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Re: [PATCH 5/5] xfs: use shared ilock mode for direct IO writes by defau

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 5/5] xfs: use shared ilock mode for direct IO writes by default
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Tue, 03 Apr 2012 12:01:20 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120327143826.969369776@xxxxxxxxxxxxxxxxxxxxxx>
References: <20120327143445.196524266@xxxxxxxxxxxxxxxxxxxxxx> <20120327143826.969369776@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 03/27/12 09:34, Christoph Hellwig wrote:
From: Dave Chinner<dchinner@xxxxxxxxxx>

For the direct IO write path, we only really need the ilock to be taken in
exclusive mode during IO submission if we need to do extent allocation
instaled of all the time.

Change the block mapping code to take the ilock in shared mode for the
initial block mapping, and only retake it exclusively when we actually
have to perform extent allocations.  We were already dropping the ilock
for the transaction allocation, so this doesn't introduce new race windows.

Based on an earlier patch from Dave Chinner.

Signed-off-by: Christoph Hellwig<hch@xxxxxx>


Looks good.

Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>

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