diff -u --recursive --new-file linux-3.5.orig/drivers/md/linear.c linux-3.5/drivers/md/linear.c
--- linux-3.5.orig/drivers/md/linear.c	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/drivers/md/linear.c	2012-07-27 06:53:39.507121434 +0000
@@ -138,6 +138,7 @@
 	struct linear_conf *conf;
 	struct md_rdev *rdev;
 	int i, cnt;
+	bool discard_supported = false;
 
 	conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(struct dev_info),
 			GFP_KERNEL);
@@ -171,6 +172,8 @@
 		conf->array_sectors += rdev->sectors;
 		cnt++;
 
+		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+			discard_supported = true;
 	}
 	if (cnt != raid_disks) {
 		printk(KERN_ERR "md/linear:%s: not enough drives present. Aborting!\n",
@@ -178,6 +181,11 @@
 		goto out;
 	}
 
+	if (!discard_supported)
+		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	else
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
 	/*
 	 * Here we calculate the device offsets.
 	 */
@@ -326,6 +334,14 @@
 	bio->bi_sector = bio->bi_sector - start_sector
 		+ tmp_dev->rdev->data_offset;
 	rcu_read_unlock();
+
+	if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		!blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
+		/* Just ignore it */
+		bio_endio(bio, 0);
+		return;
+	}
+
 	generic_make_request(bio);
 }
 
diff -u --recursive --new-file linux-3.5.orig/drivers/md/raid0.c linux-3.5/drivers/md/raid0.c
--- linux-3.5.orig/drivers/md/raid0.c	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/drivers/md/raid0.c	2012-07-27 06:53:39.507121434 +0000
@@ -88,6 +88,7 @@
 	char b[BDEVNAME_SIZE];
 	char b2[BDEVNAME_SIZE];
 	struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
+	bool discard_supported = false;
 
 	if (!conf)
 		return -ENOMEM;
@@ -195,6 +196,9 @@
 		if (!smallest || (rdev1->sectors < smallest->sectors))
 			smallest = rdev1;
 		cnt++;
+
+		if (blk_queue_discard(bdev_get_queue(rdev1->bdev)))
+			discard_supported = true;
 	}
 	if (cnt != mddev->raid_disks) {
 		printk(KERN_ERR "md/raid0:%s: too few disks (%d of %d) - "
@@ -272,6 +276,11 @@
 	blk_queue_io_opt(mddev->queue,
 			 (mddev->chunk_sectors << 9) * mddev->raid_disks);
 
+	if (!discard_supported)
+		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	else
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
 	pr_debug("md/raid0:%s: done.\n", mdname(mddev));
 	*private_conf = conf;
 
@@ -422,6 +431,7 @@
 	if (md_check_no_bitmap(mddev))
 		return -EINVAL;
 	blk_queue_max_hw_sectors(mddev->queue, mddev->chunk_sectors);
+	blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
 
 	/* if private is not null, we are here after takeover */
 	if (mddev->private == NULL) {
@@ -509,7 +519,7 @@
 		sector_t sector = bio->bi_sector;
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if (bio->bi_vcnt != 1 ||
+		if ((bio->bi_vcnt != 1 && bio->bi_vcnt != 0) ||
 		    bio->bi_idx != 0)
 			goto bad_map;
 		/* This is a one page bio that upper layers
@@ -535,6 +545,13 @@
 	bio->bi_sector = sector_offset + zone->dev_start +
 		tmp_dev->data_offset;
 
+	if (unlikely((bio->bi_rw & REQ_DISCARD) &&
+		!blk_queue_discard(bdev_get_queue(bio->bi_bdev)))) {
+		/* Just ignore it */
+		bio_endio(bio, 0);
+		return;
+	}
+
 	generic_make_request(bio);
 	return;
 
diff -u --recursive --new-file linux-3.5.orig/drivers/md/raid10.c linux-3.5/drivers/md/raid10.c
--- linux-3.5.orig/drivers/md/raid10.c	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/drivers/md/raid10.c	2012-07-27 06:53:39.507121435 +0000
@@ -887,7 +887,12 @@
 		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;
 		}
 	} else
@@ -1017,7 +1022,7 @@
 }
 
 static sector_t choose_data_offset(struct r10bio *r10_bio,
-				   struct md_rdev *rdev)
+				struct md_rdev *rdev)
 {
 	if (!test_bit(MD_RECOVERY_RESHAPE, &rdev->mddev->recovery) ||
 	    test_bit(R10BIO_Previous, &r10_bio->state))
@@ -1037,6 +1042,7 @@
 	const int rw = bio_data_dir(bio);
 	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
 	const unsigned long do_fua = (bio->bi_rw & REQ_FUA);
+	const unsigned long do_discard = (bio->bi_rw & (REQ_DISCARD | REQ_SECURE));
 	unsigned long flags;
 	struct md_rdev *blocked_rdev;
 	int sectors_handled;
@@ -1057,7 +1063,7 @@
 			 || conf->prev.near_copies < conf->prev.raid_disks))) {
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if (bio->bi_vcnt != 1 ||
+		if ((bio->bi_vcnt != 1 && bio->bi_vcnt !=0) ||
 		    bio->bi_idx != 0)
 			goto bad_map;
 		/* This is a one page bio that upper layers
@@ -1386,7 +1392,7 @@
 						      conf->mirrors[d].rdev));
 		mbio->bi_bdev = conf->mirrors[d].rdev->bdev;
 		mbio->bi_end_io	= raid10_end_write_request;
-		mbio->bi_rw = WRITE | do_sync | do_fua;
+		mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
 		mbio->bi_private = r10_bio;
 
 		atomic_inc(&r10_bio->remaining);
@@ -1415,7 +1421,7 @@
 					   conf->mirrors[d].replacement));
 		mbio->bi_bdev = conf->mirrors[d].replacement->bdev;
 		mbio->bi_end_io	= raid10_end_write_request;
-		mbio->bi_rw = WRITE | do_sync | do_fua;
+		mbio->bi_rw = WRITE | do_sync | do_fua | do_discard;
 		mbio->bi_private = r10_bio;
 
 		atomic_inc(&r10_bio->remaining);
@@ -1699,6 +1705,9 @@
 		clear_bit(Unmerged, &rdev->flags);
 	}
 	md_integrity_add_rdev(rdev, mddev);
+	if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
 	print_conf(conf);
 	return err;
 }
@@ -3457,6 +3466,7 @@
 	sector_t size;
 	sector_t min_offset_diff = 0;
 	int first = 1;
+	bool discard_supported = false;
 
 	if (mddev->private == NULL) {
 		conf = setup_conf(mddev);
@@ -3471,6 +3481,7 @@
 	mddev->thread = conf->thread;
 	conf->thread = NULL;
 
+	blk_queue_max_discard_sectors(mddev->queue, mddev->chunk_sectors);
 	chunk_size = mddev->chunk_sectors << 9;
 	blk_queue_io_min(mddev->queue, chunk_size);
 	if (conf->geo.raid_disks % conf->geo.near_copies)
@@ -3515,8 +3526,16 @@
 				  rdev->data_offset << 9);
 
 		disk->head_position = 0;
+
+		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+			discard_supported = true;
 	}
 
+	if (discard_supported)
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	else
+		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
 	/* need to check that every block has at least one working mirror */
 	if (!enough(conf, -1)) {
 		printk(KERN_ERR "md/raid10:%s: not enough operational mirrors.\n",
diff -u --recursive --new-file linux-3.5.orig/drivers/md/raid1.c linux-3.5/drivers/md/raid1.c
--- linux-3.5.orig/drivers/md/raid1.c	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/drivers/md/raid1.c	2012-07-27 06:53:39.507121435 +0000
@@ -707,7 +707,12 @@
 		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;
 		}
 	} else
@@ -882,6 +887,7 @@
 	const int rw = bio_data_dir(bio);
 	const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
 	const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+	const unsigned long do_discard = (bio->bi_rw & (REQ_DISCARD | REQ_SECURE));
 	struct md_rdev *blocked_rdev;
 	int first_clone;
 	int sectors_handled;
@@ -1181,7 +1187,7 @@
 				   conf->mirrors[i].rdev->data_offset);
 		mbio->bi_bdev = conf->mirrors[i].rdev->bdev;
 		mbio->bi_end_io	= raid1_end_write_request;
-		mbio->bi_rw = WRITE | do_flush_fua | do_sync;
+		mbio->bi_rw = WRITE | do_flush_fua | do_sync | do_discard;
 		mbio->bi_private = r1_bio;
 
 		atomic_inc(&r1_bio->remaining);
@@ -1424,6 +1430,8 @@
 		clear_bit(Unmerged, &rdev->flags);
 	}
 	md_integrity_add_rdev(rdev, mddev);
+	if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
 	print_conf(conf);
 	return err;
 }
@@ -2654,6 +2662,7 @@
 	int i;
 	struct md_rdev *rdev;
 	int ret;
+	bool discard_supported = false;
 
 	if (mddev->level != 1) {
 		printk(KERN_ERR "md/raid1:%s: raid level not set to mirroring (%d)\n",
@@ -2683,8 +2692,16 @@
 			continue;
 		disk_stack_limits(mddev->gendisk, rdev->bdev,
 				  rdev->data_offset << 9);
+
+		if (blk_queue_discard(bdev_get_queue(rdev->bdev)))
+			discard_supported = true;
 	}
 
+	if (discard_supported)
+		queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+	else
+		queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, mddev->queue);
+
 	mddev->degraded = 0;
 	for (i=0; i < conf->raid_disks; i++)
 		if (conf->mirrors[i].rdev == NULL ||
diff -u --recursive --new-file linux-3.5.orig/fs/bio.c linux-3.5/fs/bio.c
--- linux-3.5.orig/fs/bio.c	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/fs/bio.c	2012-07-27 06:53:39.507121435 +0000
@@ -1500,7 +1500,7 @@
 	trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
 				bi->bi_sector + first_sectors);
 
-	BUG_ON(bi->bi_vcnt != 1);
+	BUG_ON(bi->bi_vcnt != 1 && bi->bi_vcnt != 0);
 	BUG_ON(bi->bi_idx != 0);
 	atomic_set(&bp->cnt, 3);
 	bp->error = 0;
@@ -1510,17 +1510,19 @@
 	bp->bio2.bi_size -= first_sectors << 9;
 	bp->bio1.bi_size = first_sectors << 9;
 
-	bp->bv1 = bi->bi_io_vec[0];
-	bp->bv2 = bi->bi_io_vec[0];
-	bp->bv2.bv_offset += first_sectors << 9;
-	bp->bv2.bv_len -= first_sectors << 9;
-	bp->bv1.bv_len = first_sectors << 9;
+	if (bi->bi_vcnt != 0) {
+		bp->bv1 = bi->bi_io_vec[0];
+		bp->bv2 = bi->bi_io_vec[0];
+		bp->bv2.bv_offset += first_sectors << 9;
+		bp->bv2.bv_len -= first_sectors << 9;
+		bp->bv1.bv_len = first_sectors << 9;
 
-	bp->bio1.bi_io_vec = &bp->bv1;
-	bp->bio2.bi_io_vec = &bp->bv2;
+		bp->bio1.bi_io_vec = &bp->bv1;
+		bp->bio2.bi_io_vec = &bp->bv2;
 
-	bp->bio1.bi_max_vecs = 1;
-	bp->bio2.bi_max_vecs = 1;
+		bp->bio1.bi_max_vecs = 1;
+		bp->bio2.bi_max_vecs = 1;
+	}
 
 	bp->bio1.bi_end_io = bio_pair_end_1;
 	bp->bio2.bi_end_io = bio_pair_end_2;
diff -u --recursive --new-file linux-3.5.orig/include/linux/blkdev.h linux-3.5/include/linux/blkdev.h
--- linux-3.5.orig/include/linux/blkdev.h	2012-07-21 20:58:29.000000000 +0000
+++ linux-3.5/include/linux/blkdev.h	2012-07-27 06:53:39.507121435 +0000
@@ -590,7 +590,7 @@
  * 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) || \