Revert "md/raid10: improve raid10 discard request"

This reverts commit bcc90d2.

Matthew Ruffell reported data corruption in raid10 due to the changes
in discard handling [1]. Revert these changes before we find a proper fix.

[1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1907262/
Cc: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

Author: liu-song-6

drivers/md/raid10.c

@@ -1516,256 +1516,6 @@ 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 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;
-	}
-
-	if (atomic_dec_and_test(&r10_bio->remaining)) {
-		md_write_end(r10_bio->mddev);
-		raid_end_bio_io(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;
-
-	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 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 (geo->far_offset && remainder) {
-		split_size = stripe_size - remainder;
-		bio = raid10_split_bio(conf, bio, split_size, false);
-	}
-	div_u64_rem(bio_end, stripe_size, &remainder);
-	if (geo->far_offset && remainder) {
-		split_size = bio_sectors(bio) - remainder;
-		bio = raid10_split_bio(conf, bio, split_size, true);
-	}
-
-	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);
-
-	r10_bio->master_bio = bio;
-
-	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);
-
-	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 (atomic_dec_and_test(&r10_bio->remaining)) {
-		md_write_end(r10_bio->mddev);
-		raid_end_bio_io(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;
@@ -1780,10 +1530,6 @@ 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.
@@ -4023,7 +3769,7 @@ 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);