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Date: Mon, 21 May 2007 12:00:24 +1000
From: Vlad Apostolov <vapo@sgi.com>
MIME-Version: 1.0
Subject: Re: review: make xfs_dm_punch_hole() atomic when punching EOF
References: <20070419071856.GR48531920@melbourne.sgi.com>
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To: David Chinner <dgc@sgi.com>
Cc: xfs-dev <xfs-dev@sgi.com>, xfs-oss <xfs@oss.sgi.com>

It is looking good Dave.

Regards,
Vlad

David Chinner wrote:
> Currently punching a hole to EOF via xfs_dm_punch_hole()
> truncates the file and then extends it. This leaves a small
> window where applications can see an incorrect file size
> while the punch is in progress. This can cause problems
> with DMF leading to premature completion of recalls and
> hence data corruption.
>
> Use the UNRESVSP ioctl rather than FREESP+setattr to punch the
> hole at EOF. This can leave specualtive allocations past EOF,
> so truncate them off so we don't leave blocks that can't be
> migrated away around in the filesystem.
>
> Cheers,
>
> Dave.
>