WARNING in unaccount_page_cache_page

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 089cf7f6 Linux 5.3-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1210a761600000
kernel config: https://syzkaller.appspot.com/x/.config?x=b89bb446a3faaba4
dashboard link: https://syzkaller.appspot.com/bug?extid=fe601f9e887449d40112
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fe601f...@syzkaller.appspotmail.com

WARNING: CPU: 0 PID: 12560 at mm/filemap.c:220
unaccount_page_cache_page+0x65b/0xda0 mm/filemap.c:220
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 12560 Comm: syz-executor.2 Not tainted 5.3.0-rc7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x2dc/0x755 kernel/panic.c:219
__warn.cold+0x20/0x4c kernel/panic.c:576
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:179 [inline]
fixup_bug arch/x86/kernel/traps.c:174 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1028
RIP: 0010:unaccount_page_cache_page+0x65b/0xda0 mm/filemap.c:220
Code: 00 0f 85 be 06 00 00 49 8b 5d 00 31 ff 48 c1 eb 03 83 e3 01 48 89 de
e8 c3 25 e4 ff 48 85 db 0f 84 c0 fb ff ff e8 15 24 e4 ff <0f> 0b 48 b8 00
00 00 00 00 fc ff df 48 8b 55 d0 48 c1 ea 03 80 3c
RSP: 0018:ffff888060b7f9b8 EFLAGS: 00010016
RAX: 0000000000040000 RBX: 0000000000000001 RCX: ffffc9000a781000
RDX: 0000000000001dcb RSI: ffffffff818e513b RDI: 0000000000000007
RBP: ffff888060b7f9f8 R08: ffff8880584de400 R09: fffff940003f9169
R10: fffff940003f9168 R11: ffffea0001fc8b47 R12: ffffea0001fc8b40
R13: ffffea0001fc8b40 R14: ffffea0001fc8b40 R15: ffffea0001fc8b88
delete_from_page_cache_batch+0x1e9/0x1170 mm/filemap.c:350
truncate_inode_pages_range+0x622/0x1740 mm/truncate.c:366
blkdev_fallocate+0x23a/0x410 fs/block_dev.c:2081
vfs_fallocate+0x4aa/0xa50 fs/open.c:309
ksys_fallocate+0x58/0xa0 fs/open.c:332
__do_sys_fallocate fs/open.c:340 [inline]
__se_sys_fallocate fs/open.c:338 [inline]
__x64_sys_fallocate+0x97/0xf0 fs/open.c:338
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459879
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd75e4bfc78 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000459879
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000369e5d84 R11: 0000000000000246 R12: 00007fd75e4c06d4
R13: 00000000004bffbd R14: 00000000004d1fc0 R15: 00000000ffffffff
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[Vlastimil Babka]

On 11/29/19 9:19 AM, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 089cf7f6 Linux 5.3-rc7

Ugh, why test previous cycle's rc7 now? Typo for 5.4?

> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1210a761600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=b89bb446a3faaba4
> dashboard link: https://syzkaller.appspot.com/bug?extid=fe601f9e887449d40112
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+fe601f...@syzkaller.appspotmail.com
>
> WARNING: CPU: 0 PID: 12560 at mm/filemap.c:220
> unaccount_page_cache_page+0x65b/0xda0 mm/filemap.c:220

That's this warning:

/*
* At this point page must be either written or cleaned by
* truncate. Dirty page here signals a bug and loss of
* unwritten data.
*
* This fixes dirty accounting after removing the page entirely
* but leaves PageDirty set: it has no effect for truncated
* page and anyway will be cleared before returning page into
* buddy allocator.
*/
if (WARN_ON_ONCE(PageDirty(page)))
account_page_cleaned(page, mapping,
inode_to_wb(mapping->host));

CC Jan

[Tetsuo Handa]

On 2019/11/29 23:41, Vlastimil Babka wrote:
> On 11/29/19 9:19 AM, syzbot wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 089cf7f6 Linux 5.3-rc7
>
> Ugh, why test previous cycle's rc7 now? Typo for 5.4?
>
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=1210a761600000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=b89bb446a3faaba4
>> dashboard link: https://syzkaller.appspot.com/bug?extid=fe601f9e887449d40112
>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Please open the dashboard link. The first occurrence was 5.3-rc7 and the last
occurrence was 5.4-rc7+. In other words, this bug is likely not yet fixed.

[Jan Kara]

I've briefly looked at this so I'll dump my memory state here in case
someone wants to have a look (or for me when I get more time to look into
this):

The problem always happens on block device mapping. What I think is
happening is that truncate_inode_pages() races with some filesystem on top
of that block device holding buffer_head reference and calling
mark_buffer_dirty(). The buffer_head reference makes block_invalidatepage()
fail invalidating page buffers (try_to_release_page() respectively) and
following mark_buffer_dirty() call will happily redirty the page in
whatever state it is.

Now I didn't yet made up my mind what would be a proper way to fix this...

Honza
--
Jan Kara <ja...@suse.com>
SUSE Labs, CR

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.