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From: Ben Myers <bpm@sgi.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 2/5] xfs: reduce ilock hold times in xfs_file_aio_write_checks
Date: Thu, 19 Apr 2012 15:30:16 -0500	[thread overview]
Message-ID: <20120419203016.GE16881@sgi.com> (raw)
In-Reply-To: <20120327143826.433267717@bombadil.infradead.org>

On Tue, Mar 27, 2012 at 10:34:47AM -0400, Christoph Hellwig wrote:
> We do not need the ilock for generic_write_checks and the i_size read,
> which are protected by i_mutex and/or iolock, so reduce the ilock
> critical section to just the call to xfs_zero_eof.

So.. I agree that it looks like the only thing we need to protect in
generic_write_checks is the i_size_read.

For buffered io i_size_write is done in generic_write_end, and protected
XFS_IOLOCK_EXCL in xfs_file_buffered_write.  

For direct io i_size_write is done in generic_file_direct_write and also
protected by the iolock in xfs_file_dio_aio_write.  It's not as clear here
whether that lock is taken exclusive at that time.  However, this is handled in
xfs_file_aio_write_checks, where we go io exclusive for xfs_zero_eof.  Maybe it
would be best for this to be done more explicitly with respect to the inode
size in xfs_file_dio_aio_write.

Just wanting to show why generic_write_checks is ok protected with just the
iolock...

Reviewed-by: Ben Myers <bpm@sgi.com>

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  parent reply	other threads:[~2012-04-19 20:28 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-27 14:34 [PATCH 0/5] reduce exclusive ilock hold times V2 Christoph Hellwig
2012-03-27 14:34 ` [PATCH 1/5] xfs: avoid taking the ilock unnessecarily in xfs_qm_dqattach Christoph Hellwig
2012-04-02 19:24   ` Mark Tinguely
2012-03-27 14:34 ` [PATCH 2/5] xfs: reduce ilock hold times in xfs_file_aio_write_checks Christoph Hellwig
2012-04-02 19:26   ` Mark Tinguely
2012-04-19 20:30   ` Ben Myers [this message]
2012-03-27 14:34 ` [PATCH 3/5] xfs: reduce ilock hold times in xfs_setattr_size Christoph Hellwig
2012-04-02 19:26   ` Mark Tinguely
2012-04-19 21:00   ` Ben Myers
2012-04-19 22:43     ` Dave Chinner
2012-03-27 14:34 ` [PATCH 4/5] xfs: push the ilock into xfs_zero_eof Christoph Hellwig
2012-04-02 20:39   ` Mark Tinguely
2012-03-27 14:34 ` [PATCH 5/5] xfs: use shared ilock mode for direct IO writes by default Christoph Hellwig
2012-04-03 17:01   ` Mark Tinguely
2012-03-27 20:52 ` [PATCH 0/5] reduce exclusive ilock hold times V2 Dave Chinner
  -- strict thread matches above, loose matches on Subject: below --
2012-03-26 21:14 [PATCH 0/5] reduce exclusive ilock hold times Christoph Hellwig
2012-03-26 21:14 ` [PATCH 2/5] xfs: reduce ilock hold times in xfs_file_aio_write_checks Christoph Hellwig
2012-03-26 22:15   ` Dave Chinner

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