Re: xfs: list corruption in xfs_setup_inode()

[Dave Chinner <david@fromorbit.com>]

On Mon, Oct 30, 2017 at 02:55:43PM -0700, Cong Wang wrote:
> Hello,
> 
> We triggered a list corruption (double add) warning below on our 4.9
> kernel (the 4.9 kernel we use is based on -stable release, with only a
> few unrelated networking backports):
> 
> 
> WARNING: CPU: 5 PID: 628 at lib/list_debug.c:36 __list_add+0xac/0xb0
> list_add double add: new=ffff8d9d691e0aa0, prev=ffff8d9d7a716608,
> next=ffff8d9d691e0aa0.
> Modules linked in: raid0 tcp_diag inet_diag intel_rapl
> x86_pkg_temp_thermal coretemp iTCO_wdt iTCO_vendor_support
> crct10dif_pclmul crc32_pclmul ghash_clmulni_intel mpt3sas raid_class
> scsi_transport_sas i2c_i801 i2c_smbus i2c_core ie31200_edac lpc_ich
> shpchp edac_core video ipmi_si ipmi_devintf ipmi_msghandler
> acpi_cpufreq sch_fq_codel xfs libcrc32c crc32c_intel e1000e ptp
> pps_core
> CPU: 5 PID: 628 Comm: systemd-tmpfile Tainted: G        W

Kernel was already tainted before this warning was triggered. What
was the previous warning(s) that the kernel threw?

> 4.9.34.el7.x86_64 #1
> Hardware name: TYAN S5512/S5512, BIOS V8.B13 03/20/2014
>  ffffb0d48a0abb30 ffffffff8e389f47 ffffb0d48a0abb80 0000000000000000
>  ffffb0d48a0abb70 ffffffff8e08989b 0000002400000000 ffff8d9d691e0aa0
>  ffff8d9d7a716608 ffff8d9d691e0aa0 0000000000004000 ffff8d9d7de6d800
> Call Trace:
>  [<ffffffff8e389f47>] dump_stack+0x4d/0x66
>  [<ffffffff8e08989b>] __warn+0xcb/0xf0
>  [<ffffffff8e08991f>] warn_slowpath_fmt+0x5f/0x80
>  [<ffffffff8e3a979c>] __list_add+0xac/0xb0
>  [<ffffffff8e2355bb>] inode_sb_list_add+0x3b/0x50
>  [<ffffffffc040157c>] xfs_setup_inode+0x2c/0x170 [xfs]
>  [<ffffffffc0402097>] xfs_ialloc+0x317/0x5c0 [xfs]
>  [<ffffffffc0404347>] xfs_dir_ialloc+0x77/0x220 [xfs]

Inode allocation, so should be a new inode straight from the slab
cache. THat implies memory corruption of some kind. Please turn on
slab poisoning and try to reproduce.

>  [<ffffffff8e74cf32>] ? down_write+0x12/0x40
>  [<ffffffffc0404972>] xfs_create+0x482/0x760 [xfs]
>  [<ffffffffc04019ae>] xfs_generic_create+0x21e/0x2c0 [xfs]
>  [<ffffffffc0401a84>] xfs_vn_mknod+0x14/0x20 [xfs]
>  [<ffffffffc0401aa6>] xfs_vn_mkdir+0x16/0x20 [xfs]
>  [<ffffffff8e226698>] vfs_mkdir+0xe8/0x140
>  [<ffffffff8e22aa4a>] SyS_mkdir+0x7a/0xf0
>  [<ffffffff8e74f8e0>] entry_SYSCALL_64_fastpath+0x13/0x94
> 
> _Without_ looking deeper, it seems this warning could be shut up by:
> 
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -1138,6 +1138,8 @@ xfs_reclaim_inode(
>         xfs_iunlock(ip, XFS_ILOCK_EXCL);
> 
>         XFS_STATS_INC(ip->i_mount, xs_ig_reclaims);
> +
> +       inode_sb_list_del(VFS_I(ip));
> 
> with properly exporting inode_sb_list_del(). Does this make any sense?

No, because by this stage the inode has already been removed from
the superblock indoe list. Doing this sort of thing here would just
paper over whatever the underlying problem might be.

> Please let me know if I can provide any other information.

How do you reproduce the problem?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com