[patch]MD: ignore discard request for hard disks of hybid raid1/raid10 array

[Shaohua Li <shli@kernel.org>]

In SSD/hard disk hybid storage, discard request should be ignored for hard
disk. We used to be doing this way, but the unplug path forgets it.

This is suitable for stable tree since v3.6.

Reported-and-tested-by: Markus <M4rkusXXL@web.de>
Signed-off-by: Shaohua Li <shli@fusionio.com>
---
 drivers/md/raid1.c  |    7 ++++++-
 drivers/md/raid10.c |    7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

Index: linux/drivers/md/raid1.c
===================================================================
--- linux.orig/drivers/md/raid1.c	2013-03-07 14:14:05.950824173 +0800
+++ linux/drivers/md/raid1.c	2013-04-28 08:57:17.874058434 +0800
@@ -981,7 +981,12 @@ static void raid1_unplug(struct blk_plug
 	while (bio) { /* submit pending writes */
 		struct bio *next = bio->bi_next;
 		bio->bi_next = NULL;
-		generic_make_request(bio);
+		if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+			/* Just ignore it */
+			bio_endio(bio, 0);
+		else
+			generic_make_request(bio);
 		bio = next;
 	}
 	kfree(plug);
Index: linux/drivers/md/raid10.c
===================================================================
--- linux.orig/drivers/md/raid10.c	2013-03-07 14:14:05.950824173 +0800
+++ linux/drivers/md/raid10.c	2013-04-28 08:57:44.765719067 +0800
@@ -1133,7 +1133,12 @@ static void raid10_unplug(struct blk_plu
 	while (bio) { /* submit pending writes */
 		struct bio *next = bio->bi_next;
 		bio->bi_next = NULL;
-		generic_make_request(bio);
+		if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		    !blk_queue_discard(bdev_get_queue(bio->bi_bdev))))
+			/* Just ignore it */
+			bio_endio(bio, 0);
+		else
+			generic_make_request(bio);
 		bio = next;
 	}
 	kfree(plug);