linux-kernel - Re: [PATCH v2] md: Call blk_queue_flush() to establish flush/fua support

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Message-ID: <20101124161813.2f5bc0d6@notabene.brown>
Date:	Wed, 24 Nov 2010 16:18:13 +1100
From:	Neil Brown <neilb@...e.de>
To:	djwong@...ibm.com
Cc:	linux-raid@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] md: Call blk_queue_flush() to establish flush/fua
 support

On Tue, 23 Nov 2010 11:01:03 -0800
"Darrick J. Wong" <djwong@...ibm.com> wrote:

> Here's a shorter version that sets up flush/fua unconditionally.
> ---
> Before 2.6.37, the md layer had a mechanism for catching I/Os with the barrier
> flag set, and translating the barrier into barriers for all the underlying
> devices.  With 2.6.37, I/O barriers have become plain old flushes, and the md
> code was updated to reflect this.  However, one piece was left out -- the md
> layer does not tell the block layer that it supports flushes or FUA access at
> all, which results in md silently dropping flush requests.
> 
> Since the support already seems there, just add this one piece of bookkeeping.
> 
> Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
> ---
> 
>  drivers/md/md.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 324a366..43243a4 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4338,6 +4338,8 @@ static int md_alloc(dev_t dev, char *name)
>  	if (mddev->kobj.sd &&
>  	    sysfs_create_group(&mddev->kobj, &md_bitmap_group))
>  		printk(KERN_DEBUG "pointless warning\n");
> +
> +	blk_queue_flush(mddev->queue, REQ_FLUSH | REQ_FUA);
>   abort:
>  	mutex_unlock(&disks_mutex);
>  	if (!error && mddev->kobj.sd) {


Applied, thanks.

NeilBrown

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