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Re: [PATCH 4/7][TAKE5] support new modes in fallocate

To: "Amit K. Arora" <aarora@xxxxxxxxxxxxxxxxxx>
Subject: Re: [PATCH 4/7][TAKE5] support new modes in fallocate
From: Andreas Dilger <adilger@xxxxxxxxxxxxx>
Date: Mon, 25 Jun 2007 15:52:39 -0600
Cc: linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, David Chinner <dgc@xxxxxxx>, suparna@xxxxxxxxxx, cmm@xxxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <20070625134500.GE1951@amitarora.in.ibm.com>
Mail-followup-to: "Amit K. Arora" <aarora@xxxxxxxxxxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, David Chinner <dgc@xxxxxxx>, suparna@xxxxxxxxxx, cmm@xxxxxxxxxx, xfs@xxxxxxxxxxx
References: <20070510223950.GD86004887@sgi.com> <20070511110301.GB28425@in.ibm.com> <20070512080157.GF85884050@sgi.com> <20070612061652.GA6320@amitarora.in.ibm.com> <20070613235217.GS86004887@sgi.com> <20070614091458.GH5181@schatzie.adilger.int> <20070614120413.GD86004887@sgi.com> <20070614193347.GN5181@schatzie.adilger.int> <20070625132810.GA1951@amitarora.in.ibm.com> <20070625134500.GE1951@amitarora.in.ibm.com>
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On Jun 25, 2007  19:15 +0530, Amit K. Arora wrote:
> +#define FA_FL_DEALLOC        0x01 /* default is allocate */
> +#define FA_FL_KEEP_SIZE      0x02 /* default is extend/shrink size */
> +#define FA_FL_DEL_DATA       0x04 /* default is keep written data on DEALLOC 
> */

In XFS one of the (many) ALLOC modes is to zero existing data on allocate.
For ext4 all this would mean is calling ext4_ext_mark_uninitialized() on
each extent.  For some workloads this would be much faster than truncate
and reallocate of all the blocks in a file.

In that light, please change the comment to /* default is keep existing data */
so that it doesn't imply this is only for DEALLOC.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.


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