When lazysbcount is enabled, fsstress and loop mount/unmount test report
the following problems:
XFS (loop0): SB summary counter sanity check failed
XFS (loop0): Metadata corruption detected at xfs_sb_write_verify+0x13b/0x460,
xfs_sb block 0x0
XFS (loop0): Unmount and run xfs_repair
XFS (loop0): First 128 bytes of corrupted metadata buffer:
00000000: 58 46 53 42 00 00 10 00 00 00 00 00 00 28 00 00 XFSB.........(..
00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00000020: 69 fb 7c cd 5f dc 44 af 85 74 e0 cc d4 e3 34 5a i.|._.D..t....4Z
00000030: 00 00 00 00 00 20 00 06 00 00 00 00 00 00 00 80 ..... ..........
00000040: 00 00 00 00 00 00 00 81 00 00 00 00 00 00 00 82 ................
00000050: 00 00 00 01 00 0a 00 00 00 00 00 04 00 00 00 00 ................
00000060: 00 00 0a 00 b4 b5 02 00 02 00 00 08 00 00 00 00 ................
00000070: 00 00 00 00 00 00 00 00 0c 09 09 03 14 00 00 19 ................
XFS (loop0): Corruption of in-memory data (0x8) detected at _xfs_buf_ioapply
+0xe1e/0x10e0 (fs/xfs/xfs_buf.c:1580). Shutting down filesystem.
XFS (loop0): Please unmount the filesystem and rectify the problem(s)
XFS (loop0): log mount/recovery failed: error -117
XFS (loop0): log mount failed
This corruption will shutdown the file system and the file system will
no longer be mountable. The following script can reproduce the problem,
but it may take a long time.
#!/bin/bash
device=/dev/sda
testdir=/mnt/test
round=0
function fail()
{
echo "$*"
exit 1
}
mkdir -p $testdir
while [ $round -lt 10000 ]
do
echo "******* round $round ********"
mkfs.xfs -f $device
mount $device $testdir || fail "mount failed!"
fsstress -d $testdir -l 0 -n 10000 -p 4 >/dev/null &
sleep 4
killall -w fsstress
umount $testdir
xfs_repair -e $device > /dev/null
if [ $? -eq 2 ];then
echo "ERR CODE 2: Dirty log exception during repair."
exit 1
fi
round=$(($round+1))
done
With lazysbcount is enabled, There is no additional lock protection for
reading m_ifree and m_icount in xfs_log_sb(), if other cpu modifies the
m_ifree, this will make the m_ifree greater than m_icount. For example,
consider the following sequence and ifreedelta is postive:
CPU0 CPU1
xfs_log_sb xfs_trans_unreserve_and_mod_sb
---------- ------------------------------
percpu_counter_sum(&mp->m_icount)
percpu_counter_add_batch(&mp->m_icount,
idelta, XFS_ICOUNT_BATCH)
percpu_counter_add(&mp->m_ifree, ifreedelta);
percpu_counter_sum(&mp->m_ifree)
After this, incorrect inode count (sb_ifree > sb_icount) will be writen to
the log. In the subsequent writing of sb, incorrect inode count (sb_ifree >
sb_icount) will fail to pass the boundary check in xfs_validate_sb_write()
that cause the file system shutdown.
When lazysbcount is enabled, we don't need to guarantee that Lazy sb
counters are completely correct, but we do need to guarantee that sb_ifree
<= sb_icount. On the other hand, the constraint that m_ifree <= m_icount
must be satisfied any time that there /cannot/ be other threads allocating
or freeing inode chunks. If the constraint is violated under these
circumstances, sb_i{count,free} (the ondisk superblock inode counters)
maybe incorrect and need to be marked sick at unmount, the count will
be rebuilt on the next mount.
Fixes: 8756a5af1819 ("libxfs: add more bounds checking to sb sanity checks")
Signed-off-by: Long Li <leo.lilong@xxxxxxxxxx>
---
v3:
- Corrected the description of the cause of the problem
- Add a check for m_icount and m_ifree at unmout
v2:
- Add scripts that could reproduce the problem
- Guaranteed that ifree will never be logged as being greater than icount
fs/xfs/libxfs/xfs_sb.c | 4 +++-
fs/xfs/xfs_mount.c | 15 +++++++++++++++
2 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index a20cade590e9..1eeecf2eb2a7 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -972,7 +972,9 @@ xfs_log_sb(
*/
if (xfs_has_lazysbcount(mp)) {
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_ifree = min_t(uint64_t,
+ percpu_counter_sum(&mp->m_ifree),
+ mp->m_sb.sb_icount);
mp->m_sb.sb_fdblocks = percpu_counter_sum(&mp->m_fdblocks);
}
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index e8bb3c2e847e..fb87ffb48f7f 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -538,6 +538,20 @@ xfs_check_summary_counts(
return 0;
}
+static void
+xfs_unmount_check(
+ struct xfs_mount *mp)
+{
+ if (xfs_is_shutdown(mp))
+ return;
+
+ if (percpu_counter_sum(&mp->m_ifree) >
+ percpu_counter_sum(&mp->m_icount)) {
+ xfs_alert(mp, "ifree/icount mismatch at unmount");
+ xfs_fs_mark_sick(mp, XFS_SICK_FS_COUNTERS);
+ }
+}
+
/*
* Flush and reclaim dirty inodes in preparation for unmount. Inodes and
* internal inode structures can be sitting in the CIL and AIL at this point,
@@ -1077,6 +1091,7 @@ xfs_unmountfs(
if (error)
xfs_warn(mp, "Unable to free reserved block pool. "
"Freespace may not be correct on next mount.");
+ xfs_unmount_check(mp);
xfs_log_unmount(mp);
xfs_da_unmount(mp);
--
2.31.1
