Richard W.M. Jones
2019-Mar-13 12:45 UTC
[Libguestfs] [PATCH nbdkit] server: Implement extents/can_extents calls for plugins and filters.
I'm not sure which version we're up to now. Anyway I believe this addresses all the points that Eric raised in: https://www.redhat.com/archives/libguestfs/2019-March/msg00038.html https://www.redhat.com/archives/libguestfs/2019-March/msg00040.html In particular: - default state of extents_map is all allocated disk - support hole + non-zero - you can now iterate with bounds - removed the nbdkit_extents_clear function; the name is confusing and it doesn't seem like it would be useful - lots of doc changes and clarifications Rich.
Richard W.M. Jones
2019-Mar-13 12:45 UTC
[Libguestfs] [PATCH nbdkit] server: Implement extents/can_extents calls for plugins and filters.
This pair of calls allows plugins to describe which extents in the
virtual disk are allocated, holes or zeroes.
---
docs/nbdkit-filter.pod | 64 +++++++++++++++++++++
docs/nbdkit-plugin.pod | 123 ++++++++++++++++++++++++++++++++++++++++
include/nbdkit-common.h | 20 ++++++-
include/nbdkit-filter.h | 15 ++++-
include/nbdkit-plugin.h | 6 +-
server/internal.h | 7 ++-
server/extents.c | 71 +++++++++++++++++++++++
server/filters.c | 61 ++++++++++++++++++++
server/plugins.c | 62 +++++++++++++++++++-
server/Makefile.am | 1 +
10 files changed, 425 insertions(+), 5 deletions(-)
diff --git a/docs/nbdkit-filter.pod b/docs/nbdkit-filter.pod
index dc9a262..6e81e0c 100644
--- a/docs/nbdkit-filter.pod
+++ b/docs/nbdkit-filter.pod
@@ -350,6 +350,8 @@ calls.
=head2 C<.can_zero>
+=head2 C<.can_extents>
+
=head2 C<.can_fua>
=head2 C<.can_multi_conn>
@@ -365,6 +367,8 @@ calls.
void *handle);
int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle);
+ int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle);
int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle);
int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata,
@@ -513,6 +517,66 @@ value to return to the client. The filter should never
fail with
C<EOPNOTSUPP> (while plugins have automatic fallback to C<.pwrite>,
filters do not).
+=head2 C<.extents>
+
+ int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset, uint32_t flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err);
+
+This intercepts the plugin C<.extents> method and can be used to
+modify extent requests.
+
+This function will not be called if C<.can_extents> returned false; in
+turn, the filter should not call C<next_ops-E<gt>extents> if
+C<next_ops-E<gt>can_extents> did not return true.
+
+The C<extents_map> parameter passed to this function is empty
+(representing a fully allocated disk). If the filter does not need to
+adjust extents from the underlying plugin it can simply pass this
+through to the layer below:
+
+ myfilter_extents (...)
+ {
+ return next_ops->extents (nxdata, count, offset, flags,
+ extents_map, err);
+ }
+
+It is also possible for filters to transform the extents map received
+back from the layer below. Usually this must be done by allocating a
+new, empty map which is passed to the layer below. Without error
+handling it would look like this:
+
+ myfilter_extents (...)
+ {
+ struct nbdkit_extents_map *map2 = nbdkit_extents_new ();
+ next_ops->extents (nxdata, count, offset, flags, map2, err);
+ /* transform map2 and return results in extents_map */
+ nbdkit_extents_foreach (map2, transform_offset, extents_map);
+ nbdkit_extents_free (map2);
+ }
+
+If there is an error, C<.extents> should call C<nbdkit_error> with
an
+error message B<and> return -1 with C<err> set to the positive
errno
+value to return to the client.
+
+=head3 Allocating and freeing nbdkit_extents_map
+
+Two functions are provided to filters for allocating and freeing the
+map:
+
+ struct nbdkit_extents_map *nbdkit_extents_new ();
+
+Allocates and returns a new, empty extents map. The initial state is
+that the whole disk is allocated with data.
+
+On error this function can return C<NULL>. In this case it calls
+C<nbdkit_error> and/or C<nbdkit_set_error> as required.
+
+ void nbdkit_extents_free (struct nbdkit_extents_map *);
+
+Frees an existing extents map.
+
=head1 ERROR HANDLING
If there is an error in the filter itself, the filter should call
diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod
index 47545f3..406019d 100644
--- a/docs/nbdkit-plugin.pod
+++ b/docs/nbdkit-plugin.pod
@@ -555,6 +555,20 @@ This callback is not required. If omitted, then nbdkit
always tries
C<.zero> first if it is present, and gracefully falls back to
C<.pwrite> if C<.zero> was absent or failed with
C<EOPNOTSUPP>.
+=head2 C<.can_extents>
+
+ int can_extents (void *handle);
+
+This is called during the option negotiation phase to find out if the
+plugin supports detecting allocated (non-sparse) regions of the disk
+with the C<.extents> callback.
+
+If there is an error, C<.can_extents> should call C<nbdkit_error>
with
+an error message and return C<-1>.
+
+This callback is not required. If omitted, then we return true iff a
+C<.extents> callback has been defined.
+
=head2 C<.can_fua>
int can_fua (void *handle);
@@ -717,6 +731,115 @@ If there is an error, C<.zero> should call
C<nbdkit_error> with an
error message, and C<nbdkit_set_error> to record an appropriate error
(unless C<errno> is sufficient), then return C<-1>.
+=head2 C<.extents>
+
+ int extents (void *handle, uint32_t count, uint64_t offset,
+ uint32_t flags,
+ struct nbdkit_extents_map *extents_map);
+
+During the data serving phase, this callback is used to detect
+allocated, sparse and zeroed regions of the disk.
+
+This function will not be called if C<.can_extents> returned false.
+nbdkit's default behaviour in this case is to treat the whole virtual
+disk as if it was allocated.
+
+The callback should detect and return the list of extents overlapping
+the range C<[offset...offset+count-1]>. The C<extents_map>
parameter
+points to an opaque object which the callback should fill in by
+calling C<nbdkit_extent_add> etc. See L</Extents map> below.
+
+The C<flags> parameter may contain the flag C<NBDKIT_FLAG_REQ_ONE>
+which means that the client is only requesting information about the
+extent overlapping C<offset>. The plugin may ignore this flag, or as
+an optimization it may return just a single extent for C<offset>.
+
+If there is an error, C<.extents> should call C<nbdkit_error> with
an
+error message, and C<nbdkit_set_error> to record an appropriate error
+(unless C<errno> is sufficient), then return C<-1>.
+
+=head3 Extents map
+
+The plugin C<extents> callback is passed an opaque pointer C<struct
+nbdkit_extents_map *extents_map>. This structure represents a list of
+L<filesystem extents|https://en.wikipedia.org/wiki/Extent_(file_systems)>
+describing which areas of the disk are allocated, which are sparse
+(“holes”), and, if supported, which are zeroes. Initially the map
+describes a single allocated data extent covering the entire virtual
+disk.
+
+The C<extents> callback has to fill in any holes or zeroes areas by
+calling C<nbdkit_extent*> functions, to describe all extents
+overlapping the range C<[offset...offset+count-1]>. (nbdkit will
+ignore extents outside this range so plugins may, if it is easier to
+implement, return all extent information for the whole disk.)
+
+The following functions are available for plugins or filters to call:
+
+ int nbdkit_extent_add (struct nbdkit_extents_map *extents_map,
+ uint64_t offset, uint64_t length, uint32_t type);
+
+Add an extent covering C<[offset...offset+length-1]> of one of
+the following four types:
+
+=over 4
+
+=item C<type = 0>
+
+A normal, allocated data extent.
+
+=item C<type = NBDKIT_EXTENT_HOLE|NBDKIT_EXTENT_ZERO>
+
+An unallocated extent, a.k.a. a “hole”, which reads back as zeroes.
+This is the normal type of hole applicable to most disks.
+
+=item C<type = NBDKIT_EXTENT_ZERO>
+
+An allocated extent which is known to contain only zeroes.
+
+=item C<type = NBDKIT_EXTENT_HOLE>
+
+An unallocated extent (hole) which does not read back as zeroes. Note
+this should only be used in specialized circumstances such as when
+writing a plugin for (or to emulate) certain SCSI drives which do not
+guarantee that trimmed blocks read back as zeroes.
+
+=back
+
+If the new extent overlaps some previous extent in the map then the
+overlapping part(s) are overwritten with the new type. Adjacent
+extents of the same type may also be coalesced. Thus you shouldn't
+assume that C<nbdkit_extent_add> always adds exactly one more extent
+to the map.
+
+C<nbdkit_extent_add> returns C<0> on success or C<-1> on
failure. On
+failure C<nbdkit_error> and/or C<nbdkit_set_error> has already been
+called.
+
+ int nbdkit_extents_foreach (
+ const struct nbdkit_extents_map *extents_map,
+ int (*fn) (uint64_t offset, uint64_t length,
+ uint32_t type, void *opaque),
+ void *opaque);
+
+ int nbdkit_extents_foreach_range (
+ const struct nbdkit_extents_map *extents_map,
+ uint64_t range_offset, uint64_t range_length,
+ int (*fn) (uint64_t offset, uint64_t length,
+ uint32_t type, void *opaque),
+ void *opaque);
+
+Iterate over the extents in ascending order, calling C<fn> for each.
+C<fn> should return 0 on success or -1 on failure. If a call to
C<fn>
+fails then C<nbdkit_extents_foreach*> also fails immediately.
+
+The C<nbdkit_extents_foreach_range> variant only iterates over extents
+overlapping C<[range_offset...range_offset+range_length-1]>.
+
+C<nbdkit_extents_foreach*> returns C<0> on success or C<-1>
on failure.
+However it does not call C<nbdkit_error> or C<nbdkit_set_error> -
it
+is expected that C<fn> will call those functions on failure.
+
=head1 THREADS
Each nbdkit plugin must declare its thread safety model by defining
diff --git a/include/nbdkit-common.h b/include/nbdkit-common.h
index cb9954e..860a7c4 100644
--- a/include/nbdkit-common.h
+++ b/include/nbdkit-common.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2018 Red Hat Inc.
+ * Copyright (C) 2013-2019 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -60,11 +60,15 @@ extern "C" {
#define NBDKIT_FLAG_MAY_TRIM (1<<0) /* Maps to !NBD_CMD_FLAG_NO_HOLE */
#define NBDKIT_FLAG_FUA (1<<1) /* Maps to NBD_CMD_FLAG_FUA */
+#define NBDKIT_FLAG_REQ_ONE (1<<2) /* Maps to NBD_CMD_FLAG_REQ_ONE */
#define NBDKIT_FUA_NONE 0
#define NBDKIT_FUA_EMULATE 1
#define NBDKIT_FUA_NATIVE 2
+#define NBDKIT_EXTENT_HOLE (1<<0) /* Same as NBD_STATE_HOLE */
+#define NBDKIT_EXTENT_ZERO (1<<1) /* Same as NBD_STATE_ZERO */
+
extern void nbdkit_error (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2);
extern void nbdkit_verror (const char *msg, va_list args);
extern void nbdkit_debug (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2);
@@ -76,6 +80,20 @@ extern int nbdkit_parse_bool (const char *str);
extern int nbdkit_read_password (const char *value, char **password);
extern char *nbdkit_realpath (const char *path);
+struct nbdkit_extents_map;
+extern int nbdkit_extent_add (struct nbdkit_extents_map *,
+ uint64_t offset, uint64_t length, uint32_t type);
+extern int nbdkit_extents_foreach (const struct nbdkit_extents_map *,
+ int (*fn) (uint64_t offset, uint64_t length,
+ uint32_t type, void *opaque),
+ void *opaque);
+extern int nbdkit_extents_foreach_range (const struct nbdkit_extents_map *,
+ uint64_t range_offset,
+ uint64_t range_length,
+ int (*fn) (uint64_t offset, uint64_t
length,
+ uint32_t type, void
*opaque),
+ void *opaque);
+
/* A static non-NULL pointer which can be used when you don't need a
* per-connection handle.
*/
diff --git a/include/nbdkit-filter.h b/include/nbdkit-filter.h
index 71c06c8..689f209 100644
--- a/include/nbdkit-filter.h
+++ b/include/nbdkit-filter.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2018 Red Hat Inc.
+ * Copyright (C) 2013-2019 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -44,6 +44,9 @@ extern "C" {
#define NBDKIT_FILTER_API_VERSION 2
+extern struct nbdkit_extents_map *nbdkit_extents_new (void);
+extern void nbdkit_extents_free (struct nbdkit_extents_map *);
+
typedef int nbdkit_next_config (void *nxdata,
const char *key, const char *value);
typedef int nbdkit_next_config_complete (void *nxdata);
@@ -58,6 +61,7 @@ struct nbdkit_next_ops {
int (*is_rotational) (void *nxdata);
int (*can_trim) (void *nxdata);
int (*can_zero) (void *nxdata);
+ int (*can_extents) (void *nxdata);
int (*can_fua) (void *nxdata);
int (*can_multi_conn) (void *nxdata);
@@ -71,6 +75,9 @@ struct nbdkit_next_ops {
int *err);
int (*zero) (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags,
int *err);
+ int (*extents) (void *nxdata, uint32_t count, uint64_t offset, uint32_t
flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err);
};
struct nbdkit_filter {
@@ -120,6 +127,8 @@ struct nbdkit_filter {
void *handle);
int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle);
+ int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle);
int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle);
int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata,
@@ -140,6 +149,10 @@ struct nbdkit_filter {
int (*zero) (struct nbdkit_next_ops *next_ops, void *nxdata,
void *handle, uint32_t count, uint64_t offset, uint32_t flags,
int *err);
+ int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata,
+ void *handle, uint32_t count, uint64_t offset, uint32_t
flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err);
};
#define NBDKIT_REGISTER_FILTER(filter) \
diff --git a/include/nbdkit-plugin.h b/include/nbdkit-plugin.h
index d43b2f5..76cec54 100644
--- a/include/nbdkit-plugin.h
+++ b/include/nbdkit-plugin.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2018 Red Hat Inc.
+ * Copyright (C) 2013-2019 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -125,6 +125,10 @@ struct nbdkit_plugin {
const char *magic_config_key;
int (*can_multi_conn) (void *handle);
+
+ int (*can_extents) (void *handle);
+ int (*extents) (void *handle, uint32_t count, uint64_t offset, uint32_t
flags,
+ struct nbdkit_extents_map *extents_map);
};
extern void nbdkit_set_error (int err);
diff --git a/server/internal.h b/server/internal.h
index 506882b..e05e5b5 100644
--- a/server/internal.h
+++ b/server/internal.h
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2018 Red Hat Inc.
+ * Copyright (C) 2013-2019 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -235,6 +235,7 @@ struct backend {
int (*is_rotational) (struct backend *, struct connection *conn);
int (*can_trim) (struct backend *, struct connection *conn);
int (*can_zero) (struct backend *, struct connection *conn);
+ int (*can_extents) (struct backend *, struct connection *conn);
int (*can_fua) (struct backend *, struct connection *conn);
int (*can_multi_conn) (struct backend *, struct connection *conn);
@@ -248,6 +249,10 @@ struct backend {
uint64_t offset, uint32_t flags, int *err);
int (*zero) (struct backend *, struct connection *conn, uint32_t count,
uint64_t offset, uint32_t flags, int *err);
+ int (*extents) (struct backend *, struct connection *conn, uint32_t count,
+ uint64_t offset, uint32_t flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err);
};
/* plugins.c */
diff --git a/server/extents.c b/server/extents.c
new file mode 100644
index 0000000..4b257db
--- /dev/null
+++ b/server/extents.c
@@ -0,0 +1,71 @@
+/* nbdkit
+ * Copyright (C) 2019 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 "internal.h"
+
+struct nbdkit_extents_map {
+ // TBD XXX
+};
+
+#if 0
+struct nbdkit_extents_map *nbdkit_extents_new (void);
+void nbdkit_extents_free (struct nbdkit_extents_map *);
+#endif
+
+int nbdkit_extent_add (struct nbdkit_extents_map *extents_map,
+ uint64_t offset, uint64_t length, uint32_t type)
+{
+ // XXX
+ return 0;
+}
+
+#if 0
+int nbdkit_extents_foreach (const struct nbdkit_extents_map *,
+ int (*fn) (uint64_t offset, uint64_t length,
+ uint32_t type, void *opaque),
+ void *opaque);
+int nbdkit_extents_foreach_range (const struct nbdkit_extents_map *,
+ uint64_t range_offset, uint64_t range_length,
+ int (*fn) (uint64_t offset, uint64_t length,
+ uint32_t type, void *opaque),
+ void *opaque);
+#endif
diff --git a/server/filters.c b/server/filters.c
index 5b7abc4..e284080 100644
--- a/server/filters.c
+++ b/server/filters.c
@@ -309,6 +309,13 @@ next_can_zero (void *nxdata)
return b_conn->b->can_zero (b_conn->b, b_conn->conn);
}
+static int
+next_can_extents (void *nxdata)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->can_extents (b_conn->b, b_conn->conn);
+}
+
static int
next_can_fua (void *nxdata)
{
@@ -364,6 +371,16 @@ next_zero (void *nxdata, uint32_t count, uint64_t offset,
uint32_t flags,
return b_conn->b->zero (b_conn->b, b_conn->conn, count, offset,
flags, err);
}
+static int
+next_extents (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err)
+{
+ struct b_conn *b_conn = nxdata;
+ return b_conn->b->extents (b_conn->b, b_conn->conn, count,
offset, flags,
+ extents_map, err);
+}
+
static struct nbdkit_next_ops next_ops = {
.get_size = next_get_size,
.can_write = next_can_write,
@@ -371,6 +388,7 @@ static struct nbdkit_next_ops next_ops = {
.is_rotational = next_is_rotational,
.can_trim = next_can_trim,
.can_zero = next_can_zero,
+ .can_extents = next_can_extents,
.can_fua = next_can_fua,
.can_multi_conn = next_can_multi_conn,
.pread = next_pread,
@@ -378,6 +396,7 @@ static struct nbdkit_next_ops next_ops = {
.flush = next_flush,
.trim = next_trim,
.zero = next_zero,
+ .extents = next_extents,
};
static int
@@ -511,6 +530,21 @@ filter_can_zero (struct backend *b, struct connection
*conn)
return f->backend.next->can_zero (f->backend.next, conn);
}
+static int
+filter_can_extents (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 ("%s: can_extents", f->name);
+
+ if (f->filter.can_extents)
+ return f->filter.can_extents (&next_ops, &nxdata, handle);
+ else
+ return f->backend.next->can_extents (f->backend.next, conn);
+}
+
static int
filter_can_fua (struct backend *b, struct connection *conn)
{
@@ -646,6 +680,31 @@ filter_zero (struct backend *b, struct connection *conn,
count, offset, flags, err);
}
+static int
+filter_extents (struct backend *b, struct connection *conn,
+ uint32_t count, uint64_t offset, uint32_t flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err)
+{
+ 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 };
+
+ assert (!(flags & ~NBDKIT_FLAG_REQ_ONE));
+
+ debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64
" flags=0x%" PRIx32,
+ f->name, count, offset, flags);
+
+ if (f->filter.extents)
+ return f->filter.extents (&next_ops, &nxdata, handle,
+ count, offset, flags,
+ extents_map, err);
+ else
+ return f->backend.next->extents (f->backend.next, conn,
+ count, offset, flags,
+ extents_map, err);
+}
+
static struct backend filter_functions = {
.free = filter_free,
.thread_model = filter_thread_model,
@@ -667,6 +726,7 @@ static struct backend filter_functions = {
.is_rotational = filter_is_rotational,
.can_trim = filter_can_trim,
.can_zero = filter_can_zero,
+ .can_extents = filter_can_extents,
.can_fua = filter_can_fua,
.can_multi_conn = filter_can_multi_conn,
.pread = filter_pread,
@@ -674,6 +734,7 @@ static struct backend filter_functions = {
.flush = filter_flush,
.trim = filter_trim,
.zero = filter_zero,
+ .extents = filter_extents,
};
/* Register and load a filter. */
diff --git a/server/plugins.c b/server/plugins.c
index 28b96ad..1882b00 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -1,5 +1,5 @@
/* nbdkit
- * Copyright (C) 2013-2018 Red Hat Inc.
+ * Copyright (C) 2013-2019 Red Hat Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
@@ -199,6 +199,8 @@ plugin_dump_fields (struct backend *b)
HAS (trim);
HAS (zero);
HAS (can_multi_conn);
+ HAS (can_extents);
+ HAS (extents);
#undef HAS
/* Custom fields. */
@@ -392,6 +394,21 @@ plugin_can_zero (struct backend *b, struct connection
*conn)
return plugin_can_write (b, conn);
}
+static int
+plugin_can_extents (struct backend *b, struct connection *conn)
+{
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+
+ assert (connection_get_handle (conn, 0));
+
+ debug ("can_extents");
+
+ if (p->plugin.can_extents)
+ return p->plugin.can_extents (connection_get_handle (conn, 0));
+ else
+ return p->plugin.extents != NULL;
+}
+
static int
plugin_can_fua (struct backend *b, struct connection *conn)
{
@@ -651,6 +668,47 @@ plugin_zero (struct backend *b, struct connection *conn,
return r;
}
+static int
+plugin_extents (struct backend *b, struct connection *conn,
+ uint32_t count, uint64_t offset, uint32_t flags,
+ struct nbdkit_extents_map *extents_map,
+ int *err)
+{
+ struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
+ bool req_one = flags & NBDKIT_FLAG_REQ_ONE;
+ int r;
+ int can_extents = 0; /* XXX probably should be cached per connection */
+
+ assert (connection_get_handle (conn, 0));
+ assert (!(flags & ~NBDKIT_FLAG_REQ_ONE));
+
+ debug ("extents count=%" PRIu32 " offset=%" PRIu64 "
req_one=%d",
+ count, offset, req_one);
+
+ if (!count)
+ return 0;
+
+ if (p->plugin.can_extents) {
+ can_extents = p->plugin.can_extents (connection_get_handle (conn, 0));
+ if (can_extents == -1) {
+ *err = get_error (p);
+ return -1;
+ }
+ }
+
+ if (can_extents) {
+ r = p->plugin.extents (connection_get_handle (conn, 0), count, offset,
+ flags, extents_map);
+ if (r == -1)
+ *err = get_error (p);
+ return r;
+ }
+ else {
+ /* By default we assume that everything in the range is allocated. */
+ return nbdkit_extent_add (extents_map, offset, count, 0);
+ }
+}
+
static struct backend plugin_functions = {
.free = plugin_free,
.thread_model = plugin_thread_model,
@@ -672,6 +730,7 @@ static struct backend plugin_functions = {
.is_rotational = plugin_is_rotational,
.can_trim = plugin_can_trim,
.can_zero = plugin_can_zero,
+ .can_extents = plugin_can_extents,
.can_fua = plugin_can_fua,
.can_multi_conn = plugin_can_multi_conn,
.pread = plugin_pread,
@@ -679,6 +738,7 @@ static struct backend plugin_functions = {
.flush = plugin_flush,
.trim = plugin_trim,
.zero = plugin_zero,
+ .extents = plugin_extents,
};
/* Register and load a plugin. */
diff --git a/server/Makefile.am b/server/Makefile.am
index b198afb..1c2fe06 100644
--- a/server/Makefile.am
+++ b/server/Makefile.am
@@ -43,6 +43,7 @@ nbdkit_SOURCES = \
connections.c \
crypto.c \
debug.c \
+ extents.c \
filters.c \
internal.h \
locks.c \
--
2.20.1
Eric Blake
2019-Mar-13 13:20 UTC
Re: [Libguestfs] [PATCH nbdkit] server: Implement extents/can_extents calls for plugins and filters.
On 3/13/19 7:45 AM, Richard W.M. Jones wrote:> This pair of calls allows plugins to describe which extents in the > virtual disk are allocated, holes or zeroes. > ---> + int nbdkit_extents_foreach_range ( > + const struct nbdkit_extents_map *extents_map, > + uint64_t range_offset, uint64_t range_length, > + int (*fn) (uint64_t offset, uint64_t length, > + uint32_t type, void *opaque), > + void *opaque); > + > +Iterate over the extents in ascending order, calling C<fn> for each. > +C<fn> should return 0 on success or -1 on failure. If a call to C<fn> > +fails then C<nbdkit_extents_foreach*> also fails immediately. > + > +The C<nbdkit_extents_foreach_range> variant only iterates over extents > +overlapping C<[range_offset...range_offset+range_length-1]>. > + > +C<nbdkit_extents_foreach*> returns C<0> on success or C<-1> on failure. > +However it does not call C<nbdkit_error> or C<nbdkit_set_error> - it > +is expected that C<fn> will call those functions on failure.expected that either C<fn> or the caller will call those functions on failure> +++ b/server/extents.c > @@ -0,0 +1,71 @@ > +/* nbdkit> +#if 0 > +int nbdkit_extents_foreach (const struct nbdkit_extents_map *, > + int (*fn) (uint64_t offset, uint64_t length, > + uint32_t type, void *opaque), > + void *opaque); > +int nbdkit_extents_foreach_range (const struct nbdkit_extents_map *, > + uint64_t range_offset, uint64_t range_length, > + int (*fn) (uint64_t offset, uint64_t length,Indentation glitch?> + uint32_t type, void *opaque), > + void *opaque);Otherwise I think we're ready for the implementation, because the framework is looking good. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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