From: Darrick J. Wong djwong@kernel.org
[ Upstream commit 86d40f1e49e9a909d25c35ba01bea80dbcd758cb ]
xfs/434 and xfs/436 have been reporting occasional memory leaks of xfs_dquot objects. These tests themselves were the messenger, not the culprit, since they unload the xfs module, which trips the slub debugging code while tearing down all the xfs slab caches:
============================================================================= BUG xfs_dquot (Tainted: G W ): Objects remaining in xfs_dquot on __kmem_cache_shutdown() -----------------------------------------------------------------------------
Slab 0xffffea000606de00 objects=30 used=5 fp=0xffff888181b78a78 flags=0x17ff80000010200(slab|head|node=0|zone=2|lastcpupid=0xfff) CPU: 0 PID: 3953166 Comm: modprobe Tainted: G W 5.18.0-rc6-djwx #rc6 d5824be9e46a2393677bda868f9b154d917ca6a7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20171121_152543-x86-ol7-builder-01.us.oracle.com-4.el7.1 04/01/2014
Since we don't generally rmmod the xfs module between fstests, this means that xfs/434 is really just the canary in the coal mine -- something leaked a dquot, but we don't know who. After days of pounding on fstests with kmemleak enabled, I finally got it to spit this out:
unreferenced object 0xffff8880465654c0 (size 536): comm "u10:4", pid 88, jiffies 4294935810 (age 29.512s) hex dump (first 32 bytes): 60 4a 56 46 80 88 ff ff 58 ea e4 5c 80 88 ff ff `JVF....X...... 00 e0 52 49 80 88 ff ff 01 00 01 00 00 00 00 00 ..RI............ backtrace: [<ffffffffa0740f6c>] xfs_dquot_alloc+0x2c/0x530 [xfs] [<ffffffffa07443df>] xfs_qm_dqread+0x6f/0x330 [xfs] [<ffffffffa07462a2>] xfs_qm_dqget+0x132/0x4e0 [xfs] [<ffffffffa0756bb0>] xfs_qm_quotacheck_dqadjust+0xa0/0x3e0 [xfs] [<ffffffffa075724d>] xfs_qm_dqusage_adjust+0x35d/0x4f0 [xfs] [<ffffffffa06c9068>] xfs_iwalk_ag_recs+0x348/0x5d0 [xfs] [<ffffffffa06c95d3>] xfs_iwalk_run_callbacks+0x273/0x540 [xfs] [<ffffffffa06c9e8d>] xfs_iwalk_ag+0x5ed/0x890 [xfs] [<ffffffffa06ca22f>] xfs_iwalk_ag_work+0xff/0x170 [xfs] [<ffffffffa06d22c9>] xfs_pwork_work+0x79/0x130 [xfs] [<ffffffff81170bb2>] process_one_work+0x672/0x1040 [<ffffffff81171b1b>] worker_thread+0x59b/0xec0 [<ffffffff8118711e>] kthread+0x29e/0x340 [<ffffffff810032bf>] ret_from_fork+0x1f/0x30
Now we know that quotacheck is at fault, but even this report was canaryish -- it was triggered by xfs/494, which doesn't actually mount any filesystems. (kmemleak can be a little slow to notice leaks, even with fstests repeatedly whacking it to look for them.) Looking at the *previous* fstest, however, showed that the test run before xfs/494 was xfs/117. The tipoff to the problem is in this excerpt from dmesg:
XFS (sda4): Quotacheck needed: Please wait. XFS (sda4): Metadata corruption detected at xfs_dinode_verify.part.0+0xdb/0x7b0 [xfs], inode 0x119 dinode XFS (sda4): Unmount and run xfs_repair XFS (sda4): First 128 bytes of corrupted metadata buffer: 00000000: 49 4e 81 a4 03 02 00 00 00 00 00 00 00 00 00 00 IN.............. 00000010: 00 00 00 01 00 00 00 00 00 90 57 54 54 1a 4c 68 ..........WTT.Lh 00000020: 81 f9 7d e1 6d ee 16 00 34 bd 7d e1 6d ee 16 00 ..}.m...4.}.m... 00000030: 34 bd 7d e1 6d ee 16 00 00 00 00 00 00 00 00 00 4.}.m........... 00000040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00000050: 00 00 00 02 00 00 00 00 00 00 00 00 96 80 f3 ab ................ 00000060: ff ff ff ff da 57 7b 11 00 00 00 00 00 00 00 03 .....W{......... 00000070: 00 00 00 01 00 00 00 10 00 00 00 00 00 00 00 08 ................ XFS (sda4): Quotacheck: Unsuccessful (Error -117): Disabling quotas.
The dinode verifier decided that the inode was corrupt, which causes iget to return with EFSCORRUPTED. Since this happened during quotacheck, it is obvious that the kernel aborted the inode walk on account of the corruption error and disabled quotas. Unfortunately, we neglect to purge the dquot cache before doing that, which is how the dquots leaked.
The problems started 10 years ago in commit b84a3a, when the dquot lists were converted to a radix tree, but the error handling behavior was not correctly preserved -- in that commit, if the bulkstat failed and usrquota was enabled, the bulkstat failure code would be overwritten by the result of flushing all the dquots to disk. As long as that succeeds, we'd continue the quota mount as if everything were ok, but instead we're now operating with a corrupt inode and incorrect quota usage counts. I didn't notice this bug in 2019 when I wrote commit ebd126a, which changed quotacheck to skip the dqflush when the scan doesn't complete due to inode walk failures.
Introduced-by: b84a3a96751f ("xfs: remove the per-filesystem list of dquots") Fixes: ebd126a651f8 ("xfs: convert quotacheck to use the new iwalk functions") Signed-off-by: Darrick J. Wong djwong@kernel.org Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Dave Chinner dchinner@redhat.com Signed-off-by: Dave Chinner david@fromorbit.com Signed-off-by: Leah Rumancik leah.rumancik@gmail.com Acked-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/xfs/xfs_qm.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c index 5608066d6e539..623244650a2f0 100644 --- a/fs/xfs/xfs_qm.c +++ b/fs/xfs/xfs_qm.c @@ -1317,8 +1317,15 @@ xfs_qm_quotacheck(
error = xfs_iwalk_threaded(mp, 0, 0, xfs_qm_dqusage_adjust, 0, true, NULL); - if (error) + if (error) { + /* + * The inode walk may have partially populated the dquot + * caches. We must purge them before disabling quota and + * tearing down the quotainfo, or else the dquots will leak. + */ + xfs_qm_dqpurge_all(mp); goto error_return; + }
/* * We've made all the changes that we need to make incore. Flush them