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Date: Thu, 25 Feb 2010 17:42:38 -0500
From: Rik van Riel <riel@redhat.com>
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To: Wu Fengguang <fengguang.wu@intel.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
       Jens Axboe <jens.axboe@oracle.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Chris Mason <chris.mason@oracle.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Clemens Ladisch <clemens@ladisch.de>,
       Olivier Galibert <galibert@pobox.com>, Vivek Goyal <vgoyal@redhat.com>,
       Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>,
       Matt Mackall <mpm@selenic.com>, Nick Piggin <npiggin@suse.de>,
       Linux Memory Management List <linux-mm@kvack.org>,
       linux-fsdevel@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 11/15] readahead: dont do start-of-file readahead after
 lseek()
References: <20100224031001.026464755@intel.com> <20100224031055.164120692@intel.com>
In-Reply-To: <20100224031055.164120692@intel.com>
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On 02/23/2010 10:10 PM, Wu Fengguang wrote:
> Some applications (eg. blkid, id3tool etc.) seek around the file
> to get information. For example, blkid does
> 	     seek to	0
> 	     read	1024
> 	     seek to	1536
> 	     read	16384
>
> The start-of-file readahead heuristic is wrong for them, whose
> access pattern can be identified by lseek() calls.
>
> So test-and-set a READAHEAD_LSEEK flag on lseek() and don't
> do start-of-file readahead on seeing it. Proposed by Linus.
>
> Acked-by: Linus Torvalds<torvalds@linux-foundation.org>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>

Acked-by: Rik van Riel <riel@redhat.com>