Merge branch 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-5.20/drivers

Pull MD updates from Song:

"1. Improve raid5 lock contention, by Logan Gunthorpe.
 2. Misc fixes to raid5, by Logan Gunthorpe.
 3. Fix race condition with md_reap_sync_thread(), by Guoqing Jiang."

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md: (29 commits)
  md: Fix spelling mistake in comments
  md/raid5: Increase restriction on max segments per request
  md/raid5: Improve debug prints
  md/raid5: Pivot raid5_make_request()
  md/raid5: Check all disks in a stripe_head for reshape progress
  md/raid5: Refactor add_stripe_bio()
  md/raid5: Keep a reference to last stripe_head for batch
  md/raid5: Refactor for loop in raid5_make_request() into while loop
  md/raid5: Move read_seqcount_begin() into make_stripe_request()
  md/raid5: Drop the do_prepare flag in raid5_make_request()
  md/raid5: Factor out helper from raid5_make_request() loop
  md/raid5: Move common stripe get code into new find_get_stripe() helper
  md/raid5: Move stripe_add_to_batch_list() call out of add_stripe_bio()
  md/raid5: Refactor raid5_make_request loop
  md/raid5: Factor out ahead_of_reshape() function
  md/raid5: Make logic blocking check consistent with logic that blocks
  md: unlock mddev before reap sync_thread in action_store
  md: Explicitly create command-line configured devices
  md: Notify sysfs sync_completed in md_reap_sync_thread()
  md: Ensure resync is reported after it starts
  ...

10 files changed, 549 insertions, 315 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index fe5daf141501..68147e525440 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -18540,6 +18540,7 @@ SOFTWARE RAID (Multiple Disks) SUPPORT
 M:	Song Liu <song@kernel.org>
 L:	linux-raid@vger.kernel.org
 S:	Supported
+Q:	https://patchwork.kernel.org/project/linux-raid/list/
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/song/md.git
 F:	drivers/md/Kconfig
 F:	drivers/md/Makefile
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 9526ccbedafb..d43b8075c055 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -3725,6 +3725,7 @@ static int raid_message(struct dm_target *ti, unsigned int argc, char **argv,
 	if (!strcasecmp(argv[0], "idle") || !strcasecmp(argv[0], "frozen")) {
 		if (mddev->sync_thread) {
 			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+			md_unregister_thread(&mddev->sync_thread);
 			md_reap_sync_thread(mddev);
 		}
 	} else if (decipher_sync_action(mddev, mddev->recovery) != st_idle)
diff --git a/drivers/md/md-autodetect.c b/drivers/md/md-autodetect.c
index 2cf973722f59..344910ba435c 100644
--- a/drivers/md/md-autodetect.c
+++ b/drivers/md/md-autodetect.c
@@ -169,6 +169,7 @@ static void __init md_setup_drive(struct md_setup_args *args)
 
 	pr_info("md: Loading %s: %s\n", name, args->device_names);
 
+	md_alloc(mdev, name);
 	bdev = blkdev_get_by_dev(mdev, FMODE_READ, NULL);
 	if (IS_ERR(bdev)) {
 		pr_err("md: open failed - cannot start array %s\n", name);
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 37cbcce3cc66..742b2349fea3 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -40,7 +40,7 @@ struct resync_info {
 
 /* Lock the send communication. This is done through
  * bit manipulation as opposed to a mutex in order to
- * accomodate lock and hold. See next comment.
+ * accommodate lock and hold. See next comment.
  */
 #define		MD_CLUSTER_SEND_LOCK			4
 /* If cluster operations (such as adding a disk) must lock the
@@ -689,7 +689,7 @@ static int lock_comm(struct md_cluster_info *cinfo, bool mddev_locked)
 	/*
 	 * If resync thread run after raid1d thread, then process_metadata_update
 	 * could not continue if raid1d held reconfig_mutex (and raid1d is blocked
-	 * since another node already got EX on Token and waitting the EX of Ack),
+	 * since another node already got EX on Token and waiting the EX of Ack),
 	 * so let resync wake up thread in case flag is set.
 	 */
 	if (mddev_locked && !test_bit(MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD,
diff --git a/drivers/md/md.c b/drivers/md/md.c
index c7ecb0bffda0..b64de313838f 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4830,6 +4830,19 @@ action_store(struct mddev *mddev, const char *page, size_t len)
 			if (work_pending(&mddev->del_work))
 				flush_workqueue(md_misc_wq);
 			if (mddev->sync_thread) {
+				sector_t save_rp = mddev->reshape_position;
+
+				mddev_unlock(mddev);
+				set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+				md_unregister_thread(&mddev->sync_thread);
+				mddev_lock_nointr(mddev);
+				/*
+				 * set RECOVERY_INTR again and restore reshape
+				 * position in case others changed them after
+				 * got lock, eg, reshape_position_store and
+				 * md_check_recovery.
+				 */
+				mddev->reshape_position = save_rp;
 				set_bit(MD_RECOVERY_INTR, &mddev->recovery);
 				md_reap_sync_thread(mddev);
 			}
@@ -5001,7 +5014,7 @@ static ssize_t
 sync_speed_show(struct mddev *mddev, char *page)
 {
 	unsigned long resync, dt, db;
-	if (mddev->curr_resync == 0)
+	if (mddev->curr_resync == MD_RESYNC_NONE)
 		return sprintf(page, "none\n");
 	resync = mddev->curr_mark_cnt - atomic_read(&mddev->recovery_active);
 	dt = (jiffies - mddev->resync_mark) / HZ;
@@ -5020,8 +5033,8 @@ sync_completed_show(struct mddev *mddev, char *page)
 	if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
 		return sprintf(page, "none\n");
 
-	if (mddev->curr_resync == 1 ||
-	    mddev->curr_resync == 2)
+	if (mddev->curr_resync == MD_RESYNC_YIELDED ||
+	    mddev->curr_resync == MD_RESYNC_DELAYED)
 		return sprintf(page, "delayed\n");
 
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
@@ -5623,7 +5636,7 @@ int mddev_init_writes_pending(struct mddev *mddev)
 }
 EXPORT_SYMBOL_GPL(mddev_init_writes_pending);
 
-static int md_alloc(dev_t dev, char *name)
+int md_alloc(dev_t dev, char *name)
 {
 	/*
 	 * If dev is zero, name is the name of a device to allocate with
@@ -6197,6 +6210,7 @@ static void __md_stop_writes(struct mddev *mddev)
 		flush_workqueue(md_misc_wq);
 	if (mddev->sync_thread) {
 		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+		md_unregister_thread(&mddev->sync_thread);
 		md_reap_sync_thread(mddev);
 	}
 
@@ -8018,16 +8032,26 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev)
 		max_sectors = mddev->dev_sectors;
 
 	resync = mddev->curr_resync;
-	if (resync <= 3) {
+	if (resync < MD_RESYNC_ACTIVE) {
 		if (test_bit(MD_RECOVERY_DONE, &mddev->recovery))
 			/* Still cleaning up */
 			resync = max_sectors;
-	} else if (resync > max_sectors)
+	} else if (resync > max_sectors) {
 		resync = max_sectors;
-	else
+	} else {
 		resync -= atomic_read(&mddev->recovery_active);
+		if (resync < MD_RESYNC_ACTIVE) {
+			/*
+			 * Resync has started, but the subtraction has
+			 * yielded one of the special values. Force it
+			 * to active to ensure the status reports an
+			 * active resync.
+			 */
+			resync = MD_RESYNC_ACTIVE;
+		}
+	}
 
-	if (resync == 0) {
+	if (resync == MD_RESYNC_NONE) {
 		if (test_bit(MD_RESYNCING_REMOTE, &mddev->recovery)) {
 			struct md_rdev *rdev;
 
@@ -8051,7 +8075,7 @@ static int status_resync(struct seq_file *seq, struct mddev *mddev)
 		}
 		return 0;
 	}
-	if (resync < 3) {
+	if (resync < MD_RESYNC_ACTIVE) {
 		seq_printf(seq, "\tresync=DELAYED");
 		return 1;
 	}
@@ -8729,13 +8753,7 @@ void md_do_sync(struct md_thread *thread)
 
 	mddev->last_sync_action = action ?: desc;
 
-	/* we overload curr_resync somewhat here.
-	 * 0 == not engaged in resync at all
-	 * 2 == checking that there is no conflict with another sync
-	 * 1 == like 2, but have yielded to allow conflicting resync to
-	 *		commence
-	 * other == active in resync - this many blocks
-	 *
+	/*
 	 * Before starting a resync we must have set curr_resync to
 	 * 2, and then checked that every "conflicting" array has curr_resync
 	 * less than ours.  When we find one that is the same or higher
@@ -8747,7 +8765,7 @@ void md_do_sync(struct md_thread *thread)
 
 	do {
 		int mddev2_minor = -1;
-		mddev->curr_resync = 2;
+		mddev->curr_resync = MD_RESYNC_DELAYED;
 
 	try_again:
 		if (test_bit(MD_RECOVERY_INTR, &mddev->recovery))
@@ -8759,12 +8777,14 @@ void md_do_sync(struct md_thread *thread)
 			&&  mddev2->curr_resync
 			&&  match_mddev_units(mddev, mddev2)) {
 				DEFINE_WAIT(wq);
-				if (mddev < mddev2 && mddev->curr_resync == 2) {
+				if (mddev < mddev2 &&
+				    mddev->curr_resync == MD_RESYNC_DELAYED) {
 					/* arbitrarily yield */
-					mddev->curr_resync = 1;
+					mddev->curr_resync = MD_RESYNC_YIELDED;
 					wake_up(&resync_wait);
 				}
-				if (mddev > mddev2 && mddev->curr_resync == 1)
+				if (mddev > mddev2 &&
+				    mddev->curr_resync == MD_RESYNC_YIELDED)
 					/* no need to wait here, we can wait the next
 					 * time 'round when curr_resync == 2
 					 */
@@ -8792,7 +8812,7 @@ void md_do_sync(struct md_thread *thread)
 				finish_wait(&resync_wait, &wq);
 			}
 		}
-	} while (mddev->curr_resync < 2);
+	} while (mddev->curr_resync < MD_RESYNC_DELAYED);
 
 	j = 0;
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
@@ -8876,7 +8896,7 @@ void md_do_sync(struct md_thread *thread)
 			 desc, mdname(mddev));
 		mddev->curr_resync = j;
 	} else
-		mddev->curr_resync = 3; /* no longer delayed */
+		mddev->curr_resync = MD_RESYNC_ACTIVE; /* no longer delayed */
 	mddev->curr_resync_completed = j;
 	sysfs_notify_dirent_safe(mddev->sysfs_completed);
 	md_new_event();
@@ -9011,14 +9031,14 @@ void md_do_sync(struct md_thread *thread)
 
 	if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
 	    !test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
-	    mddev->curr_resync > 3) {
+	    mddev->curr_resync >= MD_RESYNC_ACTIVE) {
 		mddev->curr_resync_completed = mddev->curr_resync;
 		sysfs_notify_dirent_safe(mddev->sysfs_completed);
 	}
 	mddev->pers->sync_request(mddev, max_sectors, &skipped);
 
 	if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
-	    mddev->curr_resync > 3) {
+	    mddev->curr_resync >= MD_RESYNC_ACTIVE) {
 		if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
 			if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
 				if (mddev->curr_resync >= mddev->recovery_cp) {
@@ -9082,7 +9102,7 @@ void md_do_sync(struct md_thread *thread)
 	} else if (test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery))
 		mddev->resync_min = mddev->curr_resync_completed;
 	set_bit(MD_RECOVERY_DONE, &mddev->recovery);
-	mddev->curr_resync = 0;
+	mddev->curr_resync = MD_RESYNC_NONE;
 	spin_unlock(&mddev->lock);
 
 	wake_up(&resync_wait);
@@ -9303,6 +9323,7 @@ void md_check_recovery(struct mddev *mddev)
 			 * ->spare_active and clear saved_raid_disk
 			 */
 			set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+			md_unregister_thread(&mddev->sync_thread);
 			md_reap_sync_thread(mddev);
 			clear_bit(MD_RECOVERY_RECOVER, &mddev->recovery);
 			clear_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
@@ -9338,6 +9359,7 @@ void md_check_recovery(struct mddev *mddev)
 			goto unlock;
 		}
 		if (mddev->sync_thread) {
+			md_unregister_thread(&mddev->sync_thread);
 			md_reap_sync_thread(mddev);
 			goto unlock;
 		}
@@ -9417,8 +9439,7 @@ void md_reap_sync_thread(struct mddev *mddev)
 	sector_t old_dev_sectors = mddev->dev_sectors;
 	bool is_reshaped = false;
 
-	/* resync has finished, collect result */
-	md_unregister_thread(&mddev->sync_thread);
+	/* sync_thread should be unregistered, collect result */
 	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
 	    !test_bit(MD_RECOVERY_REQUESTED, &mddev->recovery) &&
 	    mddev->degraded != mddev->raid_disks) {
@@ -9466,6 +9487,7 @@ void md_reap_sync_thread(struct mddev *mddev)
 	wake_up(&resync_wait);
 	/* flag recovery needed just to double check */
 	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
+	sysfs_notify_dirent_safe(mddev->sysfs_completed);
 	sysfs_notify_dirent_safe(mddev->sysfs_action);
 	md_new_event();
 	if (mddev->event_work.func)
diff --git a/drivers/md/md.h b/drivers/md/md.h
index cf2cbb17acbd..1a85dbe78a71 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -288,6 +288,21 @@ struct serial_info {
 	sector_t _subtree_last; /* highest sector in subtree of rb node */
 };
 
+/*
+ * mddev->curr_resync stores the current sector of the resync but
+ * also has some overloaded values.
+ */
+enum {
+	/* No resync in progress */
+	MD_RESYNC_NONE = 0,
+	/* Yielded to allow another conflicting resync to commence */
+	MD_RESYNC_YIELDED = 1,
+	/* Delayed to check that there is no conflict with another sync */
+	MD_RESYNC_DELAYED = 2,
+	/* Any value greater than or equal to this is in an active resync */
+	MD_RESYNC_ACTIVE = 3,
+};
+
 struct mddev {
 	void				*private;
 	struct md_personality		*pers;
@@ -751,6 +766,7 @@ extern int md_integrity_add_rdev(struct md_rdev *rdev, struct mddev *mddev);
 extern int strict_strtoul_scaled(const char *cp, unsigned long *res, int scale);
 
 extern void mddev_init(struct mddev *mddev);
+int md_alloc(dev_t dev, char *name);
 extern int md_run(struct mddev *mddev);
 extern int md_start(struct mddev *mddev);
 extern void md_stop(struct mddev *mddev);
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 83c184eddbda..b2e6016934ee 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1590,18 +1590,13 @@ void r5l_quiesce(struct r5l_log *log, int quiesce)
 
 bool r5l_log_disk_error(struct r5conf *conf)
 {
-	struct r5l_log *log;
-	bool ret;
-	/* don't allow write if journal disk is missing */
-	rcu_read_lock();
-	log = rcu_dereference(conf->log);
+	struct r5l_log *log = conf->log;
 
+	/* don't allow write if journal disk is missing */
 	if (!log)
-		ret = test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
+		return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
 	else
-		ret = test_bit(Faulty, &log->rdev->flags);
-	rcu_read_unlock();
-	return ret;
+		return test_bit(Faulty, &log->rdev->flags);
 }
 
 #define R5L_RECOVERY_PAGE_POOL_SIZE 256
@@ -2534,12 +2529,13 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 	struct r5conf *conf;
 	int ret;
 
-	spin_lock(&mddev->lock);
+	ret = mddev_lock(mddev);
+	if (ret)
+		return ret;
+
 	conf = mddev->private;
-	if (!conf || !conf->log) {
-		spin_unlock(&mddev->lock);
-		return 0;
-	}
+	if (!conf || !conf->log)
+		goto out_unlock;
 
 	switch (conf->log->r5c_journal_mode) {
 	case R5C_JOURNAL_MODE_WRITE_THROUGH:
@@ -2557,7 +2553,9 @@ static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
 	default:
 		ret = 0;
 	}
-	spin_unlock(&mddev->lock);
+
+out_unlock:
+	mddev_unlock(mddev);
 	return ret;
 }
 
@@ -2639,7 +2637,7 @@ int r5c_try_caching_write(struct r5conf *conf,
 	int i;
 	struct r5dev *dev;
 	int to_cache = 0;
-	void **pslot;
+	void __rcu **pslot;
 	sector_t tree_index;
 	int ret;
 	uintptr_t refcount;
@@ -2806,7 +2804,7 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
 	int i;
 	int do_wakeup = 0;
 	sector_t tree_index;
-	void **pslot;
+	void __rcu **pslot;
 	uintptr_t refcount;
 
 	if (!log || !test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags))
@@ -3145,7 +3143,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
 	spin_lock_init(&log->stripe_in_journal_lock);
 	atomic_set(&log->stripe_in_journal_count, 0);
 
-	rcu_assign_pointer(conf->log, log);
+	conf->log = log;
 
 	set_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
 	return 0;
@@ -3167,13 +3165,13 @@ void r5l_exit_log(struct r5conf *conf)
 {
 	struct r5l_log *log = conf->log;
 
-	conf->log = NULL;
-	synchronize_rcu();
-
 	/* Ensure disable_writeback_work wakes up and exits */
 	wake_up(&conf->mddev->sb_wait);
 	flush_work(&log->disable_writeback_work);
 	md_unregister_thread(&log->reclaim_thread);
+
+	conf->log = NULL;
+
 	mempool_exit(&log->meta_pool);
 	bioset_exit(&log->bs);
 	mempool_exit(&log->io_pool);
diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h
index 43c714a8798c..c8332502669e 100644
--- a/drivers/md/raid5-log.h
+++ b/drivers/md/raid5-log.h
@@ -2,49 +2,46 @@
 #ifndef _RAID5_LOG_H
 #define _RAID5_LOG_H
 
-extern int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev);
-extern void r5l_exit_log(struct r5conf *conf);
-extern int r5l_write_stripe(struct r5l_log *log, struct stripe_head *head_sh);
-extern void r5l_write_stripe_run(struct r5l_log *log);
-extern void r5l_flush_stripe_to_raid(struct r5l_log *log);
-extern void r5l_stripe_write_finished(struct stripe_head *sh);
-extern int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
-extern void r5l_quiesce(struct r5l_log *log, int quiesce);
-extern bool r5l_log_disk_error(struct r5conf *conf);
-extern bool r5c_is_writeback(struct r5l_log *log);
-extern int
-r5c_try_caching_write(struct r5conf *conf, struct stripe_head *sh,
-		      struct stripe_head_state *s, int disks);
-extern void
-r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh,
-			    struct stripe_head_state *s);
-extern void r5c_release_extra_page(struct stripe_head *sh);
-extern void r5c_use_extra_page(struct stripe_head *sh);
-extern void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
-extern void r5c_handle_cached_data_endio(struct r5conf *conf,
-	struct stripe_head *sh, int disks);
-extern int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh);
-extern void r5c_make_stripe_write_out(struct stripe_head *sh);
-extern void r5c_flush_cache(struct r5conf *conf, int num);
-extern void r5c_check_stripe_cache_usage(struct r5conf *conf);
-extern void r5c_check_cached_full_stripe(struct r5conf *conf);
+int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev);
+void r5l_exit_log(struct r5conf *conf);
+int r5l_write_stripe(struct r5l_log *log, struct stripe_head *head_sh);
+void r5l_write_stripe_run(struct r5l_log *log);
+void r5l_flush_stripe_to_raid(struct r5l_log *log);
+void r5l_stripe_write_finished(struct stripe_head *sh);
+int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
+void r5l_quiesce(struct r5l_log *log, int quiesce);
+bool r5l_log_disk_error(struct r5conf *conf);
+bool r5c_is_writeback(struct r5l_log *log);
+int r5c_try_caching_write(struct r5conf *conf, struct stripe_head *sh,
+			  struct stripe_head_state *s, int disks);
+void r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh,
+				 struct stripe_head_state *s);
+void r5c_release_extra_page(struct stripe_head *sh);
+void r5c_use_extra_page(struct stripe_head *sh);
+void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
+void r5c_handle_cached_data_endio(struct r5conf *conf,
+				  struct stripe_head *sh, int disks);
+int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh);
+void r5c_make_stripe_write_out(struct stripe_head *sh);
+void r5c_flush_cache(struct r5conf *conf, int num);
+void r5c_check_stripe_cache_usage(struct r5conf *conf);
+void r5c_check_cached_full_stripe(struct r5conf *conf);
 extern struct md_sysfs_entry r5c_journal_mode;
-extern void r5c_update_on_rdev_error(struct mddev *mddev,
-				     struct md_rdev *rdev);
-extern bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect);
-extern int r5l_start(struct r5l_log *log);
+void r5c_update_on_rdev_error(struct mddev *mddev, struct md_rdev *rdev);
+bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect);
+int r5l_start(struct r5l_log *log);
 
-extern struct dma_async_tx_descriptor *
+struct dma_async_tx_descriptor *
 ops_run_partial_parity(struct stripe_head *sh, struct raid5_percpu *percpu,
 		       struct dma_async_tx_descriptor *tx);
-extern int ppl_init_log(struct r5conf *conf);
-extern void ppl_exit_log(struct r5conf *conf);
-extern int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh);
-extern void ppl_write_stripe_run(struct r5conf *conf);
-extern void ppl_stripe_write_finished(struct stripe_head *sh);
-extern int ppl_modify_log(struct r5conf *conf, struct md_rdev *rdev, bool add);
-extern void ppl_quiesce(struct r5conf *conf, int quiesce);
-extern int ppl_handle_flush_request(struct r5l_log *log, struct bio *bio);
+int ppl_init_log(struct r5conf *conf);
+void ppl_exit_log(struct r5conf *conf);
+int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh);
+void ppl_write_stripe_run(struct r5conf *conf);
+void ppl_stripe_write_finished(struct stripe_head *sh);
+int ppl_modify_log(struct r5conf *conf, struct md_rdev *rdev, bool add);
+void ppl_quiesce(struct r5conf *conf, int quiesce);
+int ppl_handle_flush_request(struct bio *bio);
 extern struct md_sysfs_entry ppl_write_hint;
 
 static inline bool raid5_has_log(struct r5conf *conf)
@@ -111,7 +108,7 @@ static inline int log_handle_flush_request(struct r5conf *conf, struct bio *bio)
 	if (conf->log)
 		ret = r5l_handle_flush_request(conf->log, bio);
 	else if (raid5_has_ppl(conf))
-		ret = ppl_handle_flush_request(conf->log, bio);
+		ret = ppl_handle_flush_request(bio);
 
 	return ret;
 }
diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index 0a2e4806b1ec..db49edec362a 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -679,7 +679,7 @@ void ppl_quiesce(struct r5conf *conf, int quiesce)
 	}
 }
 
-int ppl_handle_flush_request(struct r5l_log *log, struct bio *bio)
+int ppl_handle_flush_request(struct bio *bio)
 {
 	if (bio->bi_iter.bi_size == 0) {
 		bio_endio(bio);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5d09256d7f81..184145b49b7c 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -61,6 +61,8 @@
 #define cpu_to_group(cpu) cpu_to_node(cpu)
 #define ANY_GROUP NUMA_NO_NODE
 
+#define RAID5_MAX_REQ_STRIPES 256
+
 static bool devices_handle_discard_safely = false;
 module_param(devices_handle_discard_safely, bool, 0644);
 MODULE_PARM_DESC(devices_handle_discard_safely,
@@ -624,6 +626,49 @@ static struct stripe_head *__find_stripe(struct r5conf *conf, sector_t sector,
 	return NULL;
 }
 
+static struct stripe_head *find_get_stripe(struct r5conf *conf,
+		sector_t sector, short generation, int hash)
+{
+	int inc_empty_inactive_list_flag;
+	struct stripe_head *sh;
+
+	sh = __find_stripe(conf, sector, generation);
+	if (!sh)
+		return NULL;
+
+	if (atomic_inc_not_zero(&sh->count))
+		return sh;
+
+	/*
+	 * Slow path. The reference count is zero which means the stripe must
+	 * be on a list (sh->lru). Must remove the stripe from the list that
+	 * references it with the device_lock held.
+	 */
+
+	spin_lock(&conf->device_lock);
+	if (!atomic_read(&sh->count)) {
+		if (!test_bit(STRIPE_HANDLE, &sh->state))
+			atomic_inc(&conf->active_stripes);
+		BUG_ON(list_empty(&sh->lru) &&
+		       !test_bit(STRIPE_EXPANDING, &sh->state));
+		inc_empty_inactive_list_flag = 0;
+		if (!list_empty(conf->inactive_list + hash))
+			inc_empty_inactive_list_flag = 1;
+		list_del_init(&sh->lru);
+		if (list_empty(conf->inactive_list + hash) &&
+		    inc_empty_inactive_list_flag)
+			atomic_inc(&conf->empty_inactive_list_nr);
+		if (sh->group) {
+			sh->group->stripes_cnt--;
+			sh->group = NULL;
+		}
+	}
+	atomic_inc(&sh->count);
+	spin_unlock(&conf->device_lock);
+
+	return sh;
+}
+
 /*
  * Need to check if array has failed when deciding whether to:
  *  - start an array
@@ -716,7 +761,6 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
 {
 	struct stripe_head *sh;
 	int hash = stripe_hash_locks_hash(conf, sector);
-	int inc_empty_inactive_list_flag;
 
 	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
 
@@ -726,57 +770,34 @@ raid5_get_active_stripe(struct r5conf *conf, sector_t sector,
 		wait_event_lock_irq(conf->wait_for_quiescent,
 				    conf->quiesce == 0 || noquiesce,
 				    *(conf->hash_locks + hash));
-		sh = __find_stripe(conf, sector, conf->generation - previous);
-		if (!sh) {
-			if (!test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)) {
-				sh = get_free_stripe(conf, hash);
-				if (!sh && !test_bit(R5_DID_ALLOC,
-						     &conf->cache_state))
-					set_bit(R5_ALLOC_MORE,
-						&conf->cache_state);
-			}
-			if (noblock && sh == NULL)
-				break;
+		sh = find_get_stripe(conf, sector, conf->generation - previous,
+				     hash);
+		if (sh)
+			break;
 
-			r5c_check_stripe_cache_usage(conf);
-			if (!sh) {
-				set_bit(R5_INACTIVE_BLOCKED,
-					&conf->cache_state);
-				r5l_wake_reclaim(conf->log, 0);
-				wait_event_lock_irq(
-					conf->wait_for_stripe,
+		if (!test_bit(R5_INACTIVE_BLOCKED, &conf->cache_state)) {
+			sh = get_free_stripe(conf, hash);
+			if (!sh && !test_bit(R5_DID_ALLOC, &conf->cache_state))
+				set_bit(R5_ALLOC_MORE, &conf->cache_state);
+		}
+		if (noblock && !sh)
+			break;
+
+		r5c_check_stripe_cache_usage(conf);
+		if (!sh) {
+			set_bit(R5_INACTIVE_BLOCKED, &conf->cache_state);
+			r5l_wake_reclaim(conf->log, 0);
+			wait_event_lock_irq(conf->wait_for_stripe,
 					!list_empty(conf->inactive_list + hash) &&
 					(atomic_read(&conf->active_stripes)
 					 < (conf->max_nr_stripes * 3 / 4)
 					 || !test_bit(R5_INACTIVE_BLOCKED,
 						      &conf->cache_state)),
 					*(conf->hash_locks + hash));
-				clear_bit(R5_INACTIVE_BLOCKED,
-					  &conf->cache_state);
-			} else {
-				init_stripe(sh, sector, previous);
-				atomic_inc(&sh->count);
-			}
-		} else if (!atomic_inc_not_zero(&sh->count)) {
-			spin_lock(&conf->device_lock);
-			if (!atomic_read(&sh->count)) {
-				if (!test_bit(STRIPE_HANDLE, &sh->state))
-					atomic_inc(&conf->active_stripes);
-				BUG_ON(list_empty(&sh->lru) &&
-				       !test_bit(STRIPE_EXPANDING, &sh->state));
-				inc_empty_inactive_list_flag = 0;
-				if (!list_empty(conf->inactive_list + hash))
-					inc_empty_inactive_list_flag = 1;
-				list_del_init(&sh->lru);
-				if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag)
-					atomic_inc(&conf->empty_inactive_list_nr);
-				if (sh->group) {
-					sh->group->stripes_cnt--;
-					sh->group = NULL;
-				}
-			}
+			clear_bit(R5_INACTIVE_BLOCKED, &conf->cache_state);
+		} else {
+			init_stripe(sh, sector, previous);
 			atomic_inc(&sh->count);
-			spin_unlock(&conf->device_lock);
 		}
 	} while (sh == NULL);
 
@@ -824,13 +845,13 @@ static bool stripe_can_batch(struct stripe_head *sh)
 }
 
 /* we only do back search */
-static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh)
+static void stripe_add_to_batch_list(struct r5conf *conf,
+		struct stripe_head *sh, struct stripe_head *last_sh)
 {
 	struct stripe_head *head;
 	sector_t head_sector, tmp_sec;
 	int hash;
 	int dd_idx;
-	int inc_empty_inactive_list_flag;
 
 	/* Don't cross chunks, so stripe pd_idx/qd_idx is the same */
 	tmp_sec = sh->sector;
@@ -838,36 +859,20 @@ static void stripe_add_to_batch_list(struct r5conf *conf, struct stripe_head *sh
 		return;
 	head_sector = sh->sector - RAID5_STRIPE_SECTORS(conf);
 
-	hash = stripe_hash_locks_hash(conf, 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));
-			inc_empty_inactive_list_flag = 0;
-			if (!list_empty(conf->inactive_list + hash))
-				inc_empty_inactive_list_flag = 1;
-			list_del_init(&head->lru);
-			if (list_empty(conf->inactive_list + hash) && inc_empty_inactive_list_flag)
-				atomic_inc(&conf->empty_inactive_list_nr);
-			if (head->group) {
-				head->group->stripes_cnt--;
-				head->group = NULL;
-			}
-		}
+	if (last_sh && head_sector == last_sh->sector) {
+		head = last_sh;
 		atomic_inc(&head->count);
-		spin_unlock(&conf->device_lock);
+	} else {
+		hash = stripe_hash_locks_hash(conf, head_sector);
+		spin_lock_irq(conf->hash_locks + hash);
+		head = find_get_stripe(conf, head_sector, conf->generation,
+				       hash);
+		spin_unlock_irq(conf->hash_locks + hash);
+		if (!head)
+			return;
+		if (!stripe_can_batch(head))
+			goto out;
 	}
-	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 */
@@ -3412,39 +3417,32 @@ schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
 		s->locked, s->ops_request);
 }
 
-/*
- * Each stripe/dev can have one or more bion attached.
- * toread/towrite point to the first in a chain.
- * The bi_next chain must be in order.
- */
-static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
-			  int forwrite, int previous)
+static bool stripe_bio_overlaps(struct stripe_head *sh, struct bio *bi,
+				int dd_idx, int forwrite)
 {
-	struct bio **bip;
 	struct r5conf *conf = sh->raid_conf;
-	int firstwrite=0;
+	struct bio **bip;
 
-	pr_debug("adding bi b#%llu to stripe s#%llu\n",
-		(unsigned long long)bi->bi_iter.bi_sector,
-		(unsigned long long)sh->sector);
+	pr_debug("checking bi b#%llu to stripe s#%llu\n",
+		 bi->bi_iter.bi_sector, sh->sector);
 
-	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) {
+		return true;
+
+	if (forwrite)
 		bip = &sh->dev[dd_idx].towrite;
-		if (*bip == NULL)
-			firstwrite = 1;
-	} else
+	else
 		bip = &sh->dev[dd_idx].toread;
+
 	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector) {
 		if (bio_end_sector(*bip) > bi->bi_iter.bi_sector)
-			goto overlap;
-		bip = & (*bip)->bi_next;
+			return true;
+		bip = &(*bip)->bi_next;
 	}
+
 	if (*bip && (*bip)->bi_iter.bi_sector < bio_end_sector(bi))
-		goto overlap;
+		return true;
 
 	if (forwrite && raid5_has_ppl(conf)) {
 		/*
@@ -3473,9 +3471,30 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		}
 
 		if (first + conf->chunk_sectors * (count - 1) != last)
-			goto overlap;
+			return true;
 	}
 
+	return false;
+}
+
+static void __add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			     int dd_idx, int forwrite, int previous)
+{
+	struct r5conf *conf = sh->raid_conf;
+	struct bio **bip;
+	int firstwrite = 0;
+
+	if (forwrite) {
+		bip = &sh->dev[dd_idx].towrite;
+		if (!*bip)
+			firstwrite = 1;
+	} else {
+		bip = &sh->dev[dd_idx].toread;
+	}
+
+	while (*bip && (*bip)->bi_iter.bi_sector < bi->bi_iter.bi_sector)
+		bip = &(*bip)->bi_next;
+
 	if (!forwrite || previous)
 		clear_bit(STRIPE_BATCH_READY, &sh->state);
 
@@ -3501,9 +3520,9 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 				sh->overwrite_disks++;
 	}
 
-	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
-		(unsigned long long)(*bip)->bi_iter.bi_sector,
-		(unsigned long long)sh->sector, dd_idx);
+	pr_debug("added bi b#%llu to stripe s#%llu, disk %d, logical %llu\n",
+		 (*bip)->bi_iter.bi_sector, sh->sector, dd_idx,
+		 sh->dev[dd_idx].sector);
 
 	if (conf->mddev->bitmap && firstwrite) {
 		/* Cannot hold spinlock over bitmap_startwrite,
@@ -3511,7 +3530,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 		 * we have added to the bitmap and set bm_seq.
 		 * So set STRIPE_BITMAP_PENDING to prevent
 		 * batching.
-		 * If multiple add_stripe_bio() calls race here they
+		 * If multiple __add_stripe_bio() calls race here they
 		 * much all set STRIPE_BITMAP_PENDING.  So only the first one
 		 * to complete "bitmap_startwrite" gets to set
 		 * STRIPE_BIT_DELAY.  This is important as once a stripe
@@ -3529,16 +3548,27 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx,
 			set_bit(STRIPE_BIT_DELAY, &sh->state);
 		}
 	}
-	spin_unlock_irq(&sh->stripe_lock);
+}
 
-	if (stripe_can_batch(sh))
-		stripe_add_to_batch_list(conf, sh);
-	return 1;
+/*
+ * Each stripe/dev can have one or more bios attached.
+ * toread/towrite point to the first in a chain.
+ * The bi_next chain must be in order.
+ */
+static bool add_stripe_bio(struct stripe_head *sh, struct bio *bi,
+			   int dd_idx, int forwrite, int previous)
+{
+	spin_lock_irq(&sh->stripe_lock);
+
+	if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
+		set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
+		spin_unlock_irq(&sh->stripe_lock);
+		return false;
+	}
 
- overlap:
-	set_bit(R5_Overlap, &sh->dev[dd_idx].flags);
+	__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
 	spin_unlock_irq(&sh->stripe_lock);
-	return 0;
+	return true;
 }
 
 static void end_reshape(struct r5conf *conf);
@@ -5784,17 +5814,239 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
 	bio_endio(bi);
 }
 
-static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
+static bool ahead_of_reshape(struct mddev *mddev, sector_t sector,
+			     sector_t reshape_sector)
 {
-	struct r5conf *conf = mddev->private;
+	return mddev->reshape_backwards ? sector < reshape_sector :
+					  sector >= reshape_sector;
+}
+
+static bool range_ahead_of_reshape(struct mddev *mddev, sector_t min,
+				   sector_t max, sector_t reshape_sector)
+{
+	return mddev->reshape_backwards ? max < reshape_sector :
+					  min >= reshape_sector;
+}
+
+static bool stripe_ahead_of_reshape(struct mddev *mddev, struct r5conf *conf,
+				    struct stripe_head *sh)
+{
+	sector_t max_sector = 0, min_sector = MaxSector;
+	bool ret = false;
 	int dd_idx;
-	sector_t new_sector;
-	sector_t logical_sector, last_sector;
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		if (dd_idx == sh->pd_idx)
+			continue;
+
+		min_sector = min(min_sector, sh->dev[dd_idx].sector);
+		max_sector = min(max_sector, sh->dev[dd_idx].sector);
+	}
+
+	spin_lock_irq(&conf->device_lock);
+
+	if (!range_ahead_of_reshape(mddev, min_sector, max_sector,
+				     conf->reshape_progress))
+		/* mismatch, need to try again */
+		ret = true;
+
+	spin_unlock_irq(&conf->device_lock);
+
+	return ret;
+}
+
+enum stripe_result {
+	STRIPE_SUCCESS = 0,
+	STRIPE_RETRY,
+	STRIPE_SCHEDULE_AND_RETRY,
+	STRIPE_FAIL,
+};
+
+struct stripe_request_ctx {
+	/* a reference to the last stripe_head for batching */
+	struct stripe_head *batch_last;
+
+	/* first sector in the request */
+	sector_t first_sector;
+
+	/* last sector in the request */
+	sector_t last_sector;
+
+	/* bitmap to track stripe sectors that have been added to stripes */
+	DECLARE_BITMAP(sectors_to_do, RAID5_MAX_REQ_STRIPES);
+
+	/* the request had REQ_PREFLUSH, cleared after the first stripe_head */
+	bool do_flush;
+};
+
+static int add_all_stripe_bios(struct r5conf *conf,
+		struct stripe_request_ctx *ctx, struct stripe_head *sh,
+		struct bio *bi, int forwrite, int previous)
+{
+	int dd_idx;
+	int ret = 1;
+
+	spin_lock_irq(&sh->stripe_lock);
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		struct r5dev *dev = &sh->dev[dd_idx];
+
+		if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+			continue;
+
+		if (dev->sector < ctx->first_sector ||
+		    dev->sector >= ctx->last_sector)
+			continue;
+
+		if (stripe_bio_overlaps(sh, bi, dd_idx, forwrite)) {
+			set_bit(R5_Overlap, &dev->flags);
+			ret = 0;
+			continue;
+		}
+	}
+
+	if (!ret)
+		goto out;
+
+	for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
+		struct r5dev *dev = &sh->dev[dd_idx];
+
+		if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
+			continue;
+
+		if (dev->sector < ctx->first_sector ||
+		    dev->sector >= ctx->last_sector)
+			continue;
+
+		__add_stripe_bio(sh, bi, dd_idx, forwrite, previous);
+		clear_bit((dev->sector - ctx->first_sector) >>
+			  RAID5_STRIPE_SHIFT(conf), ctx->sectors_to_do);
+	}
+
+out:
+	spin_unlock_irq(&sh->stripe_lock);
+	return ret;
+}
+
+static enum stripe_result make_stripe_request(struct mddev *mddev,
+		struct r5conf *conf, struct stripe_request_ctx *ctx,
+		sector_t logical_sector, struct bio *bi)
+{
+	const int rw = bio_data_dir(bi);
+	enum stripe_result ret;
 	struct stripe_head *sh;
+	sector_t new_sector;
+	int previous = 0;
+	int seq, dd_idx;
+
+	seq = read_seqcount_begin(&conf->gen_lock);
+
+	if (unlikely(conf->reshape_progress != MaxSector)) {
+		/*
+		 * Spinlock is needed as reshape_progress may be
+		 * 64bit on a 32bit platform, and so it might be
+		 * possible to see a half-updated value
+		 * Of course reshape_progress could change after
+		 * the lock is dropped, so once we get a reference
+		 * to the stripe that we think it is, we will have
+		 * to check again.
+		 */
+		spin_lock_irq(&conf->device_lock);
+		if (ahead_of_reshape(mddev, logical_sector,
+				     conf->reshape_progress)) {
+			previous = 1;
+		} else {
+			if (ahead_of_reshape(mddev, logical_sector,
+					     conf->reshape_safe)) {
+				spin_unlock_irq(&conf->device_lock);
+				return STRIPE_SCHEDULE_AND_RETRY;
+			}
+		}
+		spin_unlock_irq(&conf->device_lock);
+	}
+
+	new_sector = raid5_compute_sector(conf, logical_sector, previous,
+					  &dd_idx, NULL);
+	pr_debug("raid456: %s, sector %llu logical %llu\n", __func__,
+		 new_sector, logical_sector);
+
+	sh = raid5_get_active_stripe(conf, new_sector, previous,
+				     (bi->bi_opf & REQ_RAHEAD), 0);
+	if (unlikely(!sh)) {
+		/* cannot get stripe, just give-up */
+		bi->bi_status = BLK_STS_IOERR;
+		return STRIPE_FAIL;
+	}
+
+	if (unlikely(previous) &&
+	    stripe_ahead_of_reshape(mddev, conf, sh)) {
+		/*
+		 * Expansion moved on while waiting for a stripe.
+		 * Expansion could still move past after this
+		 * test, but as we are holding a reference to
+		 * 'sh', we know that if that happens,
+		 *  STRIPE_EXPANDING will get set and the expansion
+		 * won't proceed until we finish with the stripe.
+		 */
+		ret = STRIPE_SCHEDULE_AND_RETRY;
+		goto out_release;
+	}
+
+	if (read_seqcount_retry(&conf->gen_lock, seq)) {
+		/* Might have got the wrong stripe_head by accident */
+		ret = STRIPE_RETRY;
+		goto out_release;
+	}
+
+	if (test_bit(STRIPE_EXPANDING, &sh->state) ||
+	    !add_all_stripe_bios(conf, ctx, sh, bi, rw, previous)) {
+		/*
+		 * Stripe is busy expanding or add failed due to
+		 * overlap. Flush everything and wait a while.
+		 */
+		md_wakeup_thread(mddev->thread);
+		ret = STRIPE_SCHEDULE_AND_RETRY;
+		goto out_release;
+	}
+
+	if (stripe_can_batch(sh)) {
+		stripe_add_to_batch_list(conf, sh, ctx->batch_last);
+		if (ctx->batch_last)
+			raid5_release_stripe(ctx->batch_last);
+		atomic_inc(&sh->count);
+		ctx->batch_last = sh;
+	}
+
+	if (ctx->do_flush) {
+		set_bit(STRIPE_R5C_PREFLUSH, &sh->state);
+		/* we only need flush for one stripe */
+		ctx->do_flush = false;
+	}
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+	clear_bit(STRIPE_DELAYED, &sh->state);
+	if ((!sh->batch_head || sh == sh->batch_head) &&
+	    (bi->bi_opf & REQ_SYNC) &&
+	    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+		atomic_inc(&conf->preread_active_stripes);
+
+	release_stripe_plug(mddev, sh);
+	return STRIPE_SUCCESS;
+
+out_release:
+	raid5_release_stripe(sh);
+	return ret;
+}
+
+static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
+{
+	struct r5conf *conf = mddev->private;
+	sector_t logical_sector;
+	struct stripe_request_ctx ctx = {};
 	const int rw = bio_data_dir(bi);
+	enum stripe_result res;
 	DEFINE_WAIT(w);
-	bool do_prepare;
-	bool do_flush = false;
+	int s;
 
 	if (unlikely(bi->bi_opf & REQ_PREFLUSH)) {
 		int ret = log_handle_flush_request(conf, bi);
@@ -5810,7 +6062,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 		 * if r5l_handle_flush_request() didn't clear REQ_PREFLUSH,
 		 * we need to flush journal device
 		 */
-		do_flush = bi->bi_opf & REQ_PREFLUSH;
+		ctx.do_flush = bi->bi_opf & REQ_PREFLUSH;
 	}
 
 	if (!md_write_start(mddev, bi))
@@ -5834,15 +6086,22 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 	}
 
 	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
-	last_sector = bio_end_sector(bi);
+	ctx.first_sector = logical_sector;
+	ctx.last_sector = bio_end_sector(bi);
 	bi->bi_next = NULL;
 
+	bitmap_set(ctx.sectors_to_do, 0,
+		   DIV_ROUND_UP_SECTOR_T(ctx.last_sector - logical_sector,
+					 RAID5_STRIPE_SECTORS(conf)));
+
+	pr_debug("raid456: %s, logical %llu to %llu\n", __func__,
+		 bi->bi_iter.bi_sector, ctx.last_sector);
+
 	/* Bail out if conflicts with reshape and REQ_NOWAIT is set */
 	if ((bi->bi_opf & REQ_NOWAIT) &&
 	    (conf->reshape_progress != MaxSector) &&
-	    (mddev->reshape_backwards
-	    ? (logical_sector > conf->reshape_progress && logical_sector <= conf->reshape_safe)
-	    : (logical_sector >= conf->reshape_safe && logical_sector < conf->reshape_progress))) {
+	    !ahead_of_reshape(mddev, logical_sector, conf->reshape_progress) &&
+	    ahead_of_reshape(mddev, logical_sector, conf->reshape_safe)) {
 		bio_wouldblock_error(bi);
 		if (rw == WRITE)
 			md_write_end(mddev);
@@ -5850,119 +6109,47 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 	}
 	md_account_bio(mddev, &bi);
 	prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
-	for (; logical_sector < last_sector; logical_sector += RAID5_STRIPE_SECTORS(conf)) {
-		int previous;
-		int seq;
-
-		do_prepare = false;
-	retry:
-		seq = read_seqcount_begin(&conf->gen_lock);
-		previous = 0;
-		if (do_prepare)
-			prepare_to_wait(&conf->wait_for_overlap, &w,
-				TASK_UNINTERRUPTIBLE);
-		if (unlikely(conf->reshape_progress != MaxSector)) {
-			/* spinlock is needed as reshape_progress may be
-			 * 64bit on a 32bit platform, and so it might be
-			 * possible to see a half-updated value
-			 * Of course reshape_progress could change after
-			 * the lock is dropped, so once we get a reference
-			 * to the stripe that we think it is, we will have
-			 * to check again.
-			 */
-			spin_lock_irq(&conf->device_lock);
-			if (mddev->reshape_backwards
-			    ? logical_sector < conf->reshape_progress
-			    : logical_sector >= conf->reshape_progress) {
-				previous = 1;
-			} else {
-				if (mddev->reshape_backwards
-				    ? logical_sector < conf->reshape_safe
-				    : logical_sector >= conf->reshape_safe) {
-					spin_unlock_irq(&conf->device_lock);
-					schedule();
-					do_prepare = true;
-					goto retry;
-				}
-			}
-			spin_unlock_irq(&conf->device_lock);
-		}
+	while (1) {
+		res = make_stripe_request(mddev, conf, &ctx, logical_sector,
+					  bi);
+		if (res == STRIPE_FAIL)
+			break;
 
-		new_sector = raid5_compute_sector(conf, logical_sector,
-						  previous,
-						  &dd_idx, NULL);
-		pr_debug("raid456: raid5_make_request, sector %llu logical %llu\n",
-			(unsigned long long)new_sector,
-			(unsigned long long)logical_sector);
+		if (res == STRIPE_RETRY)
+			continue;
 
-		sh = raid5_get_active_stripe(conf, new_sector, previous,
-				       (bi->bi_opf & REQ_RAHEAD), 0);
-		if (sh) {
-			if (unlikely(previous)) {
-				/* expansion might have moved on while waiting for a
-				 * stripe, so we must do the range check again.
-				 * Expansion could still move past after this
-				 * test, but as we are holding a reference to
-				 * 'sh', we know that if that happens,
-				 *  STRIPE_EXPANDING will get set and the expansion
-				 * won't proceed until we finish with the stripe.
-				 */
-				int must_retry = 0;
-				spin_lock_irq(&conf->device_lock);
-				if (mddev->reshape_backwards
-				    ? logical_sector >= conf->reshape_progress
-				    : logical_sector < conf->reshape_progress)
-					/* mismatch, need to try again */
-					must_retry = 1;
-				spin_unlock_irq(&conf->device_lock);
-				if (must_retry) {
-					raid5_release_stripe(sh);
-					schedule();
-					do_prepare = true;
-					goto retry;
-				}
-			}
-			if (read_seqcount_retry(&conf->gen_lock, seq)) {
-				/* Might have got the wrong stripe_head
-				 * by accident
-				 */
-				raid5_release_stripe(sh);
-				goto retry;
+		if (res == STRIPE_SCHEDULE_AND_RETRY) {
+			/*
+			 * Must release the reference to batch_last before
+			 * scheduling and waiting for work to be done,
+			 * otherwise the batch_last stripe head could prevent
+			 * raid5_activate_delayed() from making progress
+			 * and thus deadlocking.
+			 */
+			if (ctx.batch_last) {
+				raid5_release_stripe(ctx.batch_last);
+				ctx.batch_last = NULL;
 			}
 
-			if (test_bit(STRIPE_EXPANDING, &sh->state) ||
-			    !add_stripe_bio(sh, bi, dd_idx, rw, previous)) {
-				/* Stripe is busy expanding or
-				 * add failed due to overlap.  Flush everything
-				 * and wait a while
-				 */
-				md_wakeup_thread(mddev->thread);
-				raid5_release_stripe(sh);
-				schedule();
-				do_prepare = true;
-				goto retry;
-			}
-			if (do_flush) {
-				set_bit(STRIPE_R5C_PREFLUSH, &sh->state);
-				/* we only need flush for one stripe */
-				do_flush = false;
-			}
+			schedule();
+			prepare_to_wait(&conf->wait_for_overlap, &w,
+					TASK_UNINTERRUPTIBLE);
+			continue;
+		}
 
-			set_bit(STRIPE_HANDLE, &sh->state);
-			clear_bit(STRIPE_DELAYED, &sh->state);
-			if ((!sh->batch_head || sh == sh->batch_head) &&
-			    (bi->bi_opf & REQ_SYNC) &&
-			    !test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
-				atomic_inc(&conf->preread_active_stripes);
-			release_stripe_plug(mddev, sh);
-		} else {
-			/* cannot get stripe for read-ahead, just give-up */
-			bi->bi_status = BLK_STS_IOERR;
+		s = find_first_bit(ctx.sectors_to_do, RAID5_MAX_REQ_STRIPES);
+		if (s == RAID5_MAX_REQ_STRIPES)
 			break;
-		}
+
+		logical_sector = ctx.first_sector +
+			(s << RAID5_STRIPE_SHIFT(conf));
 	}
+
 	finish_wait(&conf->wait_for_overlap, &w);
 
+	if (ctx.batch_last)
+		raid5_release_stripe(ctx.batch_last);
+
 	if (rw == WRITE)
 		md_write_end(mddev);
 	bio_endio(bi);
@@ -7812,7 +7999,15 @@ static int raid5_run(struct mddev *mddev)
 		    mddev->queue->limits.discard_granularity < stripe)
 			blk_queue_max_discard_sectors(mddev->queue, 0);
 
-		blk_queue_max_hw_sectors(mddev->queue, UINT_MAX);
+		/*
+		 * Requests require having a bitmap for each stripe.
+		 * Limit the max sectors based on this.
+		 */
+		blk_queue_max_hw_sectors(mddev->queue,
+			RAID5_MAX_REQ_STRIPES << RAID5_STRIPE_SHIFT(conf));
+
+		/* No restrictions on the number of segments in the request */
+		blk_queue_max_segments(mddev->queue, USHRT_MAX);
 	}
 
 	if (log_init(conf, journal_dev, raid5_has_ppl(conf)))
@@ -8697,8 +8892,11 @@ static int raid5_change_consistency_policy(struct mddev *mddev, const char *buf)
 			err = log_init(conf, NULL, true);
 			if (!err) {
 				err = resize_stripes(conf, conf->pool_size);
-				if (err)
+				if (err) {
+					mddev_suspend(mddev);
 					log_exit(conf);
+					mddev_resume(mddev);
+				}
 			}
 		} else
 			err = -EINVAL;