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btrfs-util: Add BTRFS_SNAPSHOT_LOCK_BSD

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When making ephemeral snapshots of subvolumes whose cleanup depends on
whether they're locked or not, it's necessary to have the lock from the
very beginning, so let's support that with a new BTRFS_SNAPSHOT_LOCK_BSD
flag.
This commit is contained in:
Daan De Meyer
2023-03-28 12:32:51 +02:00
parent 01428141ba
commit d54f60c2af
3 changed files with 61 additions and 8 deletions
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49
src/shared/btrfs-util.c
View File

@@ -1363,9 +1363,26 @@ static int subvol_snapshot_children(
if (ioctl(new_fd, BTRFS_IOC_SNAP_CREATE_V2, &vol_args) < 0)
return -errno;
if (FLAGS_SET(flags, BTRFS_SNAPSHOT_LOCK_BSD)) {
subvolume_fd = xopenat_lock(new_fd, subvolume,
O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW,
/* xopen_flags = */ 0,
/* mode = */ 0,
LOCK_BSD,
LOCK_EX);
if (subvolume_fd < 0)
return subvolume_fd;
r = btrfs_is_subvol_fd(subvolume_fd);
if (r < 0)
return r;
if (r == 0)
return -EEXIST;
}
if (!(flags & BTRFS_SNAPSHOT_RECURSIVE) &&
!(flags & BTRFS_SNAPSHOT_QUOTA))
return 0;
return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
if (old_subvol_id == 0) {
r = btrfs_subvol_get_id_fd(old_fd, &old_subvol_id);
@@ -1385,7 +1402,7 @@ static int subvol_snapshot_children(
if (flags & BTRFS_SNAPSHOT_QUOTA)
(void) copy_subtree_quota_limits(new_fd, old_subvol_id, new_subvol_id);
return 0;
return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
}
args.key.min_offset = args.key.max_offset = old_subvol_id;
@@ -1480,7 +1497,8 @@ static int subvol_snapshot_children(
return k;
}
r = subvol_snapshot_children(old_child_fd, new_child_fd, p, sh->objectid, flags & ~BTRFS_SNAPSHOT_FALLBACK_COPY);
r = subvol_snapshot_children(old_child_fd, new_child_fd, p, sh->objectid,
flags & ~(BTRFS_SNAPSHOT_FALLBACK_COPY|BTRFS_SNAPSHOT_LOCK_BSD));
/* Restore the readonly flag */
if (flags & BTRFS_SNAPSHOT_READ_ONLY) {
@@ -1503,7 +1521,7 @@ static int subvol_snapshot_children(
if (flags & BTRFS_SNAPSHOT_QUOTA)
(void) copy_subtree_quota_limits(new_fd, old_subvol_id, new_subvol_id);
return 0;
return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
}
int btrfs_subvol_snapshot_at_full(
@@ -1517,7 +1535,7 @@ int btrfs_subvol_snapshot_at_full(
void *userdata) {
_cleanup_free_ char *subvolume = NULL;
_cleanup_close_ int old_fd = -EBADF, new_fd = -EBADF;
_cleanup_close_ int old_fd = -EBADF, new_fd = -EBADF, subvolume_fd = -EBADF;
int r;
assert(dir_fdf >= 0 || dir_fdf == AT_FDCWD);
@@ -1556,6 +1574,25 @@ int btrfs_subvol_snapshot_at_full(
} else if (r < 0)
return r;
if (FLAGS_SET(flags, BTRFS_SNAPSHOT_LOCK_BSD)) {
subvolume_fd = xopenat_lock(new_fd, subvolume,
O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW,
/* xopen_flags = */ 0,
/* mode = */ 0,
LOCK_BSD,
LOCK_EX);
if (subvolume_fd < 0)
return subvolume_fd;
if (!plain_directory) {
r = btrfs_is_subvol_fd(subvolume_fd);
if (r < 0)
return r;
if (r == 0)
return -EEXIST;
}
}
r = copy_directory_at_full(
dir_fdf, from,
new_fd, subvolume,
@@ -1587,7 +1624,7 @@ int btrfs_subvol_snapshot_at_full(
}
}
return 0;
return flags & BTRFS_SNAPSHOT_LOCK_BSD ? TAKE_FD(subvolume_fd) : 0;
fallback_fail:
(void) rm_rf_at(new_fd, subvolume, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME);

1
src/shared/btrfs-util.h
View File

@@ -36,6 +36,7 @@ typedef enum BtrfsSnapshotFlags {
BTRFS_SNAPSHOT_FALLBACK_IMMUTABLE = 1 << 5, /* When we can't create a subvolume, use the FS_IMMUTABLE attribute for indicating read-only */
BTRFS_SNAPSHOT_SIGINT = 1 << 6, /* Check for SIGINT regularly, and return EINTR if seen */
BTRFS_SNAPSHOT_SIGTERM = 1 << 7, /* Ditto, but for SIGTERM */
BTRFS_SNAPSHOT_LOCK_BSD = 1 << 8, /* Return a BSD exclusively locked file descriptor referring to snapshot subvolume/directory. */
} BtrfsSnapshotFlags;
typedef enum BtrfsRemoveFlags {

19
src/test/test-btrfs.c
View File

@@ -4,6 +4,7 @@
#include "btrfs-util.h"
#include "fd-util.h"
#include "fs-util.h"
#include "fileio.h"
#include "format-util.h"
#include "log.h"
@@ -62,6 +63,14 @@ int main(int argc, char *argv[]) {
if (r < 0)
log_error_errno(r, "Failed to make snapshot: %m");
r = btrfs_subvol_snapshot_at(AT_FDCWD, "/xxxtest", AT_FDCWD, "/xxxtest4", BTRFS_SNAPSHOT_LOCK_BSD);
if (r < 0)
log_error_errno(r, "Failed to make snapshot: %m");
if (r >= 0)
assert_se(xopenat_lock(AT_FDCWD, "/xxxtest4", 0, 0, 0, LOCK_BSD, LOCK_EX|LOCK_NB) == -EAGAIN);
safe_close(r);
r = btrfs_subvol_remove("/xxxtest", BTRFS_REMOVE_QUOTA);
if (r < 0)
log_error_errno(r, "Failed to remove subvolume: %m");
@@ -74,6 +83,10 @@ int main(int argc, char *argv[]) {
if (r < 0)
log_error_errno(r, "Failed to remove subvolume: %m");
r = btrfs_subvol_remove("/xxxtest4", BTRFS_REMOVE_QUOTA);
if (r < 0)
log_error_errno(r, "Failed to remove subvolume: %m");
r = btrfs_subvol_snapshot_at(AT_FDCWD, "/etc", AT_FDCWD, "/etc2",
BTRFS_SNAPSHOT_READ_ONLY|BTRFS_SNAPSHOT_FALLBACK_COPY);
if (r < 0)
@@ -161,13 +174,15 @@ int main(int argc, char *argv[]) {
if (r < 0)
log_error_errno(r, "Failed to query quota: %m");
assert_se(quota.referenced_max == 4ULL * 1024 * 1024 * 1024);
if (r >= 0)
assert_se(quota.referenced_max == 4ULL * 1024 * 1024 * 1024);
r = btrfs_subvol_get_subtree_quota("/xxxquotatest2", 0, &quota);
if (r < 0)
log_error_errno(r, "Failed to query quota: %m");
assert_se(quota.referenced_max == 5ULL * 1024 * 1024 * 1024);
if (r >= 0)
assert_se(quota.referenced_max == 5ULL * 1024 * 1024 * 1024);
r = btrfs_subvol_remove("/xxxquotatest", BTRFS_REMOVE_QUOTA|BTRFS_REMOVE_RECURSIVE);
if (r < 0)