Commit d84d6c1a7f1e for kernel
commit d84d6c1a7f1e2de9e601703a326a4c1b7b421943
Author: Norbert Szetei <norbert@doyensec.com>
Date: Wed Oct 7 16:43:22 2026 +0200
xfs: stop exchanging reflink flags when exchanging mappings
When an exchange covers both files from offset 0 to i_disk_size,
xmi_can_exchange_reflink_flags() assumes every mapping moved and hands
the reflink flag over to the other file.
That assumption is wrong. A file can still own shared blocks past
i_disk_size, e.g. after EXCHANGE_RANGE_TO_EOF sets a smaller size
without unmapping anything. The flag is cleared anyway, and the next
write to such a block happens in place instead of CoW, corrupting the
other file that shares it.
Commit a23eca88448e ("xfs: fix exchange-range reflink flag clearing
issue with INO1_WRITTEN") fixed one instance of this. Rather than add
another special case, stop moving the flags.
xfs_exchmaps_ensure_reflink() already sets the flag on both inodes
before the exchange, so both just keep it.
Nothing sets CLEAR_INO{1,2}_REFLINK anymore. Intents logged by older
kernels may still carry them; recovery already masks them off, so they
stay in the log format mask and are ignored.
XFS_IOC_SWAPEXT has the same problem: it moves the reflink flag from
one inode to the other along with the extents. Just removing that is
not enough here: the exchange path flags both inodes up front in
xfs_exchmaps_ensure_reflink(), but swapext has no such step, so the
inode receiving the shared extents would be left without the flag.
Set it on both inodes instead, and make sure both have a CoW fork,
since an inode with the reflink flag is expected to have one.
The flag now stays until FALLOC_FL_UNSHARE_RANGE, xfs_scrub, or a
truncate to zero removes it.
Fixes: 966ceafc7a43 ("xfs: create deferred log items for file mapping exchanges")
Fixes: f0bc4d134b46 ("xfs: swap inode reflink flags when swapping inode extents")
Cc: stable@vger.kernel.org # v6.10
Assisted-by: LLM
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
diff --git a/fs/xfs/libxfs/xfs_exchmaps.c b/fs/xfs/libxfs/xfs_exchmaps.c
index 6a66b6075e0a..7af8ee35c89d 100644
--- a/fs/xfs/libxfs/xfs_exchmaps.c
+++ b/fs/xfs/libxfs/xfs_exchmaps.c
@@ -49,7 +49,7 @@ struct xfs_exchmaps_adjacent {
.right2 = { .br_startblock = HOLESTARTBLOCK }, \
}
-/* Information to reset reflink flag / CoW fork state after an exchange. */
+/* Information to reset CoW fork state after an exchange. */
/*
* If the reflink flag is set on either inode, make sure it has an incore CoW
@@ -127,9 +127,7 @@ xmi_has_more_exchange_work(const struct xfs_exchmaps_intent *xmi)
static inline bool
xmi_has_postop_work(const struct xfs_exchmaps_intent *xmi)
{
- return xmi->xmi_flags & (XFS_EXCHMAPS_CLEAR_INO1_REFLINK |
- XFS_EXCHMAPS_CLEAR_INO2_REFLINK |
- __XFS_EXCHMAPS_INO2_SHORTFORM);
+ return xmi->xmi_flags & __XFS_EXCHMAPS_INO2_SHORTFORM;
}
/* Check all mappings to make sure we can actually exchange them. */
@@ -525,18 +523,6 @@ xfs_exchmaps_link_to_sf(
return error;
}
-/* Clear the reflink flag after an exchange. */
-static inline void
-xfs_exchmaps_clear_reflink(
- struct xfs_trans *tp,
- struct xfs_inode *ip)
-{
- trace_xfs_reflink_unset_inode_flag(ip);
-
- ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
- xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
-}
-
/* Finish whatever work might come after an exchange operation. */
static int
xfs_exchmaps_do_postop_work(
@@ -557,16 +543,6 @@ xfs_exchmaps_do_postop_work(
return error;
}
- if (xmi->xmi_flags & XFS_EXCHMAPS_CLEAR_INO1_REFLINK) {
- xfs_exchmaps_clear_reflink(tp, xmi->xmi_ip1);
- xmi->xmi_flags &= ~XFS_EXCHMAPS_CLEAR_INO1_REFLINK;
- }
-
- if (xmi->xmi_flags & XFS_EXCHMAPS_CLEAR_INO2_REFLINK) {
- xfs_exchmaps_clear_reflink(tp, xmi->xmi_ip2);
- xmi->xmi_flags &= ~XFS_EXCHMAPS_CLEAR_INO2_REFLINK;
- }
-
return 0;
}
@@ -948,46 +924,13 @@ xfs_exchmaps_intent_destroy_cache(void)
}
/*
- * Decide if we will exchange the reflink flags between the two files after the
- * exchange. The only time we want to do this is if we're exchanging all
- * mappings under EOF and the inode reflink flags have different states.
+ * Allocate and initialize a new incore intent item from a request.
*/
-static inline bool
-xmi_can_exchange_reflink_flags(
- const struct xfs_exchmaps_req *req,
- unsigned int reflink_state)
-{
- struct xfs_mount *mp = req->ip1->i_mount;
-
- /*
- * The INO1_WRITTEN optimization can skip exchanging hole and
- * unwritten mappings, which means we cannot guarantee that all
- * shared extents actually moved to the other file. Clearing the
- * reflink flag of an inode that still holds shared extents breaks
- * the CoW write path, so refuse to exchange the flags in that case.
- */
- if (req->flags & XFS_EXCHMAPS_INO1_WRITTEN)
- return false;
-
- if (hweight32(reflink_state) != 1)
- return false;
- if (req->startoff1 != 0 || req->startoff2 != 0)
- return false;
- if (req->blockcount != XFS_B_TO_FSB(mp, req->ip1->i_disk_size))
- return false;
- if (req->blockcount != XFS_B_TO_FSB(mp, req->ip2->i_disk_size))
- return false;
- return true;
-}
-
-
-/* Allocate and initialize a new incore intent item from a request. */
struct xfs_exchmaps_intent *
xfs_exchmaps_init_intent(
const struct xfs_exchmaps_req *req)
{
struct xfs_exchmaps_intent *xmi;
- unsigned int rs = 0;
xmi = kmem_cache_zalloc(xfs_exchmaps_intent_cache,
GFP_NOFS | __GFP_NOFAIL);
@@ -1011,23 +954,6 @@ xfs_exchmaps_init_intent(
xmi->xmi_isize2 = req->ip1->i_disk_size;
}
- /* Record the state of each inode's reflink flag before the op. */
- if (xfs_is_reflink_inode(req->ip1))
- rs |= 1;
- if (xfs_is_reflink_inode(req->ip2))
- rs |= 2;
-
- /*
- * Figure out if we're clearing the reflink flags (which effectively
- * exchanges them) after the operation.
- */
- if (xmi_can_exchange_reflink_flags(req, rs)) {
- if (rs & 1)
- xmi->xmi_flags |= XFS_EXCHMAPS_CLEAR_INO1_REFLINK;
- if (rs & 2)
- xmi->xmi_flags |= XFS_EXCHMAPS_CLEAR_INO2_REFLINK;
- }
-
if (S_ISDIR(VFS_I(xmi->xmi_ip2)->i_mode) ||
S_ISLNK(VFS_I(xmi->xmi_ip2)->i_mode))
xmi->xmi_flags |= __XFS_EXCHMAPS_INO2_SHORTFORM;
diff --git a/fs/xfs/libxfs/xfs_log_format.h b/fs/xfs/libxfs/xfs_log_format.h
index a4e1b3eb425c..6e620380d5dc 100644
--- a/fs/xfs/libxfs/xfs_log_format.h
+++ b/fs/xfs/libxfs/xfs_log_format.h
@@ -927,10 +927,8 @@ struct xfs_xmi_log_format {
*/
#define XFS_EXCHMAPS_INO1_WRITTEN (1ULL << 2)
-/* Clear the reflink flag from inode1 after the operation. */
+/* No longer set, but older intents may carry them; keep them valid. */
#define XFS_EXCHMAPS_CLEAR_INO1_REFLINK (1ULL << 3)
-
-/* Clear the reflink flag from inode2 after the operation. */
#define XFS_EXCHMAPS_CLEAR_INO2_REFLINK (1ULL << 4)
#define XFS_EXCHMAPS_LOGGED_FLAGS (XFS_EXCHMAPS_ATTR_FORK | \
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 268d159339d0..865aec3ae5ab 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1544,7 +1544,6 @@ xfs_swap_extents(
struct xfs_bstat *sbp = &sxp->sx_stat;
int src_log_flags, target_log_flags;
int error = 0;
- uint64_t f;
int resblks = 0;
unsigned int flags = 0;
struct timespec64 ctime, mtime;
@@ -1700,14 +1699,12 @@ xfs_swap_extents(
if (error)
goto out_trans_cancel;
- /* Do we have to swap reflink flags? */
- if ((ip->i_diflags2 & XFS_DIFLAG2_REFLINK) ^
- (tip->i_diflags2 & XFS_DIFLAG2_REFLINK)) {
- f = ip->i_diflags2 & XFS_DIFLAG2_REFLINK;
- ip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
- ip->i_diflags2 |= tip->i_diflags2 & XFS_DIFLAG2_REFLINK;
- tip->i_diflags2 &= ~XFS_DIFLAG2_REFLINK;
- tip->i_diflags2 |= f & XFS_DIFLAG2_REFLINK;
+ /* Either inode may now own shared blocks; flag both, with CoW forks. */
+ if ((ip->i_diflags2 | tip->i_diflags2) & XFS_DIFLAG2_REFLINK) {
+ ip->i_diflags2 |= XFS_DIFLAG2_REFLINK;
+ tip->i_diflags2 |= XFS_DIFLAG2_REFLINK;
+ xfs_ifork_init_cow(ip);
+ xfs_ifork_init_cow(tip);
}
/* Swap the cow forks. */