2 files changed, 336 insertions, 25 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index e801c6669c6d..717189e74243 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -526,6 +526,7 @@ static void init_stripe(struct stripe_head *sh, sector_t sector, int previous)
 	BUG_ON(atomic_read(&sh->count) != 0);
 	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
 	BUG_ON(stripe_operations_active(sh));
+	BUG_ON(sh->batch_head);
 
 	pr_debug("init_stripe called, stripe %llu\n",
 		(unsigned long long)sector);
@@ -717,6 +718,124 @@ static bool is_full_stripe_write(struct stripe_head *sh)
 	return sh->overwrite_disks == (sh->disks - sh->raid_conf->max_degraded);
 }
 
+static void lock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
+{
+	local_irq_disable();
+	if (sh1 > sh2) {
+		spin_lock(&sh2->stripe_lock);
+		spin_lock_nested(&sh1->stripe_lock, 1);
+	} else {
+		spin_lock(&sh1->stripe_lock);
+		spin_lock_nested(&sh2->stripe_lock, 1);
+	}
+}
+
+static void unlock_two_stripes(struct stripe_head *sh1, struct stripe_head *sh2)
+{
+	spin_unlock(&sh1->stripe_lock);
+	spin_unlock(&sh2->stripe_lock);
+	local_irq_enable();
+}
+
+/* Only freshly new full stripe normal write stripe can be added to a batch list */
+static bool stripe_can_batch(struct stripe_head *sh)
+{
+	return test_bit(STRIPE_BATCH_READY, &sh->state) &&
+		is_full_stripe_write(sh);
+}
+
+/* we only do back search */
+static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh)
+{
+	struct stripe_head *head;
+	sector_t head_sector, tmp_sec;
+	int hash;
+	int dd_idx;
+
+	if (!stripe_can_batch(sh))
+		return;
+	/* Don't cross chunks, so stripe pd_idx/qd_idx is the same */
+	tmp_sec = sh->sector;
+	if (!sector_div(tmp_sec, conf->chunk_sectors))
+		return;
+	head_sector = sh->sector - STRIPE_SECTORS;
+
+	hash = stripe_hash_locks_hash(head_sector);
+	spin_lock_irq(conf->hash_locks + hash);
+	head = __find_stripe(conf, head_sector, conf->generation);
+	if (head && !atomic_inc_not_zero(&head->count)) {
+		spin_lock(&conf->device_lock);
+		if (!atomic_read(&head->count)) {
+			if (!test_bit(STRIPE_HANDLE, &head->state))
+				atomic_inc(&conf->active_stripes);
+			BUG_ON(list_empty(&head->lru) &&
+			       !test_bit(STRIPE_EXPANDING, &head->state));
+			list_del_init(&head->lru);
+			if (head->group) {
+				head->group->stripes_cnt--;
+				head->group = NULL;
+			}
+		}
+		atomic_inc(&head->count);
+		spin_unlock(&conf->device_lock);
+	}
+	spin_unlock_irq(conf->hash_locks + hash);
+
+	if (!head)
+		return;
+	if (!stripe_can_batch(head))
+		goto out;
+
+	lock_two_stripes(head, sh);
+	/* clear_batch_ready clear the flag */
+	if (!stripe_can_batch(head) || !stripe_can_batch(sh))
+		goto unlock_out;
+
+	if (sh->batch_head)
+		goto unlock_out;
+
+	dd_idx = 0;
+	while (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+		dd_idx++;
+	if (head->dev[dd_idx].towrite->bi_rw != sh->dev[dd_idx].towrite->bi_rw)
+		goto unlock_out;
+
+	if (head->batch_head) {
+		spin_lock(&head->batch_head->batch_lock);
+		/* This batch list is already running */
+		if (!stripe_can_batch(head)) {
+			spin_unlock(&head->batch_head->batch_lock);
+			goto unlock_out;
+		}
+
+		/*
+		 * at this point, head's BATCH_READY could be cleared, but we
+		 * can still add the stripe to batch list
+		 */
+		list_add(&sh->batch_list, &head->batch_list);
+		spin_unlock(&head->batch_head->batch_lock);
+
+		sh->batch_head = head->batch_head;
+	} else {
+		head->batch_head = head;
+		sh->batch_head = head->batch_head;
+		spin_lock(&head->batch_lock);
+		list_add_tail(&sh->batch_list, &head->batch_list);
+		spin_unlock(&head->batch_lock);
+	}
+
+	if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		if (atomic_dec_return(&conf->preread_active_stripes)
+		    < IO_THRESHOLD)
+			md_wakeup_thread(conf->mddev->thread);
+
+	atomic_inc(&sh->count);
+unlock_out:
+	unlock_two_stripes(head, sh);
+out:
+	release_stripe(head);
+}
+
 /* Determine if 'data_offset' or 'new_data_offset' should be used
  * in this stripe_head.
  */
@@ -747,6 +866,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 {
 	struct r5conf *conf = sh->raid_conf;
 	int i, disks = sh->disks;
+	struct stripe_head *head_sh = sh;
 
 	might_sleep();
 
@@ -755,6 +875,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 		int replace_only = 0;
 		struct bio *bi, *rbi;
 		struct md_rdev *rdev, *rrdev = NULL;
+
+		sh = head_sh;
 		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags)) {
 			if (test_and_clear_bit(R5_WantFUA, &sh->dev[i].flags))
 				rw = WRITE_FUA;
@@ -773,6 +895,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 		if (test_and_clear_bit(R5_SyncIO, &sh->dev[i].flags))
 			rw |= REQ_SYNC;
 
+again:
 		bi = &sh->dev[i].req;
 		rbi = &sh->dev[i].rreq; /* For writing to replacement */
 
@@ -791,7 +914,7 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 				/* We raced and saw duplicates */
 				rrdev = NULL;
 		} else {
-			if (test_bit(R5_ReadRepl, &sh->dev[i].flags) && rrdev)
+			if (test_bit(R5_ReadRepl, &head_sh->dev[i].flags) && rrdev)
 				rdev = rrdev;
 			rrdev = NULL;
 		}
@@ -862,13 +985,15 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 				__func__, (unsigned long long)sh->sector,
 				bi->bi_rw, i);
 			atomic_inc(&sh->count);
+			if (sh != head_sh)
+				atomic_inc(&head_sh->count);
 			if (use_new_offset(conf, sh))
 				bi->bi_iter.bi_sector = (sh->sector
 						 + rdev->new_data_offset);
 			else
 				bi->bi_iter.bi_sector = (sh->sector
 						 + rdev->data_offset);
-			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+			if (test_bit(R5_ReadNoMerge, &head_sh->dev[i].flags))
 				bi->bi_rw |= REQ_NOMERGE;
 
 			if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
@@ -912,6 +1037,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 				__func__, (unsigned long long)sh->sector,
 				rbi->bi_rw, i);
 			atomic_inc(&sh->count);
+			if (sh != head_sh)
+				atomic_inc(&head_sh->count);
 			if (use_new_offset(conf, sh))
 				rbi->bi_iter.bi_sector = (sh->sector
 						  + rrdev->new_data_offset);
@@ -945,6 +1072,13 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
 			set_bit(STRIPE_HANDLE, &sh->state);
 		}
+
+		if (!head_sh->batch_head)
+			continue;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		if (sh != head_sh)
+			goto again;
 	}
 }
 
@@ -1060,6 +1194,7 @@ static void ops_run_biofill(struct stripe_head *sh)
 	struct async_submit_ctl submit;
 	int i;
 
+	BUG_ON(sh->batch_head);
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
@@ -1148,6 +1283,8 @@ ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
 	struct async_submit_ctl submit;
 	int i;
 
+	BUG_ON(sh->batch_head);
+
 	pr_debug("%s: stripe %llu block: %d\n",
 		__func__, (unsigned long long)sh->sector, target);
 	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
@@ -1214,6 +1351,7 @@ ops_run_compute6_1(struct stripe_head *sh, struct raid5_percpu *percpu)
 	int i;
 	int count;
 
+	BUG_ON(sh->batch_head);
 	if (sh->ops.target < 0)
 		target = sh->ops.target2;
 	else if (sh->ops.target2 < 0)
@@ -1272,6 +1410,7 @@ ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
 	struct page **blocks = to_addr_page(percpu, 0);
 	struct async_submit_ctl submit;
 
+	BUG_ON(sh->batch_head);
 	pr_debug("%s: stripe %llu block1: %d block2: %d\n",
 		 __func__, (unsigned long long)sh->sector, target, target2);
 	BUG_ON(target < 0 || target2 < 0);
@@ -1384,6 +1523,7 @@ ops_run_prexor(struct stripe_head *sh, struct raid5_percpu *percpu,
 	/* existing parity data subtracted */
 	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
 
+	BUG_ON(sh->batch_head);
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
@@ -1406,17 +1546,21 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 {
 	int disks = sh->disks;
 	int i;
+	struct stripe_head *head_sh = sh;
 
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
 	for (i = disks; i--; ) {
-		struct r5dev *dev = &sh->dev[i];
+		struct r5dev *dev;
 		struct bio *chosen;
 
-		if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
+		sh = head_sh;
+		if (test_and_clear_bit(R5_Wantdrain, &head_sh->dev[i].flags)) {
 			struct bio *wbi;
 
+again:
+			dev = &sh->dev[i];
 			spin_lock_irq(&sh->stripe_lock);
 			chosen = dev->towrite;
 			dev->towrite = NULL;
@@ -1445,6 +1589,15 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 				}
 				wbi = r5_next_bio(wbi, dev->sector);
 			}
+
+			if (head_sh->batch_head) {
+				sh = list_first_entry(&sh->batch_list,
+						      struct stripe_head,
+						      batch_list);
+				if (sh == head_sh)
+					continue;
+				goto again;
+			}
 		}
 	}
 
@@ -1500,12 +1653,15 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
 		     struct dma_async_tx_descriptor *tx)
 {
 	int disks = sh->disks;
-	struct page **xor_srcs = to_addr_page(percpu, 0);
+	struct page **xor_srcs;
 	struct async_submit_ctl submit;
-	int count = 0, pd_idx = sh->pd_idx, i;
+	int count, pd_idx = sh->pd_idx, i;
 	struct page *xor_dest;
 	int prexor = 0;
 	unsigned long flags;
+	int j = 0;
+	struct stripe_head *head_sh = sh;
+	int last_stripe;
 
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
@@ -1522,15 +1678,18 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
 		ops_complete_reconstruct(sh);
 		return;
 	}
+again:
+	count = 0;
+	xor_srcs = to_addr_page(percpu, j);
 	/* check if prexor is active which means only process blocks
 	 * that are part of a read-modify-write (written)
 	 */
-	if (sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
+	if (head_sh->reconstruct_state == reconstruct_state_prexor_drain_run) {
 		prexor = 1;
 		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
 		for (i = disks; i--; ) {
 			struct r5dev *dev = &sh->dev[i];
-			if (dev->written)
+			if (head_sh->dev[i].written)
 				xor_srcs[count++] = dev->page;
 		}
 	} else {
@@ -1547,17 +1706,32 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
 	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
 	 * for the synchronous xor case
 	 */
-	flags = ASYNC_TX_ACK |
-		(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
-
-	atomic_inc(&sh->count);
+	last_stripe = !head_sh->batch_head ||
+		list_first_entry(&sh->batch_list,
+				 struct stripe_head, batch_list) == head_sh;
+	if (last_stripe) {
+		flags = ASYNC_TX_ACK |
+			(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
+
+		atomic_inc(&head_sh->count);
+		init_async_submit(&submit, flags, tx, ops_complete_reconstruct, head_sh,
+				  to_addr_conv(sh, percpu, j));
+	} else {
+		flags = prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST;
+		init_async_submit(&submit, flags, tx, NULL, NULL,
+				  to_addr_conv(sh, percpu, j));
+	}
 
-	init_async_submit(&submit, flags, tx, ops_complete_reconstruct, sh,
-			  to_addr_conv(sh, percpu, 0));
 	if (unlikely(count == 1))
 		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
 	else
 		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);
+	if (!last_stripe) {
+		j++;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		goto again;
+	}
 }
 
 static void
@@ -1565,8 +1739,10 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
 		     struct dma_async_tx_descriptor *tx)
 {
 	struct async_submit_ctl submit;
-	struct page **blocks = to_addr_page(percpu, 0);
-	int count, i;
+	struct page **blocks;
+	int count, i, j = 0;
+	struct stripe_head *head_sh = sh;
+	int last_stripe;
 
 	pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
 
@@ -1584,13 +1760,27 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
 		return;
 	}
 
+again:
+	blocks = to_addr_page(percpu, j);
 	count = set_syndrome_sources(blocks, sh);
-
-	atomic_inc(&sh->count);
-
-	init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_reconstruct,
-			  sh, to_addr_conv(sh, percpu, 0));
+	last_stripe = !head_sh->batch_head ||
+		list_first_entry(&sh->batch_list,
+				 struct stripe_head, batch_list) == head_sh;
+
+	if (last_stripe) {
+		atomic_inc(&head_sh->count);
+		init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_reconstruct,
+				  head_sh, to_addr_conv(sh, percpu, j));
+	} else
+		init_async_submit(&submit, 0, tx, NULL, NULL,
+				  to_addr_conv(sh, percpu, j));
 	async_gen_syndrome(blocks, 0, count+2, STRIPE_SIZE,  &submit);
+	if (!last_stripe) {
+		j++;
+		sh = list_first_entry(&sh->batch_list, struct stripe_head,
+				      batch_list);
+		goto again;
+	}
 }
 
 static void ops_complete_check(void *stripe_head_ref)
@@ -1620,6 +1810,7 @@ static void ops_run_check_p(struct stripe_head *sh, struct raid5_percpu *percpu)
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
+	BUG_ON(sh->batch_head);
 	count = 0;
 	xor_dest = sh->dev[pd_idx].page;
 	xor_srcs[count++] = xor_dest;
@@ -1648,6 +1839,7 @@ static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu
 	pr_debug("%s: stripe %llu checkp: %d\n", __func__,
 		(unsigned long long)sh->sector, checkp);
 
+	BUG_ON(sh->batch_head);
 	count = set_syndrome_sources(srcs, sh);
 	if (!checkp)
 		srcs[count] = NULL;
@@ -1715,7 +1907,7 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
 			BUG();
 	}
 
-	if (overlap_clear)
+	if (overlap_clear && !sh->batch_head)
 		for (i = disks; i--; ) {
 			struct r5dev *dev = &sh->dev[i];
 			if (test_and_clear_bit(R5_Overlap, &dev->flags))
@@ -1745,6 +1937,10 @@ static int grow_one_stripe(struct r5conf *conf, int hash)
 	atomic_set(&sh->count, 1);
 	atomic_inc(&conf->active_stripes);
 	INIT_LIST_HEAD(&sh->lru);
+
+	spin_lock_init(&sh->batch_lock);
+	INIT_LIST_HEAD(&sh->batch_list);
+	sh->batch_head = NULL;
 	release_stripe(sh);
 	return 1;
 }
@@ -2188,6 +2384,9 @@ static void raid5_end_write_request(struct bio *bi, int error)
 		clear_bit(R5_LOCKED, &sh->dev[i].flags);
 	set_bit(STRIPE_HANDLE, &sh->state);
 	release_stripe(sh);
+
+	if (sh->batch_head && sh != sh->batch_head)
+		release_stripe(sh->batch_head);
 }
 
 static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous);
@@ -2674,6 +2873,9 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 	 * protect it.
 	 */
 	spin_lock_irq(&sh->stripe_lock);
+	/* Don't allow new IO added to stripes in batch list */
+	if (sh->batch_head)
+		goto overlap;
 	if (forwrite) {
 		bip = &sh->dev[dd_idx].towrite;
 		if (*bip == NULL)
@@ -2723,6 +2925,9 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		sh->bm_seq = conf->seq_flush+1;
 		set_bit(STRIPE_BIT_DELAY, &sh->state);
 	}
+
+	if (stripe_can_batch(sh))
+		stripe_add_to_batch_list(conf, sh);
 	return 1;
 
  overlap:
@@ -2755,6 +2960,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 				struct bio **return_bi)
 {
 	int i;
+	BUG_ON(sh->batch_head);
 	for (i = disks; i--; ) {
 		struct bio *bi;
 		int bitmap_end = 0;
@@ -2870,6 +3076,7 @@ handle_failed_sync(struct r5conf *conf, struct stripe_head *sh,
 	int abort = 0;
 	int i;
 
+	BUG_ON(sh->batch_head);
 	clear_bit(STRIPE_SYNCING, &sh->state);
 	if (test_and_clear_bit(R5_Overlap, &sh->dev[sh->pd_idx].flags))
 		wake_up(&conf->wait_for_overlap);
@@ -3100,6 +3307,7 @@ static void handle_stripe_fill(struct stripe_head *sh,
 {
 	int i;
 
+	BUG_ON(sh->batch_head);
 	/* look for blocks to read/compute, skip this if a compute
 	 * is already in flight, or if the stripe contents are in the
 	 * midst of changing due to a write
@@ -3123,6 +3331,9 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 	int i;
 	struct r5dev *dev;
 	int discard_pending = 0;
+	struct stripe_head *head_sh = sh;
+	bool do_endio = false;
+	int wakeup_nr = 0;
 
 	for (i = disks; i--; )
 		if (sh->dev[i].written) {
@@ -3138,8 +3349,11 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 					clear_bit(R5_UPTODATE, &dev->flags);
 				if (test_and_clear_bit(R5_SkipCopy, &dev->flags)) {
 					WARN_ON(test_bit(R5_UPTODATE, &dev->flags));
-					dev->page = dev->orig_page;
 				}
+				do_endio = true;
+
+returnbi:
+				dev->page = dev->orig_page;
 				wbi = dev->written;
 				dev->written = NULL;
 				while (wbi && wbi->bi_iter.bi_sector <
@@ -3156,6 +3370,17 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 						STRIPE_SECTORS,
 					 !test_bit(STRIPE_DEGRADED, &sh->state),
 						0);
+				if (head_sh->batch_head) {
+					sh = list_first_entry(&sh->batch_list,
+							      struct stripe_head,
+							      batch_list);
+					if (sh != head_sh) {
+						dev = &sh->dev[i];
+						goto returnbi;
+					}
+				}
+				sh = head_sh;
+				dev = &sh->dev[i];
 			} else if (test_bit(R5_Discard, &dev->flags))
 				discard_pending = 1;
 			WARN_ON(test_bit(R5_SkipCopy, &dev->flags));
@@ -3177,8 +3402,17 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 		 * will be reinitialized
 		 */
 		spin_lock_irq(&conf->device_lock);
+unhash:
 		remove_hash(sh);
+		if (head_sh->batch_head) {
+			sh = list_first_entry(&sh->batch_list,
+					      struct stripe_head, batch_list);
+			if (sh != head_sh)
+					goto unhash;
+		}
 		spin_unlock_irq(&conf->device_lock);
+		sh = head_sh;
+
 		if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state))
 			set_bit(STRIPE_HANDLE, &sh->state);
 
@@ -3187,6 +3421,39 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 	if (test_and_clear_bit(STRIPE_FULL_WRITE, &sh->state))
 		if (atomic_dec_and_test(&conf->pending_full_writes))
 			md_wakeup_thread(conf->mddev->thread);
+
+	if (!head_sh->batch_head || !do_endio)
+		return;
+	for (i = 0; i < head_sh->disks; i++) {
+		if (test_and_clear_bit(R5_Overlap, &head_sh->dev[i].flags))
+			wakeup_nr++;
+	}
+	while (!list_empty(&head_sh->batch_list)) {
+		int i;
+		sh = list_first_entry(&head_sh->batch_list,
+				      struct stripe_head, batch_list);
+		list_del_init(&sh->batch_list);
+
+		sh->state = head_sh->state & (~((1 << STRIPE_ACTIVE) |
+			(1 << STRIPE_PREREAD_ACTIVE)));
+		sh->check_state = head_sh->check_state;
+		sh->reconstruct_state = head_sh->reconstruct_state;
+		for (i = 0; i < sh->disks; i++) {
+			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+				wakeup_nr++;
+			sh->dev[i].flags = head_sh->dev[i].flags;
+		}
+
+		spin_lock_irq(&sh->stripe_lock);
+		sh->batch_head = NULL;
+		spin_unlock_irq(&sh->stripe_lock);
+		release_stripe(sh);
+	}
+
+	spin_lock_irq(&head_sh->stripe_lock);
+	head_sh->batch_head = NULL;
+	spin_unlock_irq(&head_sh->stripe_lock);
+	wake_up_nr(&conf->wait_for_overlap, wakeup_nr);
 }
 
 static void handle_stripe_dirtying(struct r5conf *conf,
@@ -3326,6 +3593,7 @@ static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
 {
 	struct r5dev *dev = NULL;
 
+	BUG_ON(sh->batch_head);
 	set_bit(STRIPE_HANDLE, &sh->state);
 
 	switch (sh->check_state) {
@@ -3416,6 +3684,7 @@ static void handle_parity_checks6(struct r5conf *conf, struct stripe_head *sh,
 	int qd_idx = sh->qd_idx;
 	struct r5dev *dev;
 
+	BUG_ON(sh->batch_head);
 	set_bit(STRIPE_HANDLE, &sh->state);
 
 	BUG_ON(s->failed > 2);
@@ -3579,6 +3848,7 @@ static void handle_stripe_expansion(struct r5conf *conf, struct stripe_head *sh)
 	 * copy some of them into a target stripe for expand.
 	 */
 	struct dma_async_tx_descriptor *tx = NULL;
+	BUG_ON(sh->batch_head);
 	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
 	for (i = 0; i < sh->disks; i++)
 		if (i != sh->pd_idx && i != sh->qd_idx) {
@@ -3822,6 +4092,38 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 	rcu_read_unlock();
 }
 
+static int clear_batch_ready(struct stripe_head *sh)
+{
+	struct stripe_head *tmp;
+	if (!test_and_clear_bit(STRIPE_BATCH_READY, &sh->state))
+		return 0;
+	spin_lock(&sh->stripe_lock);
+	if (!sh->batch_head) {
+		spin_unlock(&sh->stripe_lock);
+		return 0;
+	}
+
+	/*
+	 * this stripe could be added to a batch list before we check
+	 * BATCH_READY, skips it
+	 */
+	if (sh->batch_head != sh) {
+		spin_unlock(&sh->stripe_lock);
+		return 1;
+	}
+	spin_lock(&sh->batch_lock);
+	list_for_each_entry(tmp, &sh->batch_list, batch_list)
+		clear_bit(STRIPE_BATCH_READY, &tmp->state);
+	spin_unlock(&sh->batch_lock);
+	spin_unlock(&sh->stripe_lock);
+
+	/*
+	 * BATCH_READY is cleared, no new stripes can be added.
+	 * batch_list can be accessed without lock
+	 */
+	return 0;
+}
+
 static void handle_stripe(struct stripe_head *sh)
 {
 	struct stripe_head_state s;
@@ -3839,7 +4141,11 @@ static void handle_stripe(struct stripe_head *sh)
 		return;
 	}
 
-	clear_bit(STRIPE_BATCH_READY, &sh->state);
+	if (clear_batch_ready(sh) ) {
+		clear_bit_unlock(STRIPE_ACTIVE, &sh->state);
+		return;
+	}
+
 	if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state)) {
 		spin_lock(&sh->stripe_lock);
 		/* Cannot process 'sync' concurrently with 'discard' */
@@ -4824,7 +5130,8 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 			}
 			set_bit(STRIPE_HANDLE, &sh->state);
 			clear_bit(STRIPE_DELAYED, &sh->state);
-			if ((bi->bi_rw & REQ_SYNC) &&
+			if ((!sh->batch_head || sh == sh->batch_head) &&
+			    (bi->bi_rw & REQ_SYNC) &&
 			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
 				atomic_inc(&conf->preread_active_stripes);
 			release_stripe_plug(mddev, sh);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 4cc1a48127c7..c8d0004dca8f 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -219,6 +219,10 @@ struct stripe_head {
 	spinlock_t		stripe_lock;
 	int			cpu;
 	struct r5worker_group	*group;
+
+	struct stripe_head	*batch_head; /* protected by stripe lock */
+	spinlock_t		batch_lock; /* only header's lock is useful */
+	struct list_head	batch_list; /* protected by head's batch lock*/
 	/**
 	 * struct stripe_operations
 	 * @target - STRIPE_OP_COMPUTE_BLK target