linux-kernel - Re: rm hanging, v6.1.35

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Message-ID: <ZKy+lxkSDKs84Edr@dread.disaster.area>
Date:   Tue, 11 Jul 2023 12:29:43 +1000
From:   Dave Chinner <david@...morbit.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>
Cc:     Chris Dunlop <chris@...he.net.au>,
        Linux XFS <linux-xfs@...r.kernel.org>,
        Dave Chinner <dchinner@...hat.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Linux Stable <stable@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>
Subject: Re: rm hanging, v6.1.35

On Tue, Jul 11, 2023 at 07:53:35AM +0700, Bagas Sanjaya wrote:
> On Tue, Jul 11, 2023 at 07:53:54AM +1000, Chris Dunlop wrote:
> > Hi,
> > 
> > This box is newly booted into linux v6.1.35 (2 days ago), it was previously
> > running v5.15.118 without any problems (other than that fixed by
> > "5e672cd69f0a xfs: non-blocking inodegc pushes", the reason for the
> > upgrade).
> > 
> > I have rm operations on two files that have been stuck for in excess of 22
> > hours and 18 hours respectively:
> > 
> > $ ps -opid,lstart,state,wchan=WCHAN-xxxxxxxxxxxxxxx,cmd -C rm
> >     PID                  STARTED S WCHAN-xxxxxxxxxxxxxxx CMD
> > 2379355 Mon Jul 10 09:07:57 2023 D vfs_unlink            /bin/rm -rf /aaa/5539_tmp
> > 2392421 Mon Jul 10 09:18:27 2023 D down_write_nested     /bin/rm -rf /aaa/5539_tmp
> > 2485728 Mon Jul 10 09:28:57 2023 D down_write_nested     /bin/rm -rf /aaa/5539_tmp
> > 2488254 Mon Jul 10 09:39:27 2023 D down_write_nested     /bin/rm -rf /aaa/5539_tmp
> > 2491180 Mon Jul 10 09:49:58 2023 D down_write_nested     /bin/rm -rf /aaa/5539_tmp
> > 3014914 Mon Jul 10 13:00:33 2023 D vfs_unlink            /bin/rm -rf /bbb/5541_tmp
> > 3095893 Mon Jul 10 13:11:03 2023 D down_write_nested     /bin/rm -rf /bbb/5541_tmp
> > 3098809 Mon Jul 10 13:21:35 2023 D down_write_nested     /bin/rm -rf /bbb/5541_tmp
> > 3101387 Mon Jul 10 13:32:06 2023 D down_write_nested     /bin/rm -rf /bbb/5541_tmp
> > 3195017 Mon Jul 10 13:42:37 2023 D down_write_nested     /bin/rm -rf /bbb/5541_tmp
> > 
> > The "rm"s are run from a process that's obviously tried a few times to get
> > rid of these files.
>
> > There's nothing extraordinary about the files in terms of size:
> > 
> > $ ls -ltrn --full-time /aaa/5539_tmp /bbb/5541_tmp
> > -rw-rw-rw- 1 1482 1482 7870643 2023-07-10 06:07:58.684036505 +1000 /aaa/5539_tmp
> > -rw-rw-rw- 1 1482 1482  701240 2023-07-10 10:00:34.181064549 +1000 /bbb/5541_tmp
> > 
> > As hinted by the WCHAN in the ps output above, each "primary" rm (i.e. the
> > first one run on each file) stack trace looks like:
> > 
> > [<0>] vfs_unlink+0x48/0x270
> > [<0>] do_unlinkat+0x1f5/0x290
> > [<0>] __x64_sys_unlinkat+0x3b/0x60
> > [<0>] do_syscall_64+0x34/0x80
> > [<0>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

This looks to be stuck on the target inode lock (i.e. the locks for
the inodes at /aaa/5539_tmp and /bbb/5541_tmp).

What's holding these inode locks? This hasn't even got to XFS yet
here, so there's something else going on in the background. Attached
the full output of 'echo w > /proc/sysrq-trigger' and 'echo t >
/proc/sysrq-trigger', please?

> > 
> > And each "secondary" rm (i.e. the subsequent ones on each file) stack trace
> > looks like:
> > 
> > == blog-230710-xfs-rm-stuckd
> > [<0>] down_write_nested+0xdc/0x100
> > [<0>] do_unlinkat+0x10d/0x290
> > [<0>] __x64_sys_unlinkat+0x3b/0x60
> > [<0>] do_syscall_64+0x34/0x80
> > [<0>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

These are likely all stuck on the parent directory inode lock (i.e.
/aaa and /bbb).


> > Where to from here?
> > 
> > I'm guessing only a reboot is going to unstick this. Anything I should be
> > looking at before reverting to v5.15.118?
> > 
> > ...subsequent to starting writing all this down I have another two sets of
> > rms stuck, again on unremarkable files, and on two more separate
> > filesystems.

What's an "unremarkable file" look like? Is is a reflink copy of
something else, a hard link, a small/large regular data file or something else?

> > 
> > ...oh. And an 'ls' on those files is hanging. The reboot has become more
> > urgent.

Yup, that's most likely getting stuck on the directory locks that
the unlinks are holding....

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