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* fuse: trying to steal weird page
@ 2020-05-02 19:09 Nikolaus Rath
  2020-05-02 19:52 ` Nikolaus Rath
  0 siblings, 1 reply; 16+ messages in thread
From: Nikolaus Rath @ 2020-05-02 19:09 UTC (permalink / raw)
  To: linux-fsdevel, fuse-devel, linux-mm, miklos,
	Gabriel Krisman Bertazi, André Almeida

Hello,

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
[ 2334.595835] fuse: trying to steal weird page
[ 2334.595841] fuse:   page=000000009e8626ac index=2052288 flags=17ffffc0000097, count=1, mapcount=0, mapping=00000000125079ad
[ 2334.983568] fuse: trying to steal weird page
[ 2334.983572] fuse:   page=0000000013fdd9e4 index=2059392 flags=17ffffc0000097, count=1, mapcount=0, mapping=00000000125079ad
[ 2335.979905] fuse: trying to steal weird page
[ 2335.979911] fuse:   page=00000000a7057848 index=2078588 flags=17ffffc0000097, count=1, mapcount=0, mapping=00000000125079ad

They do not seem to correlate with userspace errors, but I noticed that
there is no significant performance difference between libfuse using
splice, splice with SPLICE_MOVE, and not using splice. This is somewhat
unexpected, so maybe it is related to the kernel messages?

What are the implications of the above kernel message? Is there a way to
provide more debugging information?

(I have reported a similar issue before
(https://marc.info/?l=linux-mm&m=155290847909996&w=2) and the patch may
not be present in the kernel that I'm using. However, the previous time
the warning had a different set of flags and a null mapping, so I think
this one is different).

$ uname -a
Linux valve 5.3.0-46-generic #38-Ubuntu SMP Fri Mar 27 17:37:05 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux


Best,
-Nikolaus


-- 
GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F

             »Time flies like an arrow, fruit flies like a Banana.«

^ permalink raw reply	[flat|nested] 16+ messages in thread
* fuse: trying to steal weird page
@ 2018-12-26 21:43 Nikolaus Rath
  2019-01-07  8:28 ` [fuse-devel] " Miklos Szeredi
  0 siblings, 1 reply; 16+ messages in thread
From: Nikolaus Rath @ 2018-12-26 21:43 UTC (permalink / raw)
  To: fuse-devel, Miklos Szeredi, linux-fsdevel

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)

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

-- 
GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F

             »Time flies like an arrow, fruit flies like a Banana.«

^ permalink raw reply	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2020-05-18 15:26 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-02 19:09 fuse: trying to steal weird page 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
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
     [not found]           ` <CAJfpegtiXDgSBWN8MRubpAdJFxy95X21nO_yycCZhpvKLVePRA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2019-01-11 15:39             ` Nikolaus Rath

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