Re: [fuse-devel] fuse: trying to steal weird page

[Miklos Szeredi <miklos@szeredi.hu>]

On Wed, Dec 26, 2018 at 10:44 PM Nikolaus Rath <Nikolaus@rath.org> wrote:
>
> Hi,
>
> I am seeing relatively regular occurences of
>
> $ sudo dmesg | tail
> [21929.138815] fuse: trying to steal weird page
> [21929.138821]   page=00000000a7dd2617 index=64 flags=17fffc0000000ad, count=1, mapcount=0, mapping=          (null)
> [21930.647338] fuse: trying to steal weird page
> [21930.647345]   page=00000000a07f32af index=2848 flags=17fffc0000000ad, count=1, mapcount=0, mapping=          (null)
> [21932.338873] fuse: trying to steal weird page
> [21932.338879]   page=0000000067e3a012 index=64 flags=17fffc0000000ad, count=1, mapcount=0, mapping=          (null)
> [21933.930703] fuse: trying to steal weird page
> [21933.930710]   page=00000000046feb25 index=845 flags=17fffc0000000ad, count=1, mapcount=0, mapping=          (null)
> [21936.163174] fuse: trying to steal weird page
> [21936.163180]   page=00000000fb80fe27 index=0 flags=17fffc0000000ad, count=1, mapcount=0, mapping=          (null)

The page has the PG_dity and PG_waiters flags set which are
incompatible with stealing.  page_cache_pipe_buf_steal() does
apparently filter out dirty ones, so it's not a regular file that we
are trying to streal the page from.  So the question is: what is the
source of the splice()?

Thanks,
Miklos


>
> They do not seem to correlate with userspace errors.
>
> (I am debugging a mysterious EBADF error that I get from an nftw() walk
> and that disappears when running under strace(), but it its occurence
> does not correlate).
>
>
> What are the implications of the above kernel message? Is there a way to
> provide more debugging information?
>
> $ uname -a
> Linux vostro.rath.org 4.18.0-0.bpo.1-amd64 #1 SMP Debian 4.18.6-1~bpo9+1 (2018-09-13) x86_64 GNU/Linux
>
> Best,
> -Nikolaus
>
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