linux-kernel - Re: Many open/close on same files yeilds "No such file or directory".

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Date:	Fri, 09 May 2008 08:09:34 +0200
From:	Jesper Krogh <jesper@...gh.cc>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: Many open/close on same files yeilds "No such file or directory".

Andrew Morton wrote:
>> My feeling is that the script below may reveal the bug on any "busy" 
>> volume, where busy is lots of activity in the OS-cache of the volume,
>> not on the actual drives.
> 
> By this do you mean that there has to be a lot of other activity on the
> system to reproduce it?  Stuff which is turning over memory?

Yes, something like that. (sorry for not being able to be more
concrete). The applications has "high activity" on a few files, not
spread activity throughout the volume.

> Because one possiblity is that the cached dentry got reclaimed by memory
> pressure and we have some race bug which causes us to think that the file
> doesn't exist.

What can i do to explore this theory? Can I disable caching of dentries
and see it go away? Does it fit the pattern that it is only the 
"open"-syscall that is hit (not read for example)?

> (That still shouldn't happen because the dentry should be marked
> recently-accessed, but perhaps the underlying inode gets reclaimed or
> something.  Grasping at straws here)

When I disabled the NFS-server and rand my "real-world" program on a
single processor (make -j 1). It ran through fine. It basically
gets around 20 million chunks out of differnet file and assemble the
chuncks in a few other files. This processes more or less 5 individual
sections, so make can run effectively with a concurrency of 5.

I dont know if there can be any technical reasons for not seeing it on
internal attached disks? (other than I just hadn't been able to
reproduce the same error conditions there.

Jesper
-- 
Jesper
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