linux-kernel - Re: [PATCH] writeback: Don't wait for completion in writeback_inodes_sb

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Message-ID: <20110629005422.GQ32466@dastard>
Date:	Wed, 29 Jun 2011 10:54:22 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Curt Wohlgemuth <curtw@...gle.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] writeback: Don't wait for completion in
 writeback_inodes_sb_nr

On Tue, Jun 28, 2011 at 04:43:35PM -0700, Curt Wohlgemuth wrote:
> Contrary to the comment block atop writeback_inodes_sb_nr(),
> we *were* calling
> 
>         wait_for_completion(&done);
> 
> which should not be done, as this is not called for data
> integrity sync.
> 
> Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>

The comment says it does not wait for IO to be -completed-.

The function as implemented waits for IO to be *submitted*.

This provides the callers with same blocking semantics (i.e. request
queue full) as if the caller submitted the IO themselves. The code
that uses this function rely on this blocking to delay the next set
of operations they do until after IO has been started, so removing
the completion will change their behaviour significantly.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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