbdkit v2 2/3] Refactor plugin_* functions into a backend struct.
- [nbdkit PATCH v3 11/15] plugins: Expose new FUA callbacks