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Allow rewrite skip cloned and snapshotted blocks

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Rewrite of cloned and snapshotted blocks can allocate additional
space, that may be undesired.  In some cases it may have sense
to still rewrite snapshotted blocks, expecting the snapshots to
rotate with time, freeing space.  In other cases rewrite of cloned
blocks may be acceptable, despite persistent space usage increase.
For this reason add them as separate flags to `zfs rewrite`.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Reviewed-by: Ameer Hamza <ahamza@ixsystems.com>
Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes #18179
This commit is contained in:
Alexander Motin
2026-02-09 13:17:56 -05:00
committed by GitHub
parent 15fbf534c6
commit 2646bd5585
13 changed files with 273 additions and 32 deletions
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module/zfs/zfs_vnops.c
+38 -1
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@@ -53,6 +53,7 @@
#include <sys/dsl_dataset.h>
#include <sys/spa.h>
#include <sys/txg.h>
#include <sys/brt.h>
#include <sys/dbuf.h>
#include <sys/policy.h>
#include <sys/zfeature.h>
@@ -1095,6 +1096,34 @@ zfs_write(znode_t *zp, zfs_uio_t *uio, int ioflag, cred_t *cr)
return (0);
}
/*
* Check if a block should be skipped during rewrite.
* Returns B_TRUE if block should be skipped.
*/
static boolean_t
zfs_rewrite_skip(dmu_buf_t *db, objset_t *os, uint64_t flags)
{
/*
* This may be slightly stale and racy, but should be OK for
* the advisory use.
*/
blkptr_t *bp = dmu_buf_get_blkptr(db);
if (bp == NULL)
return (B_TRUE);
if (flags & ZFS_REWRITE_SKIP_SNAPSHOT) {
if (dmu_objset_block_is_shared(os, bp))
return (B_TRUE);
}
if (flags & ZFS_REWRITE_SKIP_BRT) {
if (brt_maybe_exists(os->os_spa, bp))
return (B_TRUE);
}
return (B_FALSE);
}
/*
* Rewrite a range of file as-is without modification.
*
@@ -1113,7 +1142,11 @@ zfs_rewrite(znode_t *zp, uint64_t off, uint64_t len, uint64_t flags,
{
int error;
if ((flags & ~ZFS_REWRITE_PHYSICAL) != 0 || arg != 0)
#define ZFS_REWRITE_VALID_FLAGS \
(ZFS_REWRITE_PHYSICAL | ZFS_REWRITE_SKIP_SNAPSHOT | \
ZFS_REWRITE_SKIP_BRT)
if ((flags & ~ZFS_REWRITE_VALID_FLAGS) != 0 || arg != 0)
return (SET_ERROR(EINVAL));
zfsvfs_t *zfsvfs = ZTOZSB(zp);
@@ -1214,6 +1247,10 @@ zfs_rewrite(znode_t *zp, uint64_t off, uint64_t len, uint64_t flags,
nr += dbp[i]->db_size;
if (dmu_buf_is_dirty(dbp[i], tx))
continue;
if (zfs_rewrite_skip(dbp[i], zfsvfs->z_os, flags))
continue;
nw += dbp[i]->db_size;
if (flags & ZFS_REWRITE_PHYSICAL)
dmu_buf_will_rewrite(dbp[i], tx);