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From: Mark Tinguely <tinguely@sgi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 05/18] xfs: Use preallocation for inodes with extsz hints
Date: Mon, 16 Apr 2012 10:59:47 -0500	[thread overview]
Message-ID: <4F8C41F3.7020005@sgi.com> (raw)
In-Reply-To: <1334319061-12968-6-git-send-email-david@fromorbit.com>

On 04/13/12 07:10, Dave Chinner wrote:
> From: Dave Chinner<dchinner@redhat.com>
>
> xfstest 229 exposes a problem with buffered IO, delayed allocation
> and extent size hints. That is when we do delayed allocation during
> buffered IO, we reserve space for the extent size hint alignment and
> allocate the physical space to align the extent, but we do not zero
> the regions of the extent that aren't written by the write(2)
> syscall. The result is that we expose stale data in unwritten
> regions of the extent size hints.
>
> There are two ways to fix this. The first is to detect that we are
> doing unaligned writes, check if there is already a mapping or data
> over the extent size hint range, and if not zero the page cache
> first before then doing the real write. This can be very expensive
> for large extent size hints, especially if the subsequent writes
> fill then entire extent size before the data is written to disk.
>
> The second, and simpler way, is simply to turn off delayed
> allocation when the extent size hint is set and use preallocation
> instead. This results in unwritten extents being laid down on disk
> and so only the written portions will be converted. This matches the
> behaviour for direct IO, and will also work for the real time
> device. The disadvantage of this approach is that for small extent
> size hints we can get file fragmentation, but in general extent size
> hints are fairly large (e.g. stripe width sized) so this isn't a big
> deal.
>
> Implement the second approach as it is simple and effective.
>
> Signed-off-by: Dave Chinner<dchinner@redhat.com>
> ---


Looks good.

Reviewed-by: Mark Tinguely <tinguely@sgi.com>

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  parent reply	other threads:[~2012-04-16 15:59 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-13 12:10 [PATCH 0/18] xfs: current patch queue Dave Chinner
2012-04-13 12:10 ` [PATCH 01/18] xfs: Ensure inode reclaim can run during quotacheck Dave Chinner
2012-04-13 18:01   ` Mark Tinguely
2012-04-29 21:37   ` Christoph Hellwig
2012-04-13 12:10 ` [PATCH 02/18] xfs: pass shutdown method into xfs_trans_ail_delete_bulk Dave Chinner
2012-04-13 17:40   ` Mark Tinguely
2012-04-13 23:04     ` Dave Chinner
2012-04-13 23:38       ` [PATCH 02/18 V2] " Dave Chinner
2012-04-16 18:49         ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 03/18] xfs: Do background CIL flushes via a workqueue Dave Chinner
2012-04-17 17:54   ` Mark Tinguely
2012-04-17 21:21   ` Ben Myers
2012-04-17 21:49     ` Ben Myers
2012-04-18  1:47       ` Dave Chinner
2012-04-30  1:24         ` Dave Chinner
2012-04-30  6:09           ` Dave Chinner
2012-04-18  1:58     ` Dave Chinner
2012-04-13 12:10 ` [PATCH 04/18] xfs: page type check in writeback only checks last buffer Dave Chinner
2012-04-16 16:15   ` Mark Tinguely
2012-04-29 21:39   ` Christoph Hellwig
2012-04-30  0:29     ` Dave Chinner
2012-04-13 12:10 ` [PATCH 05/18] xfs: Use preallocation for inodes with extsz hints Dave Chinner
2012-04-13 16:45   ` Mark Tinguely
2012-04-16 15:59   ` Mark Tinguely [this message]
2012-04-13 12:10 ` [PATCH 06/18] xfs: fix buffer lookup race on allocation failure Dave Chinner
2012-04-13 18:32   ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 07/18] xfs: check for buffer errors before waiting Dave Chinner
2012-04-13 17:56   ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 08/18] xfs: fix incorrect b_offset initialisation Dave Chinner
2012-04-13 12:10 ` [PATCH 09/18] xfs: use kmem_zone_zalloc for buffers Dave Chinner
2012-04-13 12:10 ` [PATCH 10/18] xfs: clean up buffer get/read call API Dave Chinner
2012-04-13 12:10 ` [PATCH 11/18] xfs: kill b_file_offset Dave Chinner
2012-04-13 12:10 ` [PATCH 12/18] xfs: use blocks for counting length of buffers Dave Chinner
2012-04-13 12:10 ` [PATCH 13/18] xfs: use blocks for storing the desired IO size Dave Chinner
2012-04-13 12:10 ` [PATCH 14/18] xfs: kill xfs_buf_btoc Dave Chinner
2012-04-13 12:10 ` [PATCH 15/18] xfs: kill XBF_LOCK Dave Chinner
2012-04-13 21:20   ` Mark Tinguely
2012-04-13 12:10 ` [PATCH 16/18] xfs: kill xfs_read_buf() Dave Chinner
2012-04-13 12:11 ` [PATCH 17/18] xfs: kill XBF_DONTBLOCK Dave Chinner
2012-04-16 14:34   ` Mark Tinguely
2012-04-13 12:11 ` [PATCH 18/18] xfs: use iolock on XFS_IOC_ALLOCSP calls Dave Chinner
2012-04-16 15:10   ` Mark Tinguely
2012-04-16 21:29 ` [PATCH 0/18] xfs: current patch queue Ben Myers
2012-04-17  4:12   ` Dave Chinner
2012-04-17 14:44     ` Ben Myers

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