Patch "MD: make bio mergeable" has been added to the 4.4-stable tree

Patch "MD: make bio mergeable" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    MD: make bio mergeable

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     md-make-bio-mergeable.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 9c573de3283af007ea11c17bde1e4568d9417328 Mon Sep 17 00:00:00 2001
From: Shaohua Li <shli@fb.com>
Date: Mon, 25 Apr 2016 16:52:38 -0700
Subject: MD: make bio mergeable

From: Shaohua Li <shli@fb.com>

commit 9c573de3283af007ea11c17bde1e4568d9417328 upstream.

blk_queue_split marks bio unmergeable, which makes sense for normal bio.
But if dispatching the bio to underlayer disk, the blk_queue_split
checks are invalid, hence it's possible the bio becomes mergeable.

In the reported bug, this bug causes trim against raid0 performance slash
https://bugzilla.kernel.org/show_bug.cgi?id=117051

Reported-and-tested-by: Park Ju Hyung <qkrwngud825@gmail.com>
Fixes: 6ac45aeb6bca(block: avoid to merge splitted bio)
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Neil Brown <neilb@suse.de>
Reviewed-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/md.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -293,6 +293,8 @@ static blk_qc_t md_make_request(struct r
 	 * go away inside make_request
 	 */
 	sectors = bio_sectors(bio);
+	/* bio could be mergeable after passing to underlayer */
+	bio->bi_rw &= ~REQ_NOMERGE;
 	mddev->pers->make_request(mddev, bio);
 
 	cpu = part_stat_lock();


Patches currently in stable-queue which might be from shli@fb.com are

queue-4.4/md-make-bio-mergeable.patch