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

[Nikolaus Rath <Nikolaus@rath.org>]

On May 02 2020, Matthew Wilcox <willy@infradead.org> wrote:
> On Sat, May 02, 2020 at 08:52:48PM +0100, Nikolaus Rath wrote:
>> On May 02 2020, Nikolaus Rath <Nikolaus@rath.org> wrote:
>> > I have recently noticed that a FUSE filesystem regularly produces many
>> > kernel messages like this:
>> >
>> > [ 2333.009931] fuse: trying to steal weird page
>> > [ 2333.009937] fuse: page=00000000dd1750e3 index=2022240 flags=17ffffc0000097, count=1,
>> > mapcount=0, mapping=00000000125079ad
> ...
>> > What are the implications of the above kernel message? Is there a way to
>> > provide more debugging information?
>
> It'd be helpful to use the common debugging infrastructure which prints
> more useful information:
>
> +++ b/fs/fuse/dev.c
> @@ -772,8 +772,7 @@ static int fuse_check_page(struct page *page)
>                1 << PG_lru |
>                1 << PG_active |
>                1 << PG_reclaim))) {
> -               pr_warn("trying to steal weird page\n");
> -               pr_warn("  page=%p index=%li flags=%08lx, count=%i, mapcount=%i, mapping=%p\n", page, page->index, page->flags, page_count(page), page_mapcount(page), page->mapping);
> +               dump_page(page, "fuse: trying to steal weird page");
>                 return 1;
>         }
>         return 0;
>
> (whitespace damaged; if you can't make the equivalent change, let me
> know and I'll send you a real patch)

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
[  221.601910] page:ffffec4bbd4b2dc0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x1273
[  221.601915] flags: 0x17ffffc0000097(locked|waiters|referenced|uptodate|lru)
[  221.601919] raw: 0017ffffc0000097 ffffec4bbd51f488 ffffec4bbd4b2d48 0000000000000000
[  221.601921] raw: 0000000000001273 0000000000000000 00000001ffffffff ffff9aec11beb000
[  221.601922] page dumped because: fuse: trying to steal weird page
[  221.601923] page->mem_cgroup:ffff9aec11beb000
[  221.958699] page:ffffec4bbd424d80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x38be
[  221.958703] flags: 0x17ffffc0000097(locked|waiters|referenced|uptodate|lru)
[  221.958707] raw: 0017ffffc0000097 ffffec4bbd424048 ffffec4bbd424d48 0000000000000000
[  221.958709] raw: 00000000000038be 0000000000000000 00000001ffffffff ffff9aec11beb000
[  221.958710] page dumped because: fuse: trying to steal weird page
[  221.958711] page->mem_cgroup:ffff9aec11beb000



Best,
-Nikolaus
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