There are many paths which could trigger xfs_log_sb(), e.g.
xfs_bmap_add_attrfork()
-> xfs_log_sb()
, which overrides on-disk fdblocks by in-core per-CPU fdblocks.
However, for !lazysbcount cases, on-disk fdblocks is actually updated
by xfs_trans_apply_sb_deltas(), and generally it isn't equal to
in-core per-CPU fdblocks due to xfs_reserve_blocks() or whatever,
see the comment in xfs_unmountfs().
It could be observed by the following steps reported by Zorro:
1. mkfs.xfs -f -l lazy-count=0 -m crc=0 $dev
2. mount $dev $mnt
3. fsstress -d $mnt -p 100 -n 1000 (maybe need more or less io load)
4. umount $mnt
5. xfs_repair -n $dev
yet due to commit f46e5a174655 ("xfs: fold sbcount quiesce logging
into log covering"), xfs_sync_sb() will also be triggered if log
covering is needed and !lazysbcount when xfs_unmountfs(), so hard
to reproduce on kernel 5.12+ for clean unmount.
on-disk sb_icount and sb_ifree are also updated in
xfs_trans_apply_sb_deltas() for !lazysbcount cases, however, which
are always equal to per-CPU counters, so only fdblocks matters.
After this patch, I've seen no strange so far on older kernels
for the testcase above without lazysbcount.
Reported-by: Zorro Lang <zlang@xxxxxxxxxx>
Reviewed-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx>
---
changes since v1:
- update commit message.
fs/xfs/libxfs/xfs_sb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 60e6d255e5e2..423dada3f64c 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -928,7 +928,13 @@ xfs_log_sb(
mp->m_sb.sb_icount = percpu_counter_sum(&mp->m_icount);
mp->m_sb.sb_ifree = percpu_counter_sum(&mp->m_ifree);
- mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+ if (!xfs_sb_version_haslazysbcount(&mp->m_sb)) {
+ struct xfs_dsb *dsb = bp->b_addr;
+
+ mp->m_sb.sb_fdblocks = be64_to_cpu(dsb->sb_fdblocks);
+ } else {
+ mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
+ }
xfs_sb_to_disk(bp->b_addr, &mp->m_sb);
xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
--
2.27.0
