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SubjectRe: FS-Cache: Duplicate cookie detected
On Fri, 8 Mar 2019, David Howells wrote:
> > $ mount | grep nfs4
> > nfs:/usr/local/src on /usr/local/src type nfs4 (ro,relatime,vers=4.2,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,clientaddr=192.168.56.139,local_lock=none,addr=192.168.0.115)
> >
> > ...so FS-Cache ("fsc") isn't even used here.
>
> Interesting. Can you do:
>
> cat /proc/fs/nfsfs/volumes

That seems to confirm the mount options, fsc is disabled:

# cat /proc/fs/nfsfs/volumes
NV SERVER PORT DEV FSID FSC
v4 c0a80073 801 0:46 1cfd45bf1921474d:a795870ea80f5ff7 no

> See the attached for a patch that helps with certain kinds of collision,
> though I can't see that it should help with what you're seeing since the
> RELINQUISHED flag isn't set on the old cookie (fl=222, but 0x10 isn't in
> there). You can monitor the number of waits by looking in
> /proc/fs/fscache/stats for the:
>
> Acquire: n=289166 nul=0 noc=0 ok=286331 nbf=2 oom=0 wrq=23748

Ah, the wrq= field gets only introduced by this patch. OK, I'll see if I
can build a test kernel with that and will report back.

Thanks for looking in to this,
Christian.
--
BOFH excuse #290:

The CPU has shifted, and become decentralized.

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