Merge branch 'ioat-md-accel-for-linus' of git://lost.foo-projects.org/~dwillia2/git/iop

* 'ioat-md-accel-for-linus' of git://lost.foo-projects.org/~dwillia2/git/iop: (28 commits)
  ioatdma: add the unisys "i/oat" pci vendor/device id
  ARM: Add drivers/dma to arch/arm/Kconfig
  iop3xx: surface the iop3xx DMA and AAU units to the iop-adma driver
  iop13xx: surface the iop13xx adma units to the iop-adma driver
  dmaengine: driver for the iop32x, iop33x, and iop13xx raid engines
  md: remove raid5 compute_block and compute_parity5
  md: handle_stripe5 - request io processing in raid5_run_ops
  md: handle_stripe5 - add request/completion logic for async expand ops
  md: handle_stripe5 - add request/completion logic for async read ops
  md: handle_stripe5 - add request/completion logic for async check ops
  md: handle_stripe5 - add request/completion logic for async compute ops
  md: handle_stripe5 - add request/completion logic for async write ops
  md: common infrastructure for running operations with raid5_run_ops
  md: raid5_run_ops - run stripe operations outside sh->lock
  raid5: replace custom debug PRINTKs with standard pr_debug
  raid5: refactor handle_stripe5 and handle_stripe6 (v3)
  async_tx: add the async_tx api
  xor: make 'xor_blocks' a library routine for use with async_tx
  dmaengine: make clients responsible for managing channels
  dmaengine: refactor dmaengine around dma_async_tx_descriptor
  ...

5 files changed, 1685 insertions, 1204 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 466909f38d9..64bf3a81db9 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -109,6 +109,8 @@ config MD_RAID10
 config MD_RAID456
 	tristate "RAID-4/RAID-5/RAID-6 mode"
 	depends on BLK_DEV_MD
+	select ASYNC_MEMCPY
+	select ASYNC_XOR
 	---help---
 	  A RAID-5 set of N drives with a capacity of C MB per drive provides
 	  the capacity of C * (N - 1) MB, and protects against a failure
diff --git a/drivers/md/Makefile b/drivers/md/Makefile
index 2c45d7683ae..c49366cdc05 100644
--- a/drivers/md/Makefile
+++ b/drivers/md/Makefile
@@ -18,7 +18,7 @@ raid456-objs	:= raid5.o raid6algos.o raid6recov.o raid6tables.o \
 hostprogs-y	:= mktables
 
 # Note: link order is important.  All raid personalities
-# and xor.o must come before md.o, as they each initialise 
+# and must come before md.o, as they each initialise 
 # themselves, and md.o may use the personalities when it 
 # auto-initialised.
 
@@ -26,7 +26,7 @@ obj-$(CONFIG_MD_LINEAR)		+= linear.o
 obj-$(CONFIG_MD_RAID0)		+= raid0.o
 obj-$(CONFIG_MD_RAID1)		+= raid1.o
 obj-$(CONFIG_MD_RAID10)		+= raid10.o
-obj-$(CONFIG_MD_RAID456)	+= raid456.o xor.o
+obj-$(CONFIG_MD_RAID456)	+= raid456.o
 obj-$(CONFIG_MD_MULTIPATH)	+= multipath.o
 obj-$(CONFIG_MD_FAULTY)		+= faulty.o
 obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 1c54f3c1cca..33beaa7da08 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5814,7 +5814,7 @@ static __exit void md_exit(void)
 	}
 }
 
-module_init(md_init)
+subsys_initcall(md_init);
 module_exit(md_exit)
 
 static int get_ro(char *buffer, struct kernel_param *kp)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 061375ee659..0b66afef2d8 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -52,6 +52,7 @@
 #include "raid6.h"
 
 #include <linux/raid/bitmap.h>
+#include <linux/async_tx.h>
 
 /*
  * Stripe cache
@@ -80,7 +81,6 @@
 /*
  * The following can be used to debug the driver
  */
-#define RAID5_DEBUG	0
 #define RAID5_PARANOIA	1
 #if RAID5_PARANOIA && defined(CONFIG_SMP)
 # define CHECK_DEVLOCK() assert_spin_locked(&conf->device_lock)
@@ -88,8 +88,7 @@
 # define CHECK_DEVLOCK()
 #endif
 
-#define PRINTK(x...) ((void)(RAID5_DEBUG && printk(x)))
-#if RAID5_DEBUG
+#ifdef DEBUG
 #define inline
 #define __inline__
 #endif
@@ -104,6 +103,23 @@ static inline int raid6_next_disk(int disk, int raid_disks)
 	disk++;
 	return (disk < raid_disks) ? disk : 0;
 }
+
+static void return_io(struct bio *return_bi)
+{
+	struct bio *bi = return_bi;
+	while (bi) {
+		int bytes = bi->bi_size;
+
+		return_bi = bi->bi_next;
+		bi->bi_next = NULL;
+		bi->bi_size = 0;
+		bi->bi_end_io(bi, bytes,
+			      test_bit(BIO_UPTODATE, &bi->bi_flags)
+			        ? 0 : -EIO);
+		bi = return_bi;
+	}
+}
+
 static void print_raid5_conf (raid5_conf_t *conf);
 
 static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
@@ -125,6 +141,7 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
 			}
 			md_wakeup_thread(conf->mddev->thread);
 		} else {
+			BUG_ON(sh->ops.pending);
 			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
 				atomic_dec(&conf->preread_active_stripes);
 				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
@@ -152,7 +169,8 @@ static void release_stripe(struct stripe_head *sh)
 
 static inline void remove_hash(struct stripe_head *sh)
 {
-	PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
+	pr_debug("remove_hash(), stripe %llu\n",
+		(unsigned long long)sh->sector);
 
 	hlist_del_init(&sh->hash);
 }
@@ -161,7 +179,8 @@ static inline void insert_hash(raid5_conf_t *conf, struct stripe_head *sh)
 {
 	struct hlist_head *hp = stripe_hash(conf, sh->sector);
 
-	PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
+	pr_debug("insert_hash(), stripe %llu\n",
+		(unsigned long long)sh->sector);
 
 	CHECK_DEVLOCK();
 	hlist_add_head(&sh->hash, hp);
@@ -224,9 +243,10 @@ static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int
 
 	BUG_ON(atomic_read(&sh->count) != 0);
 	BUG_ON(test_bit(STRIPE_HANDLE, &sh->state));
-	
+	BUG_ON(sh->ops.pending || sh->ops.ack || sh->ops.complete);
+
 	CHECK_DEVLOCK();
-	PRINTK("init_stripe called, stripe %llu\n", 
+	pr_debug("init_stripe called, stripe %llu\n",
 		(unsigned long long)sh->sector);
 
 	remove_hash(sh);
@@ -240,11 +260,11 @@ static void init_stripe(struct stripe_head *sh, sector_t sector, int pd_idx, int
 	for (i = sh->disks; i--; ) {
 		struct r5dev *dev = &sh->dev[i];
 
-		if (dev->toread || dev->towrite || dev->written ||
+		if (dev->toread || dev->read || dev->towrite || dev->written ||
 		    test_bit(R5_LOCKED, &dev->flags)) {
-			printk("sector=%llx i=%d %p %p %p %d\n",
+			printk(KERN_ERR "sector=%llx i=%d %p %p %p %p %d\n",
 			       (unsigned long long)sh->sector, i, dev->toread,
-			       dev->towrite, dev->written,
+			       dev->read, dev->towrite, dev->written,
 			       test_bit(R5_LOCKED, &dev->flags));
 			BUG();
 		}
@@ -260,11 +280,11 @@ static struct stripe_head *__find_stripe(raid5_conf_t *conf, sector_t sector, in
 	struct hlist_node *hn;
 
 	CHECK_DEVLOCK();
-	PRINTK("__find_stripe, sector %llu\n", (unsigned long long)sector);
+	pr_debug("__find_stripe, sector %llu\n", (unsigned long long)sector);
 	hlist_for_each_entry(sh, hn, stripe_hash(conf, sector), hash)
 		if (sh->sector == sector && sh->disks == disks)
 			return sh;
-	PRINTK("__stripe %llu not in cache\n", (unsigned long long)sector);
+	pr_debug("__stripe %llu not in cache\n", (unsigned long long)sector);
 	return NULL;
 }
 
@@ -276,7 +296,7 @@ static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector
 {
 	struct stripe_head *sh;
 
-	PRINTK("get_stripe, sector %llu\n", (unsigned long long)sector);
+	pr_debug("get_stripe, sector %llu\n", (unsigned long long)sector);
 
 	spin_lock_irq(&conf->device_lock);
 
@@ -324,6 +344,579 @@ static struct stripe_head *get_active_stripe(raid5_conf_t *conf, sector_t sector
 	return sh;
 }
 
+/* test_and_ack_op() ensures that we only dequeue an operation once */
+#define test_and_ack_op(op, pend) \
+do {							\
+	if (test_bit(op, &sh->ops.pending) &&		\
+		!test_bit(op, &sh->ops.complete)) {	\
+		if (test_and_set_bit(op, &sh->ops.ack)) \
+			clear_bit(op, &pend);		\
+		else					\
+			ack++;				\
+	} else						\
+		clear_bit(op, &pend);			\
+} while (0)
+
+/* find new work to run, do not resubmit work that is already
+ * in flight
+ */
+static unsigned long get_stripe_work(struct stripe_head *sh)
+{
+	unsigned long pending;
+	int ack = 0;
+
+	pending = sh->ops.pending;
+
+	test_and_ack_op(STRIPE_OP_BIOFILL, pending);
+	test_and_ack_op(STRIPE_OP_COMPUTE_BLK, pending);
+	test_and_ack_op(STRIPE_OP_PREXOR, pending);
+	test_and_ack_op(STRIPE_OP_BIODRAIN, pending);
+	test_and_ack_op(STRIPE_OP_POSTXOR, pending);
+	test_and_ack_op(STRIPE_OP_CHECK, pending);
+	if (test_and_clear_bit(STRIPE_OP_IO, &sh->ops.pending))
+		ack++;
+
+	sh->ops.count -= ack;
+	BUG_ON(sh->ops.count < 0);
+
+	return pending;
+}
+
+static int
+raid5_end_read_request(struct bio *bi, unsigned int bytes_done, int error);
+static int
+raid5_end_write_request (struct bio *bi, unsigned int bytes_done, int error);
+
+static void ops_run_io(struct stripe_head *sh)
+{
+	raid5_conf_t *conf = sh->raid_conf;
+	int i, disks = sh->disks;
+
+	might_sleep();
+
+	for (i = disks; i--; ) {
+		int rw;
+		struct bio *bi;
+		mdk_rdev_t *rdev;
+		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
+			rw = WRITE;
+		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
+			rw = READ;
+		else
+			continue;
+
+		bi = &sh->dev[i].req;
+
+		bi->bi_rw = rw;
+		if (rw == WRITE)
+			bi->bi_end_io = raid5_end_write_request;
+		else
+			bi->bi_end_io = raid5_end_read_request;
+
+		rcu_read_lock();
+		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (rdev && test_bit(Faulty, &rdev->flags))
+			rdev = NULL;
+		if (rdev)
+			atomic_inc(&rdev->nr_pending);
+		rcu_read_unlock();
+
+		if (rdev) {
+			if (test_bit(STRIPE_SYNCING, &sh->state) ||
+				test_bit(STRIPE_EXPAND_SOURCE, &sh->state) ||
+				test_bit(STRIPE_EXPAND_READY, &sh->state))
+				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
+
+			bi->bi_bdev = rdev->bdev;
+			pr_debug("%s: for %llu schedule op %ld on disc %d\n",
+				__FUNCTION__, (unsigned long long)sh->sector,
+				bi->bi_rw, i);
+			atomic_inc(&sh->count);
+			bi->bi_sector = sh->sector + rdev->data_offset;
+			bi->bi_flags = 1 << BIO_UPTODATE;
+			bi->bi_vcnt = 1;
+			bi->bi_max_vecs = 1;
+			bi->bi_idx = 0;
+			bi->bi_io_vec = &sh->dev[i].vec;
+			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
+			bi->bi_io_vec[0].bv_offset = 0;
+			bi->bi_size = STRIPE_SIZE;
+			bi->bi_next = NULL;
+			if (rw == WRITE &&
+			    test_bit(R5_ReWrite, &sh->dev[i].flags))
+				atomic_add(STRIPE_SECTORS,
+					&rdev->corrected_errors);
+			generic_make_request(bi);
+		} else {
+			if (rw == WRITE)
+				set_bit(STRIPE_DEGRADED, &sh->state);
+			pr_debug("skip op %ld on disc %d for sector %llu\n",
+				bi->bi_rw, i, (unsigned long long)sh->sector);
+			clear_bit(R5_LOCKED, &sh->dev[i].flags);
+			set_bit(STRIPE_HANDLE, &sh->state);
+		}
+	}
+}
+
+static struct dma_async_tx_descriptor *
+async_copy_data(int frombio, struct bio *bio, struct page *page,
+	sector_t sector, struct dma_async_tx_descriptor *tx)
+{
+	struct bio_vec *bvl;
+	struct page *bio_page;
+	int i;
+	int page_offset;
+
+	if (bio->bi_sector >= sector)
+		page_offset = (signed)(bio->bi_sector - sector) * 512;
+	else
+		page_offset = (signed)(sector - bio->bi_sector) * -512;
+	bio_for_each_segment(bvl, bio, i) {
+		int len = bio_iovec_idx(bio, i)->bv_len;
+		int clen;
+		int b_offset = 0;
+
+		if (page_offset < 0) {
+			b_offset = -page_offset;
+			page_offset += b_offset;
+			len -= b_offset;
+		}
+
+		if (len > 0 && page_offset + len > STRIPE_SIZE)
+			clen = STRIPE_SIZE - page_offset;
+		else
+			clen = len;
+
+		if (clen > 0) {
+			b_offset += bio_iovec_idx(bio, i)->bv_offset;
+			bio_page = bio_iovec_idx(bio, i)->bv_page;
+			if (frombio)
+				tx = async_memcpy(page, bio_page, page_offset,
+					b_offset, clen,
+					ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_SRC,
+					tx, NULL, NULL);
+			else
+				tx = async_memcpy(bio_page, page, b_offset,
+					page_offset, clen,
+					ASYNC_TX_DEP_ACK | ASYNC_TX_KMAP_DST,
+					tx, NULL, NULL);
+		}
+		if (clen < len) /* hit end of page */
+			break;
+		page_offset +=  len;
+	}
+
+	return tx;
+}
+
+static void ops_complete_biofill(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	struct bio *return_bi = NULL;
+	raid5_conf_t *conf = sh->raid_conf;
+	int i, more_to_read = 0;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	/* clear completed biofills */
+	for (i = sh->disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		/* check if this stripe has new incoming reads */
+		if (dev->toread)
+			more_to_read++;
+
+		/* acknowledge completion of a biofill operation */
+		/* and check if we need to reply to a read request
+		*/
+		if (test_bit(R5_Wantfill, &dev->flags) && !dev->toread) {
+			struct bio *rbi, *rbi2;
+			clear_bit(R5_Wantfill, &dev->flags);
+
+			/* The access to dev->read is outside of the
+			 * spin_lock_irq(&conf->device_lock), but is protected
+			 * by the STRIPE_OP_BIOFILL pending bit
+			 */
+			BUG_ON(!dev->read);
+			rbi = dev->read;
+			dev->read = NULL;
+			while (rbi && rbi->bi_sector <
+				dev->sector + STRIPE_SECTORS) {
+				rbi2 = r5_next_bio(rbi, dev->sector);
+				spin_lock_irq(&conf->device_lock);
+				if (--rbi->bi_phys_segments == 0) {
+					rbi->bi_next = return_bi;
+					return_bi = rbi;
+				}
+				spin_unlock_irq(&conf->device_lock);
+				rbi = rbi2;
+			}
+		}
+	}
+	clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
+	clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
+
+	return_io(return_bi);
+
+	if (more_to_read)
+		set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+}
+
+static void ops_run_biofill(struct stripe_head *sh)
+{
+	struct dma_async_tx_descriptor *tx = NULL;
+	raid5_conf_t *conf = sh->raid_conf;
+	int i;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	for (i = sh->disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		if (test_bit(R5_Wantfill, &dev->flags)) {
+			struct bio *rbi;
+			spin_lock_irq(&conf->device_lock);
+			dev->read = rbi = dev->toread;
+			dev->toread = NULL;
+			spin_unlock_irq(&conf->device_lock);
+			while (rbi && rbi->bi_sector <
+				dev->sector + STRIPE_SECTORS) {
+				tx = async_copy_data(0, rbi, dev->page,
+					dev->sector, tx);
+				rbi = r5_next_bio(rbi, dev->sector);
+			}
+		}
+	}
+
+	atomic_inc(&sh->count);
+	async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
+		ops_complete_biofill, sh);
+}
+
+static void ops_complete_compute5(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	int target = sh->ops.target;
+	struct r5dev *tgt = &sh->dev[target];
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	set_bit(R5_UPTODATE, &tgt->flags);
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+	clear_bit(R5_Wantcompute, &tgt->flags);
+	set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute5(struct stripe_head *sh, unsigned long pending)
+{
+	/* kernel stack size limits the total number of disks */
+	int disks = sh->disks;
+	struct page *xor_srcs[disks];
+	int target = sh->ops.target;
+	struct r5dev *tgt = &sh->dev[target];
+	struct page *xor_dest = tgt->page;
+	int count = 0;
+	struct dma_async_tx_descriptor *tx;
+	int i;
+
+	pr_debug("%s: stripe %llu block: %d\n",
+		__FUNCTION__, (unsigned long long)sh->sector, target);
+	BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+
+	for (i = disks; i--; )
+		if (i != target)
+			xor_srcs[count++] = sh->dev[i].page;
+
+	atomic_inc(&sh->count);
+
+	if (unlikely(count == 1))
+		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
+			0, NULL, ops_complete_compute5, sh);
+	else
+		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+			ASYNC_TX_XOR_ZERO_DST, NULL,
+			ops_complete_compute5, sh);
+
+	/* ack now if postxor is not set to be run */
+	if (tx && !test_bit(STRIPE_OP_POSTXOR, &pending))
+		async_tx_ack(tx);
+
+	return tx;
+}
+
+static void ops_complete_prexor(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	set_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+	/* kernel stack size limits the total number of disks */
+	int disks = sh->disks;
+	struct page *xor_srcs[disks];
+	int count = 0, pd_idx = sh->pd_idx, i;
+
+	/* existing parity data subtracted */
+	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		/* Only process blocks that are known to be uptodate */
+		if (dev->towrite && test_bit(R5_Wantprexor, &dev->flags))
+			xor_srcs[count++] = dev->page;
+	}
+
+	tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+		ASYNC_TX_DEP_ACK | ASYNC_TX_XOR_DROP_DST, tx,
+		ops_complete_prexor, sh);
+
+	return tx;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+	int disks = sh->disks;
+	int pd_idx = sh->pd_idx, i;
+
+	/* check if prexor is active which means only process blocks
+	 * that are part of a read-modify-write (Wantprexor)
+	 */
+	int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		struct bio *chosen;
+		int towrite;
+
+		towrite = 0;
+		if (prexor) { /* rmw */
+			if (dev->towrite &&
+			    test_bit(R5_Wantprexor, &dev->flags))
+				towrite = 1;
+		} else { /* rcw */
+			if (i != pd_idx && dev->towrite &&
+				test_bit(R5_LOCKED, &dev->flags))
+				towrite = 1;
+		}
+
+		if (towrite) {
+			struct bio *wbi;
+
+			spin_lock(&sh->lock);
+			chosen = dev->towrite;
+			dev->towrite = NULL;
+			BUG_ON(dev->written);
+			wbi = dev->written = chosen;
+			spin_unlock(&sh->lock);
+
+			while (wbi && wbi->bi_sector <
+				dev->sector + STRIPE_SECTORS) {
+				tx = async_copy_data(1, wbi, dev->page,
+					dev->sector, tx);
+				wbi = r5_next_bio(wbi, dev->sector);
+			}
+		}
+	}
+
+	return tx;
+}
+
+static void ops_complete_postxor(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+}
+
+static void ops_complete_write(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	int disks = sh->disks, i, pd_idx = sh->pd_idx;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		if (dev->written || i == pd_idx)
+			set_bit(R5_UPTODATE, &dev->flags);
+	}
+
+	set_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
+	set_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+}
+
+static void
+ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+{
+	/* kernel stack size limits the total number of disks */
+	int disks = sh->disks;
+	struct page *xor_srcs[disks];
+
+	int count = 0, pd_idx = sh->pd_idx, i;
+	struct page *xor_dest;
+	int prexor = test_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+	unsigned long flags;
+	dma_async_tx_callback callback;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	/* check if prexor is active which means only process blocks
+	 * that are part of a read-modify-write (written)
+	 */
+	if (prexor) {
+		xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (dev->written)
+				xor_srcs[count++] = dev->page;
+		}
+	} else {
+		xor_dest = sh->dev[pd_idx].page;
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (i != pd_idx)
+				xor_srcs[count++] = dev->page;
+		}
+	}
+
+	/* check whether this postxor is part of a write */
+	callback = test_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending) ?
+		ops_complete_write : ops_complete_postxor;
+
+	/* 1/ if we prexor'd then the dest is reused as a source
+	 * 2/ if we did not prexor then we are redoing the parity
+	 * set ASYNC_TX_XOR_DROP_DST and ASYNC_TX_XOR_ZERO_DST
+	 * for the synchronous xor case
+	 */
+	flags = ASYNC_TX_DEP_ACK | ASYNC_TX_ACK |
+		(prexor ? ASYNC_TX_XOR_DROP_DST : ASYNC_TX_XOR_ZERO_DST);
+
+	atomic_inc(&sh->count);
+
+	if (unlikely(count == 1)) {
+		flags &= ~(ASYNC_TX_XOR_DROP_DST | ASYNC_TX_XOR_ZERO_DST);
+		tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
+			flags, tx, callback, sh);
+	} else
+		tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+			flags, tx, callback, sh);
+}
+
+static void ops_complete_check(void *stripe_head_ref)
+{
+	struct stripe_head *sh = stripe_head_ref;
+	int pd_idx = sh->pd_idx;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	if (test_and_clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending) &&
+		sh->ops.zero_sum_result == 0)
+		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+
+	set_bit(STRIPE_OP_CHECK, &sh->ops.complete);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+}
+
+static void ops_run_check(struct stripe_head *sh)
+{
+	/* kernel stack size limits the total number of disks */
+	int disks = sh->disks;
+	struct page *xor_srcs[disks];
+	struct dma_async_tx_descriptor *tx;
+
+	int count = 0, pd_idx = sh->pd_idx, i;
+	struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
+
+	pr_debug("%s: stripe %llu\n", __FUNCTION__,
+		(unsigned long long)sh->sector);
+
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		if (i != pd_idx)
+			xor_srcs[count++] = dev->page;
+	}
+
+	tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+		&sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
+
+	if (tx)
+		set_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
+	else
+		clear_bit(STRIPE_OP_MOD_DMA_CHECK, &sh->ops.pending);
+
+	atomic_inc(&sh->count);
+	tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
+		ops_complete_check, sh);
+}
+
+static void raid5_run_ops(struct stripe_head *sh, unsigned long pending)
+{
+	int overlap_clear = 0, i, disks = sh->disks;
+	struct dma_async_tx_descriptor *tx = NULL;
+
+	if (test_bit(STRIPE_OP_BIOFILL, &pending)) {
+		ops_run_biofill(sh);
+		overlap_clear++;
+	}
+
+	if (test_bit(STRIPE_OP_COMPUTE_BLK, &pending))
+		tx = ops_run_compute5(sh, pending);
+
+	if (test_bit(STRIPE_OP_PREXOR, &pending))
+		tx = ops_run_prexor(sh, tx);
+
+	if (test_bit(STRIPE_OP_BIODRAIN, &pending)) {
+		tx = ops_run_biodrain(sh, tx);
+		overlap_clear++;
+	}
+
+	if (test_bit(STRIPE_OP_POSTXOR, &pending))
+		ops_run_postxor(sh, tx);
+
+	if (test_bit(STRIPE_OP_CHECK, &pending))
+		ops_run_check(sh);
+
+	if (test_bit(STRIPE_OP_IO, &pending))
+		ops_run_io(sh);
+
+	if (overlap_clear)
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (test_and_clear_bit(R5_Overlap, &dev->flags))
+				wake_up(&sh->raid_conf->wait_for_overlap);
+		}
+}
+
 static int grow_one_stripe(raid5_conf_t *conf)
 {
 	struct stripe_head *sh;
@@ -537,8 +1130,8 @@ static int raid5_end_read_request(struct bio * bi, unsigned int bytes_done,
 		if (bi == &sh->dev[i].req)
 			break;
 
-	PRINTK("end_read_request %llu/%d, count: %d, uptodate %d.\n", 
-		(unsigned long long)sh->sector, i, atomic_read(&sh->count), 
+	pr_debug("end_read_request %llu/%d, count: %d, uptodate %d.\n",
+		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
 		uptodate);
 	if (i == disks) {
 		BUG();
@@ -613,7 +1206,7 @@ static int raid5_end_write_request (struct bio *bi, unsigned int bytes_done,
 		if (bi == &sh->dev[i].req)
 			break;
 
-	PRINTK("end_write_request %llu/%d, count %d, uptodate: %d.\n", 
+	pr_debug("end_write_request %llu/%d, count %d, uptodate: %d.\n",
 		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
 		uptodate);
 	if (i == disks) {
@@ -658,7 +1251,7 @@ static void error(mddev_t *mddev, mdk_rdev_t *rdev)
 {
 	char b[BDEVNAME_SIZE];
 	raid5_conf_t *conf = (raid5_conf_t *) mddev->private;
-	PRINTK("raid5: error called\n");
+	pr_debug("raid5: error called\n");
 
 	if (!test_bit(Faulty, &rdev->flags)) {
 		set_bit(MD_CHANGE_DEVS, &mddev->flags);
@@ -916,137 +1509,13 @@ static void copy_data(int frombio, struct bio *bio,
 	}
 }
 
-#define check_xor() 	do { 						\
-			   if (count == MAX_XOR_BLOCKS) {		\
-				xor_block(count, STRIPE_SIZE, ptr);	\
-				count = 1;				\
-			   }						\
+#define check_xor()	do {						  \
+				if (count == MAX_XOR_BLOCKS) {		  \
+				xor_blocks(count, STRIPE_SIZE, dest, ptr);\
+				count = 0;				  \
+			   }						  \
 			} while(0)
 
-
-static void compute_block(struct stripe_head *sh, int dd_idx)
-{
-	int i, count, disks = sh->disks;
-	void *ptr[MAX_XOR_BLOCKS], *p;
-
-	PRINTK("compute_block, stripe %llu, idx %d\n", 
-		(unsigned long long)sh->sector, dd_idx);
-
-	ptr[0] = page_address(sh->dev[dd_idx].page);
-	memset(ptr[0], 0, STRIPE_SIZE);
-	count = 1;
-	for (i = disks ; i--; ) {
-		if (i == dd_idx)
-			continue;
-		p = page_address(sh->dev[i].page);
-		if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
-			ptr[count++] = p;
-		else
-			printk(KERN_ERR "compute_block() %d, stripe %llu, %d"
-				" not present\n", dd_idx,
-				(unsigned long long)sh->sector, i);
-
-		check_xor();
-	}
-	if (count != 1)
-		xor_block(count, STRIPE_SIZE, ptr);
-	set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
-}
-
-static void compute_parity5(struct stripe_head *sh, int method)
-{
-	raid5_conf_t *conf = sh->raid_conf;
-	int i, pd_idx = sh->pd_idx, disks = sh->disks, count;
-	void *ptr[MAX_XOR_BLOCKS];
-	struct bio *chosen;
-
-	PRINTK("compute_parity5, stripe %llu, method %d\n",
-		(unsigned long long)sh->sector, method);
-
-	count = 1;
-	ptr[0] = page_address(sh->dev[pd_idx].page);
-	switch(method) {
-	case READ_MODIFY_WRITE:
-		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags));
-		for (i=disks ; i-- ;) {
-			if (i==pd_idx)
-				continue;
-			if (sh->dev[i].towrite &&
-			    test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
-				ptr[count++] = page_address(sh->dev[i].page);
-				chosen = sh->dev[i].towrite;
-				sh->dev[i].towrite = NULL;
-
-				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-					wake_up(&conf->wait_for_overlap);
-
-				BUG_ON(sh->dev[i].written);
-				sh->dev[i].written = chosen;
-				check_xor();
-			}
-		}
-		break;
-	case RECONSTRUCT_WRITE:
-		memset(ptr[0], 0, STRIPE_SIZE);
-		for (i= disks; i-- ;)
-			if (i!=pd_idx && sh->dev[i].towrite) {
-				chosen = sh->dev[i].towrite;
-				sh->dev[i].towrite = NULL;
-
-				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-					wake_up(&conf->wait_for_overlap);
-
-				BUG_ON(sh->dev[i].written);
-				sh->dev[i].written = chosen;
-			}
-		break;
-	case CHECK_PARITY:
-		break;
-	}
-	if (count>1) {
-		xor_block(count, STRIPE_SIZE, ptr);
-		count = 1;
-	}
-	
-	for (i = disks; i--;)
-		if (sh->dev[i].written) {
-			sector_t sector = sh->dev[i].sector;
-			struct bio *wbi = sh->dev[i].written;
-			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
-				copy_data(1, wbi, sh->dev[i].page, sector);
-				wbi = r5_next_bio(wbi, sector);
-			}
-
-			set_bit(R5_LOCKED, &sh->dev[i].flags);
-			set_bit(R5_UPTODATE, &sh->dev[i].flags);
-		}
-
-	switch(method) {
-	case RECONSTRUCT_WRITE:
-	case CHECK_PARITY:
-		for (i=disks; i--;)
-			if (i != pd_idx) {
-				ptr[count++] = page_address(sh->dev[i].page);
-				check_xor();
-			}
-		break;
-	case READ_MODIFY_WRITE:
-		for (i = disks; i--;)
-			if (sh->dev[i].written) {
-				ptr[count++] = page_address(sh->dev[i].page);
-				check_xor();
-			}
-	}
-	if (count != 1)
-		xor_block(count, STRIPE_SIZE, ptr);
-	
-	if (method != CHECK_PARITY) {
-		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
-	} else
-		clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-}
-
 static void compute_parity6(struct stripe_head *sh, int method)
 {
 	raid6_conf_t *conf = sh->raid_conf;
@@ -1058,7 +1527,7 @@ static void compute_parity6(struct stripe_head *sh, int method)
 	qd_idx = raid6_next_disk(pd_idx, disks);
 	d0_idx = raid6_next_disk(qd_idx, disks);
 
-	PRINTK("compute_parity, stripe %llu, method %d\n",
+	pr_debug("compute_parity, stripe %llu, method %d\n",
 		(unsigned long long)sh->sector, method);
 
 	switch(method) {
@@ -1132,20 +1601,20 @@ static void compute_parity6(struct stripe_head *sh, int method)
 static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
 {
 	int i, count, disks = sh->disks;
-	void *ptr[MAX_XOR_BLOCKS], *p;
+	void *ptr[MAX_XOR_BLOCKS], *dest, *p;
 	int pd_idx = sh->pd_idx;
 	int qd_idx = raid6_next_disk(pd_idx, disks);
 
-	PRINTK("compute_block_1, stripe %llu, idx %d\n",
+	pr_debug("compute_block_1, stripe %llu, idx %d\n",
 		(unsigned long long)sh->sector, dd_idx);
 
 	if ( dd_idx == qd_idx ) {
 		/* We're actually computing the Q drive */
 		compute_parity6(sh, UPDATE_PARITY);
 	} else {
-		ptr[0] = page_address(sh->dev[dd_idx].page);
-		if (!nozero) memset(ptr[0], 0, STRIPE_SIZE);
-		count = 1;
+		dest = page_address(sh->dev[dd_idx].page);
+		if (!nozero) memset(dest, 0, STRIPE_SIZE);
+		count = 0;
 		for (i = disks ; i--; ) {
 			if (i == dd_idx || i == qd_idx)
 				continue;
@@ -1159,8 +1628,8 @@ static void compute_block_1(struct stripe_head *sh, int dd_idx, int nozero)
 
 			check_xor();
 		}
-		if (count != 1)
-			xor_block(count, STRIPE_SIZE, ptr);
+		if (count)
+			xor_blocks(count, STRIPE_SIZE, dest, ptr);
 		if (!nozero) set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
 		else clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
 	}
@@ -1183,7 +1652,7 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
 	BUG_ON(faila == failb);
 	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
 
-	PRINTK("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
+	pr_debug("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
 	       (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
 
 	if ( failb == disks-1 ) {
@@ -1229,7 +1698,79 @@ static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
 	}
 }
 
+static int
+handle_write_operations5(struct stripe_head *sh, int rcw, int expand)
+{
+	int i, pd_idx = sh->pd_idx, disks = sh->disks;
+	int locked = 0;
 
+	if (rcw) {
+		/* if we are not expanding this is a proper write request, and
+		 * there will be bios with new data to be drained into the
+		 * stripe cache
+		 */
+		if (!expand) {
+			set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+			sh->ops.count++;
+		}
+
+		set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+		sh->ops.count++;
+
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+
+			if (dev->towrite) {
+				set_bit(R5_LOCKED, &dev->flags);
+				if (!expand)
+					clear_bit(R5_UPTODATE, &dev->flags);
+				locked++;
+			}
+		}
+	} else {
+		BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
+			test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
+
+		set_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+		set_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+		set_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+
+		sh->ops.count += 3;
+
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (i == pd_idx)
+				continue;
+
+			/* For a read-modify write there may be blocks that are
+			 * locked for reading while others are ready to be
+			 * written so we distinguish these blocks by the
+			 * R5_Wantprexor bit
+			 */
+			if (dev->towrite &&
+			    (test_bit(R5_UPTODATE, &dev->flags) ||
+			    test_bit(R5_Wantcompute, &dev->flags))) {
+				set_bit(R5_Wantprexor, &dev->flags);
+				set_bit(R5_LOCKED, &dev->flags);
+				clear_bit(R5_UPTODATE, &dev->flags);
+				locked++;
+			}
+		}
+	}
+
+	/* keep the parity disk locked while asynchronous operations
+	 * are in flight
+	 */
+	set_bit(R5_LOCKED, &sh->dev[pd_idx].flags);
+	clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+	locked++;
+
+	pr_debug("%s: stripe %llu locked: %d pending: %lx\n",
+		__FUNCTION__, (unsigned long long)sh->sector,
+		locked, sh->ops.pending);
+
+	return locked;
+}
 
 /*
  * Each stripe/dev can have one or more bion attached.
@@ -1242,7 +1783,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 	raid5_conf_t *conf = sh->raid_conf;
 	int firstwrite=0;
 
-	PRINTK("adding bh b#%llu to stripe s#%llu\n",
+	pr_debug("adding bh b#%llu to stripe s#%llu\n",
 		(unsigned long long)bi->bi_sector,
 		(unsigned long long)sh->sector);
 
@@ -1271,7 +1812,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 	spin_unlock_irq(&conf->device_lock);
 	spin_unlock(&sh->lock);
 
-	PRINTK("added bi b#%llu to stripe s#%llu, disk %d.\n",
+	pr_debug("added bi b#%llu to stripe s#%llu, disk %d.\n",
 		(unsigned long long)bi->bi_sector,
 		(unsigned long long)sh->sector, dd_idx);
 
@@ -1326,6 +1867,729 @@ static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
 	return pd_idx;
 }
 
+static void
+handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
+				struct stripe_head_state *s, int disks,
+				struct bio **return_bi)
+{
+	int i;
+	for (i = disks; i--; ) {
+		struct bio *bi;
+		int bitmap_end = 0;
+
+		if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
+			mdk_rdev_t *rdev;
+			rcu_read_lock();
+			rdev = rcu_dereference(conf->disks[i].rdev);
+			if (rdev && test_bit(In_sync, &rdev->flags))
+				/* multiple read failures in one stripe */
+				md_error(conf->mddev, rdev);
+			rcu_read_unlock();
+		}
+		spin_lock_irq(&conf->device_lock);
+		/* fail all writes first */
+		bi = sh->dev[i].towrite;
+		sh->dev[i].towrite = NULL;
+		if (bi) {
+			s->to_write--;
+			bitmap_end = 1;
+		}
+
+		if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+			wake_up(&conf->wait_for_overlap);
+
+		while (bi && bi->bi_sector <
+			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 (--bi->bi_phys_segments == 0) {
+				md_write_end(conf->mddev);
+				bi->bi_next = *return_bi;
+				*return_bi = bi;
+			}
+			bi = nextbi;
+		}
+		/* and fail all 'written' */
+		bi = sh->dev[i].written;
+		sh->dev[i].written = NULL;
+		if (bi) bitmap_end = 1;
+		while (bi && bi->bi_sector <
+		       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 (--bi->bi_phys_segments == 0) {
+				md_write_end(conf->mddev);
+				bi->bi_next = *return_bi;
+				*return_bi = bi;
+			}
+			bi = bi2;
+		}
+
+		/* fail any reads if this device is non-operational and
+		 * the data has not reached the cache yet.
+		 */
+		if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
+		    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+		      test_bit(R5_ReadError, &sh->dev[i].flags))) {
+			bi = sh->dev[i].toread;
+			sh->dev[i].toread = NULL;
+			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
+				wake_up(&conf->wait_for_overlap);
+			if (bi) s->to_read--;
+			while (bi && bi->bi_sector <
+			       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 (--bi->bi_phys_segments == 0) {
+					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);
+	}
+
+}
+
+/* __handle_issuing_new_read_requests5 - returns 0 if there are no more disks
+ * to process
+ */
+static int __handle_issuing_new_read_requests5(struct stripe_head *sh,
+			struct stripe_head_state *s, int disk_idx, int disks)
+{
+	struct r5dev *dev = &sh->dev[disk_idx];
+	struct r5dev *failed_dev = &sh->dev[s->failed_num];
+
+	/* don't schedule compute operations or reads on the parity block while
+	 * a check is in flight
+	 */
+	if ((disk_idx == sh->pd_idx) &&
+	     test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
+		return ~0;
+
+	/* is the data in this block needed, and can we get it? */
+	if (!test_bit(R5_LOCKED, &dev->flags) &&
+	    !test_bit(R5_UPTODATE, &dev->flags) && (dev->toread ||
+	    (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
+	     s->syncing || s->expanding || (s->failed &&
+	     (failed_dev->toread || (failed_dev->towrite &&
+	     !test_bit(R5_OVERWRITE, &failed_dev->flags)
+	     ))))) {
+		/* 1/ We would like to get this block, possibly by computing it,
+		 * but we might not be able to.
+		 *
+		 * 2/ Since parity check operations potentially make the parity
+		 * block !uptodate it will need to be refreshed before any
+		 * compute operations on data disks are scheduled.
+		 *
+		 * 3/ We hold off parity block re-reads until check operations
+		 * have quiesced.
+		 */
+		if ((s->uptodate == disks - 1) &&
+		    !test_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
+			set_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
+			set_bit(R5_Wantcompute, &dev->flags);
+			sh->ops.target = disk_idx;
+			s->req_compute = 1;
+			sh->ops.count++;
+			/* Careful: from this point on 'uptodate' is in the eye
+			 * of raid5_run_ops which services 'compute' operations
+			 * before writes. R5_Wantcompute flags a block that will
+			 * be R5_UPTODATE by the time it is needed for a
+			 * subsequent operation.
+			 */
+			s->uptodate++;
+			return 0; /* uptodate + compute == disks */
+		} else if ((s->uptodate < disks - 1) &&
+			test_bit(R5_Insync, &dev->flags)) {
+			/* Note: we hold off compute operations while checks are
+			 * in flight, but we still prefer 'compute' over 'read'
+			 * hence we only read if (uptodate < * disks-1)
+			 */
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantread, &dev->flags);
+			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+				sh->ops.count++;
+			s->locked++;
+			pr_debug("Reading block %d (sync=%d)\n", disk_idx,
+				s->syncing);
+		}
+	}
+
+	return ~0;
+}
+
+static void handle_issuing_new_read_requests5(struct stripe_head *sh,
+			struct stripe_head_state *s, int disks)
+{
+	int i;
+
+	/* Clear completed compute operations.  Parity recovery
+	 * (STRIPE_OP_MOD_REPAIR_PD) implies a write-back which is handled
+	 * later on in this routine
+	 */
+	if (test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete) &&
+		!test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.ack);
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
+	}
+
+	/* 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
+	 */
+	if (!test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending) &&
+		!test_bit(STRIPE_OP_PREXOR, &sh->ops.pending) &&
+		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
+		for (i = disks; i--; )
+			if (__handle_issuing_new_read_requests5(
+				sh, s, i, disks) == 0)
+				break;
+	}
+	set_bit(STRIPE_HANDLE, &sh->state);
+}
+
+static void handle_issuing_new_read_requests6(struct stripe_head *sh,
+			struct stripe_head_state *s, struct r6_state *r6s,
+			int disks)
+{
+	int i;
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		if (!test_bit(R5_LOCKED, &dev->flags) &&
+		    !test_bit(R5_UPTODATE, &dev->flags) &&
+		    (dev->toread || (dev->towrite &&
+		     !test_bit(R5_OVERWRITE, &dev->flags)) ||
+		     s->syncing || s->expanding ||
+		     (s->failed >= 1 &&
+		      (sh->dev[r6s->failed_num[0]].toread ||
+		       s->to_write)) ||
+		     (s->failed >= 2 &&
+		      (sh->dev[r6s->failed_num[1]].toread ||
+		       s->to_write)))) {
+			/* we would like to get this block, possibly
+			 * by computing it, but we might not be able to
+			 */
+			if (s->uptodate == disks-1) {
+				pr_debug("Computing stripe %llu block %d\n",
+				       (unsigned long long)sh->sector, i);
+				compute_block_1(sh, i, 0);
+				s->uptodate++;
+			} else if ( s->uptodate == disks-2 && s->failed >= 2 ) {
+				/* Computing 2-failure is *very* expensive; only
+				 * do it if failed >= 2
+				 */
+				int other;
+				for (other = disks; other--; ) {
+					if (other == i)
+						continue;
+					if (!test_bit(R5_UPTODATE,
+					      &sh->dev[other].flags))
+						break;
+				}
+				BUG_ON(other < 0);
+				pr_debug("Computing stripe %llu blocks %d,%d\n",
+				       (unsigned long long)sh->sector,
+				       i, other);
+				compute_block_2(sh, i, other);
+				s->uptodate += 2;
+			} else if (test_bit(R5_Insync, &dev->flags)) {
+				set_bit(R5_LOCKED, &dev->flags);
+				set_bit(R5_Wantread, &dev->flags);
+				s->locked++;
+				pr_debug("Reading block %d (sync=%d)\n",
+					i, s->syncing);
+			}
+		}
+	}
+	set_bit(STRIPE_HANDLE, &sh->state);
+}
+
+
+/* handle_completed_write_requests
+ * any written block on an uptodate or failed drive can be returned.
+ * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but
+ * never LOCKED, so we don't need to test 'failed' directly.
+ */
+static void handle_completed_write_requests(raid5_conf_t *conf,
+	struct stripe_head *sh, int disks, struct bio **return_bi)
+{
+	int i;
+	struct r5dev *dev;
+
+	for (i = disks; i--; )
+		if (sh->dev[i].written) {
+			dev = &sh->dev[i];
+			if (!test_bit(R5_LOCKED, &dev->flags) &&
+				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 (--wbi->bi_phys_segments == 0) {
+						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,
+					 !test_bit(STRIPE_DEGRADED, &sh->state),
+							0);
+			}
+		}
+}
+
+static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
+		struct stripe_head *sh,	struct stripe_head_state *s, int disks)
+{
+	int rmw = 0, rcw = 0, i;
+	for (i = disks; i--; ) {
+		/* would I have to read this buffer for read_modify_write */
+		struct r5dev *dev = &sh->dev[i];
+		if ((dev->towrite || i == sh->pd_idx) &&
+		    !test_bit(R5_LOCKED, &dev->flags) &&
+		    !(test_bit(R5_UPTODATE, &dev->flags) ||
+		      test_bit(R5_Wantcompute, &dev->flags))) {
+			if (test_bit(R5_Insync, &dev->flags))
+				rmw++;
+			else
+				rmw += 2*disks;  /* cannot read it */
+		}
+		/* Would I have to read this buffer for reconstruct_write */
+		if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
+		    !test_bit(R5_LOCKED, &dev->flags) &&
+		    !(test_bit(R5_UPTODATE, &dev->flags) ||
+		    test_bit(R5_Wantcompute, &dev->flags))) {
+			if (test_bit(R5_Insync, &dev->flags)) rcw++;
+			else
+				rcw += 2*disks;
+		}
+	}
+	pr_debug("for sector %llu, rmw=%d rcw=%d\n",
+		(unsigned long long)sh->sector, rmw, rcw);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	if (rmw < rcw && rmw > 0)
+		/* prefer read-modify-write, but need to get some data */
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if ((dev->towrite || i == sh->pd_idx) &&
+			    !test_bit(R5_LOCKED, &dev->flags) &&
+			    !(test_bit(R5_UPTODATE, &dev->flags) ||
+			    test_bit(R5_Wantcompute, &dev->flags)) &&
+			    test_bit(R5_Insync, &dev->flags)) {
+				if (
+				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+					pr_debug("Read_old block "
+						"%d for r-m-w\n", i);
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+					if (!test_and_set_bit(
+						STRIPE_OP_IO, &sh->ops.pending))
+						sh->ops.count++;
+					s->locked++;
+				} else {
+					set_bit(STRIPE_DELAYED, &sh->state);
+					set_bit(STRIPE_HANDLE, &sh->state);
+				}
+			}
+		}
+	if (rcw <= rmw && rcw > 0)
+		/* want reconstruct write, but need to get some data */
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (!test_bit(R5_OVERWRITE, &dev->flags) &&
+			    i != sh->pd_idx &&
+			    !test_bit(R5_LOCKED, &dev->flags) &&
+			    !(test_bit(R5_UPTODATE, &dev->flags) ||
+			    test_bit(R5_Wantcompute, &dev->flags)) &&
+			    test_bit(R5_Insync, &dev->flags)) {
+				if (
+				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+					pr_debug("Read_old block "
+						"%d for Reconstruct\n", i);
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+					if (!test_and_set_bit(
+						STRIPE_OP_IO, &sh->ops.pending))
+						sh->ops.count++;
+					s->locked++;
+				} else {
+					set_bit(STRIPE_DELAYED, &sh->state);
+					set_bit(STRIPE_HANDLE, &sh->state);
+				}
+			}
+		}
+	/* now if nothing is locked, and if we have enough data,
+	 * we can start a write request
+	 */
+	/* since handle_stripe can be called at any time we need to handle the
+	 * case where a compute block operation has been submitted and then a
+	 * subsequent call wants to start a write request.  raid5_run_ops only
+	 * handles the case where compute block and postxor are requested
+	 * simultaneously.  If this is not the case then new writes need to be
+	 * held off until the compute completes.
+	 */
+	if ((s->req_compute ||
+	    !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) &&
+		(s->locked == 0 && (rcw == 0 || rmw == 0) &&
+		!test_bit(STRIPE_BIT_DELAY, &sh->state)))
+		s->locked += handle_write_operations5(sh, rcw == 0, 0);
+}
+
+static void handle_issuing_new_write_requests6(raid5_conf_t *conf,
+		struct stripe_head *sh,	struct stripe_head_state *s,
+		struct r6_state *r6s, int disks)
+{
+	int rcw = 0, must_compute = 0, pd_idx = sh->pd_idx, i;
+	int qd_idx = r6s->qd_idx;
+	for (i = disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+		/* Would I have to read this buffer for reconstruct_write */
+		if (!test_bit(R5_OVERWRITE, &dev->flags)
+		    && i != pd_idx && i != qd_idx
+		    && (!test_bit(R5_LOCKED, &dev->flags)
+			    ) &&
+		    !test_bit(R5_UPTODATE, &dev->flags)) {
+			if (test_bit(R5_Insync, &dev->flags)) rcw++;
+			else {
+				pr_debug("raid6: must_compute: "
+					"disk %d flags=%#lx\n", i, dev->flags);
+				must_compute++;
+			}
+		}
+	}
+	pr_debug("for sector %llu, rcw=%d, must_compute=%d\n",
+	       (unsigned long long)sh->sector, rcw, must_compute);
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	if (rcw > 0)
+		/* want reconstruct write, but need to get some data */
+		for (i = disks; i--; ) {
+			struct r5dev *dev = &sh->dev[i];
+			if (!test_bit(R5_OVERWRITE, &dev->flags)
+			    && !(s->failed == 0 && (i == pd_idx || i == qd_idx))
+			    && !test_bit(R5_LOCKED, &dev->flags) &&
+			    !test_bit(R5_UPTODATE, &dev->flags) &&
+			    test_bit(R5_Insync, &dev->flags)) {
+				if (
+				  test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+					pr_debug("Read_old stripe %llu "
+						"block %d for Reconstruct\n",
+					     (unsigned long long)sh->sector, i);
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+					s->locked++;
+				} else {
+					pr_debug("Request delayed stripe %llu "
+						"block %d for Reconstruct\n",
+					     (unsigned long long)sh->sector, i);
+					set_bit(STRIPE_DELAYED, &sh->state);
+					set_bit(STRIPE_HANDLE, &sh->state);
+				}
+			}
+		}
+	/* now if nothing is locked, and if we have enough data, we can start a
+	 * write request
+	 */
+	if (s->locked == 0 && rcw == 0 &&
+	    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
+		if (must_compute > 0) {
+			/* We have failed blocks and need to compute them */
+			switch (s->failed) {
+			case 0:
+				BUG();
+			case 1:
+				compute_block_1(sh, r6s->failed_num[0], 0);
+				break;
+			case 2:
+				compute_block_2(sh, r6s->failed_num[0],
+						r6s->failed_num[1]);
+				break;
+			default: /* This request should have been failed? */
+				BUG();
+			}
+		}
+
+		pr_debug("Computing parity for stripe %llu\n",
+			(unsigned long long)sh->sector);
+		compute_parity6(sh, RECONSTRUCT_WRITE);
+		/* now every locked buffer is ready to be written */
+		for (i = disks; i--; )
+			if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
+				pr_debug("Writing stripe %llu block %d\n",
+				       (unsigned long long)sh->sector, i);
+				s->locked++;
+				set_bit(R5_Wantwrite, &sh->dev[i].flags);
+			}
+		/* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
+		set_bit(STRIPE_INSYNC, &sh->state);
+
+		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+			atomic_dec(&conf->preread_active_stripes);
+			if (atomic_read(&conf->preread_active_stripes) <
+			    IO_THRESHOLD)
+				md_wakeup_thread(conf->mddev->thread);
+		}
+	}
+}
+
+static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
+				struct stripe_head_state *s, int disks)
+{
+	set_bit(STRIPE_HANDLE, &sh->state);
+	/* Take one of the following actions:
+	 * 1/ start a check parity operation if (uptodate == disks)
+	 * 2/ finish a check parity operation and act on the result
+	 * 3/ skip to the writeback section if we previously
+	 *    initiated a recovery operation
+	 */
+	if (s->failed == 0 &&
+	    !test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
+		if (!test_and_set_bit(STRIPE_OP_CHECK, &sh->ops.pending)) {
+			BUG_ON(s->uptodate != disks);
+			clear_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags);
+			sh->ops.count++;
+			s->uptodate--;
+		} else if (
+		       test_and_clear_bit(STRIPE_OP_CHECK, &sh->ops.complete)) {
+			clear_bit(STRIPE_OP_CHECK, &sh->ops.ack);
+			clear_bit(STRIPE_OP_CHECK, &sh->ops.pending);
+
+			if (sh->ops.zero_sum_result == 0)
+				/* parity is correct (on disc,
+				 * not in buffer any more)
+				 */
+				set_bit(STRIPE_INSYNC, &sh->state);
+			else {
+				conf->mddev->resync_mismatches +=
+					STRIPE_SECTORS;
+				if (test_bit(
+				     MD_RECOVERY_CHECK, &conf->mddev->recovery))
+					/* don't try to repair!! */
+					set_bit(STRIPE_INSYNC, &sh->state);
+				else {
+					set_bit(STRIPE_OP_COMPUTE_BLK,
+						&sh->ops.pending);
+					set_bit(STRIPE_OP_MOD_REPAIR_PD,
+						&sh->ops.pending);
+					set_bit(R5_Wantcompute,
+						&sh->dev[sh->pd_idx].flags);
+					sh->ops.target = sh->pd_idx;
+					sh->ops.count++;
+					s->uptodate++;
+				}
+			}
+		}
+	}
+
+	/* check if we can clear a parity disk reconstruct */
+	if (test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete) &&
+		test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending)) {
+
+		clear_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending);
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.complete);
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.ack);
+		clear_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending);
+	}
+
+	/* Wait for check parity and compute block operations to complete
+	 * before write-back
+	 */
+	if (!test_bit(STRIPE_INSYNC, &sh->state) &&
+		!test_bit(STRIPE_OP_CHECK, &sh->ops.pending) &&
+		!test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending)) {
+		struct r5dev *dev;
+		/* either failed parity check, or recovery is happening */
+		if (s->failed == 0)
+			s->failed_num = sh->pd_idx;
+		dev = &sh->dev[s->failed_num];
+		BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
+		BUG_ON(s->uptodate != disks);
+
+		set_bit(R5_LOCKED, &dev->flags);
+		set_bit(R5_Wantwrite, &dev->flags);
+		if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+			sh->ops.count++;
+
+		clear_bit(STRIPE_DEGRADED, &sh->state);
+		s->locked++;
+		set_bit(STRIPE_INSYNC, &sh->state);
+	}
+}
+
+
+static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
+				struct stripe_head_state *s,
+				struct r6_state *r6s, struct page *tmp_page,
+				int disks)
+{
+	int update_p = 0, update_q = 0;
+	struct r5dev *dev;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = r6s->qd_idx;
+
+	set_bit(STRIPE_HANDLE, &sh->state);
+
+	BUG_ON(s->failed > 2);
+	BUG_ON(s->uptodate < disks);
+	/* Want to check and possibly repair P and Q.
+	 * However there could be one 'failed' device, in which
+	 * case we can only check one of them, possibly using the
+	 * other to generate missing data
+	 */
+
+	/* If !tmp_page, we cannot do the calculations,
+	 * but as we have set STRIPE_HANDLE, we will soon be called
+	 * by stripe_handle with a tmp_page - just wait until then.
+	 */
+	if (tmp_page) {
+		if (s->failed == r6s->q_failed) {
+			/* The only possible failed device holds 'Q', so it
+			 * makes sense to check P (If anything else were failed,
+			 * we would have used P to recreate it).
+			 */
+			compute_block_1(sh, pd_idx, 1);
+			if (!page_is_zero(sh->dev[pd_idx].page)) {
+				compute_block_1(sh, pd_idx, 0);
+				update_p = 1;
+			}
+		}
+		if (!r6s->q_failed && s->failed < 2) {
+			/* q is not failed, and we didn't use it to generate
+			 * anything, so it makes sense to check it
+			 */
+			memcpy(page_address(tmp_page),
+			       page_address(sh->dev[qd_idx].page),
+			       STRIPE_SIZE);
+			compute_parity6(sh, UPDATE_PARITY);
+			if (memcmp(page_address(tmp_page),
+				   page_address(sh->dev[qd_idx].page),
+				   STRIPE_SIZE) != 0) {
+				clear_bit(STRIPE_INSYNC, &sh->state);
+				update_q = 1;
+			}
+		}
+		if (update_p || update_q) {
+			conf->mddev->resync_mismatches += STRIPE_SECTORS;
+			if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
+				/* don't try to repair!! */
+				update_p = update_q = 0;
+		}
+
+		/* now write out any block on a failed drive,
+		 * or P or Q if they need it
+		 */
+
+		if (s->failed == 2) {
+			dev = &sh->dev[r6s->failed_num[1]];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (s->failed >= 1) {
+			dev = &sh->dev[r6s->failed_num[0]];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+
+		if (update_p) {
+			dev = &sh->dev[pd_idx];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		if (update_q) {
+			dev = &sh->dev[qd_idx];
+			s->locked++;
+			set_bit(R5_LOCKED, &dev->flags);
+			set_bit(R5_Wantwrite, &dev->flags);
+		}
+		clear_bit(STRIPE_DEGRADED, &sh->state);
+
+		set_bit(STRIPE_INSYNC, &sh->state);
+	}
+}
+
+static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
+				struct r6_state *r6s)
+{
+	int i;
+
+	/* We have read all the blocks in this stripe and now we need to
+	 * copy some of them into a target stripe for expand.
+	 */
+	struct dma_async_tx_descriptor *tx = NULL;
+	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+	for (i = 0; i < sh->disks; i++)
+		if (i != sh->pd_idx && (r6s && i != r6s->qd_idx)) {
+			int dd_idx, pd_idx, j;
+			struct stripe_head *sh2;
+
+			sector_t bn = compute_blocknr(sh, i);
+			sector_t s = raid5_compute_sector(bn, conf->raid_disks,
+						conf->raid_disks -
+						conf->max_degraded, &dd_idx,
+						&pd_idx, conf);
+			sh2 = get_active_stripe(conf, s, conf->raid_disks,
+						pd_idx, 1);
+			if (sh2 == NULL)
+				/* so far only the early blocks of this stripe
+				 * have been requested.  When later blocks
+				 * get requested, we will try again
+				 */
+				continue;
+			if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
+			   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
+				/* must have already done this block */
+				release_stripe(sh2);
+				continue;
+			}
+
+			/* place all the copies on one channel */
+			tx = async_memcpy(sh2->dev[dd_idx].page,
+				sh->dev[i].page, 0, 0, STRIPE_SIZE,
+				ASYNC_TX_DEP_ACK, tx, NULL, NULL);
+
+			set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
+			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
+			for (j = 0; j < conf->raid_disks; j++)
+				if (j != sh2->pd_idx &&
+				    (r6s && j != r6s->qd_idx) &&
+				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
+					break;
+			if (j == conf->raid_disks) {
+				set_bit(STRIPE_EXPAND_READY, &sh2->state);
+				set_bit(STRIPE_HANDLE, &sh2->state);
+			}
+			release_stripe(sh2);
+
+			/* done submitting copies, wait for them to complete */
+			if (i + 1 >= sh->disks) {
+				async_tx_ack(tx);
+				dma_wait_for_async_tx(tx);
+			}
+		}
+}
 
 /*
  * handle_stripe - do things to a stripe.
@@ -1339,81 +2603,70 @@ static int stripe_to_pdidx(sector_t stripe, raid5_conf_t *conf, int disks)
  *    schedule a write of some buffers
  *    return confirmation of parity correctness
  *
- * Parity calculations are done inside the stripe lock
  * buffers are taken off read_list or write_list, and bh_cache buffers
  * get BH_Lock set before the stripe lock is released.
  *
  */
- 
+
 static void handle_stripe5(struct stripe_head *sh)
 {
 	raid5_conf_t *conf = sh->raid_conf;
-	int disks = sh->disks;
-	struct bio *return_bi= NULL;
-	struct bio *bi;
-	int i;
-	int syncing, expanding, expanded;
-	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
-	int non_overwrite = 0;
-	int failed_num=0;
+	int disks = sh->disks, i;
+	struct bio *return_bi = NULL;
+	struct stripe_head_state s;
 	struct r5dev *dev;
+	unsigned long pending = 0;
 
-	PRINTK("handling stripe %llu, cnt=%d, pd_idx=%d\n",
-		(unsigned long long)sh->sector, atomic_read(&sh->count),
-		sh->pd_idx);
+	memset(&s, 0, sizeof(s));
+	pr_debug("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d "
+		"ops=%lx:%lx:%lx\n", (unsigned long long)sh->sector, sh->state,
+		atomic_read(&sh->count), sh->pd_idx,
+		sh->ops.pending, sh->ops.ack, sh->ops.complete);
 
 	spin_lock(&sh->lock);
 	clear_bit(STRIPE_HANDLE, &sh->state);
 	clear_bit(STRIPE_DELAYED, &sh->state);
 
-	syncing = test_bit(STRIPE_SYNCING, &sh->state);
-	expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
-	expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
+	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
+	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
 	/* Now to look around and see what can be done */
 
 	rcu_read_lock();
 	for (i=disks; i--; ) {
 		mdk_rdev_t *rdev;
-		dev = &sh->dev[i];
+		struct r5dev *dev = &sh->dev[i];
 		clear_bit(R5_Insync, &dev->flags);
 
-		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
-			i, dev->flags, dev->toread, dev->towrite, dev->written);
-		/* maybe we can reply to a read */
-		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
-			struct bio *rbi, *rbi2;
-			PRINTK("Return read for disc %d\n", i);
-			spin_lock_irq(&conf->device_lock);
-			rbi = dev->toread;
-			dev->toread = NULL;
-			if (test_and_clear_bit(R5_Overlap, &dev->flags))
-				wake_up(&conf->wait_for_overlap);
-			spin_unlock_irq(&conf->device_lock);
-			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
-				copy_data(0, rbi, dev->page, dev->sector);
-				rbi2 = r5_next_bio(rbi, dev->sector);
-				spin_lock_irq(&conf->device_lock);
-				if (--rbi->bi_phys_segments == 0) {
-					rbi->bi_next = return_bi;
-					return_bi = rbi;
-				}
-				spin_unlock_irq(&conf->device_lock);
-				rbi = rbi2;
-			}
-		}
+		pr_debug("check %d: state 0x%lx toread %p read %p write %p "
+			"written %p\n",	i, dev->flags, dev->toread, dev->read,
+			dev->towrite, dev->written);
 
-		/* now count some things */
-		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
-		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
+		/* maybe we can request a biofill operation
+		 *
+		 * new wantfill requests are only permitted while
+		 * STRIPE_OP_BIOFILL is clear
+		 */
+		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
+			!test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
+			set_bit(R5_Wantfill, &dev->flags);
 
-		
-		if (dev->toread) to_read++;
+		/* now count some things */
+		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
+		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
+		if (test_bit(R5_Wantcompute, &dev->flags)) s.compute++;
+
+		if (test_bit(R5_Wantfill, &dev->flags))
+			s.to_fill++;
+		else if (dev->toread)
+			s.to_read++;
 		if (dev->towrite) {
-			to_write++;
+			s.to_write++;
 			if (!test_bit(R5_OVERWRITE, &dev->flags))
-				non_overwrite++;
+				s.non_overwrite++;
 		}
-		if (dev->written) written++;
+		if (dev->written)
+			s.written++;
 		rdev = rcu_dereference(conf->disks[i].rdev);
 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
 			/* The ReadError flag will just be confusing now */
@@ -1422,306 +2675,131 @@ static void handle_stripe5(struct stripe_head *sh)
 		}
 		if (!rdev || !test_bit(In_sync, &rdev->flags)
 		    || test_bit(R5_ReadError, &dev->flags)) {
-			failed++;
-			failed_num = i;
+			s.failed++;
+			s.failed_num = i;
 		} else
 			set_bit(R5_Insync, &dev->flags);
 	}
 	rcu_read_unlock();
-	PRINTK("locked=%d uptodate=%d to_read=%d"
+
+	if (s.to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
+		sh->ops.count++;
+
+	pr_debug("locked=%d uptodate=%d to_read=%d"
 		" to_write=%d failed=%d failed_num=%d\n",
-		locked, uptodate, to_read, to_write, failed, failed_num);
+		s.locked, s.uptodate, s.to_read, s.to_write,
+		s.failed, s.failed_num);
 	/* check if the array has lost two devices and, if so, some requests might
 	 * need to be failed
 	 */
-	if (failed > 1 && to_read+to_write+written) {
-		for (i=disks; i--; ) {
-			int bitmap_end = 0;
-
-			if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
-				mdk_rdev_t *rdev;
-				rcu_read_lock();
-				rdev = rcu_dereference(conf->disks[i].rdev);
-				if (rdev && test_bit(In_sync, &rdev->flags))
-					/* multiple read failures in one stripe */
-					md_error(conf->mddev, rdev);
-				rcu_read_unlock();
-			}
-
-			spin_lock_irq(&conf->device_lock);
-			/* fail all writes first */
-			bi = sh->dev[i].towrite;
-			sh->dev[i].towrite = NULL;
-			if (bi) { to_write--; bitmap_end = 1; }
-
-			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-				wake_up(&conf->wait_for_overlap);
-
-			while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-					md_write_end(conf->mddev);
-					bi->bi_next = return_bi;
-					return_bi = bi;
-				}
-				bi = nextbi;
-			}
-			/* and fail all 'written' */
-			bi = sh->dev[i].written;
-			sh->dev[i].written = NULL;
-			if (bi) bitmap_end = 1;
-			while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-					md_write_end(conf->mddev);
-					bi->bi_next = return_bi;
-					return_bi = bi;
-				}
-				bi = bi2;
-			}
-
-			/* fail any reads if this device is non-operational */
-			if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
-			    test_bit(R5_ReadError, &sh->dev[i].flags)) {
-				bi = sh->dev[i].toread;
-				sh->dev[i].toread = NULL;
-				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-					wake_up(&conf->wait_for_overlap);
-				if (bi) to_read--;
-				while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-						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);
-		}
-	}
-	if (failed > 1 && syncing) {
+	if (s.failed > 1 && s.to_read+s.to_write+s.written)
+		handle_requests_to_failed_array(conf, sh, &s, disks,
+						&return_bi);
+	if (s.failed > 1 && s.syncing) {
 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
 		clear_bit(STRIPE_SYNCING, &sh->state);
-		syncing = 0;
+		s.syncing = 0;
 	}
 
 	/* might be able to return some write requests if the parity block
 	 * is safe, or on a failed drive
 	 */
 	dev = &sh->dev[sh->pd_idx];
-	if ( written &&
-	     ( (test_bit(R5_Insync, &dev->flags) && !test_bit(R5_LOCKED, &dev->flags) &&
-		test_bit(R5_UPTODATE, &dev->flags))
-	       || (failed == 1 && failed_num == sh->pd_idx))
-	    ) {
-	    /* any written block on an uptodate or failed drive can be returned.
-	     * Note that if we 'wrote' to a failed drive, it will be UPTODATE, but 
-	     * never LOCKED, so we don't need to test 'failed' directly.
-	     */
-	    for (i=disks; i--; )
-		if (sh->dev[i].written) {
-		    dev = &sh->dev[i];
-		    if (!test_bit(R5_LOCKED, &dev->flags) &&
-			 test_bit(R5_UPTODATE, &dev->flags) ) {
-			/* We can return any write requests */
-			    struct bio *wbi, *wbi2;
-			    int bitmap_end = 0;
-			    PRINTK("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 (--wbi->bi_phys_segments == 0) {
-					    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,
-						    !test_bit(STRIPE_DEGRADED, &sh->state), 0);
-		    }
-		}
-	}
+	if ( s.written &&
+	     ((test_bit(R5_Insync, &dev->flags) &&
+	       !test_bit(R5_LOCKED, &dev->flags) &&
+	       test_bit(R5_UPTODATE, &dev->flags)) ||
+	       (s.failed == 1 && s.failed_num == sh->pd_idx)))
+		handle_completed_write_requests(conf, sh, disks, &return_bi);
 
 	/* Now we might consider reading some blocks, either to check/generate
 	 * parity, or to satisfy requests
 	 * or to load a block that is being partially written.
 	 */
-	if (to_read || non_overwrite || (syncing && (uptodate < disks)) || expanding) {
-		for (i=disks; i--;) {
-			dev = &sh->dev[i];
-			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
-			    (dev->toread ||
-			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
-			     syncing ||
-			     expanding ||
-			     (failed && (sh->dev[failed_num].toread ||
-					 (sh->dev[failed_num].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num].flags))))
-				    )
-				) {
-				/* we would like to get this block, possibly
-				 * by computing it, but we might not be able to
-				 */
-				if (uptodate == disks-1) {
-					PRINTK("Computing block %d\n", i);
-					compute_block(sh, i);
-					uptodate++;
-				} else if (test_bit(R5_Insync, &dev->flags)) {
-					set_bit(R5_LOCKED, &dev->flags);
-					set_bit(R5_Wantread, &dev->flags);
-					locked++;
-					PRINTK("Reading block %d (sync=%d)\n", 
-						i, syncing);
-				}
-			}
-		}
-		set_bit(STRIPE_HANDLE, &sh->state);
+	if (s.to_read || s.non_overwrite ||
+	    (s.syncing && (s.uptodate + s.compute < disks)) || s.expanding ||
+	    test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending))
+		handle_issuing_new_read_requests5(sh, &s, disks);
+
+	/* Now we check to see if any write operations have recently
+	 * completed
+	 */
+
+	/* leave prexor set until postxor is done, allows us to distinguish
+	 * a rmw from a rcw during biodrain
+	 */
+	if (test_bit(STRIPE_OP_PREXOR, &sh->ops.complete) &&
+		test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
+
+		clear_bit(STRIPE_OP_PREXOR, &sh->ops.complete);
+		clear_bit(STRIPE_OP_PREXOR, &sh->ops.ack);
+		clear_bit(STRIPE_OP_PREXOR, &sh->ops.pending);
+
+		for (i = disks; i--; )
+			clear_bit(R5_Wantprexor, &sh->dev[i].flags);
 	}
 
-	/* now to consider writing and what else, if anything should be read */
-	if (to_write) {
-		int rmw=0, rcw=0;
-		for (i=disks ; i--;) {
-			/* would I have to read this buffer for read_modify_write */
+	/* if only POSTXOR is set then this is an 'expand' postxor */
+	if (test_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete) &&
+		test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete)) {
+
+		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.complete);
+		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.ack);
+		clear_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending);
+
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+
+		/* All the 'written' buffers and the parity block are ready to
+		 * be written back to disk
+		 */
+		BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+		for (i = disks; i--; ) {
 			dev = &sh->dev[i];
-			if ((dev->towrite || i == sh->pd_idx) &&
-			    (!test_bit(R5_LOCKED, &dev->flags) 
-				    ) &&
-			    !test_bit(R5_UPTODATE, &dev->flags)) {
-				if (test_bit(R5_Insync, &dev->flags)
-/*				    && !(!mddev->insync && i == sh->pd_idx) */
-					)
-					rmw++;
-				else rmw += 2*disks;  /* cannot read it */
-			}
-			/* Would I have to read this buffer for reconstruct_write */
-			if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
-			    (!test_bit(R5_LOCKED, &dev->flags) 
-				    ) &&
-			    !test_bit(R5_UPTODATE, &dev->flags)) {
-				if (test_bit(R5_Insync, &dev->flags)) rcw++;
-				else rcw += 2*disks;
+			if (test_bit(R5_LOCKED, &dev->flags) &&
+				(i == sh->pd_idx || dev->written)) {
+				pr_debug("Writing block %d\n", i);
+				set_bit(R5_Wantwrite, &dev->flags);
+				if (!test_and_set_bit(
+				    STRIPE_OP_IO, &sh->ops.pending))
+					sh->ops.count++;
+				if (!test_bit(R5_Insync, &dev->flags) ||
+				    (i == sh->pd_idx && s.failed == 0))
+					set_bit(STRIPE_INSYNC, &sh->state);
 			}
 		}
-		PRINTK("for sector %llu, rmw=%d rcw=%d\n", 
-			(unsigned long long)sh->sector, rmw, rcw);
-		set_bit(STRIPE_HANDLE, &sh->state);
-		if (rmw < rcw && rmw > 0)
-			/* prefer read-modify-write, but need to get some data */
-			for (i=disks; i--;) {
-				dev = &sh->dev[i];
-				if ((dev->towrite || i == sh->pd_idx) &&
-				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
-				    test_bit(R5_Insync, &dev->flags)) {
-					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
-					{
-						PRINTK("Read_old block %d for r-m-w\n", i);
-						set_bit(R5_LOCKED, &dev->flags);
-						set_bit(R5_Wantread, &dev->flags);
-						locked++;
-					} else {
-						set_bit(STRIPE_DELAYED, &sh->state);
-						set_bit(STRIPE_HANDLE, &sh->state);
-					}
-				}
-			}
-		if (rcw <= rmw && rcw > 0)
-			/* want reconstruct write, but need to get some data */
-			for (i=disks; i--;) {
-				dev = &sh->dev[i];
-				if (!test_bit(R5_OVERWRITE, &dev->flags) && i != sh->pd_idx &&
-				    !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
-				    test_bit(R5_Insync, &dev->flags)) {
-					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
-					{
-						PRINTK("Read_old block %d for Reconstruct\n", i);
-						set_bit(R5_LOCKED, &dev->flags);
-						set_bit(R5_Wantread, &dev->flags);
-						locked++;
-					} else {
-						set_bit(STRIPE_DELAYED, &sh->state);
-						set_bit(STRIPE_HANDLE, &sh->state);
-					}
-				}
-			}
-		/* now if nothing is locked, and if we have enough data, we can start a write request */
-		if (locked == 0 && (rcw == 0 ||rmw == 0) &&
-		    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
-			PRINTK("Computing parity...\n");
-			compute_parity5(sh, rcw==0 ? RECONSTRUCT_WRITE : READ_MODIFY_WRITE);
-			/* now every locked buffer is ready to be written */
-			for (i=disks; i--;)
-				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
-					PRINTK("Writing block %d\n", i);
-					locked++;
-					set_bit(R5_Wantwrite, &sh->dev[i].flags);
-					if (!test_bit(R5_Insync, &sh->dev[i].flags)
-					    || (i==sh->pd_idx && failed == 0))
-						set_bit(STRIPE_INSYNC, &sh->state);
-				}
-			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
-				atomic_dec(&conf->preread_active_stripes);
-				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
-					md_wakeup_thread(conf->mddev->thread);
-			}
+		if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+			atomic_dec(&conf->preread_active_stripes);
+			if (atomic_read(&conf->preread_active_stripes) <
+				IO_THRESHOLD)
+				md_wakeup_thread(conf->mddev->thread);
 		}
 	}
 
-	/* maybe we need to check and possibly fix the parity for this stripe
-	 * Any reads will already have been scheduled, so we just see if enough data
-	 * is available
+	/* Now to consider new write requests and what else, if anything
+	 * should be read.  We do not handle new writes when:
+	 * 1/ A 'write' operation (copy+xor) is already in flight.
+	 * 2/ A 'check' operation is in flight, as it may clobber the parity
+	 *    block.
 	 */
-	if (syncing && locked == 0 &&
-	    !test_bit(STRIPE_INSYNC, &sh->state)) {
-		set_bit(STRIPE_HANDLE, &sh->state);
-		if (failed == 0) {
-			BUG_ON(uptodate != disks);
-			compute_parity5(sh, CHECK_PARITY);
-			uptodate--;
-			if (page_is_zero(sh->dev[sh->pd_idx].page)) {
-				/* parity is correct (on disc, not in buffer any more) */
-				set_bit(STRIPE_INSYNC, &sh->state);
-			} else {
-				conf->mddev->resync_mismatches += STRIPE_SECTORS;
-				if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
-					/* don't try to repair!! */
-					set_bit(STRIPE_INSYNC, &sh->state);
-				else {
-					compute_block(sh, sh->pd_idx);
-					uptodate++;
-				}
-			}
-		}
-		if (!test_bit(STRIPE_INSYNC, &sh->state)) {
-			/* either failed parity check, or recovery is happening */
-			if (failed==0)
-				failed_num = sh->pd_idx;
-			dev = &sh->dev[failed_num];
-			BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
-			BUG_ON(uptodate != disks);
+	if (s.to_write && !test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending) &&
+			  !test_bit(STRIPE_OP_CHECK, &sh->ops.pending))
+		handle_issuing_new_write_requests5(conf, sh, &s, disks);
 
-			set_bit(R5_LOCKED, &dev->flags);
-			set_bit(R5_Wantwrite, &dev->flags);
-			clear_bit(STRIPE_DEGRADED, &sh->state);
-			locked++;
-			set_bit(STRIPE_INSYNC, &sh->state);
-		}
-	}
-	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
+	/* maybe we need to check and possibly fix the parity for this stripe
+	 * Any reads will already have been scheduled, so we just see if enough
+	 * data is available.  The parity check is held off while parity
+	 * dependent operations are in flight.
+	 */
+	if ((s.syncing && s.locked == 0 &&
+	     !test_bit(STRIPE_OP_COMPUTE_BLK, &sh->ops.pending) &&
+	     !test_bit(STRIPE_INSYNC, &sh->state)) ||
+	      test_bit(STRIPE_OP_CHECK, &sh->ops.pending) ||
+	      test_bit(STRIPE_OP_MOD_REPAIR_PD, &sh->ops.pending))
+		handle_parity_checks5(conf, sh, &s, disks);
+
+	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
 		clear_bit(STRIPE_SYNCING, &sh->state);
 	}
@@ -1729,186 +2807,102 @@ static void handle_stripe5(struct stripe_head *sh)
 	/* If the failed drive is just a ReadError, then we might need to progress
 	 * the repair/check process
 	 */
-	if (failed == 1 && ! conf->mddev->ro &&
-	    test_bit(R5_ReadError, &sh->dev[failed_num].flags)
-	    && !test_bit(R5_LOCKED, &sh->dev[failed_num].flags)
-	    && test_bit(R5_UPTODATE, &sh->dev[failed_num].flags)
+	if (s.failed == 1 && !conf->mddev->ro &&
+	    test_bit(R5_ReadError, &sh->dev[s.failed_num].flags)
+	    && !test_bit(R5_LOCKED, &sh->dev[s.failed_num].flags)
+	    && test_bit(R5_UPTODATE, &sh->dev[s.failed_num].flags)
 		) {
-		dev = &sh->dev[failed_num];
+		dev = &sh->dev[s.failed_num];
 		if (!test_bit(R5_ReWrite, &dev->flags)) {
 			set_bit(R5_Wantwrite, &dev->flags);
+			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+				sh->ops.count++;
 			set_bit(R5_ReWrite, &dev->flags);
 			set_bit(R5_LOCKED, &dev->flags);
-			locked++;
+			s.locked++;
 		} else {
 			/* let's read it back */
 			set_bit(R5_Wantread, &dev->flags);
+			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+				sh->ops.count++;
 			set_bit(R5_LOCKED, &dev->flags);
-			locked++;
+			s.locked++;
 		}
 	}
 
-	if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
-		/* Need to write out all blocks after computing parity */
-		sh->disks = conf->raid_disks;
-		sh->pd_idx = stripe_to_pdidx(sh->sector, conf, conf->raid_disks);
-		compute_parity5(sh, RECONSTRUCT_WRITE);
-		for (i= conf->raid_disks; i--;) {
-			set_bit(R5_LOCKED, &sh->dev[i].flags);
-			locked++;
+	/* Finish postxor operations initiated by the expansion
+	 * process
+	 */
+	if (test_bit(STRIPE_OP_POSTXOR, &sh->ops.complete) &&
+		!test_bit(STRIPE_OP_BIODRAIN, &sh->ops.pending)) {
+
+		clear_bit(STRIPE_EXPANDING, &sh->state);
+
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.pending);
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.ack);
+		clear_bit(STRIPE_OP_POSTXOR, &sh->ops.complete);
+
+		for (i = conf->raid_disks; i--; ) {
 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
+			if (!test_and_set_bit(STRIPE_OP_IO, &sh->ops.pending))
+				sh->ops.count++;
 		}
-		clear_bit(STRIPE_EXPANDING, &sh->state);
-	} else if (expanded) {
+	}
+
+	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
+		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
+		/* Need to write out all blocks after computing parity */
+		sh->disks = conf->raid_disks;
+		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
+			conf->raid_disks);
+		s.locked += handle_write_operations5(sh, 0, 1);
+	} else if (s.expanded &&
+		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
 		atomic_dec(&conf->reshape_stripes);
 		wake_up(&conf->wait_for_overlap);
 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
 	}
 
-	if (expanding && locked == 0) {
-		/* We have read all the blocks in this stripe and now we need to
-		 * copy some of them into a target stripe for expand.
-		 */
-		clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
-		for (i=0; i< sh->disks; i++)
-			if (i != sh->pd_idx) {
-				int dd_idx, pd_idx, j;
-				struct stripe_head *sh2;
-
-				sector_t bn = compute_blocknr(sh, i);
-				sector_t s = raid5_compute_sector(bn, conf->raid_disks,
-								  conf->raid_disks-1,
-								  &dd_idx, &pd_idx, conf);
-				sh2 = get_active_stripe(conf, s, conf->raid_disks, pd_idx, 1);
-				if (sh2 == NULL)
-					/* so far only the early blocks of this stripe
-					 * have been requested.  When later blocks
-					 * get requested, we will try again
-					 */
-					continue;
-				if(!test_bit(STRIPE_EXPANDING, &sh2->state) ||
-				   test_bit(R5_Expanded, &sh2->dev[dd_idx].flags)) {
-					/* must have already done this block */
-					release_stripe(sh2);
-					continue;
-				}
-				memcpy(page_address(sh2->dev[dd_idx].page),
-				       page_address(sh->dev[i].page),
-				       STRIPE_SIZE);
-				set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
-				set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
-				for (j=0; j<conf->raid_disks; j++)
-					if (j != sh2->pd_idx &&
-					    !test_bit(R5_Expanded, &sh2->dev[j].flags))
-						break;
-				if (j == conf->raid_disks) {
-					set_bit(STRIPE_EXPAND_READY, &sh2->state);
-					set_bit(STRIPE_HANDLE, &sh2->state);
-				}
-				release_stripe(sh2);
-			}
-	}
+	if (s.expanding && s.locked == 0)
+		handle_stripe_expansion(conf, sh, NULL);
+
+	if (sh->ops.count)
+		pending = get_stripe_work(sh);
 
 	spin_unlock(&sh->lock);
 
-	while ((bi=return_bi)) {
-		int bytes = bi->bi_size;
+	if (pending)
+		raid5_run_ops(sh, pending);
 
-		return_bi = bi->bi_next;
-		bi->bi_next = NULL;
-		bi->bi_size = 0;
-		bi->bi_end_io(bi, bytes,
-			      test_bit(BIO_UPTODATE, &bi->bi_flags)
-			        ? 0 : -EIO);
-	}
-	for (i=disks; i-- ;) {
-		int rw;
-		struct bio *bi;
-		mdk_rdev_t *rdev;
-		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
-			rw = WRITE;
-		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
-			rw = READ;
-		else
-			continue;
- 
-		bi = &sh->dev[i].req;
- 
-		bi->bi_rw = rw;
-		if (rw == WRITE)
-			bi->bi_end_io = raid5_end_write_request;
-		else
-			bi->bi_end_io = raid5_end_read_request;
- 
-		rcu_read_lock();
-		rdev = rcu_dereference(conf->disks[i].rdev);
-		if (rdev && test_bit(Faulty, &rdev->flags))
-			rdev = NULL;
-		if (rdev)
-			atomic_inc(&rdev->nr_pending);
-		rcu_read_unlock();
- 
-		if (rdev) {
-			if (syncing || expanding || expanded)
-				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
+	return_io(return_bi);
 
-			bi->bi_bdev = rdev->bdev;
-			PRINTK("for %llu schedule op %ld on disc %d\n",
-				(unsigned long long)sh->sector, bi->bi_rw, i);
-			atomic_inc(&sh->count);
-			bi->bi_sector = sh->sector + rdev->data_offset;
-			bi->bi_flags = 1 << BIO_UPTODATE;
-			bi->bi_vcnt = 1;	
-			bi->bi_max_vecs = 1;
-			bi->bi_idx = 0;
-			bi->bi_io_vec = &sh->dev[i].vec;
-			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
-			bi->bi_io_vec[0].bv_offset = 0;
-			bi->bi_size = STRIPE_SIZE;
-			bi->bi_next = NULL;
-			if (rw == WRITE &&
-			    test_bit(R5_ReWrite, &sh->dev[i].flags))
-				atomic_add(STRIPE_SECTORS, &rdev->corrected_errors);
-			generic_make_request(bi);
-		} else {
-			if (rw == WRITE)
-				set_bit(STRIPE_DEGRADED, &sh->state);
-			PRINTK("skip op %ld on disc %d for sector %llu\n",
-				bi->bi_rw, i, (unsigned long long)sh->sector);
-			clear_bit(R5_LOCKED, &sh->dev[i].flags);
-			set_bit(STRIPE_HANDLE, &sh->state);
-		}
-	}
 }
 
 static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 {
 	raid6_conf_t *conf = sh->raid_conf;
 	int disks = sh->disks;
-	struct bio *return_bi= NULL;
-	struct bio *bi;
-	int i;
-	int syncing, expanding, expanded;
-	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
-	int non_overwrite = 0;
-	int failed_num[2] = {0, 0};
+	struct bio *return_bi = NULL;
+	int i, pd_idx = sh->pd_idx;
+	struct stripe_head_state s;
+	struct r6_state r6s;
 	struct r5dev *dev, *pdev, *qdev;
-	int pd_idx = sh->pd_idx;
-	int qd_idx = raid6_next_disk(pd_idx, disks);
-	int p_failed, q_failed;
 
-	PRINTK("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d, qd_idx=%d\n",
-	       (unsigned long long)sh->sector, sh->state, atomic_read(&sh->count),
-	       pd_idx, qd_idx);
+	r6s.qd_idx = raid6_next_disk(pd_idx, disks);
+	pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
+		"pd_idx=%d, qd_idx=%d\n",
+	       (unsigned long long)sh->sector, sh->state,
+	       atomic_read(&sh->count), pd_idx, r6s.qd_idx);
+	memset(&s, 0, sizeof(s));
 
 	spin_lock(&sh->lock);
 	clear_bit(STRIPE_HANDLE, &sh->state);
 	clear_bit(STRIPE_DELAYED, &sh->state);
 
-	syncing = test_bit(STRIPE_SYNCING, &sh->state);
-	expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
-	expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
+	s.syncing = test_bit(STRIPE_SYNCING, &sh->state);
+	s.expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
+	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
 	/* Now to look around and see what can be done */
 
 	rcu_read_lock();
@@ -1917,12 +2911,12 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		dev = &sh->dev[i];
 		clear_bit(R5_Insync, &dev->flags);
 
-		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
+		pr_debug("check %d: state 0x%lx read %p write %p written %p\n",
 			i, dev->flags, dev->toread, dev->towrite, dev->written);
 		/* maybe we can reply to a read */
 		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
 			struct bio *rbi, *rbi2;
-			PRINTK("Return read for disc %d\n", i);
+			pr_debug("Return read for disc %d\n", i);
 			spin_lock_irq(&conf->device_lock);
 			rbi = dev->toread;
 			dev->toread = NULL;
@@ -1943,17 +2937,19 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		}
 
 		/* now count some things */
-		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
-		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
+		if (test_bit(R5_LOCKED, &dev->flags)) s.locked++;
+		if (test_bit(R5_UPTODATE, &dev->flags)) s.uptodate++;
 
 
-		if (dev->toread) to_read++;
+		if (dev->toread)
+			s.to_read++;
 		if (dev->towrite) {
-			to_write++;
+			s.to_write++;
 			if (!test_bit(R5_OVERWRITE, &dev->flags))
-				non_overwrite++;
+				s.non_overwrite++;
 		}
-		if (dev->written) written++;
+		if (dev->written)
+			s.written++;
 		rdev = rcu_dereference(conf->disks[i].rdev);
 		if (!rdev || !test_bit(In_sync, &rdev->flags)) {
 			/* The ReadError flag will just be confusing now */
@@ -1962,96 +2958,27 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		}
 		if (!rdev || !test_bit(In_sync, &rdev->flags)
 		    || test_bit(R5_ReadError, &dev->flags)) {
-			if ( failed < 2 )
-				failed_num[failed] = i;
-			failed++;
+			if (s.failed < 2)
+				r6s.failed_num[s.failed] = i;
+			s.failed++;
 		} else
 			set_bit(R5_Insync, &dev->flags);
 	}
 	rcu_read_unlock();
-	PRINTK("locked=%d uptodate=%d to_read=%d"
+	pr_debug("locked=%d uptodate=%d to_read=%d"
 	       " to_write=%d failed=%d failed_num=%d,%d\n",
-	       locked, uptodate, to_read, to_write, failed,
-	       failed_num[0], failed_num[1]);
-	/* check if the array has lost >2 devices and, if so, some requests might
-	 * need to be failed
+	       s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
+	       r6s.failed_num[0], r6s.failed_num[1]);
+	/* check if the array has lost >2 devices and, if so, some requests
+	 * might need to be failed
 	 */
-	if (failed > 2 && to_read+to_write+written) {
-		for (i=disks; i--; ) {
-			int bitmap_end = 0;
-
-			if (test_bit(R5_ReadError, &sh->dev[i].flags)) {
-				mdk_rdev_t *rdev;
-				rcu_read_lock();
-				rdev = rcu_dereference(conf->disks[i].rdev);
-				if (rdev && test_bit(In_sync, &rdev->flags))
-					/* multiple read failures in one stripe */
-					md_error(conf->mddev, rdev);
-				rcu_read_unlock();
-			}
-
-			spin_lock_irq(&conf->device_lock);
-			/* fail all writes first */
-			bi = sh->dev[i].towrite;
-			sh->dev[i].towrite = NULL;
-			if (bi) { to_write--; bitmap_end = 1; }
-
-			if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-				wake_up(&conf->wait_for_overlap);
-
-			while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-					md_write_end(conf->mddev);
-					bi->bi_next = return_bi;
-					return_bi = bi;
-				}
-				bi = nextbi;
-			}
-			/* and fail all 'written' */
-			bi = sh->dev[i].written;
-			sh->dev[i].written = NULL;
-			if (bi) bitmap_end = 1;
-			while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-					md_write_end(conf->mddev);
-					bi->bi_next = return_bi;
-					return_bi = bi;
-				}
-				bi = bi2;
-			}
-
-			/* fail any reads if this device is non-operational */
-			if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
-			    test_bit(R5_ReadError, &sh->dev[i].flags)) {
-				bi = sh->dev[i].toread;
-				sh->dev[i].toread = NULL;
-				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-					wake_up(&conf->wait_for_overlap);
-				if (bi) to_read--;
-				while (bi && bi->bi_sector < 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 (--bi->bi_phys_segments == 0) {
-						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);
-		}
-	}
-	if (failed > 2 && syncing) {
+	if (s.failed > 2 && s.to_read+s.to_write+s.written)
+		handle_requests_to_failed_array(conf, sh, &s, disks,
+						&return_bi);
+	if (s.failed > 2 && s.syncing) {
 		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
 		clear_bit(STRIPE_SYNCING, &sh->state);
-		syncing = 0;
+		s.syncing = 0;
 	}
 
 	/*
@@ -2059,279 +2986,41 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 	 * are safe, or on a failed drive
 	 */
 	pdev = &sh->dev[pd_idx];
-	p_failed = (failed >= 1 && failed_num[0] == pd_idx)
-		|| (failed >= 2 && failed_num[1] == pd_idx);
-	qdev = &sh->dev[qd_idx];
-	q_failed = (failed >= 1 && failed_num[0] == qd_idx)
-		|| (failed >= 2 && failed_num[1] == qd_idx);
-
-	if ( written &&
-	     ( p_failed || ((test_bit(R5_Insync, &pdev->flags)
+	r6s.p_failed = (s.failed >= 1 && r6s.failed_num[0] == pd_idx)
+		|| (s.failed >= 2 && r6s.failed_num[1] == pd_idx);
+	qdev = &sh->dev[r6s.qd_idx];
+	r6s.q_failed = (s.failed >= 1 && r6s.failed_num[0] == r6s.qd_idx)
+		|| (s.failed >= 2 && r6s.failed_num[1] == r6s.qd_idx);
+
+	if ( s.written &&
+	     ( r6s.p_failed || ((test_bit(R5_Insync, &pdev->flags)
 			     && !test_bit(R5_LOCKED, &pdev->flags)
-			     && test_bit(R5_UPTODATE, &pdev->flags))) ) &&
-	     ( q_failed || ((test_bit(R5_Insync, &qdev->flags)
+			     && test_bit(R5_UPTODATE, &pdev->flags)))) &&
+	     ( r6s.q_failed || ((test_bit(R5_Insync, &qdev->flags)
 			     && !test_bit(R5_LOCKED, &qdev->flags)
-			     && test_bit(R5_UPTODATE, &qdev->flags))) ) ) {
-		/* any written block on an uptodate or failed drive can be
-		 * returned.  Note that if we 'wrote' to a failed drive,
-		 * it will be UPTODATE, but never LOCKED, so we don't need
-		 * to test 'failed' directly.
-		 */
-		for (i=disks; i--; )
-			if (sh->dev[i].written) {
-				dev = &sh->dev[i];
-				if (!test_bit(R5_LOCKED, &dev->flags) &&
-				    test_bit(R5_UPTODATE, &dev->flags) ) {
-					/* We can return any write requests */
-					int bitmap_end = 0;
-					struct bio *wbi, *wbi2;
-					PRINTK("Return write for stripe %llu disc %d\n",
-					       (unsigned long long)sh->sector, 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 (--wbi->bi_phys_segments == 0) {
-							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,
-								!test_bit(STRIPE_DEGRADED, &sh->state), 0);
-				}
-			}
-	}
+			     && test_bit(R5_UPTODATE, &qdev->flags)))))
+		handle_completed_write_requests(conf, sh, disks, &return_bi);
 
 	/* Now we might consider reading some blocks, either to check/generate
 	 * parity, or to satisfy requests
 	 * or to load a block that is being partially written.
 	 */
-	if (to_read || non_overwrite || (to_write && failed) ||
-	    (syncing && (uptodate < disks)) || expanding) {
-		for (i=disks; i--;) {
-			dev = &sh->dev[i];
-			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
-			    (dev->toread ||
-			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
-			     syncing ||
-			     expanding ||
-			     (failed >= 1 && (sh->dev[failed_num[0]].toread || to_write)) ||
-			     (failed >= 2 && (sh->dev[failed_num[1]].toread || to_write))
-				    )
-				) {
-				/* we would like to get this block, possibly
-				 * by computing it, but we might not be able to
-				 */
-				if (uptodate == disks-1) {
-					PRINTK("Computing stripe %llu block %d\n",
-					       (unsigned long long)sh->sector, i);
-					compute_block_1(sh, i, 0);
-					uptodate++;
-				} else if ( uptodate == disks-2 && failed >= 2 ) {
-					/* Computing 2-failure is *very* expensive; only do it if failed >= 2 */
-					int other;
-					for (other=disks; other--;) {
-						if ( other == i )
-							continue;
-						if ( !test_bit(R5_UPTODATE, &sh->dev[other].flags) )
-							break;
-					}
-					BUG_ON(other < 0);
-					PRINTK("Computing stripe %llu blocks %d,%d\n",
-					       (unsigned long long)sh->sector, i, other);
-					compute_block_2(sh, i, other);
-					uptodate += 2;
-				} else if (test_bit(R5_Insync, &dev->flags)) {
-					set_bit(R5_LOCKED, &dev->flags);
-					set_bit(R5_Wantread, &dev->flags);
-					locked++;
-					PRINTK("Reading block %d (sync=%d)\n",
-						i, syncing);
-				}
-			}
-		}
-		set_bit(STRIPE_HANDLE, &sh->state);
-	}
+	if (s.to_read || s.non_overwrite || (s.to_write && s.failed) ||
+	    (s.syncing && (s.uptodate < disks)) || s.expanding)
+		handle_issuing_new_read_requests6(sh, &s, &r6s, disks);
 
 	/* now to consider writing and what else, if anything should be read */
-	if (to_write) {
-		int rcw=0, must_compute=0;
-		for (i=disks ; i--;) {
-			dev = &sh->dev[i];
-			/* Would I have to read this buffer for reconstruct_write */
-			if (!test_bit(R5_OVERWRITE, &dev->flags)
-			    && i != pd_idx && i != qd_idx
-			    && (!test_bit(R5_LOCKED, &dev->flags)
-				    ) &&
-			    !test_bit(R5_UPTODATE, &dev->flags)) {
-				if (test_bit(R5_Insync, &dev->flags)) rcw++;
-				else {
-					PRINTK("raid6: must_compute: disk %d flags=%#lx\n", i, dev->flags);
-					must_compute++;
-				}
-			}
-		}
-		PRINTK("for sector %llu, rcw=%d, must_compute=%d\n",
-		       (unsigned long long)sh->sector, rcw, must_compute);
-		set_bit(STRIPE_HANDLE, &sh->state);
-
-		if (rcw > 0)
-			/* want reconstruct write, but need to get some data */
-			for (i=disks; i--;) {
-				dev = &sh->dev[i];
-				if (!test_bit(R5_OVERWRITE, &dev->flags)
-				    && !(failed == 0 && (i == pd_idx || i == qd_idx))
-				    && !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
-				    test_bit(R5_Insync, &dev->flags)) {
-					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
-					{
-						PRINTK("Read_old stripe %llu block %d for Reconstruct\n",
-						       (unsigned long long)sh->sector, i);
-						set_bit(R5_LOCKED, &dev->flags);
-						set_bit(R5_Wantread, &dev->flags);
-						locked++;
-					} else {
-						PRINTK("Request delayed stripe %llu block %d for Reconstruct\n",
-						       (unsigned long long)sh->sector, i);
-						set_bit(STRIPE_DELAYED, &sh->state);
-						set_bit(STRIPE_HANDLE, &sh->state);
-					}
-				}
-			}
-		/* now if nothing is locked, and if we have enough data, we can start a write request */
-		if (locked == 0 && rcw == 0 &&
-		    !test_bit(STRIPE_BIT_DELAY, &sh->state)) {
-			if ( must_compute > 0 ) {
-				/* We have failed blocks and need to compute them */
-				switch ( failed ) {
-				case 0:	BUG();
-				case 1: compute_block_1(sh, failed_num[0], 0); break;
-				case 2: compute_block_2(sh, failed_num[0], failed_num[1]); break;
-				default: BUG();	/* This request should have been failed? */
-				}
-			}
-
-			PRINTK("Computing parity for stripe %llu\n", (unsigned long long)sh->sector);
-			compute_parity6(sh, RECONSTRUCT_WRITE);
-			/* now every locked buffer is ready to be written */
-			for (i=disks; i--;)
-				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
-					PRINTK("Writing stripe %llu block %d\n",
-					       (unsigned long long)sh->sector, i);
-					locked++;
-					set_bit(R5_Wantwrite, &sh->dev[i].flags);
-				}
-			/* after a RECONSTRUCT_WRITE, the stripe MUST be in-sync */
-			set_bit(STRIPE_INSYNC, &sh->state);
-
-			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
-				atomic_dec(&conf->preread_active_stripes);
-				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
-					md_wakeup_thread(conf->mddev->thread);
-			}
-		}
-	}
+	if (s.to_write)
+		handle_issuing_new_write_requests6(conf, sh, &s, &r6s, disks);
 
 	/* maybe we need to check and possibly fix the parity for this stripe
-	 * Any reads will already have been scheduled, so we just see if enough data
-	 * is available
+	 * Any reads will already have been scheduled, so we just see if enough
+	 * data is available
 	 */
-	if (syncing && locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state)) {
-		int update_p = 0, update_q = 0;
-		struct r5dev *dev;
-
-		set_bit(STRIPE_HANDLE, &sh->state);
-
-		BUG_ON(failed>2);
-		BUG_ON(uptodate < disks);
-		/* Want to check and possibly repair P and Q.
-		 * However there could be one 'failed' device, in which
-		 * case we can only check one of them, possibly using the
-		 * other to generate missing data
-		 */
-
-		/* If !tmp_page, we cannot do the calculations,
-		 * but as we have set STRIPE_HANDLE, we will soon be called
-		 * by stripe_handle with a tmp_page - just wait until then.
-		 */
-		if (tmp_page) {
-			if (failed == q_failed) {
-				/* The only possible failed device holds 'Q', so it makes
-				 * sense to check P (If anything else were failed, we would
-				 * have used P to recreate it).
-				 */
-				compute_block_1(sh, pd_idx, 1);
-				if (!page_is_zero(sh->dev[pd_idx].page)) {
-					compute_block_1(sh,pd_idx,0);
-					update_p = 1;
-				}
-			}
-			if (!q_failed && failed < 2) {
-				/* q is not failed, and we didn't use it to generate
-				 * anything, so it makes sense to check it
-				 */
-				memcpy(page_address(tmp_page),
-				       page_address(sh->dev[qd_idx].page),
-				       STRIPE_SIZE);
-				compute_parity6(sh, UPDATE_PARITY);
-				if (memcmp(page_address(tmp_page),
-					   page_address(sh->dev[qd_idx].page),
-					   STRIPE_SIZE)!= 0) {
-					clear_bit(STRIPE_INSYNC, &sh->state);
-					update_q = 1;
-				}
-			}
-			if (update_p || update_q) {
-				conf->mddev->resync_mismatches += STRIPE_SECTORS;
-				if (test_bit(MD_RECOVERY_CHECK, &conf->mddev->recovery))
-					/* don't try to repair!! */
-					update_p = update_q = 0;
-			}
-
-			/* now write out any block on a failed drive,
-			 * or P or Q if they need it
-			 */
+	if (s.syncing && s.locked == 0 && !test_bit(STRIPE_INSYNC, &sh->state))
+		handle_parity_checks6(conf, sh, &s, &r6s, tmp_page, disks);
 
-			if (failed == 2) {
-				dev = &sh->dev[failed_num[1]];
-				locked++;
-				set_bit(R5_LOCKED, &dev->flags);
-				set_bit(R5_Wantwrite, &dev->flags);
-			}
-			if (failed >= 1) {
-				dev = &sh->dev[failed_num[0]];
-				locked++;
-				set_bit(R5_LOCKED, &dev->flags);
-				set_bit(R5_Wantwrite, &dev->flags);
-			}
-
-			if (update_p) {
-				dev = &sh->dev[pd_idx];
-				locked ++;
-				set_bit(R5_LOCKED, &dev->flags);
-				set_bit(R5_Wantwrite, &dev->flags);
-			}
-			if (update_q) {
-				dev = &sh->dev[qd_idx];
-				locked++;
-				set_bit(R5_LOCKED, &dev->flags);
-				set_bit(R5_Wantwrite, &dev->flags);
-			}
-			clear_bit(STRIPE_DEGRADED, &sh->state);
-
-			set_bit(STRIPE_INSYNC, &sh->state);
-		}
-	}
-
-	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
+	if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
 		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
 		clear_bit(STRIPE_SYNCING, &sh->state);
 	}
@@ -2339,9 +3028,9 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 	/* If the failed drives are just a ReadError, then we might need
 	 * to progress the repair/check process
 	 */
-	if (failed <= 2 && ! conf->mddev->ro)
-		for (i=0; i<failed;i++) {
-			dev = &sh->dev[failed_num[i]];
+	if (s.failed <= 2 && !conf->mddev->ro)
+		for (i = 0; i < s.failed; i++) {
+			dev = &sh->dev[r6s.failed_num[i]];
 			if (test_bit(R5_ReadError, &dev->flags)
 			    && !test_bit(R5_LOCKED, &dev->flags)
 			    && test_bit(R5_UPTODATE, &dev->flags)
@@ -2358,7 +3047,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 			}
 		}
 
-	if (expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
+	if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
 		/* Need to write out all blocks after computing P&Q */
 		sh->disks = conf->raid_disks;
 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
@@ -2366,82 +3055,24 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		compute_parity6(sh, RECONSTRUCT_WRITE);
 		for (i = conf->raid_disks ; i-- ;  ) {
 			set_bit(R5_LOCKED, &sh->dev[i].flags);
-			locked++;
+			s.locked++;
 			set_bit(R5_Wantwrite, &sh->dev[i].flags);
 		}
 		clear_bit(STRIPE_EXPANDING, &sh->state);
-	} else if (expanded) {
+	} else if (s.expanded) {
 		clear_bit(STRIPE_EXPAND_READY, &sh->state);
 		atomic_dec(&conf->reshape_stripes);
 		wake_up(&conf->wait_for_overlap);
 		md_done_sync(conf->mddev, STRIPE_SECTORS, 1);
 	}
 
-	if (expanding && locked == 0) {
-		/* We have read all the blocks in this stripe and now we need to
-		 * copy some of them into a target stripe for expand.
-		 */
-		clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
-		for (i = 0; i < sh->disks ; i++)
-			if (i != pd_idx && i != qd_idx) {
-				int dd_idx2, pd_idx2, j;
-				struct stripe_head *sh2;
-
-				sector_t bn = compute_blocknr(sh, i);
-				sector_t s = raid5_compute_sector(
-					bn, conf->raid_disks,
-					conf->raid_disks - conf->max_degraded,
-					&dd_idx2, &pd_idx2, conf);
-				sh2 = get_active_stripe(conf, s,
-							conf->raid_disks,
-						       pd_idx2, 1);
-				if (sh2 == NULL)
-					/* so for only the early blocks of
-					 * this stripe have been requests.
-					 * When later blocks get requests, we
-					 * will try again
-					 */
-					continue;
-				if (!test_bit(STRIPE_EXPANDING, &sh2->state) ||
-				    test_bit(R5_Expanded,
-					     &sh2->dev[dd_idx2].flags)) {
-					/* must have already done this block */
-					release_stripe(sh2);
-					continue;
-				}
-				memcpy(page_address(sh2->dev[dd_idx2].page),
-				       page_address(sh->dev[i].page),
-				       STRIPE_SIZE);
-				set_bit(R5_Expanded, &sh2->dev[dd_idx2].flags);
-				set_bit(R5_UPTODATE, &sh2->dev[dd_idx2].flags);
-				for (j = 0 ; j < conf->raid_disks ; j++)
-					if (j != sh2->pd_idx &&
-					    j != raid6_next_disk(sh2->pd_idx,
-							   sh2->disks) &&
-					    !test_bit(R5_Expanded,
-						      &sh2->dev[j].flags))
-						break;
-				if (j == conf->raid_disks) {
-					set_bit(STRIPE_EXPAND_READY,
-						&sh2->state);
-					set_bit(STRIPE_HANDLE, &sh2->state);
-				}
-				release_stripe(sh2);
-			}
-	}
+	if (s.expanding && s.locked == 0)
+		handle_stripe_expansion(conf, sh, &r6s);
 
 	spin_unlock(&sh->lock);
 
-	while ((bi=return_bi)) {
-		int bytes = bi->bi_size;
+	return_io(return_bi);
 
-		return_bi = bi->bi_next;
-		bi->bi_next = NULL;
-		bi->bi_size = 0;
-		bi->bi_end_io(bi, bytes,
-			      test_bit(BIO_UPTODATE, &bi->bi_flags)
-			        ? 0 : -EIO);
-	}
 	for (i=disks; i-- ;) {
 		int rw;
 		struct bio *bi;
@@ -2470,11 +3101,11 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		rcu_read_unlock();
 
 		if (rdev) {
-			if (syncing || expanding || expanded)
+			if (s.syncing || s.expanding || s.expanded)
 				md_sync_acct(rdev->bdev, STRIPE_SECTORS);
 
 			bi->bi_bdev = rdev->bdev;
-			PRINTK("for %llu schedule op %ld on disc %d\n",
+			pr_debug("for %llu schedule op %ld on disc %d\n",
 				(unsigned long long)sh->sector, bi->bi_rw, i);
 			atomic_inc(&sh->count);
 			bi->bi_sector = sh->sector + rdev->data_offset;
@@ -2494,7 +3125,7 @@ static void handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 		} else {
 			if (rw == WRITE)
 				set_bit(STRIPE_DEGRADED, &sh->state);
-			PRINTK("skip op %ld on disc %d for sector %llu\n",
+			pr_debug("skip op %ld on disc %d for sector %llu\n",
 				bi->bi_rw, i, (unsigned long long)sh->sector);
 			clear_bit(R5_LOCKED, &sh->dev[i].flags);
 			set_bit(STRIPE_HANDLE, &sh->state);
@@ -2738,7 +3369,7 @@ static int raid5_align_endio(struct bio *bi, unsigned int bytes, int error)
 	}
 
 
-	PRINTK("raid5_align_endio : io error...handing IO for a retry\n");
+	pr_debug("raid5_align_endio : io error...handing IO for a retry\n");
 
 	add_bio_to_retry(raid_bi, conf);
 	return 0;
@@ -2776,7 +3407,7 @@ static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
 	mdk_rdev_t *rdev;
 
 	if (!in_chunk_boundary(mddev, raid_bio)) {
-		PRINTK("chunk_aligned_read : non aligned\n");
+		pr_debug("chunk_aligned_read : non aligned\n");
 		return 0;
 	}
 	/*
@@ -2900,7 +3531,7 @@ static int make_request(request_queue_t *q, struct bio * bi)
 
  		new_sector = raid5_compute_sector(logical_sector, disks, data_disks,
 						  &dd_idx, &pd_idx, conf);
-		PRINTK("raid5: make_request, sector %llu logical %llu\n",
+		pr_debug("raid5: make_request, sector %llu logical %llu\n",
 			(unsigned long long)new_sector, 
 			(unsigned long long)logical_sector);
 
@@ -3273,7 +3904,7 @@ static void raid5d (mddev_t *mddev)
 	raid5_conf_t *conf = mddev_to_conf(mddev);
 	int handled;
 
-	PRINTK("+++ raid5d active\n");
+	pr_debug("+++ raid5d active\n");
 
 	md_check_recovery(mddev);
 
@@ -3308,8 +3939,10 @@ static void raid5d (mddev_t *mddev)
 			handled++;
 		}
 
-		if (list_empty(&conf->handle_list))
+		if (list_empty(&conf->handle_list)) {
+			async_tx_issue_pending_all();
 			break;
+		}
 
 		first = conf->handle_list.next;
 		sh = list_entry(first, struct stripe_head, lru);
@@ -3325,13 +3958,13 @@ static void raid5d (mddev_t *mddev)
 
 		spin_lock_irq(&conf->device_lock);
 	}
-	PRINTK("%d stripes handled\n", handled);
+	pr_debug("%d stripes handled\n", handled);
 
 	spin_unlock_irq(&conf->device_lock);
 
 	unplug_slaves(mddev);
 
-	PRINTK("--- raid5d inactive\n");
+	pr_debug("--- raid5d inactive\n");
 }
 
 static ssize_t
@@ -3507,7 +4140,7 @@ static int run(mddev_t *mddev)
 	atomic_set(&conf->preread_active_stripes, 0);
 	atomic_set(&conf->active_aligned_reads, 0);
 
-	PRINTK("raid5: run(%s) called.\n", mdname(mddev));
+	pr_debug("raid5: run(%s) called.\n", mdname(mddev));
 
 	ITERATE_RDEV(mddev,rdev,tmp) {
 		raid_disk = rdev->raid_disk;
@@ -3690,7 +4323,7 @@ static int stop(mddev_t *mddev)
 	return 0;
 }
 
-#if RAID5_DEBUG
+#ifdef DEBUG
 static void print_sh (struct seq_file *seq, struct stripe_head *sh)
 {
 	int i;
@@ -3737,7 +4370,7 @@ static void status (struct seq_file *seq, mddev_t *mddev)
 			       conf->disks[i].rdev &&
 			       test_bit(In_sync, &conf->disks[i].rdev->flags) ? "U" : "_");
 	seq_printf (seq, "]");
-#if RAID5_DEBUG
+#ifdef DEBUG
 	seq_printf (seq, "\n");
 	printall(seq, conf);
 #endif
diff --git a/drivers/md/xor.c b/drivers/md/xor.c
deleted file mode 100644
index 324897c4be4..00000000000
--- a/drivers/md/xor.c
+++ /dev/null
@@ -1,154 +0,0 @@
-/*
- * xor.c : Multiple Devices driver for Linux
- *
- * Copyright (C) 1996, 1997, 1998, 1999, 2000,
- * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
- *
- * Dispatch optimized RAID-5 checksumming functions.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2, or (at your option)
- * any later version.
- *
- * You should have received a copy of the GNU General Public License
- * (for example /usr/src/linux/COPYING); if not, write to the Free
- * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-
-#define BH_TRACE 0
-#include <linux/module.h>
-#include <linux/raid/md.h>
-#include <linux/raid/xor.h>
-#include <asm/xor.h>
-
-/* The xor routines to use.  */
-static struct xor_block_template *active_template;
-
-void
-xor_block(unsigned int count, unsigned int bytes, void **ptr)
-{
-	unsigned long *p0, *p1, *p2, *p3, *p4;
-
-	p0 = (unsigned long *) ptr[0];
-	p1 = (unsigned long *) ptr[1];
-	if (count == 2) {
-		active_template->do_2(bytes, p0, p1);
-		return;
-	}
-
-	p2 = (unsigned long *) ptr[2];
-	if (count == 3) {
-		active_template->do_3(bytes, p0, p1, p2);
-		return;
-	}
-
-	p3 = (unsigned long *) ptr[3];
-	if (count == 4) {
-		active_template->do_4(bytes, p0, p1, p2, p3);
-		return;
-	}
-
-	p4 = (unsigned long *) ptr[4];
-	active_template->do_5(bytes, p0, p1, p2, p3, p4);
-}
-
-/* Set of all registered templates.  */
-static struct xor_block_template *template_list;
-
-#define BENCH_SIZE (PAGE_SIZE)
-
-static void
-do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
-{
-	int speed;
-	unsigned long now;
-	int i, count, max;
-
-	tmpl->next = template_list;
-	template_list = tmpl;
-
-	/*
-	 * Count the number of XORs done during a whole jiffy, and use
-	 * this to calculate the speed of checksumming.  We use a 2-page
-	 * allocation to have guaranteed color L1-cache layout.
-	 */
-	max = 0;
-	for (i = 0; i < 5; i++) {
-		now = jiffies;
-		count = 0;
-		while (jiffies == now) {
-			mb();
-			tmpl->do_2(BENCH_SIZE, b1, b2);
-			mb();
-			count++;
-			mb();
-		}
-		if (count > max)
-			max = count;
-	}
-
-	speed = max * (HZ * BENCH_SIZE / 1024);
-	tmpl->speed = speed;
-
-	printk("   %-10s: %5d.%03d MB/sec\n", tmpl->name,
-	       speed / 1000, speed % 1000);
-}
-
-static int
-calibrate_xor_block(void)
-{
-	void *b1, *b2;
-	struct xor_block_template *f, *fastest;
-
-	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
-	if (! b1) {
-		printk("raid5: Yikes!  No memory available.\n");
-		return -ENOMEM;
-	}
-	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
-
-	/*
-	 * If this arch/cpu has a short-circuited selection, don't loop through all
-	 * the possible functions, just test the best one
-	 */
-
-	fastest = NULL;
-
-#ifdef XOR_SELECT_TEMPLATE
-		fastest = XOR_SELECT_TEMPLATE(fastest);
-#endif
-
-#define xor_speed(templ)	do_xor_speed((templ), b1, b2)
-
-	if (fastest) {
-		printk(KERN_INFO "raid5: automatically using best checksumming function: %s\n",
-			fastest->name);
-		xor_speed(fastest);
-	} else {
-		printk(KERN_INFO "raid5: measuring checksumming speed\n");
-		XOR_TRY_TEMPLATES;
-		fastest = template_list;
-		for (f = fastest; f; f = f->next)
-			if (f->speed > fastest->speed)
-				fastest = f;
-	}
-
-	printk("raid5: using function: %s (%d.%03d MB/sec)\n",
-	       fastest->name, fastest->speed / 1000, fastest->speed % 1000);
-
-#undef xor_speed
-
-	free_pages((unsigned long)b1, 2);
-
-	active_template = fastest;
-	return 0;
-}
-
-static __exit void xor_exit(void) { }
-
-EXPORT_SYMBOL(xor_block);
-MODULE_LICENSE("GPL");
-
-module_init(calibrate_xor_block);
-module_exit(xor_exit);