On May 02 2020, Nikolaus Rath <Nikolaus@xxxxxxxx> wrote: > 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 I have now reproduced this with a vanilla 5.6 kernel. I also found that the "mapping" and "flags" parameters always have the same values - even across different workloads and when re-mounting the filesystem. The "page" parameter varies. Best, -Nikolaus -- GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.«
