Merge tag 'block-5.10-2020-12-12' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "This should be it for 5.10.

  Mike and Song looked into the warning case, and thankfully it appears
  the fix was pretty trivial - we can just change the md device chunk
  type to unsigned int to get rid of it. They cannot currently be < 0,
  and nobody is checking for that either.

  We're reverting the discard changes as the corruption reports came in
  very late, and there's just no time to attempt to deal with it at this
  point. Reverting the changes in question is the right call for 5.10"

* tag 'block-5.10-2020-12-12' of git://git.kernel.dk/linux-block:
  md: change mddev 'chunk_sectors' from int to unsigned
  Revert "md: add md_submit_discard_bio() for submitting discard bio"
  Revert "md/raid10: extend r10bio devs to raid disks"
  Revert "md/raid10: pull codes that wait for blocked dev into one function"
  Revert "md/raid10: improve raid10 discard request"
  Revert "md/raid10: improve discard request for far layout"
  Revert "dm raid: remove unnecessary discard limits for raid10"

6 files changed, 82 insertions, 393 deletions

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 9c1f7c4de65b..dc8568ab96f2 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3728,6 +3728,17 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 	blk_limits_io_min(limits, chunk_size_bytes);
 	blk_limits_io_opt(limits, chunk_size_bytes * mddev_data_stripes(rs));
+
+	/*
+	 * RAID10 personality requires bio splitting,
+	 * RAID0/1/4/5/6 don't and process large discard bios properly.
+	 */
+	if (rs_is_raid10(rs)) {
+		limits->discard_granularity = max(chunk_size_bytes,
+						  limits->discard_granularity);
+		limits->max_discard_sectors = min_not_zero(rs->md.chunk_sectors,
+							   limits->max_discard_sectors);
+	}
 }
 
 static void raid_postsuspend(struct dm_target *ti)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 98bac4f304ae..0037c6ecab65 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8582,26 +8582,6 @@ void md_write_end(struct mddev *mddev)
 
 EXPORT_SYMBOL(md_write_end);
 
-/* This is used by raid0 and raid10 */
-void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
-			struct bio *bio, sector_t start, sector_t size)
-{
-	struct bio *discard_bio = NULL;
-
-	if (__blkdev_issue_discard(rdev->bdev, start, size,
-		GFP_NOIO, 0, &discard_bio) || !discard_bio)
-		return;
-
-	bio_chain(discard_bio, bio);
-	bio_clone_blkg_association(discard_bio, bio);
-	if (mddev->gendisk)
-		trace_block_bio_remap(bdev_get_queue(rdev->bdev),
-			discard_bio, disk_devt(mddev->gendisk),
-			bio->bi_iter.bi_sector);
-	submit_bio_noacct(discard_bio);
-}
-EXPORT_SYMBOL(md_submit_discard_bio);
-
 /* md_allow_write(mddev)
  * Calling this ensures that the array is marked 'active' so that writes
  * may proceed without blocking.  It is important to call this before
diff --git a/drivers/md/md.h b/drivers/md/md.h
index ccfb69868c2e..bb645bc3ba6d 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -311,7 +311,7 @@ struct mddev {
 	int				external;	/* metadata is
 							 * managed externally */
 	char				metadata_type[17]; /* externally set*/
-	int				chunk_sectors;
+	unsigned int			chunk_sectors;
 	time64_t			ctime, utime;
 	int				level, layout;
 	char				clevel[16];
@@ -339,7 +339,7 @@ struct mddev {
 	 */
 	sector_t			reshape_position;
 	int				delta_disks, new_level, new_layout;
-	int				new_chunk_sectors;
+	unsigned int			new_chunk_sectors;
 	int				reshape_backwards;
 
 	struct md_thread		*thread;	/* management thread */
@@ -713,8 +713,6 @@ extern void md_write_end(struct mddev *mddev);
 extern void md_done_sync(struct mddev *mddev, int blocks, int ok);
 extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
 extern void md_finish_reshape(struct mddev *mddev);
-extern void md_submit_discard_bio(struct mddev *mddev, struct md_rdev *rdev,
-			struct bio *bio, sector_t start, sector_t size);
 
 extern bool __must_check md_flush_request(struct mddev *mddev, struct bio *bio);
 extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 6f44177593a5..35843df15b5e 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -477,6 +477,7 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 
 	for (disk = 0; disk < zone->nb_dev; disk++) {
 		sector_t dev_start, dev_end;
+		struct bio *discard_bio = NULL;
 		struct md_rdev *rdev;
 
 		if (disk < start_disk_index)
@@ -499,9 +500,18 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 
 		rdev = conf->devlist[(zone - conf->strip_zone) *
 			conf->strip_zone[0].nb_dev + disk];
-		md_submit_discard_bio(mddev, rdev, bio,
+		if (__blkdev_issue_discard(rdev->bdev,
 			dev_start + zone->dev_start + rdev->data_offset,
-			dev_end - dev_start);
+			dev_end - dev_start, GFP_NOIO, 0, &discard_bio) ||
+		    !discard_bio)
+			continue;
+		bio_chain(discard_bio, bio);
+		bio_clone_blkg_association(discard_bio, bio);
+		if (mddev->gendisk)
+			trace_block_bio_remap(bdev_get_queue(rdev->bdev),
+				discard_bio, disk_devt(mddev->gendisk),
+				bio->bi_iter.bi_sector);
+		submit_bio_noacct(discard_bio);
 	}
 	bio_endio(bio);
 }
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index b7bca6703df8..3b598a3cb462 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -91,7 +91,7 @@ static inline struct r10bio *get_resync_r10bio(struct bio *bio)
 static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
 {
 	struct r10conf *conf = data;
-	int size = offsetof(struct r10bio, devs[conf->geo.raid_disks]);
+	int size = offsetof(struct r10bio, devs[conf->copies]);
 
 	/* allocate a r10bio with room for raid_disks entries in the
 	 * bios array */
@@ -238,7 +238,7 @@ static void put_all_bios(struct r10conf *conf, struct r10bio *r10_bio)
 {
 	int i;
 
-	for (i = 0; i < conf->geo.raid_disks; i++) {
+	for (i = 0; i < conf->copies; i++) {
 		struct bio **bio = & r10_bio->devs[i].bio;
 		if (!BIO_SPECIAL(*bio))
 			bio_put(*bio);
@@ -327,7 +327,7 @@ static int find_bio_disk(struct r10conf *conf, struct r10bio *r10_bio,
 	int slot;
 	int repl = 0;
 
-	for (slot = 0; slot < conf->geo.raid_disks; slot++) {
+	for (slot = 0; slot < conf->copies; slot++) {
 		if (r10_bio->devs[slot].bio == bio)
 			break;
 		if (r10_bio->devs[slot].repl_bio == bio) {
@@ -336,6 +336,7 @@ static int find_bio_disk(struct r10conf *conf, struct r10bio *r10_bio,
 		}
 	}
 
+	BUG_ON(slot == conf->copies);
 	update_head_pos(slot, r10_bio);
 
 	if (slotp)
@@ -1275,75 +1276,12 @@ static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
 	}
 }
 
-static void wait_blocked_dev(struct mddev *mddev, struct r10bio *r10_bio)
-{
-	int i;
-	struct r10conf *conf = mddev->private;
-	struct md_rdev *blocked_rdev;
-
-retry_wait:
-	blocked_rdev = NULL;
-	rcu_read_lock();
-	for (i = 0; i < conf->copies; i++) {
-		struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
-		struct md_rdev *rrdev = rcu_dereference(
-			conf->mirrors[i].replacement);
-		if (rdev == rrdev)
-			rrdev = NULL;
-		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
-			atomic_inc(&rdev->nr_pending);
-			blocked_rdev = rdev;
-			break;
-		}
-		if (rrdev && unlikely(test_bit(Blocked, &rrdev->flags))) {
-			atomic_inc(&rrdev->nr_pending);
-			blocked_rdev = rrdev;
-			break;
-		}
-
-		if (rdev && test_bit(WriteErrorSeen, &rdev->flags)) {
-			sector_t first_bad;
-			sector_t dev_sector = r10_bio->devs[i].addr;
-			int bad_sectors;
-			int is_bad;
-
-			/* Discard request doesn't care the write result
-			 * so it doesn't need to wait blocked disk here.
-			 */
-			if (!r10_bio->sectors)
-				continue;
-
-			is_bad = is_badblock(rdev, dev_sector, r10_bio->sectors,
-					     &first_bad, &bad_sectors);
-			if (is_bad < 0) {
-				/* Mustn't write here until the bad block
-				 * is acknowledged
-				 */
-				atomic_inc(&rdev->nr_pending);
-				set_bit(BlockedBadBlocks, &rdev->flags);
-				blocked_rdev = rdev;
-				break;
-			}
-		}
-	}
-	rcu_read_unlock();
-
-	if (unlikely(blocked_rdev)) {
-		/* Have to wait for this device to get unblocked, then retry */
-		allow_barrier(conf);
-		raid10_log(conf->mddev, "%s wait rdev %d blocked",
-				__func__, blocked_rdev->raid_disk);
-		md_wait_for_blocked_rdev(blocked_rdev, mddev);
-		wait_barrier(conf);
-		goto retry_wait;
-	}
-}
-
 static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 				 struct r10bio *r10_bio)
 {
 	struct r10conf *conf = mddev->private;
 	int i;
+	struct md_rdev *blocked_rdev;
 	sector_t sectors;
 	int max_sectors;
 
@@ -1401,9 +1339,8 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 
 	r10_bio->read_slot = -1; /* make sure repl_bio gets freed */
 	raid10_find_phys(conf, r10_bio);
-
-	wait_blocked_dev(mddev, r10_bio);
-
+retry_write:
+	blocked_rdev = NULL;
 	rcu_read_lock();
 	max_sectors = r10_bio->sectors;
 
@@ -1414,6 +1351,16 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 			conf->mirrors[d].replacement);
 		if (rdev == rrdev)
 			rrdev = NULL;
+		if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
+			atomic_inc(&rdev->nr_pending);
+			blocked_rdev = rdev;
+			break;
+		}
+		if (rrdev && unlikely(test_bit(Blocked, &rrdev->flags))) {
+			atomic_inc(&rrdev->nr_pending);
+			blocked_rdev = rrdev;
+			break;
+		}
 		if (rdev && (test_bit(Faulty, &rdev->flags)))
 			rdev = NULL;
 		if (rrdev && (test_bit(Faulty, &rrdev->flags)))
@@ -1434,6 +1381,15 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 
 			is_bad = is_badblock(rdev, dev_sector, max_sectors,
 					     &first_bad, &bad_sectors);
+			if (is_bad < 0) {
+				/* Mustn't write here until the bad block
+				 * is acknowledged
+				 */
+				atomic_inc(&rdev->nr_pending);
+				set_bit(BlockedBadBlocks, &rdev->flags);
+				blocked_rdev = rdev;
+				break;
+			}
 			if (is_bad && first_bad <= dev_sector) {
 				/* Cannot write here at all */
 				bad_sectors -= (dev_sector - first_bad);
@@ -1469,6 +1425,35 @@ static void raid10_write_request(struct mddev *mddev, struct bio *bio,
 	}
 	rcu_read_unlock();
 
+	if (unlikely(blocked_rdev)) {
+		/* Have to wait for this device to get unblocked, then retry */
+		int j;
+		int d;
+
+		for (j = 0; j < i; j++) {
+			if (r10_bio->devs[j].bio) {
+				d = r10_bio->devs[j].devnum;
+				rdev_dec_pending(conf->mirrors[d].rdev, mddev);
+			}
+			if (r10_bio->devs[j].repl_bio) {
+				struct md_rdev *rdev;
+				d = r10_bio->devs[j].devnum;
+				rdev = conf->mirrors[d].replacement;
+				if (!rdev) {
+					/* Race with remove_disk */
+					smp_mb();
+					rdev = conf->mirrors[d].rdev;
+				}
+				rdev_dec_pending(rdev, mddev);
+			}
+		}
+		allow_barrier(conf);
+		raid10_log(conf->mddev, "wait rdev %d blocked", blocked_rdev->raid_disk);
+		md_wait_for_blocked_rdev(blocked_rdev, mddev);
+		wait_barrier(conf);
+		goto retry_write;
+	}
+
 	if (max_sectors < r10_bio->sectors)
 		r10_bio->sectors = max_sectors;
 
@@ -1508,7 +1493,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 	r10_bio->mddev = mddev;
 	r10_bio->sector = bio->bi_iter.bi_sector;
 	r10_bio->state = 0;
-	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * conf->geo.raid_disks);
+	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * conf->copies);
 
 	if (bio_data_dir(bio) == READ)
 		raid10_read_request(mddev, bio, r10_bio);
@@ -1516,296 +1501,6 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 		raid10_write_request(mddev, bio, r10_bio);
 }
 
-static struct bio *raid10_split_bio(struct r10conf *conf,
-			struct bio *bio, sector_t sectors, bool want_first)
-{
-	struct bio *split;
-
-	split = bio_split(bio, sectors,	GFP_NOIO, &conf->bio_split);
-	bio_chain(split, bio);
-	allow_barrier(conf);
-	if (want_first) {
-		submit_bio_noacct(bio);
-		bio = split;
-	} else
-		submit_bio_noacct(split);
-	wait_barrier(conf);
-
-	return bio;
-}
-
-static void raid_end_discard_bio(struct r10bio *r10bio)
-{
-	struct r10conf *conf = r10bio->mddev->private;
-	struct r10bio *first_r10bio;
-
-	while (atomic_dec_and_test(&r10bio->remaining)) {
-
-		allow_barrier(conf);
-
-		if (!test_bit(R10BIO_Discard, &r10bio->state)) {
-			first_r10bio = (struct r10bio *)r10bio->master_bio;
-			free_r10bio(r10bio);
-			r10bio = first_r10bio;
-		} else {
-			md_write_end(r10bio->mddev);
-			bio_endio(r10bio->master_bio);
-			free_r10bio(r10bio);
-			break;
-		}
-	}
-}
-
-static void raid10_end_discard_request(struct bio *bio)
-{
-	struct r10bio *r10_bio = bio->bi_private;
-	struct r10conf *conf = r10_bio->mddev->private;
-	struct md_rdev *rdev = NULL;
-	int dev;
-	int slot, repl;
-
-	/*
-	 * We don't care the return value of discard bio
-	 */
-	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
-		set_bit(R10BIO_Uptodate, &r10_bio->state);
-
-	dev = find_bio_disk(conf, r10_bio, bio, &slot, &repl);
-	if (repl)
-		rdev = conf->mirrors[dev].replacement;
-	if (!rdev) {
-		/* raid10_remove_disk uses smp_mb to make sure rdev is set to
-		 * replacement before setting replacement to NULL. It can read
-		 * rdev first without barrier protect even replacment is NULL
-		 */
-		smp_rmb();
-		rdev = conf->mirrors[dev].rdev;
-	}
-
-	raid_end_discard_bio(r10_bio);
-	rdev_dec_pending(rdev, conf->mddev);
-}
-
-/* There are some limitations to handle discard bio
- * 1st, the discard size is bigger than stripe_size*2.
- * 2st, if the discard bio spans reshape progress, we use the old way to
- * handle discard bio
- */
-static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
-{
-	struct r10conf *conf = mddev->private;
-	struct geom *geo = &conf->geo;
-	struct r10bio *r10_bio, *first_r10bio;
-	int far_copies = geo->far_copies;
-	bool first_copy = true;
-
-	int disk;
-	sector_t chunk;
-	unsigned int stripe_size;
-	sector_t split_size;
-
-	sector_t bio_start, bio_end;
-	sector_t first_stripe_index, last_stripe_index;
-	sector_t start_disk_offset;
-	unsigned int start_disk_index;
-	sector_t end_disk_offset;
-	unsigned int end_disk_index;
-	unsigned int remainder;
-
-	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
-		return -EAGAIN;
-
-	wait_barrier(conf);
-
-	/* Check reshape again to avoid reshape happens after checking
-	 * MD_RECOVERY_RESHAPE and before wait_barrier
-	 */
-	if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
-		goto out;
-
-	stripe_size = geo->raid_disks << geo->chunk_shift;
-	bio_start = bio->bi_iter.bi_sector;
-	bio_end = bio_end_sector(bio);
-
-	/* Maybe one discard bio is smaller than strip size or across one stripe
-	 * and discard region is larger than one stripe size. For far offset layout,
-	 * if the discard region is not aligned with stripe size, there is hole
-	 * when we submit discard bio to member disk. For simplicity, we only
-	 * handle discard bio which discard region is bigger than stripe_size*2
-	 */
-	if (bio_sectors(bio) < stripe_size*2)
-		goto out;
-
-	/* For far and far offset layout, if bio is not aligned with stripe size,
-	 * it splits the part that is not aligned with strip size.
-	 */
-	div_u64_rem(bio_start, stripe_size, &remainder);
-	if ((far_copies > 1) && remainder) {
-		split_size = stripe_size - remainder;
-		bio = raid10_split_bio(conf, bio, split_size, false);
-	}
-	div_u64_rem(bio_end, stripe_size, &remainder);
-	if ((far_copies > 1) && remainder) {
-		split_size = bio_sectors(bio) - remainder;
-		bio = raid10_split_bio(conf, bio, split_size, true);
-	}
-
-	bio_start = bio->bi_iter.bi_sector;
-	bio_end = bio_end_sector(bio);
-
-	/* raid10 uses chunk as the unit to store data. It's similar like raid0.
-	 * One stripe contains the chunks from all member disk (one chunk from
-	 * one disk at the same HBA address). For layout detail, see 'man md 4'
-	 */
-	chunk = bio_start >> geo->chunk_shift;
-	chunk *= geo->near_copies;
-	first_stripe_index = chunk;
-	start_disk_index = sector_div(first_stripe_index, geo->raid_disks);
-	if (geo->far_offset)
-		first_stripe_index *= geo->far_copies;
-	start_disk_offset = (bio_start & geo->chunk_mask) +
-				(first_stripe_index << geo->chunk_shift);
-
-	chunk = bio_end >> geo->chunk_shift;
-	chunk *= geo->near_copies;
-	last_stripe_index = chunk;
-	end_disk_index = sector_div(last_stripe_index, geo->raid_disks);
-	if (geo->far_offset)
-		last_stripe_index *= geo->far_copies;
-	end_disk_offset = (bio_end & geo->chunk_mask) +
-				(last_stripe_index << geo->chunk_shift);
-
-retry_discard:
-	r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
-	r10_bio->mddev = mddev;
-	r10_bio->state = 0;
-	r10_bio->sectors = 0;
-	memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) * geo->raid_disks);
-	wait_blocked_dev(mddev, r10_bio);
-
-	/* For far layout it needs more than one r10bio to cover all regions.
-	 * Inspired by raid10_sync_request, we can use the first r10bio->master_bio
-	 * to record the discard bio. Other r10bio->master_bio record the first
-	 * r10bio. The first r10bio only release after all other r10bios finish.
-	 * The discard bio returns only first r10bio finishes
-	 */
-	if (first_copy) {
-		r10_bio->master_bio = bio;
-		set_bit(R10BIO_Discard, &r10_bio->state);
-		first_copy = false;
-		first_r10bio = r10_bio;
-	} else
-		r10_bio->master_bio = (struct bio *)first_r10bio;
-
-	rcu_read_lock();
-	for (disk = 0; disk < geo->raid_disks; disk++) {
-		struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
-		struct md_rdev *rrdev = rcu_dereference(
-			conf->mirrors[disk].replacement);
-
-		r10_bio->devs[disk].bio = NULL;
-		r10_bio->devs[disk].repl_bio = NULL;
-
-		if (rdev && (test_bit(Faulty, &rdev->flags)))
-			rdev = NULL;
-		if (rrdev && (test_bit(Faulty, &rrdev->flags)))
-			rrdev = NULL;
-		if (!rdev && !rrdev)
-			continue;
-
-		if (rdev) {
-			r10_bio->devs[disk].bio = bio;
-			atomic_inc(&rdev->nr_pending);
-		}
-		if (rrdev) {
-			r10_bio->devs[disk].repl_bio = bio;
-			atomic_inc(&rrdev->nr_pending);
-		}
-	}
-	rcu_read_unlock();
-
-	atomic_set(&r10_bio->remaining, 1);
-	for (disk = 0; disk < geo->raid_disks; disk++) {
-		sector_t dev_start, dev_end;
-		struct bio *mbio, *rbio = NULL;
-		struct md_rdev *rdev = rcu_dereference(conf->mirrors[disk].rdev);
-		struct md_rdev *rrdev = rcu_dereference(
-			conf->mirrors[disk].replacement);
-
-		/*
-		 * Now start to calculate the start and end address for each disk.
-		 * The space between dev_start and dev_end is the discard region.
-		 *
-		 * For dev_start, it needs to consider three conditions:
-		 * 1st, the disk is before start_disk, you can imagine the disk in
-		 * the next stripe. So the dev_start is the start address of next
-		 * stripe.
-		 * 2st, the disk is after start_disk, it means the disk is at the
-		 * same stripe of first disk
-		 * 3st, the first disk itself, we can use start_disk_offset directly
-		 */
-		if (disk < start_disk_index)
-			dev_start = (first_stripe_index + 1) * mddev->chunk_sectors;
-		else if (disk > start_disk_index)
-			dev_start = first_stripe_index * mddev->chunk_sectors;
-		else
-			dev_start = start_disk_offset;
-
-		if (disk < end_disk_index)
-			dev_end = (last_stripe_index + 1) * mddev->chunk_sectors;
-		else if (disk > end_disk_index)
-			dev_end = last_stripe_index * mddev->chunk_sectors;
-		else
-			dev_end = end_disk_offset;
-
-		/* It only handles discard bio which size is >= stripe size, so
-		 * dev_end > dev_start all the time
-		 */
-		if (r10_bio->devs[disk].bio) {
-			mbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
-			mbio->bi_end_io = raid10_end_discard_request;
-			mbio->bi_private = r10_bio;
-			r10_bio->devs[disk].bio = mbio;
-			r10_bio->devs[disk].devnum = disk;
-			atomic_inc(&r10_bio->remaining);
-			md_submit_discard_bio(mddev, rdev, mbio,
-					dev_start + choose_data_offset(r10_bio, rdev),
-					dev_end - dev_start);
-			bio_endio(mbio);
-		}
-		if (r10_bio->devs[disk].repl_bio) {
-			rbio = bio_clone_fast(bio, GFP_NOIO, &mddev->bio_set);
-			rbio->bi_end_io = raid10_end_discard_request;
-			rbio->bi_private = r10_bio;
-			r10_bio->devs[disk].repl_bio = rbio;
-			r10_bio->devs[disk].devnum = disk;
-			atomic_inc(&r10_bio->remaining);
-			md_submit_discard_bio(mddev, rrdev, rbio,
-					dev_start + choose_data_offset(r10_bio, rrdev),
-					dev_end - dev_start);
-			bio_endio(rbio);
-		}
-	}
-
-	if (!geo->far_offset && --far_copies) {
-		first_stripe_index += geo->stride >> geo->chunk_shift;
-		start_disk_offset += geo->stride;
-		last_stripe_index += geo->stride >> geo->chunk_shift;
-		end_disk_offset += geo->stride;
-		atomic_inc(&first_r10bio->remaining);
-		raid_end_discard_bio(r10_bio);
-		wait_barrier(conf);
-		goto retry_discard;
-	}
-
-	raid_end_discard_bio(r10_bio);
-
-	return 0;
-out:
-	allow_barrier(conf);
-	return -EAGAIN;
-}
-
 static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
 {
 	struct r10conf *conf = mddev->private;
@@ -1820,10 +1515,6 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
 	if (!md_write_start(mddev, bio))
 		return false;
 
-	if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
-		if (!raid10_handle_discard(mddev, bio))
-			return true;
-
 	/*
 	 * If this request crosses a chunk boundary, we need to split
 	 * it.
@@ -4063,7 +3754,7 @@ static int raid10_run(struct mddev *mddev)
 
 	if (mddev->queue) {
 		blk_queue_max_discard_sectors(mddev->queue,
-					      UINT_MAX);
+					      mddev->chunk_sectors);
 		blk_queue_max_write_same_sectors(mddev->queue, 0);
 		blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
 		blk_queue_io_min(mddev->queue, mddev->chunk_sectors << 9);
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 1461fd55311b..79cd2b7d3128 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -179,6 +179,5 @@ enum r10bio_state {
 	R10BIO_Previous,
 /* failfast devices did receive failfast requests. */
 	R10BIO_FailFast,
-	R10BIO_Discard,
 };
 #endif