linux-kernel - Re: 9p EBADF with cache enabled (Was: 9p fs-cache tests/benchmark (was: 9p fscache Duplicate cookie detected))

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Message-ID: <6688504.ZJKUV3z3ry@silver>
Date:   Wed, 04 May 2022 20:33:36 +0200
From:   Christian Schoenebeck <linux_oss@...debyte.com>
To:     asmadeus@...ewreck.org
Cc:     David Howells <dhowells@...hat.com>,
        David Kahurani <k.kahurani@...il.com>, davem@...emloft.net,
        ericvh@...il.com, kuba@...nel.org, linux-kernel@...r.kernel.org,
        lucho@...kov.net, netdev@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net, Greg Kurz <groug@...d.org>
Subject: Re: 9p EBADF with cache enabled (Was: 9p fs-cache tests/benchmark (was: 9p
 fscache Duplicate cookie detected))

On Dienstag, 3. Mai 2022 12:21:23 CEST asmadeus@...ewreck.org wrote:
[...]
>  - add some complex code to track the exact byte range that got updated
> in some conditions e.g. WRONLY or read fails?
> That'd still be useful depending on how the backend tracks file mode,
> qemu as user with security_model=mapped-file keeps files 600 but with
> passthrough or none qemu wouldn't be able to read the file regardless of
> what we do on client...
> Christian, if you still have an old kernel around did that use to work?

Sorry, what was the question, i.e. what should I test / look for precisely? :)

[...]
> > > Also, can you get the contents of /proc/fs/fscache/stats from after
> > > reproducing the problem?
> > 
> > FS-Cache statistics
> 
> (He probably wanted to confirm the new trace he added got hit with the
> workaround pattern, I didn't get that far as I couldn't compile my
> reproducer on that fs...)

Yeah, I got that. But since his patch did not apply, I just dumped what I got 
so far in case the existing stats might be useful anyway.

Best regards,
Christian Schoenebeck