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From: David Howells <dhowells@redhat.com>
To: Luis Henriques <lhenriques@suse.de>
Cc: dhowells@redhat.com, Eric Van Hensbergen <ericvh@gmail.com>,
	Latchesar Ionkov <lucho@ionkov.net>,
	Dominique Martinet <asmadeus@codewreck.org>,
	linux-fsdevel@vger.kernel.org,
	v9fs-developer@lists.sourceforge.net
Subject: Re: 9p: fscache duplicate cookie
Date: Tue, 11 May 2021 13:38:54 +0100	[thread overview]
Message-ID: <2507722.1620736734@warthog.procyon.org.uk> (raw)
In-Reply-To: <87czu45gcs.fsf@suse.de>

Hi Luis,

> I've been seeing fscache complaining about duplicate cookies in 9p:
> 
>  FS-Cache: Duplicate cookie detected
>  FS-Cache: O-cookie c=00000000ba929e80 [p=000000002e706df1 fl=226 nc=0 na=1]

This cookie is marked acquired (fl=2xx), but not relinquished (fl=4xx), so it
would still seem to be active:-/.  Pretty much one of the first things
__fscache_relinquish_cookie() does is to set that bit (should be bit 10).

One thing that might be useful is if you can turn on a couple of fscache
tracepoints:

echo 1 >/sys/kernel/debug/tracing/events/fscache/fscache_acquire/enable
echo 1 >/sys/kernel/debug/tracing/events/fscache/fscache_relinquish/enable

The cookie pointers in the duplicate cookie report should match the entries in
the trace output.

Note that my fscache-iter branch[1] improves the situation where the disk I/O
required to effect the destruction of a cache object delays the completion of
relinquishment by inserting waits, but that oughtn't to help here.

David

[1] https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-iter


  parent reply	other threads:[~2021-05-11 12:39 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-06 10:03 9p: fscache duplicate cookie Luis Henriques
2021-05-06 10:45 ` Dominique Martinet
2021-05-06 12:18   ` Luis Henriques
2021-05-07 16:36     ` Luis Henriques
2021-05-08  0:47       ` Dominique Martinet
2021-05-10 10:54         ` Luis Henriques
2021-05-10 11:47           ` Luis Henriques
2021-05-11 12:44           ` David Howells
2021-05-12 10:10             ` Luis Henriques
2021-05-11 12:53         ` David Howells
2021-05-11 12:38 ` David Howells [this message]
2021-05-12 10:07   ` Luis Henriques
2021-05-12 11:04   ` David Howells
2021-05-12 11:58     ` Luis Henriques
2021-05-12 12:26       ` Dominique Martinet
2021-05-12 12:57       ` What sort of inode state does ->evict_inode() expect to see? [was Re: 9p: fscache duplicate cookie] David Howells
2021-05-12 13:45         ` Al Viro
2021-05-12 14:12         ` David Howells
2021-05-14 16:10           ` Luis Henriques
2021-05-14 21:16             ` Dominique Martinet
2021-05-17 15:56               ` Luis Henriques
2021-05-17 17:39               ` Aneesh Kumar K.V
2021-05-12 11:09   ` 9p: fscache duplicate cookie David Howells

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