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From: Vivek Goyal <vgoyal@redhat.com>
To: Shaohua Li <shli@fusionio.com>
Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
	neilb@suse.de, axboe@kernel.dk, martin.petersen@oracle.com
Subject: Re: [patch v2 2/6] blk: dont allow discard request merge temporarily
Date: Tue, 20 Mar 2012 12:21:57 -0400	[thread overview]
Message-ID: <20120320162157.GE17071@redhat.com> (raw)
In-Reply-To: <20120316073512.485027511@fusionio.com>

On Fri, Mar 16, 2012 at 03:32:15PM +0800, Shaohua Li wrote:
> Didn't allow discard request merge temporarily, as SCSI layer isn't ready
> for discard merge as Martin Petersen pointed out. This isn't fair for
> non-scsi device, but looks this is the only way I can do currently.
> 
> We should have the same issue before, but maybe because discard merge is
> very rare case. But now raid0/10 makes the merge quite possible, so we need
> disable it explicitly.
> 
> Signed-off-by: Shaohua Li <shli@fusionio.com>
> ---
>  include/linux/blkdev.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux/include/linux/blkdev.h
> ===================================================================
> --- linux.orig/include/linux/blkdev.h	2012-03-14 09:20:06.787261188 +0800
> +++ linux/include/linux/blkdev.h	2012-03-14 09:20:47.797261248 +0800
> @@ -575,7 +575,7 @@ static inline void blk_clear_queue_full(
>   * it already be started by driver.
>   */
>  #define RQ_NOMERGE_FLAGS	\
> -	(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA)
> +	(REQ_NOMERGE | REQ_STARTED | REQ_SOFTBARRIER | REQ_FLUSH | REQ_FUA | REQ_DISCARD)
>  #define rq_mergeable(rq)	\
>  	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
>  	 (((rq)->cmd_flags & REQ_DISCARD) || \

I think you will need to do little more cleanup to make discard
unmergeable.

- Change rq_mergeable(rq)
- Change attempt_merge() and get rid of special conditions of allowing
  discard merge.

Martin had a bigger patch where he wanted to cleanup many discard specific
condition checks.

As you are just focusing on disabling merging for discard requests, you
might as well just pick the relevant pieces from the patch.

http://www.spinics.net/lists/linux-scsi/msg57779.html

Thanks
Vivek

  reply	other threads:[~2012-03-20 16:22 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-03-16  7:32 [patch v2 0/6] Add TRIM support for raid linear/0/1/10 Shaohua Li
2012-03-16  7:32 ` [patch v2 1/6] block: makes bio_split support bio without data Shaohua Li
2012-03-16  7:32 ` [patch v2 2/6] blk: dont allow discard request merge temporarily Shaohua Li
2012-03-20 16:21   ` Vivek Goyal [this message]
2012-03-21  1:22     ` Shaohua Li
2012-03-21 12:14       ` [patch 1/2]block: handle merged discard request Shaohua Li
2012-03-22  2:32         ` Martin K. Petersen
2012-03-22  2:39           ` Shaohua Li
2012-03-22  2:53             ` Martin K. Petersen
2012-06-20  8:57               ` Christoph Hellwig
2012-06-22  3:46                 ` Martin K. Petersen
2012-08-03  2:10                   ` Shaohua Li
2012-08-18  3:06                   ` Mike Snitzer
2012-08-18  3:47                     ` Martin K. Petersen
2012-08-20 13:57                       ` Mike Snitzer
2012-08-20 13:58                         ` Christoph Hellwig
2012-08-20 14:12                           ` Mike Snitzer
2012-08-20 14:15                             ` Christoph Hellwig
2012-03-22  2:18       ` [patch v2 2/6] blk: dont allow discard request merge temporarily Martin K. Petersen
2012-03-22  2:33         ` Shaohua Li
2012-03-22  6:28         ` Christoph Hellwig
2012-03-16  7:32 ` [patch v2 3/6] md: linear supports TRIM Shaohua Li
2012-03-16  7:32 ` [patch v2 4/6] md: raid 0 " Shaohua Li
2012-03-16  7:32 ` [patch v2 5/6] md: raid 1 " Shaohua Li
2012-03-16  7:32 ` [patch v2 6/6] md: raid 10 " Shaohua Li
2012-03-19 19:38 ` [patch v2 0/6] Add TRIM support for raid linear/0/1/10 Holger Kiehl
2012-03-20  1:27   ` Shaohua Li
2012-03-20  9:50     ` Holger Kiehl
2012-03-20 12:09       ` Shaohua Li
2012-03-21  2:08         ` Shaohua Li
2012-03-21  2:24           ` Roberto Spadim
2012-03-21  2:29             ` Mathias Burén
2012-03-21  2:29           ` Mathias Burén
2012-05-08  9:59 ` Patelczyk, Maciej
2012-05-09  2:27   ` Shaohua Li

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