From: Dave Chinner <david@fromorbit.com>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: Eric Sandeen <sandeen@redhat.com>, xfs-oss <xfs@oss.sgi.com>
Subject: Re: [PATCH 3/3 V3] xfs: allow logical-sector sized O_DIRECT
Date: Thu, 23 Jan 2014 10:14:39 +1100 [thread overview]
Message-ID: <20140122231439.GH27606@dastard> (raw)
In-Reply-To: <52DEF8BF.5070106@sandeen.net>
On Tue, Jan 21, 2014 at 04:46:23PM -0600, Eric Sandeen wrote:
> Some time ago, mkfs.xfs started picking the storage physical
> sector size as the default filesystem "sector size" in order
> to avoid RMW costs incurred by doing IOs at logical sector
> size alignments.
>
> However, this means that for a filesystem made with i.e.
> a 4k sector size on an "advanced format" 4k/512 disk,
> 512-byte direct IOs are no longer allowed. This means
> that XFS has essentially turned this AF drive into a hard
> 4K device, from the filesystem on up.
>
> XFS's mkfs-specified "sector size" is really just controlling
> the minimum size & alignment of filesystem metadata.
>
> There is no real need to tightly couple XFS's minimal
> metadata size to the minimum allowed direct IO size;
> XFS can continue doing metadata in optimal sizes, but
> still allow smaller DIOs for apps which issue them,
> for whatever reason.
>
> This patch adds a new field to the xfs_buftarg, so that
> we now track 2 sizes:
>
> 1) The metadata sector size, which is the minimum unit and
> alignment of IO which will be performed by metadata operations.
> 2) The device logical sector size
>
> The first is used internally by the file system for metadata
> alignment and IOs.
> The second is used for the minimum allowed direct IO alignment.
>
> This has passed xfstests on filesystems made with 4k sectors,
> including when run under the patch I sent to ignore
> XFS_IOC_DIOINFO, and issue 512 DIOs anyway. I also directly
> tested end of block behavior on preallocated, sparse, and
> existing files when we do a 512 IO into a 4k file on a
> 4k-sector filesystem, to be sure there were no unexpected
> behaviors.
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Looks good. Nice work with the comments.
Reviewed-by: Dave Chinner <dchinner@redhat.com>
--
Dave Chinner
david@fromorbit.com
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prev parent reply other threads:[~2014-01-22 23:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-21 22:43 [PATCH 0/3 V3] xfs: allow logical-sector sized O_DIRECT for any fs sector size Eric Sandeen
2014-01-21 22:44 ` [PATCH 1/3 V3] xfs: clean up xfs_buftarg Eric Sandeen
2014-01-22 23:12 ` Dave Chinner
2014-01-21 22:45 ` [PATCH 2/3 V3] xfs: rename xfs_buftarg structure members Eric Sandeen
2014-01-22 23:13 ` Dave Chinner
2014-01-21 22:46 ` [PATCH 3/3 V3] xfs: allow logical-sector sized O_DIRECT Eric Sandeen
2014-01-22 13:54 ` Brian Foster
2014-01-22 23:14 ` Dave Chinner [this message]
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