Stefan Behrens
2013-Apr-23 10:18 UTC
[PATCH] Btrfs-progs: add function to map subvol ID to path
Several tools like btrfs-send and btrfs-receive need to map a
subvolume ID to a filesystem path. The so far existing methods
in btrfs-list.c cause a horrible effort when performing this
operation (and the effort is dependent on the number of
existing subvolumes with quadratic effort). This commit adds a
function that is able to map a subvolume ID to a filesystem path
with an effort that is independent of the number of existing
subvolumes.
In addition to this function, a command line frontend is added as well:
btrfs inspect-internal subvolid-resolve <subvolid> <path>
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
---
A following commit will also use this function (in addition to the
usage in "btrfs inspect-internal"). I send this commit on its own
because the function is of general use IMO. The effort of the
btrfs-list.c functions is incredible and not required to map a
subvol ID to a filesystem path.
cmds-inspect.c | 46 +++++++++++++++++++++++++++
man/btrfs.8.in | 6 ++++
send-utils.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
send-utils.h | 2 +-
4 files changed, 152 insertions(+), 1 deletion(-)
diff --git a/cmds-inspect.c b/cmds-inspect.c
index 7761759..30b41fc 100644
--- a/cmds-inspect.c
+++ b/cmds-inspect.c
@@ -24,6 +24,8 @@
#include "kerncompat.h"
#include "ioctl.h"
#include "utils.h"
+#include "ctree.h"
+#include "send-utils.h"
#include "commands.h"
#include "btrfs-list.h"
@@ -253,12 +255,56 @@ out:
return ret;
}
+static const char * const cmd_subvolid_resolve_usage[] = {
+ "btrfs inspect-internal subvolid-resolve <subvolid>
<path>",
+ "Get file system paths for the given subvolume ID.",
+ NULL
+};
+
+static int cmd_subvolid_resolve(int argc, char **argv)
+{
+ int ret;
+ int fd = -1;
+ u64 subvol_id;
+ char path[BTRFS_PATH_NAME_MAX + 1];
+
+ if (check_argc_exact(argc, 3))
+ usage(cmd_subvolid_resolve_usage);
+
+ fd = open_file_or_dir(argv[2]);
+ if (fd < 0) {
+ fprintf(stderr, "ERROR: can''t access
''%s''\n", argv[2]);
+ ret = -ENOENT;
+ goto out;
+ }
+
+ subvol_id = atoll(argv[1]);
+ ret = btrfs_subvolid_resolve(fd, path, sizeof(path), subvol_id);
+
+ if (ret) {
+ fprintf(stderr,
+ "%s: btrfs_subvolid_resolve(subvol_id %llu) failed with ret=%d\n",
+ argv[0], (unsigned long long)subvol_id, ret);
+ goto out;
+ }
+
+ path[BTRFS_PATH_NAME_MAX] = ''\0'';
+ printf("%s\n", path);
+
+out:
+ if (fd >= 0)
+ close(fd);
+ return ret ? 1 : 0;
+}
+
const struct cmd_group inspect_cmd_group = {
inspect_cmd_group_usage, NULL, {
{ "inode-resolve", cmd_inode_resolve, cmd_inode_resolve_usage,
NULL, 0 },
{ "logical-resolve", cmd_logical_resolve,
cmd_logical_resolve_usage, NULL, 0 },
+ { "subvolid-resolve", cmd_subvolid_resolve,
+ cmd_subvolid_resolve_usage, NULL, 0 },
{ 0, 0, 0, 0, 0 }
}
};
diff --git a/man/btrfs.8.in b/man/btrfs.8.in
index 0b2538e..d9af323 100644
--- a/man/btrfs.8.in
+++ b/man/btrfs.8.in
@@ -60,6 +60,8 @@ btrfs \- control a btrfs filesystem
\fBbtrfs\fP \fBinspect-internal logical-resolve\fP
[-Pv] [-s size] \fI<logical>\fP \fI<path>\fP
.PP
+\fBbtrfs\fP \fBinspect-internal subvolid-resolve\fP \fI<subvolid>\fP
\fI<path>\fP
+.PP
\fBbtrfs\fP \fBqgroup assign\fP \fI<src>\fP \fI<dst>\fP
\fI<path>\fP
.PP
\fBbtrfs\fP \fBqgroup remove\fP \fI<src>\fP \fI<dst>\fP
\fI<path>\fP
@@ -456,6 +458,10 @@ not enough to read all the resolved results. The max value
one can set is 64k.
.RE
.TP
+\fBinspect-internal subvolid-resolve\fP \fI<subvolid>\fP
\fI<path>\fP
+Get file system paths for the given subvolume ID.
+.TP
+
\fBbtrfs qgroup assign\fP \fI<src>\fP \fI<dst>\fP
\fI<path>\fP
Enable subvolume qgroup support for a filesystem.
.TP
diff --git a/send-utils.c b/send-utils.c
index bc0feb8..bacd47e 100644
--- a/send-utils.c
+++ b/send-utils.c
@@ -23,6 +23,105 @@
#include "ioctl.h"
#include "btrfs-list.h"
+static int btrfs_subvolid_resolve_sub(int fd, char *path, size_t *path_len,
+ u64 subvol_id);
+
+int btrfs_subvolid_resolve(int fd, char *path, size_t path_len, u64 subvol_id)
+{
+ if (path_len < 1)
+ return -EOVERFLOW;
+ path[0] = ''\0'';
+ path_len--;
+ path[path_len] = ''\0'';
+ return btrfs_subvolid_resolve_sub(fd, path, &path_len, subvol_id);
+}
+
+static int btrfs_subvolid_resolve_sub(int fd, char *path, size_t *path_len,
+ u64 subvol_id)
+{
+ int ret;
+ struct btrfs_ioctl_search_args search_arg;
+ struct btrfs_ioctl_ino_lookup_args ino_lookup_arg;
+ struct btrfs_ioctl_search_header *search_header;
+ struct btrfs_root_ref *backref_item;
+
+ if (subvol_id == BTRFS_FS_TREE_OBJECTID) {
+ if (*path_len < 1)
+ return -EOVERFLOW;
+ *path = ''\0'';
+ (*path_len)--;
+ return 0;
+ }
+
+ memset(&search_arg, 0, sizeof(search_arg));
+ search_arg.key.tree_id = BTRFS_ROOT_TREE_OBJECTID;
+ search_arg.key.min_objectid = subvol_id;
+ search_arg.key.max_objectid = subvol_id;
+ search_arg.key.min_type = BTRFS_ROOT_BACKREF_KEY;
+ search_arg.key.max_type = BTRFS_ROOT_BACKREF_KEY;
+ search_arg.key.max_offset = (u64)-1;
+ search_arg.key.max_transid = (u64)-1;
+ search_arg.key.nr_items = 1;
+ ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &search_arg);
+ if (ret) {
+ fprintf(stderr,
+ "ioctl(BTRFS_IOC_TREE_SEARCH, subvol_id %llu) ret=%d, error:
%s\n",
+ (unsigned long long)subvol_id, ret, strerror(errno));
+ return ret;
+ }
+
+ if (search_arg.key.nr_items < 1) {
+ fprintf(stderr,
+ "failed to lookup subvol_id %llu!\n",
+ (unsigned long long)subvol_id);
+ return -ENOENT;
+ }
+ search_header = (struct btrfs_ioctl_search_header *)search_arg.buf;
+ backref_item = (struct btrfs_root_ref *)(search_header + 1);
+ if (search_header->offset != BTRFS_FS_TREE_OBJECTID) {
+ int sub_ret;
+
+ sub_ret = btrfs_subvolid_resolve_sub(fd, path, path_len,
+ search_header->offset);
+ if (sub_ret)
+ return sub_ret;
+ if (*path_len < 1)
+ return -EOVERFLOW;
+ strcat(path, "/");
+ (*path_len)--;
+ }
+
+ if (btrfs_stack_root_ref_dirid(backref_item) !+ BTRFS_FIRST_FREE_OBJECTID)
{
+ int len;
+
+ memset(&ino_lookup_arg, 0, sizeof(ino_lookup_arg));
+ ino_lookup_arg.treeid = search_header->offset;
+ ino_lookup_arg.objectid + btrfs_stack_root_ref_dirid(backref_item);
+ ret = ioctl(fd, BTRFS_IOC_INO_LOOKUP, &ino_lookup_arg);
+ if (ret) {
+ fprintf(stderr,
+ "ioctl(BTRFS_IOC_INO_LOOKUP) ret=%d, error: %s\n",
+ ret, strerror(errno));
+ return ret;
+ }
+
+ len = strlen(ino_lookup_arg.name);
+ if (*path_len < len)
+ return -EOVERFLOW;
+ strcat(path, ino_lookup_arg.name);
+ (*path_len) -= len;
+ }
+
+ if (*path_len < btrfs_stack_root_ref_name_len(backref_item))
+ return -EOVERFLOW;
+ strncat(path, (char *)(backref_item + 1),
+ btrfs_stack_root_ref_name_len(backref_item));
+ (*path_len) -= btrfs_stack_root_ref_name_len(backref_item);
+ return 0;
+}
+
static struct rb_node *tree_insert(struct rb_root *root,
struct subvol_info *si,
enum subvol_search_type type)
diff --git a/send-utils.h b/send-utils.h
index 78abf94..06af75f 100644
--- a/send-utils.h
+++ b/send-utils.h
@@ -70,7 +70,7 @@ struct subvol_info *subvol_uuid_search(struct
subvol_uuid_search *s,
void subvol_uuid_search_add(struct subvol_uuid_search *s,
struct subvol_info *si);
-
+int btrfs_subvolid_resolve(int fd, char *path, size_t path_len, u64 subvol_id);
char *path_cat(const char *p1, const char *p2);
char *path_cat3(const char *p1, const char *p2, const char *p3);
--
1.8.2.1
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David Sterba
2013-Apr-23 17:25 UTC
Re: [PATCH] Btrfs-progs: add function to map subvol ID to path
On Tue, Apr 23, 2013 at 12:18:55PM +0200, Stefan Behrens wrote:> Several tools like btrfs-send and btrfs-receive need to map a > subvolume ID to a filesystem path. The so far existing methods > in btrfs-list.c cause a horrible effort when performing this > operation (and the effort is dependent on the number of > existing subvolumes with quadratic effort). This commit adds a > function that is able to map a subvolume ID to a filesystem path > with an effort that is independent of the number of existing > subvolumes. > > In addition to this function, a command line frontend is added as well: > btrfs inspect-internal subvolid-resolve <subvolid> <path>Nice. The ''inspect'' section is imo right for such simple lookup. We could possibly extend it to print the path relative to the current default or currently mounted subvol, or teach ''subvol show'' to accept subvol ids as well. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html