Patch "xfs: make sure sb_fdblocks is non-negative" has been added to the 6.1-stable tree

This is a note to let you know that I've just added the patch titled

    xfs: make sure sb_fdblocks is non-negative

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xfs-make-sure-sb_fdblocks-is-non-negative.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.


From [email protected] Wed Apr 30 23:32:01 2025
From: Leah Rumancik <[email protected]>
Date: Wed, 30 Apr 2025 14:27:00 -0700
Subject: xfs: make sure sb_fdblocks is non-negative
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], Wengang Wang <[email protected]>, Chandan Babu R <[email protected]>, Leah Rumancik <[email protected]>
Message-ID: <[email protected]>

From: Wengang Wang <[email protected]>

[ Upstream commit 58f880711f2ba53fd5e959875aff5b3bf6d5c32e ]

A user with a completely full filesystem experienced an unexpected
shutdown when the filesystem tried to write the superblock during
runtime.
kernel shows the following dmesg:

[    8.176281] XFS (dm-4): Metadata corruption detected at xfs_sb_write_verify+0x60/0x120 [xfs], xfs_sb block 0x0
[    8.177417] XFS (dm-4): Unmount and run xfs_repair
[    8.178016] XFS (dm-4): First 128 bytes of corrupted metadata buffer:
[    8.178703] 00000000: 58 46 53 42 00 00 10 00 00 00 00 00 01 90 00 00  XFSB............
[    8.179487] 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
[    8.180312] 00000020: cf 12 dc 89 ca 26 45 29 92 e6 e3 8d 3b b8 a2 c3  .....&E)....;...
[    8.181150] 00000030: 00 00 00 00 01 00 00 06 00 00 00 00 00 00 00 80  ................
[    8.182003] 00000040: 00 00 00 00 00 00 00 81 00 00 00 00 00 00 00 82  ................
[    8.182004] 00000050: 00 00 00 01 00 64 00 00 00 00 00 04 00 00 00 00  .....d..........
[    8.182004] 00000060: 00 00 64 00 b4 a5 02 00 02 00 00 08 00 00 00 00  ..d.............
[    8.182005] 00000070: 00 00 00 00 00 00 00 00 0c 09 09 03 17 00 00 19  ................
[    8.182008] XFS (dm-4): Corruption of in-memory data detected.  Shutting down filesystem
[    8.182010] XFS (dm-4): Please unmount the filesystem and rectify the problem(s)

When xfs_log_sb writes super block to disk, b_fdblocks is fetched from
m_fdblocks without any lock. As m_fdblocks can experience a positive ->
negative -> positive changing when the FS reaches fullness (see
xfs_mod_fdblocks). So there is a chance that sb_fdblocks is negative, and
because sb_fdblocks is type of unsigned long long, it reads super big.
And sb_fdblocks being bigger than sb_dblocks is a problem during log
recovery, xfs_validate_sb_write() complains.

Fix:
As sb_fdblocks will be re-calculated during mount when lazysbcount is
enabled, We just need to make xfs_validate_sb_write() happy -- make sure
sb_fdblocks is not nenative. This patch also takes care of other percpu
counters in xfs_log_sb.

Signed-off-by: Wengang Wang <[email protected]>
Reviewed-by: Darrick J. Wong <[email protected]>
Signed-off-by: Chandan Babu R <[email protected]>
Signed-off-by: Leah Rumancik <[email protected]>
Acked-by: "Darrick J. Wong" <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 fs/xfs/libxfs/xfs_sb.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -1022,11 +1022,12 @@ xfs_log_sb(
 	 * and hence we don't need have to update it here.
 	 */
 	if (xfs_has_lazysbcount(mp)) {
-		mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount);
+		mp->m_sb.sb_icount = percpu_counter_sum_positive(&mp->m_icount);
 		mp->m_sb.sb_ifree = min_t(uint64_t,
-				percpu_counter_sum(&mp->m_ifree),
+				percpu_counter_sum_positive(&mp->m_ifree),
 				mp->m_sb.sb_icount);
-		mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+		mp->m_sb.sb_fdblocks =
+				percpu_counter_sum_positive(&mp->m_fdblocks);
 	}
 
 	xfs_sb_to_disk(bp->b_addr, &mp->m_sb);


Patches currently in stable-queue which might be from [email protected] are

queue-6.1/xfs-revert-commit-44af6c7e59b12.patch
queue-6.1/xfs-make-the-seq-argument-to-xfs_bmapi_convert_delalloc-optional.patch
queue-6.1/xfs-check-opcode-and-iovec-count-match-in-xlog_recover_attri_commit_pass2.patch
queue-6.1/xfs-allow-symlinks-with-short-remote-targets.patch
queue-6.1/xfs-match-lock-mode-in-xfs_buffered_write_iomap_begin.patch
queue-6.1/xfs-require-xfs_sb_feat_incompat_log_xattrs-for-attr-log-intent-item-recovery.patch
queue-6.1/xfs-allow-unlinked-symlinks-and-dirs-with-zero-size.patch
queue-6.1/xfs-restrict-when-we-try-to-align-cow-fork-delalloc-to-cowextsz-hints.patch
queue-6.1/xfs-fix-xfs_bmap_add_extent_delay_real-for-partial-conversions.patch
queue-6.1/xfs-validate-recovered-name-buffers-when-recovering-xattr-items.patch
queue-6.1/xfs-make-xfs_bmapi_convert_delalloc-to-allocate-the-target-offset.patch
queue-6.1/xfs-convert-delayed-extents-to-unwritten-when-zeroing-post-eof-blocks.patch
queue-6.1/xfs-fix-freeing-speculative-preallocations-for-preallocated-files.patch
queue-6.1/xfs-make-sure-sb_fdblocks-is-non-negative.patch
queue-6.1/xfs-remove-a-racy-if_bytes-check-in-xfs_reflink_end_cow_extent.patch
queue-6.1/xfs-fix-error-returns-from-xfs_bmapi_write.patch