[PATCH] xfs: update superblock counters correctly for !lazysbcount

Gao Xiang
2021-04-27T01:12:26Z

From: Dave Chinner <dchinner@redhat.com>

Keep the mount superblock counters up to date for !lazysbcount
filesystems so that when we log the superblock they do not need
updating in any way because they are already correct.

It's found by what Zorro reported:
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
and I've seen no problem with this patch.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reported-by: Zorro Lang <zlang@redhat.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---

As per discussion earilier [1], use the way Dave suggested instead.
Also update the line to
mp->m_sb.sb_fdblocks += tp->t_fdblocks_delta + tp->t_res_fdblocks_delta;
so it can fix the case above.

with XFS debug off, xfstests auto testcases fail on my loop-device-based
testbed with this patch and Darrick's [2]:

generic/095 generic/300 generic/600 generic/607 xfs/073 xfs/148 xfs/273
xfs/293 xfs/491 xfs/492 xfs/495 xfs/503 xfs/505 xfs/506 xfs/514 xfs/515

MKFS_OPTIONS="-mcrc=0 -llazy-count=0"

and these testcases above still fail without these patches or with
XFS debug on, so I've seen no regression due to this patch.

[1] https://lore.kernel.org/r/20210422030102.GA63242@dread.disaster.area/
[2] https://lore.kernel.org/r/20210425154634.GZ3122264@magnolia/

fs/xfs/libxfs/xfs_sb.c | 16 +++++++++++++---
fs/xfs/xfs_trans.c | 3 +++
2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 60e6d255e5e2..dfbbcbd448c1 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -926,9 +926,19 @@ xfs_log_sb(
struct xfs_mount *mp = tp->t_mountp;
struct xfs_buf *bp = xfs_trans_getsb(tp);

- 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);
+ /*
+ * Lazy sb counters don't update the in-core superblock so do that now.
+ * If this is at unmount, the counters will be exactly correct, but at
+ * any other time they will only be ballpark correct because of
+ * reservations that have been taken out percpu counters. If we have an
+ * unclean shutdown, this will be corrected by log recovery rebuilding
+ * the counters from the AGF block counts.
+ */
+ if (xfs_sb_version_haslazysbcount(&mp->m_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);
+ }

xfs_sb_to_disk(bp->b_addr, &mp->m_sb);
xfs_trans_buf_set_type(tp, bp, XFS_BLFT_SB_BUF);
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index bcc978011869..1e37aa8eca5a 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -629,6 +629,9 @@ xfs_trans_unreserve_and_mod_sb(

/* apply remaining deltas */
spin_lock(&mp->m_sb_lock);
+ mp->m_sb.sb_fdblocks += tp->t_fdblocks_delta + tp->t_res_fdblocks_delta;
+ mp->m_sb.sb_icount += idelta;
+ mp->m_sb.sb_ifree += ifreedelta;
mp->m_sb.sb_frextents += rtxdelta;
mp->m_sb.sb_dblocks += tp->t_dblocks_delta;
mp->m_sb.sb_agcount += tp->t_agcount_delta;
--
2.27.0