linux-kernel - Re: [syzbot] [xfs?] INFO: task hung in xfs_ail_push_all

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Message-ID: <ZxBgAU7aasIzcBfj@dread.disaster.area>
Date: Thu, 17 Oct 2024 11:53:21 +1100
From: Dave Chinner <david@...morbit.com>
To: syzbot <syzbot+611be8174be36ca5dbc9@...kaller.appspotmail.com>
Cc: cem@...nel.org, chandan.babu@...cle.com, djwong@...nel.org,
	linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [xfs?] INFO: task hung in xfs_ail_push_all_sync (2)

On Wed, Oct 16, 2024 at 04:22:27PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    09f6b0c8904b Merge tag 'linux_kselftest-fixes-6.12-rc3' of..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14af3fd0580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7cd9e7e4a8a0a15b
> dashboard link: https://syzkaller.appspot.com/bug?extid=611be8174be36ca5dbc9
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16c7705f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14d2fb27980000

I explained this last time syzbot triggered this: this is a syzbot
configuration problem, not a filesystem bug.

[   96.418071][ T5112] XFS (loop0): Mounting V5 Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
[   96.593743][ T5112] XFS (loop0): Ending clean mount
[   96.791357][ T5112] loop0: detected capacity change from 32768 to 0
[   96.814808][ T5127] xfsaild/loop0: attempt to access beyond end of device
[   96.814808][ T5127] loop0: rw=4097, sector=2, nr_sectors = 1 limit=0
[   96.851235][ T5127] xfsaild/loop0: attempt to access beyond end of device
[   96.851235][ T5127] loop0: rw=4097, sector=24, nr_sectors = 8 limit=0
[   96.860284][    T9] XFS (loop0): metadata I/O error in "xfs_buf_ioerror_alert_ratelimited+0x7b/0x1e0" at daddr 0x2 len 1 error 5
[   96.886045][    T9] kworker/0:1: attempt to access beyond end of device
[   96.886045][    T9] loop0: rw=4097, sector=2, nr_sectors = 1 limit=0
[   96.900489][ T5127] xfsaild/loop0: attempt to access beyond end of device
[   96.900489][ T5127] loop0: rw=4097, sector=32, nr_sectors = 8 limit=0
[   96.932892][    T9] kworker/0:1: attempt to access beyond end of device
[   96.932892][    T9] loop0: rw=4097, sector=24, nr_sectors = 8 limit=0
[   96.940364][ T5127] xfsaild/loop0: attempt to access beyond end of device
[   96.940364][ T5127] loop0: rw=4097, sector=8832, nr_sectors = 64 limit=0
.....

And so it goes until something tries to freeze the filesystem and
gets stuck waiting for writeback of metadata that is not making
progress because XFS defaults to -retry metadata write errors
forever- until the filesystem is shut down.

If the user expects an XFS filesystem to fail fast when they
accidentally shrink the block device under a mounted filesytem, then
they need to configure XFS to fail metadata IO fast. Otherwise
metadata will remain dirty and be retried until the filesystem is
shut down or the error behaviour is reconfigured.

Please fix your syzbot configurations and/or tests that screw with
the block device under filesystems to configure XFS filesystems to
fail fast so that these tests no longer generate unwanted noise.

#syz invalid

-Dave.
-- 
Dave Chinner
david@...morbit.com