Re: 6.6.8 stable: crash in folio_mark_dirty

[Matthew Wilcox <willy@infradead.org>]

On Sat, Dec 30, 2023 at 10:23:26AM -0500, Genes Lists wrote:
> Apologies in advance, but I cannot git bisect this since machine was
> running for 10 days on 6.6.8 before this happened.

Thanks for the report.  Apologies, I'm on holiday until the middle of
the week so this will be extremely terse.

>  - Root, efi is on nvme
>  - Spare root,efi is on sdg
>  - md raid6 on sda-sd with lvmcache from one partition on nvme drive.
>  - all filesystems are ext4 (other than efi).
>  - 32 GB mem.

> Dec 30 07:00:36 s6 kernel: ------------[ cut here ]------------
> Dec 30 07:00:36 s6 kernel: WARNING: CPU: 0 PID: 521524 at mm/page-writeback.c:2668 __folio_mark_dirty (??:?) 

This is:

                WARN_ON_ONCE(warn && !folio_test_uptodate(folio));

> Dec 30 07:00:36 s6 kernel: CPU: 0 PID: 521524 Comm: rsync Not tainted 6.6.8-stable-1 #13 d238f5ab6a206cdb0cc5cd72f8688230f23d58df

So rsync is exiting.  Do you happen to know what rsync is doing?

> Dec 30 07:00:36 s6 kernel: block_dirty_folio (??:?) 
> Dec 30 07:00:36 s6 kernel: unmap_page_range (??:?) 
> Dec 30 07:00:36 s6 kernel: unmap_vmas (??:?) 
> Dec 30 07:00:36 s6 kernel: exit_mmap (??:?) 
> Dec 30 07:00:36 s6 kernel: __mmput (??:?) 
> Dec 30 07:00:36 s6 kernel: do_exit (??:?) 
> Dec 30 07:00:36 s6 kernel: do_group_exit (??:?) 
> Dec 30 07:00:36 s6 kernel: __x64_sys_exit_group (??:?) 
> Dec 30 07:00:36 s6 kernel: do_syscall_64 (??:?) 

It looks llike rsync has a page from the block device mmaped?  I'll have
to investigate this properly when I'm back.  If you haven't heard from
me in a week, please ping me.

(I don't think I caused this, but I think I stand a fighting chance of
tracking down what the problem is, just not right now).