1 files changed, 205 insertions, 112 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 04348d76bb30..adda94df5eb2 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -99,34 +99,40 @@ static inline struct bio *r5_next_bio(struct bio *bio, sector_t sector)
  * We maintain a biased count of active stripes in the bottom 16 bits of
  * bi_phys_segments, and a count of processed stripes in the upper 16 bits
  */
-static inline int raid5_bi_phys_segments(struct bio *bio)
+static inline int raid5_bi_processed_stripes(struct bio *bio)
 {
-	return bio->bi_phys_segments & 0xffff;
+	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
+	return (atomic_read(segments) >> 16) & 0xffff;
 }
 
-static inline int raid5_bi_hw_segments(struct bio *bio)
+static inline int raid5_dec_bi_active_stripes(struct bio *bio)
 {
-	return (bio->bi_phys_segments >> 16) & 0xffff;
+	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
+	return atomic_sub_return(1, segments) & 0xffff;
 }
 
-static inline int raid5_dec_bi_phys_segments(struct bio *bio)
+static inline void raid5_inc_bi_active_stripes(struct bio *bio)
 {
-	--bio->bi_phys_segments;
-	return raid5_bi_phys_segments(bio);
+	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
+	atomic_inc(segments);
 }
 
-static inline int raid5_dec_bi_hw_segments(struct bio *bio)
+static inline void raid5_set_bi_processed_stripes(struct bio *bio,
+	unsigned int cnt)
 {
-	unsigned short val = raid5_bi_hw_segments(bio);
+	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
+	int old, new;
 
-	--val;
-	bio->bi_phys_segments = (val << 16) | raid5_bi_phys_segments(bio);
-	return val;
+	do {
+		old = atomic_read(segments);
+		new = (old & 0xffff) | (cnt << 16);
+	} while (atomic_cmpxchg(segments, old, new) != old);
 }
 
-static inline void raid5_set_bi_hw_segments(struct bio *bio, unsigned int cnt)
+static inline void raid5_set_bi_stripes(struct bio *bio, unsigned int cnt)
 {
-	bio->bi_phys_segments = raid5_bi_phys_segments(bio) | (cnt << 16);
+	atomic_t *segments = (atomic_t *)&bio->bi_phys_segments;
+	atomic_set(segments, cnt);
 }
 
 /* Find first data disk in a raid6 stripe */
@@ -190,49 +196,56 @@ static int stripe_operations_active(struct stripe_head *sh)
 	       test_bit(STRIPE_COMPUTE_RUN, &sh->state);
 }
 
-static void __release_stripe(struct r5conf *conf, struct stripe_head *sh)
+static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh)
 {
-	if (atomic_dec_and_test(&sh->count)) {
-		BUG_ON(!list_empty(&sh->lru));
-		BUG_ON(atomic_read(&conf->active_stripes)==0);
-		if (test_bit(STRIPE_HANDLE, &sh->state)) {
-			if (test_bit(STRIPE_DELAYED, &sh->state) &&
-			    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
-				list_add_tail(&sh->lru, &conf->delayed_list);
-			else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
-				   sh->bm_seq - conf->seq_write > 0)
-				list_add_tail(&sh->lru, &conf->bitmap_list);
-			else {
-				clear_bit(STRIPE_DELAYED, &sh->state);
-				clear_bit(STRIPE_BIT_DELAY, &sh->state);
-				list_add_tail(&sh->lru, &conf->handle_list);
-			}
-			md_wakeup_thread(conf->mddev->thread);
-		} else {
-			BUG_ON(stripe_operations_active(sh));
-			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_dec(&conf->active_stripes);
-			if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
-				list_add_tail(&sh->lru, &conf->inactive_list);
-				wake_up(&conf->wait_for_stripe);
-				if (conf->retry_read_aligned)
-					md_wakeup_thread(conf->mddev->thread);
-			}
+	BUG_ON(!list_empty(&sh->lru));
+	BUG_ON(atomic_read(&conf->active_stripes)==0);
+	if (test_bit(STRIPE_HANDLE, &sh->state)) {
+		if (test_bit(STRIPE_DELAYED, &sh->state) &&
+		    !test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+			list_add_tail(&sh->lru, &conf->delayed_list);
+		else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
+			   sh->bm_seq - conf->seq_write > 0)
+			list_add_tail(&sh->lru, &conf->bitmap_list);
+		else {
+			clear_bit(STRIPE_DELAYED, &sh->state);
+			clear_bit(STRIPE_BIT_DELAY, &sh->state);
+			list_add_tail(&sh->lru, &conf->handle_list);
+		}
+		md_wakeup_thread(conf->mddev->thread);
+	} else {
+		BUG_ON(stripe_operations_active(sh));
+		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_dec(&conf->active_stripes);
+		if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
+			list_add_tail(&sh->lru, &conf->inactive_list);
+			wake_up(&conf->wait_for_stripe);
+			if (conf->retry_read_aligned)
+				md_wakeup_thread(conf->mddev->thread);
 		}
 	}
 }
 
+static void __release_stripe(struct r5conf *conf, struct stripe_head *sh)
+{
+	if (atomic_dec_and_test(&sh->count))
+		do_release_stripe(conf, sh);
+}
+
 static void release_stripe(struct stripe_head *sh)
 {
 	struct r5conf *conf = sh->raid_conf;
 	unsigned long flags;
 
-	spin_lock_irqsave(&conf->device_lock, flags);
-	__release_stripe(conf, sh);
-	spin_unlock_irqrestore(&conf->device_lock, flags);
+	local_irq_save(flags);
+	if (atomic_dec_and_lock(&sh->count, &conf->device_lock)) {
+		do_release_stripe(conf, sh);
+		spin_unlock(&conf->device_lock);
+	}
+	local_irq_restore(flags);
 }
 
 static inline void remove_hash(struct stripe_head *sh)
@@ -471,7 +484,8 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
 		} else {
 			if (atomic_read(&sh->count)) {
 				BUG_ON(!list_empty(&sh->lru)
-				    && !test_bit(STRIPE_EXPANDING, &sh->state));
+				    && !test_bit(STRIPE_EXPANDING, &sh->state)
+				    && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state));
 			} else {
 				if (!test_bit(STRIPE_HANDLE, &sh->state))
 					atomic_inc(&conf->active_stripes);
@@ -640,6 +654,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 			else
 				bi->bi_sector = (sh->sector
 						 + rdev->data_offset);
+			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+				bi->bi_rw |= REQ_FLUSH;
+
 			bi->bi_flags = 1 << BIO_UPTODATE;
 			bi->bi_idx = 0;
 			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
@@ -749,14 +766,12 @@ static void ops_complete_biofill(void *stripe_head_ref)
 {
 	struct stripe_head *sh = stripe_head_ref;
 	struct bio *return_bi = NULL;
-	struct r5conf *conf = sh->raid_conf;
 	int i;
 
 	pr_debug("%s: stripe %llu\n", __func__,
 		(unsigned long long)sh->sector);
 
 	/* clear completed biofills */
-	spin_lock_irq(&conf->device_lock);
 	for (i = sh->disks; i--; ) {
 		struct r5dev *dev = &sh->dev[i];
 
@@ -774,7 +789,7 @@ static void ops_complete_biofill(void *stripe_head_ref)
 			while (rbi && rbi->bi_sector <
 				dev->sector + STRIPE_SECTORS) {
 				rbi2 = r5_next_bio(rbi, dev->sector);
-				if (!raid5_dec_bi_phys_segments(rbi)) {
+				if (!raid5_dec_bi_active_stripes(rbi)) {
 					rbi->bi_next = return_bi;
 					return_bi = rbi;
 				}
@@ -782,7 +797,6 @@ static void ops_complete_biofill(void *stripe_head_ref)
 			}
 		}
 	}
-	spin_unlock_irq(&conf->device_lock);
 	clear_bit(STRIPE_BIOFILL_RUN, &sh->state);
 
 	return_io(return_bi);
@@ -794,7 +808,6 @@ static void ops_complete_biofill(void *stripe_head_ref)
 static void ops_run_biofill(struct stripe_head *sh)
 {
 	struct dma_async_tx_descriptor *tx = NULL;
-	struct r5conf *conf = sh->raid_conf;
 	struct async_submit_ctl submit;
 	int i;
 
@@ -805,10 +818,10 @@ static void ops_run_biofill(struct stripe_head *sh)
 		struct r5dev *dev = &sh->dev[i];
 		if (test_bit(R5_Wantfill, &dev->flags)) {
 			struct bio *rbi;
-			spin_lock_irq(&conf->device_lock);
+			spin_lock_irq(&sh->stripe_lock);
 			dev->read = rbi = dev->toread;
 			dev->toread = NULL;
-			spin_unlock_irq(&conf->device_lock);
+			spin_unlock_irq(&sh->stripe_lock);
 			while (rbi && rbi->bi_sector <
 				dev->sector + STRIPE_SECTORS) {
 				tx = async_copy_data(0, rbi, dev->page,
@@ -1144,12 +1157,12 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
 		if (test_and_clear_bit(R5_Wantdrain, &dev->flags)) {
 			struct bio *wbi;
 
-			spin_lock_irq(&sh->raid_conf->device_lock);
+			spin_lock_irq(&sh->stripe_lock);
 			chosen = dev->towrite;
 			dev->towrite = NULL;
 			BUG_ON(dev->written);
 			wbi = dev->written = chosen;
-			spin_unlock_irq(&sh->raid_conf->device_lock);
+			spin_unlock_irq(&sh->stripe_lock);
 
 			while (wbi && wbi->bi_sector <
 				dev->sector + STRIPE_SECTORS) {
@@ -1454,6 +1467,8 @@ static int grow_one_stripe(struct r5conf *conf)
 	init_waitqueue_head(&sh->ops.wait_for_ops);
 	#endif
 
+	spin_lock_init(&sh->stripe_lock);
+
 	if (grow_buffers(sh)) {
 		shrink_buffers(sh);
 		kmem_cache_free(conf->slab_cache, sh);
@@ -1739,7 +1754,9 @@ static void raid5_end_read_request(struct bio * bi, int error)
 			atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
-		}
+		} else if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
+			clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+
 		if (atomic_read(&rdev->read_errors))
 			atomic_set(&rdev->read_errors, 0);
 	} else {
@@ -1784,7 +1801,11 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		else
 			retry = 1;
 		if (retry)
-			set_bit(R5_ReadError, &sh->dev[i].flags);
+			if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags)) {
+				set_bit(R5_ReadError, &sh->dev[i].flags);
+				clear_bit(R5_ReadNoMerge, &sh->dev[i].flags);
+			} else
+				set_bit(R5_ReadNoMerge, &sh->dev[i].flags);
 		else {
 			clear_bit(R5_ReadError, &sh->dev[i].flags);
 			clear_bit(R5_ReWrite, &sh->dev[i].flags);
@@ -2340,11 +2361,18 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 		(unsigned long long)bi->bi_sector,
 		(unsigned long long)sh->sector);
 
-
-	spin_lock_irq(&conf->device_lock);
+	/*
+	 * If several bio share a stripe. The bio bi_phys_segments acts as a
+	 * reference count to avoid race. The reference count should already be
+	 * increased before this function is called (for example, in
+	 * make_request()), so other bio sharing this stripe will not free the
+	 * stripe. If a stripe is owned by one stripe, the stripe lock will
+	 * protect it.
+	 */
+	spin_lock_irq(&sh->stripe_lock);
 	if (forwrite) {
 		bip = &sh->dev[dd_idx].towrite;
-		if (*bip == NULL && sh->dev[dd_idx].written == NULL)
+		if (*bip == NULL)
 			firstwrite = 1;
 	} else
 		bip = &sh->dev[dd_idx].toread;
@@ -2360,7 +2388,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 	if (*bip)
 		bi->bi_next = *bip;
 	*bip = bi;
-	bi->bi_phys_segments++;
+	raid5_inc_bi_active_stripes(bi);
 
 	if (forwrite) {
 		/* check if page is covered */
@@ -2375,7 +2403,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 		if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
 			set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
 	}
-	spin_unlock_irq(&conf->device_lock);
+	spin_unlock_irq(&sh->stripe_lock);
 
 	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
 		(unsigned long long)(*bip)->bi_sector,
@@ -2391,7 +2419,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 
  overlap:
 	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
-	spin_unlock_irq(&conf->device_lock);
+	spin_unlock_irq(&sh->stripe_lock);
 	return 0;
 }
 
@@ -2441,10 +2469,11 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 				rdev_dec_pending(rdev, conf->mddev);
 			}
 		}
-		spin_lock_irq(&conf->device_lock);
+		spin_lock_irq(&sh->stripe_lock);
 		/* fail all writes first */
 		bi = sh->dev[i].towrite;
 		sh->dev[i].towrite = NULL;
+		spin_unlock_irq(&sh->stripe_lock);
 		if (bi) {
 			s->to_write--;
 			bitmap_end = 1;
@@ -2457,13 +2486,17 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 			sh->dev[i].sector + STRIPE_SECTORS) {
 			struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
-			if (!raid5_dec_bi_phys_segments(bi)) {
+			if (!raid5_dec_bi_active_stripes(bi)) {
 				md_write_end(conf->mddev);
 				bi->bi_next = *return_bi;
 				*return_bi = bi;
 			}
 			bi = nextbi;
 		}
+		if (bitmap_end)
+			bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+				STRIPE_SECTORS, 0, 0);
+		bitmap_end = 0;
 		/* and fail all 'written' */
 		bi = sh->dev[i].written;
 		sh->dev[i].written = NULL;
@@ -2472,7 +2505,7 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 		       sh->dev[i].sector + STRIPE_SECTORS) {
 			struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
-			if (!raid5_dec_bi_phys_segments(bi)) {
+			if (!raid5_dec_bi_active_stripes(bi)) {
 				md_write_end(conf->mddev);
 				bi->bi_next = *return_bi;
 				*return_bi = bi;
@@ -2496,14 +2529,13 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
 				struct bio *nextbi =
 					r5_next_bio(bi, sh->dev[i].sector);
 				clear_bit(BIO_UPTODATE, &bi->bi_flags);
-				if (!raid5_dec_bi_phys_segments(bi)) {
+				if (!raid5_dec_bi_active_stripes(bi)) {
 					bi->bi_next = *return_bi;
 					*return_bi = bi;
 				}
 				bi = nextbi;
 			}
 		}
-		spin_unlock_irq(&conf->device_lock);
 		if (bitmap_end)
 			bitmap_endwrite(conf->mddev->bitmap, sh->sector,
 					STRIPE_SECTORS, 0, 0);
@@ -2707,30 +2739,23 @@ static void handle_stripe_clean_event(struct r5conf *conf,
 				test_bit(R5_UPTODATE, &dev->flags)) {
 				/* We can return any write requests */
 				struct bio *wbi, *wbi2;
-				int bitmap_end = 0;
 				pr_debug("Return write for disc %d\n", i);
-				spin_lock_irq(&conf->device_lock);
 				wbi = dev->written;
 				dev->written = NULL;
 				while (wbi && wbi->bi_sector <
 					dev->sector + STRIPE_SECTORS) {
 					wbi2 = r5_next_bio(wbi, dev->sector);
-					if (!raid5_dec_bi_phys_segments(wbi)) {
+					if (!raid5_dec_bi_active_stripes(wbi)) {
 						md_write_end(conf->mddev);
 						wbi->bi_next = *return_bi;
 						*return_bi = wbi;
 					}
 					wbi = wbi2;
 				}
-				if (dev->towrite == NULL)
-					bitmap_end = 1;
-				spin_unlock_irq(&conf->device_lock);
-				if (bitmap_end)
-					bitmap_endwrite(conf->mddev->bitmap,
-							sh->sector,
-							STRIPE_SECTORS,
+				bitmap_endwrite(conf->mddev->bitmap, sh->sector,
+						STRIPE_SECTORS,
 					 !test_bit(STRIPE_DEGRADED, &sh->state),
-							0);
+						0);
 			}
 		}
 
@@ -3182,7 +3207,6 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 
 	/* Now to look around and see what can be done */
 	rcu_read_lock();
-	spin_lock_irq(&conf->device_lock);
 	for (i=disks; i--; ) {
 		struct md_rdev *rdev;
 		sector_t first_bad;
@@ -3328,7 +3352,6 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s)
 				do_recovery = 1;
 		}
 	}
-	spin_unlock_irq(&conf->device_lock);
 	if (test_bit(STRIPE_SYNCING, &sh->state)) {
 		/* If there is a failed device being replaced,
 		 *     we must be recovering.
@@ -3791,7 +3814,7 @@ static struct bio *remove_bio_from_retry(struct r5conf *conf)
 		 * this sets the active strip count to 1 and the processed
 		 * strip count to zero (upper 8 bits)
 		 */
-		bi->bi_phys_segments = 1; /* biased count of active stripes */
+		raid5_set_bi_stripes(bi, 1); /* biased count of active stripes */
 	}
 
 	return bi;
@@ -3988,6 +4011,62 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf)
 	return sh;
 }
 
+struct raid5_plug_cb {
+	struct blk_plug_cb	cb;
+	struct list_head	list;
+};
+
+static void raid5_unplug(struct blk_plug_cb *blk_cb, bool from_schedule)
+{
+	struct raid5_plug_cb *cb = container_of(
+		blk_cb, struct raid5_plug_cb, cb);
+	struct stripe_head *sh;
+	struct mddev *mddev = cb->cb.data;
+	struct r5conf *conf = mddev->private;
+
+	if (cb->list.next && !list_empty(&cb->list)) {
+		spin_lock_irq(&conf->device_lock);
+		while (!list_empty(&cb->list)) {
+			sh = list_first_entry(&cb->list, struct stripe_head, lru);
+			list_del_init(&sh->lru);
+			/*
+			 * avoid race release_stripe_plug() sees
+			 * STRIPE_ON_UNPLUG_LIST clear but the stripe
+			 * is still in our list
+			 */
+			smp_mb__before_clear_bit();
+			clear_bit(STRIPE_ON_UNPLUG_LIST, &sh->state);
+			__release_stripe(conf, sh);
+		}
+		spin_unlock_irq(&conf->device_lock);
+	}
+	kfree(cb);
+}
+
+static void release_stripe_plug(struct mddev *mddev,
+				struct stripe_head *sh)
+{
+	struct blk_plug_cb *blk_cb = blk_check_plugged(
+		raid5_unplug, mddev,
+		sizeof(struct raid5_plug_cb));
+	struct raid5_plug_cb *cb;
+
+	if (!blk_cb) {
+		release_stripe(sh);
+		return;
+	}
+
+	cb = container_of(blk_cb, struct raid5_plug_cb, cb);
+
+	if (cb->list.next == NULL)
+		INIT_LIST_HEAD(&cb->list);
+
+	if (!test_and_set_bit(STRIPE_ON_UNPLUG_LIST, &sh->state))
+		list_add_tail(&sh->lru, &cb->list);
+	else
+		release_stripe(sh);
+}
+
 static void make_request(struct mddev *mddev, struct bio * bi)
 {
 	struct r5conf *conf = mddev->private;
@@ -4113,11 +4192,10 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 			finish_wait(&conf->wait_for_overlap, &w);
 			set_bit(STRIPE_HANDLE, &sh->state);
 			clear_bit(STRIPE_DELAYED, &sh->state);
-			if ((bi->bi_rw & REQ_SYNC) &&
+			if ((bi->bi_rw & REQ_NOIDLE) &&
 			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
 				atomic_inc(&conf->preread_active_stripes);
-			mddev_check_plugged(mddev);
-			release_stripe(sh);
+			release_stripe_plug(mddev, sh);
 		} else {
 			/* cannot get stripe for read-ahead, just give-up */
 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
@@ -4126,9 +4204,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 		}
 	}
 
-	spin_lock_irq(&conf->device_lock);
-	remaining = raid5_dec_bi_phys_segments(bi);
-	spin_unlock_irq(&conf->device_lock);
+	remaining = raid5_dec_bi_active_stripes(bi);
 	if (remaining == 0) {
 
 		if ( rw == WRITE )
@@ -4484,7 +4560,7 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
 		     sector += STRIPE_SECTORS,
 		     scnt++) {
 
-		if (scnt < raid5_bi_hw_segments(raid_bio))
+		if (scnt < raid5_bi_processed_stripes(raid_bio))
 			/* already done this stripe */
 			continue;
 
@@ -4492,25 +4568,24 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
 
 		if (!sh) {
 			/* failed to get a stripe - must wait */
-			raid5_set_bi_hw_segments(raid_bio, scnt);
+			raid5_set_bi_processed_stripes(raid_bio, scnt);
 			conf->retry_read_aligned = raid_bio;
 			return handled;
 		}
 
 		if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
 			release_stripe(sh);
-			raid5_set_bi_hw_segments(raid_bio, scnt);
+			raid5_set_bi_processed_stripes(raid_bio, scnt);
 			conf->retry_read_aligned = raid_bio;
 			return handled;
 		}
 
+		set_bit(R5_ReadNoMerge, &sh->dev[dd_idx].flags);
 		handle_stripe(sh);
 		release_stripe(sh);
 		handled++;
 	}
-	spin_lock_irq(&conf->device_lock);
-	remaining = raid5_dec_bi_phys_segments(raid_bio);
-	spin_unlock_irq(&conf->device_lock);
+	remaining = raid5_dec_bi_active_stripes(raid_bio);
 	if (remaining == 0)
 		bio_endio(raid_bio, 0);
 	if (atomic_dec_and_test(&conf->active_aligned_reads))
@@ -4518,6 +4593,30 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
 	return handled;
 }
 
+#define MAX_STRIPE_BATCH 8
+static int handle_active_stripes(struct r5conf *conf)
+{
+	struct stripe_head *batch[MAX_STRIPE_BATCH], *sh;
+	int i, batch_size = 0;
+
+	while (batch_size < MAX_STRIPE_BATCH &&
+			(sh = __get_priority_stripe(conf)) != NULL)
+		batch[batch_size++] = sh;
+
+	if (batch_size == 0)
+		return batch_size;
+	spin_unlock_irq(&conf->device_lock);
+
+	for (i = 0; i < batch_size; i++)
+		handle_stripe(batch[i]);
+
+	cond_resched();
+
+	spin_lock_irq(&conf->device_lock);
+	for (i = 0; i < batch_size; i++)
+		__release_stripe(conf, batch[i]);
+	return batch_size;
+}
 
 /*
  * This is our raid5 kernel thread.
@@ -4528,7 +4627,6 @@ static int  retry_aligned_read(struct r5conf *conf, struct bio *raid_bio)
  */
 static void raid5d(struct mddev *mddev)
 {
-	struct stripe_head *sh;
 	struct r5conf *conf = mddev->private;
 	int handled;
 	struct blk_plug plug;
@@ -4542,8 +4640,9 @@ static void raid5d(struct mddev *mddev)
 	spin_lock_irq(&conf->device_lock);
 	while (1) {
 		struct bio *bio;
+		int batch_size;
 
-		if (atomic_read(&mddev->plug_cnt) == 0 &&
+		if (
 		    !list_empty(&conf->bitmap_list)) {
 			/* Now is a good time to flush some bitmap updates */
 			conf->seq_flush++;
@@ -4553,8 +4652,7 @@ static void raid5d(struct mddev *mddev)
 			conf->seq_write = conf->seq_flush;
 			activate_bit_delay(conf);
 		}
-		if (atomic_read(&mddev->plug_cnt) == 0)
-			raid5_activate_delayed(conf);
+		raid5_activate_delayed(conf);
 
 		while ((bio = remove_bio_from_retry(conf))) {
 			int ok;
@@ -4566,21 +4664,16 @@ static void raid5d(struct mddev *mddev)
 			handled++;
 		}
 
-		sh = __get_priority_stripe(conf);
-
-		if (!sh)
+		batch_size = handle_active_stripes(conf);
+		if (!batch_size)
 			break;
-		spin_unlock_irq(&conf->device_lock);
-		
-		handled++;
-		handle_stripe(sh);
-		release_stripe(sh);
-		cond_resched();
+		handled += batch_size;
 
-		if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
+		if (mddev->flags & ~(1<<MD_CHANGE_PENDING)) {
+			spin_unlock_irq(&conf->device_lock);
 			md_check_recovery(mddev);
-
-		spin_lock_irq(&conf->device_lock);
+			spin_lock_irq(&conf->device_lock);
+		}
 	}
 	pr_debug("%d stripes handled\n", handled);