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Restrict cloning with different properties

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While technically its not a problem to clone between datasets with
different properties, it might create expectation of new properties
being applied during data move, while actually it won't happen.
For copies and checksum it may mean incorrect safety expectations.
For dedup, compression and special_small_blocks -- performance and
space usage. New zfs_bclone_strict_properties tunable controls it.

Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes #18180
This commit is contained in:
Alexander Motin
2026-02-10 12:53:24 -05:00
committed by GitHub
parent 1412bdc6c2
commit aa29455dd7
17 changed files with 193 additions and 24 deletions
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module/zfs/zfs_vnops.c
+44
View File
@@ -69,6 +69,12 @@
*/
int zfs_bclone_enabled = 1;
/*
* Restricts block cloning between datasets with different properties
* (checksum, compression, copies, dedup, or special_small_blocks).
*/
int zfs_bclone_strict_properties = 1;
/*
* When set to 1 the FICLONE and FICLONERANGE ioctls will wait for any dirty
* data to be written to disk before proceeding. This ensures that the clone
@@ -1677,6 +1683,21 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
return (SET_ERROR(EXDEV));
}
/*
* Cloning between datasets with different properties is possible,
* but it may cause confusions when copying data between them and
* expecting new properties to apply.
*/
if (zfs_bclone_strict_properties && inos != outos &&
!inzfsvfs->z_issnap &&
(inos->os_checksum != outos->os_checksum ||
inos->os_compress != outos->os_compress ||
inos->os_copies != outos->os_copies ||
inos->os_dedup_checksum != outos->os_dedup_checksum)) {
zfs_exit_two(inzfsvfs, outzfsvfs, FTAG);
return (SET_ERROR(EXDEV));
}
error = zfs_verify_zp(inzp);
if (error == 0)
error = zfs_verify_zp(outzp);
@@ -1758,6 +1779,26 @@ zfs_clone_range(znode_t *inzp, uint64_t *inoffp, znode_t *outzp,
inblksz = inzp->z_blksz;
/*
* Cloning between datasets with different special_small_blocks would
* bypass storage tier migration that would occur with a regular copy.
*/
if (zfs_bclone_strict_properties && inos != outos &&
!inzfsvfs->z_issnap && spa_has_special(dmu_objset_spa(inos))) {
uint64_t in_smallblk = inos->os_zpl_special_smallblock;
uint64_t out_smallblk = outos->os_zpl_special_smallblock;
if (in_smallblk != out_smallblk) {
uint64_t min_smallblk = MIN(in_smallblk, out_smallblk);
uint64_t max_smallblk = MAX(in_smallblk, out_smallblk);
if (min_smallblk < inblksz &&
(inos->os_compress != ZIO_COMPRESS_OFF ||
max_smallblk >= inblksz)) {
error = SET_ERROR(EXDEV);
goto unlock;
}
}
}
/*
* We cannot clone into a file with different block size if we can't
* grow it (block size is already bigger, has more than one block, or
@@ -2116,6 +2157,9 @@ ZFS_MODULE_PARAM(zfs_vnops, zfs_vnops_, read_chunk_size, U64, ZMOD_RW,
ZFS_MODULE_PARAM(zfs, zfs_, bclone_enabled, INT, ZMOD_RW,
"Enable block cloning");
ZFS_MODULE_PARAM(zfs, zfs_, bclone_strict_properties, INT, ZMOD_RW,
"Restrict cross-dataset cloning with different properties");
ZFS_MODULE_PARAM(zfs, zfs_, bclone_wait_dirty, INT, ZMOD_RW,
"Wait for dirty blocks when cloning");