Re: FS-Cache: Duplicate cookie detected

From: Christian Kujau
Date: Fri Mar 08 2019 - 18:15:18 EST


On Fri, 8 Mar 2019, David Howells wrote:
> 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

Running Linux v5.0 with this patch applied does indeed still produce the
"Duplicate cookie detected" messages, but I only ever see wrq=0 when
running nfstest_cache:

https://paste.fedoraproject.org/paste/dkav0FQzYZxE9-V7GphjAQ

(Scroll down until the messages start to appear again)

Only the n= field seems to change during that test:


fedora0# grep wrq n2.log | sort | uniq -c | sort -n
28 Acquire: n=8 nul=0 noc=0 ok=1 nbf=0 oom=0 wrq=0
29 Acquire: n=7 nul=0 noc=0 ok=1 nbf=0 oom=0 wrq=0
34 Acquire: n=6 nul=0 noc=0 ok=1 nbf=0 oom=0 wrq=0
82 Acquire: n=9 nul=0 noc=0 ok=1 nbf=0 oom=0 wrq=0
93 Acquire: n=5 nul=0 noc=0 ok=1 nbf=0 oom=0 wrq=0

HTH,
Christian.
--
BOFH excuse #5:

static from plastic slide rules