linux-ext4 - Re: [PATCH v3] ext4: avoid wasted extent cache lookup if !PUNCH_OUT

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Message-ID: <20110718032858.GD14869@thunk.org>
Date:	Sun, 17 Jul 2011 23:28:58 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Robin Dong <hao.bigrat@...il.com>
Cc:	linux-ext4@...r.kernel.org, Robin Dong <sanbai@...bao.com>
Subject: Re: [PATCH v3] ext4: avoid wasted extent cache lookup if
 !PUNCH_OUT_EXT

On Wed, Jun 29, 2011 at 08:57:51AM +0800, Robin Dong wrote:
> This patch avoids an extraneous lookup of the extent cache
> in ext4_ext_map_blocks() when the flag
> EXT4_GET_BLOCKS_PUNCH_OUT_EXT is absent.
> 
> The existing logic was performing the lookup but not making
> use of the result. The patch simply reverses the order of evaluation
> in the condition.
> 
> Since ext4_ext_in_cache() does not initialize newex on misses, bypassing
> its invocation does not introduce any new issue in this regard.
> 
> Signed-off-by: Robin Dong <sanbai@...bao.com>
> Reviewed-by: Lukas Czerner <lczerner@...hat.com>
> Reviewed-by: Eric Gouriou <egouriou@...gle.com>

Thanks added to the ext4 tree.

						- Ted
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