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From: David Howells <dhowells@redhat.com>
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To: utz lehmann <lkml123@s2y4n2c.de>
Cc: dhowells@redhat.com, Linus Torvalds <torvalds@linux-foundation.org>,
        Jeremy Allison <jra@samba.org>, Volker.Lendecke@sernet.de,
        Jan Engelhardt <jengelh@medozas.de>, linux-cifs@vger.kernel.org,
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        linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk,
        linux-fsde@jasper.es
Subject: Re: [PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]
Date: Sat, 31 Jul 2010 20:26:49 +0100
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utz lehmann <lkml123@s2y4n2c.de> wrote:

> How does this works right with noatime or relatime (which is default)?

Don't do that then.

> We had used FS-Cache with a few 10000s files cached. Doesn't it mean
> that the cleanup has to stat them all?

Yes.

> Why didn't cachefilesd managed the cache index in a separate database
> like other caches?

Because using atime is much simpler since the filesystem updates it
automatically.  If you have a separate database then you have redundant
information and you need to maintain metadata integrity which has a cost, both
in terms of disk usage and performance.  I'm working on it, but you don't get
it for free.

David
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