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From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org,
	fuse-devel <fuse-devel@lists.sourceforge.net>,
	linux-mm <linux-mm@kvack.org>, miklos <mszeredi@redhat.com>,
	"André Almeida" <andrealmeid@collabora.com>
Subject: Re: [fuse-devel] fuse: trying to steal weird page
Date: Sun, 03 May 2020 14:28:34 -0400	[thread overview]
Message-ID: <85d07kkh4d.fsf@collabora.com> (raw)
In-Reply-To: <20200503102742.GF29705@bombadil.infradead.org> (Matthew Wilcox's message of "Sun, 3 May 2020 03:27:42 -0700")

Matthew Wilcox <willy@infradead.org> writes:

> On Sun, May 03, 2020 at 09:43:41AM +0100, Nikolaus Rath wrote:
>> Here's what I got:
>> 
>> [  221.277260] page:ffffec4bbd639880 refcount:1 mapcount:0 mapping:0000000000000000 index:0xd9
>> [  221.277265] flags: 0x17ffffc0000097(locked|waiters|referenced|uptodate|lru)
>> [  221.277269] raw: 0017ffffc0000097 ffffec4bbd62f048 ffffec4bbd619308 0000000000000000
>> [  221.277271] raw: 00000000000000d9 0000000000000000 00000001ffffffff ffff9aec11beb000
>> [  221.277272] page dumped because: fuse: trying to steal weird page
>> [  221.277273] page->mem_cgroup:ffff9aec11beb000
>
> Great!  Here's the condition:
>
>         if (page_mapcount(page) ||
>             page->mapping != NULL ||
>             page_count(page) != 1 ||
>             (page->flags & PAGE_FLAGS_CHECK_AT_PREP &
>              ~(1 << PG_locked |
>                1 << PG_referenced |
>                1 << PG_uptodate |
>                1 << PG_lru |
>                1 << PG_active |
>                1 << PG_reclaim))) {
>
> mapcount is 0, mapping is NULL, refcount is 1, so that's all fine.
> flags has 'waiters' set, which is not in the allowed list.  I don't
> know the internals of FUSE, so I don't know why that is.
>

Hi

On the first message, Nikolaus sent the following line:

>> [ 2333.009937] fuse: page=00000000dd1750e3 index=2022240 flags=17ffffc0000097, count=1,
>> mapcount=0, mapping=00000000125079ad

It should be noted that on the second run, where we got the dump_page
log, it indeed had a null mapping, which is similar to what Nikolaus
asked on the previous thread he linked to, but looks like this wasn't
the case on at least some of the reproductions of the issue.  On the
line above, the condition that triggered the warning was page->mapping
!= NULL.  I don't know what to do with this information, though.



-- 
Gabriel Krisman Bertazi

  reply	other threads:[~2020-05-03 18:28 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-02 19:09 Nikolaus Rath
2020-05-02 19:52 ` Nikolaus Rath
2020-05-03  3:26   ` Matthew Wilcox
2020-05-03  8:43     ` [fuse-devel] " Nikolaus Rath
2020-05-03 10:27       ` Matthew Wilcox
2020-05-03 18:28         ` Gabriel Krisman Bertazi [this message]
2020-05-03 20:06           ` Matthew Wilcox
2020-05-03 20:25           ` Nikolaus Rath
2020-05-06 13:57             ` Vlastimil Babka
2020-05-03 21:34         ` Hugh Dickins
2020-05-18 12:45         ` Miklos Szeredi
2020-05-18 14:48           ` Matthew Wilcox
2020-05-18 14:58             ` Miklos Szeredi
2020-05-18 15:26               ` Matthew Wilcox
  -- strict thread matches above, loose matches on Subject: below --
2018-12-26 21:43 Nikolaus Rath
2019-01-07  8:28 ` [fuse-devel] " Miklos Szeredi
2019-01-07 21:05   ` Nikolaus Rath
2019-01-08  8:27     ` Miklos Szeredi
2019-01-08 10:35       ` Nikolaus Rath
2019-01-09  8:07         ` Miklos Szeredi
2019-01-11 15:39           ` Nikolaus Rath
2019-01-11 15:39             ` [fuse-devel] " Nikolaus Rath
2019-02-10 22:05             ` Nikolaus Rath
2019-02-12 14:57               ` Miklos Szeredi
2019-02-12 21:28                 ` Nikolaus Rath
2019-02-25 21:41                   ` Nikolaus Rath
2019-02-26 12:57                     ` Miklos Szeredi
2019-02-26 13:30                       ` Miklos Szeredi

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