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Re: [PATCH 3/4] XFS: Return case-insensitive match for dentry cache

To: "Christoph Hellwig" <hch@xxxxxxxxxxxxx>, "Anton Altaparmakov" <aia21@xxxxxxxxx>
Subject: Re: [PATCH 3/4] XFS: Return case-insensitive match for dentry cache
From: "Barry Naujok" <bnaujok@xxxxxxx>
Date: Fri, 16 May 2008 10:30:37 +1000
Cc: xfs@xxxxxxxxxxx, linux-fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>
In-reply-to: <20080515141121.GA14198@xxxxxxxxxxxxx>
Organization: SGI
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On Fri, 16 May 2008 00:11:21 +1000, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

On Thu, May 15, 2008 at 02:43:44PM +0100, Anton Altaparmakov wrote:
Yes, and you can get the performance back if you allow negative dentries to be created. You just have to make sure that every time a directory entry
is created in directory X, all negative dentries which are children of
directory X are thrown away.

We might even be able to optimize this a little by calling d_compare on
each alias to see if it hashes down to the same one down in the fs.

So, I gather from this comment is that the CI FS implementation overrides
d_compare but not d_hash, and the CI purge function will behave differently
if d_compare is overridden or not? If overridden, use it as per your
suggestion and if not (due to oversight or unexpected problems), purge
all negative children?


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