Merge branch 'md-raid6-accel' into ioat3.2

Conflicts:
	include/linux/dmaengine.h

1 files changed, 910 insertions, 576 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index bb37fb1b2d82..0a5cf2171214 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -47,7 +47,9 @@
 #include <linux/kthread.h>
 #include <linux/raid/pq.h>
 #include <linux/async_tx.h>
+#include <linux/async.h>
 #include <linux/seq_file.h>
+#include <linux/cpu.h>
 #include "md.h"
 #include "raid5.h"
 #include "bitmap.h"
@@ -499,11 +501,14 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
         struct page *bio_page;
         int i;
         int page_offset;
+        struct async_submit_ctl submit;
 
         if (bio->bi_sector >= sector)
                 page_offset = (signed)(bio->bi_sector - sector) * 512;
         else
                 page_offset = (signed)(sector - bio->bi_sector) * -512;
+
+        init_async_submit(&submit, 0, tx, NULL, NULL, NULL);
         bio_for_each_segment(bvl, bio, i) {
                 int len = bio_iovec_idx(bio, i)->bv_len;
                 int clen;
@@ -525,15 +530,14 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
                         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,
-                                        tx, NULL, NULL);
+                                                  b_offset, clen, &submit);
                         else
                                 tx = async_memcpy(bio_page, page, b_offset,
-                                        page_offset, clen,
-                                        ASYNC_TX_DEP_ACK,
-                                        tx, NULL, NULL);
+                                                  page_offset, clen, &submit);
                 }
+                /* chain the operations */
+                submit.depend_tx = tx;
+
                 if (clen < len) /* hit end of page */
                         break;
                 page_offset +=  len;
@@ -592,6 +596,7 @@ static void ops_run_biofill(struct stripe_head *sh)
 {
         struct dma_async_tx_descriptor *tx = NULL;
         raid5_conf_t *conf = sh->raid_conf;
+        struct async_submit_ctl submit;
         int i;
 
         pr_debug("%s: stripe %llu\n", __func__,
@@ -615,22 +620,34 @@ static void ops_run_biofill(struct stripe_head *sh)
         }
 
         atomic_inc(&sh->count);
-        async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
-                ops_complete_biofill, sh);
+        init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_biofill, sh, NULL);
+        async_trigger_callback(&submit);
 }
 
-static void ops_complete_compute5(void *stripe_head_ref)
+static void mark_target_uptodate(struct stripe_head *sh, int target)
 {
-        struct stripe_head *sh = stripe_head_ref;
-        int target = sh->ops.target;
-        struct r5dev *tgt = &sh->dev[target];
+        struct r5dev *tgt;
 
-        pr_debug("%s: stripe %llu\n", __func__,
-                (unsigned long long)sh->sector);
+        if (target < 0)
+                return;
 
+        tgt = &sh->dev[target];
         set_bit(R5_UPTODATE, &tgt->flags);
         BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
         clear_bit(R5_Wantcompute, &tgt->flags);
+}
+
+static void ops_complete_compute(void *stripe_head_ref)
+{
+        struct stripe_head *sh = stripe_head_ref;
+
+        pr_debug("%s: stripe %llu\n", __func__,
+                (unsigned long long)sh->sector);
+
+        /* mark the computed target(s) as uptodate */
+        mark_target_uptodate(sh, sh->ops.target);
+        mark_target_uptodate(sh, sh->ops.target2);
+
         clear_bit(STRIPE_COMPUTE_RUN, &sh->state);
         if (sh->check_state == check_state_compute_run)
                 sh->check_state = check_state_compute_result;
@@ -638,16 +655,24 @@ static void ops_complete_compute5(void *stripe_head_ref)
         release_stripe(sh);
 }
 
-static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
+/* return a pointer to the address conversion region of the scribble buffer */
+static addr_conv_t *to_addr_conv(struct stripe_head *sh,
+                                 struct raid5_percpu *percpu)
+{
+        return percpu->scribble + sizeof(struct page *) * (sh->disks + 2);
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute5(struct stripe_head *sh, struct raid5_percpu *percpu)
 {
-        /* kernel stack size limits the total number of disks */
         int disks = sh->disks;
-        struct page *xor_srcs[disks];
+        struct page **xor_srcs = percpu->scribble;
         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;
+        struct async_submit_ctl submit;
         int i;
 
         pr_debug("%s: stripe %llu block: %d\n",
@@ -660,17 +685,207 @@ static struct dma_async_tx_descriptor *ops_run_compute5(struct stripe_head *sh)
 
         atomic_inc(&sh->count);
 
+        init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL,
+                          ops_complete_compute, sh, to_addr_conv(sh, percpu));
         if (unlikely(count == 1))
-                tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE,
-                        0, NULL, ops_complete_compute5, sh);
+                tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
         else
-                tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
-                        ASYNC_TX_XOR_ZERO_DST, NULL,
-                        ops_complete_compute5, sh);
+                tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);
 
         return tx;
 }
 
+/* set_syndrome_sources - populate source buffers for gen_syndrome
+ * @srcs - (struct page *) array of size sh->disks
+ * @sh - stripe_head to parse
+ *
+ * Populates srcs in proper layout order for the stripe and returns the
+ * 'count' of sources to be used in a call to async_gen_syndrome.  The P
+ * destination buffer is recorded in srcs[count] and the Q destination
+ * is recorded in srcs[count+1]].
+ */
+static int set_syndrome_sources(struct page **srcs, struct stripe_head *sh)
+{
+        int disks = sh->disks;
+        int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
+        int d0_idx = raid6_d0(sh);
+        int count;
+        int i;
+
+        for (i = 0; i < disks; i++)
+                srcs[i] = (void *)raid6_empty_zero_page;
+
+        count = 0;
+        i = d0_idx;
+        do {
+                int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
+
+                srcs[slot] = sh->dev[i].page;
+                i = raid6_next_disk(i, disks);
+        } while (i != d0_idx);
+        BUG_ON(count != syndrome_disks);
+
+        return count;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute6_1(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+        int disks = sh->disks;
+        struct page **blocks = percpu->scribble;
+        int target;
+        int qd_idx = sh->qd_idx;
+        struct dma_async_tx_descriptor *tx;
+        struct async_submit_ctl submit;
+        struct r5dev *tgt;
+        struct page *dest;
+        int i;
+        int count;
+
+        if (sh->ops.target < 0)
+                target = sh->ops.target2;
+        else if (sh->ops.target2 < 0)
+                target = sh->ops.target;
+        else
+                /* we should only have one valid target */
+                BUG();
+        BUG_ON(target < 0);
+        pr_debug("%s: stripe %llu block: %d\n",
+                __func__, (unsigned long long)sh->sector, target);
+
+        tgt = &sh->dev[target];
+        BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+        dest = tgt->page;
+
+        atomic_inc(&sh->count);
+
+        if (target == qd_idx) {
+                count = set_syndrome_sources(blocks, sh);
+                blocks[count] = NULL; /* regenerating p is not necessary */
+                BUG_ON(blocks[count+1] != dest); /* q should already be set */
+                init_async_submit(&submit, 0, NULL, ops_complete_compute, sh,
+                                  to_addr_conv(sh, percpu));
+                tx = async_gen_syndrome(blocks, 0, count+2, STRIPE_SIZE, &submit);
+        } else {
+                /* Compute any data- or p-drive using XOR */
+                count = 0;
+                for (i = disks; i-- ; ) {
+                        if (i == target || i == qd_idx)
+                                continue;
+                        blocks[count++] = sh->dev[i].page;
+                }
+
+                init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL,
+                                  ops_complete_compute, sh,
+                                  to_addr_conv(sh, percpu));
+                tx = async_xor(dest, blocks, 0, count, STRIPE_SIZE, &submit);
+        }
+
+        return tx;
+}
+
+static struct dma_async_tx_descriptor *
+ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
+{
+        int i, count, disks = sh->disks;
+        int syndrome_disks = sh->ddf_layout ? disks : disks-2;
+        int d0_idx = raid6_d0(sh);
+        int faila = -1, failb = -1;
+        int target = sh->ops.target;
+        int target2 = sh->ops.target2;
+        struct r5dev *tgt = &sh->dev[target];
+        struct r5dev *tgt2 = &sh->dev[target2];
+        struct dma_async_tx_descriptor *tx;
+        struct page **blocks = percpu->scribble;
+        struct async_submit_ctl submit;
+
+        pr_debug("%s: stripe %llu block1: %d block2: %d\n",
+                 __func__, (unsigned long long)sh->sector, target, target2);
+        BUG_ON(target < 0 || target2 < 0);
+        BUG_ON(!test_bit(R5_Wantcompute, &tgt->flags));
+        BUG_ON(!test_bit(R5_Wantcompute, &tgt2->flags));
+
+        /* we need to open-code set_syndrome_sources to handle to the
+         * slot number conversion for 'faila' and 'failb'
+         */
+        for (i = 0; i < disks ; i++)
+                blocks[i] = (void *)raid6_empty_zero_page;
+        count = 0;
+        i = d0_idx;
+        do {
+                int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
+
+                blocks[slot] = sh->dev[i].page;
+
+                if (i == target)
+                        faila = slot;
+                if (i == target2)
+                        failb = slot;
+                i = raid6_next_disk(i, disks);
+        } while (i != d0_idx);
+        BUG_ON(count != syndrome_disks);
+
+        BUG_ON(faila == failb);
+        if (failb < faila)
+                swap(faila, failb);
+        pr_debug("%s: stripe: %llu faila: %d failb: %d\n",
+                 __func__, (unsigned long long)sh->sector, faila, failb);
+
+        atomic_inc(&sh->count);
+
+        if (failb == syndrome_disks+1) {
+                /* Q disk is one of the missing disks */
+                if (faila == syndrome_disks) {
+                        /* Missing P+Q, just recompute */
+                        init_async_submit(&submit, 0, NULL, ops_complete_compute,
+                                          sh, to_addr_conv(sh, percpu));
+                        return async_gen_syndrome(blocks, 0, count+2,
+                                                  STRIPE_SIZE, &submit);
+                } else {
+                        struct page *dest;
+                        int data_target;
+                        int qd_idx = sh->qd_idx;
+
+                        /* Missing D+Q: recompute D from P, then recompute Q */
+                        if (target == qd_idx)
+                                data_target = target2;
+                        else
+                                data_target = target;
+
+                        count = 0;
+                        for (i = disks; i-- ; ) {
+                                if (i == data_target || i == qd_idx)
+                                        continue;
+                                blocks[count++] = sh->dev[i].page;
+                        }
+                        dest = sh->dev[data_target].page;
+                        init_async_submit(&submit, ASYNC_TX_XOR_ZERO_DST, NULL,
+                                          NULL, NULL, to_addr_conv(sh, percpu));
+                        tx = async_xor(dest, blocks, 0, count, STRIPE_SIZE,
+                                       &submit);
+
+                        count = set_syndrome_sources(blocks, sh);
+                        init_async_submit(&submit, 0, tx, ops_complete_compute,
+                                          sh, to_addr_conv(sh, percpu));
+                        return async_gen_syndrome(blocks, 0, count+2,
+                                                  STRIPE_SIZE, &submit);
+                }
+        }
+
+        init_async_submit(&submit, 0, NULL, ops_complete_compute, sh,
+                          to_addr_conv(sh, percpu));
+        if (failb == syndrome_disks) {
+                /* We're missing D+P. */
+                return async_raid6_datap_recov(syndrome_disks+2, STRIPE_SIZE,
+                                               faila, blocks, &submit);
+        } else {
+                /* We're missing D+D. */
+                return async_raid6_2data_recov(syndrome_disks+2, STRIPE_SIZE,
+                                               faila, failb, blocks, &submit);
+        }
+}
+
+
 static void ops_complete_prexor(void *stripe_head_ref)
 {
         struct stripe_head *sh = stripe_head_ref;
@@ -680,12 +895,13 @@ static void ops_complete_prexor(void *stripe_head_ref)
 }
 
 static struct dma_async_tx_descriptor *
-ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+ops_run_prexor(struct stripe_head *sh, struct raid5_percpu *percpu,
+               struct dma_async_tx_descriptor *tx)
 {
-        /* kernel stack size limits the total number of disks */
         int disks = sh->disks;
-        struct page *xor_srcs[disks];
+        struct page **xor_srcs = percpu->scribble;
         int count = 0, pd_idx = sh->pd_idx, i;
+        struct async_submit_ctl submit;
 
         /* existing parity data subtracted */
         struct page *xor_dest = xor_srcs[count++] = sh->dev[pd_idx].page;
@@ -700,9 +916,9 @@ ops_run_prexor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
                         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);
+        init_async_submit(&submit, ASYNC_TX_XOR_DROP_DST, tx,
+                          ops_complete_prexor, sh, to_addr_conv(sh, percpu));
+        tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);
 
         return tx;
 }
@@ -742,17 +958,21 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
         return tx;
 }
 
-static void ops_complete_postxor(void *stripe_head_ref)
+static void ops_complete_reconstruct(void *stripe_head_ref)
 {
         struct stripe_head *sh = stripe_head_ref;
-        int disks = sh->disks, i, pd_idx = sh->pd_idx;
+        int disks = sh->disks;
+        int pd_idx = sh->pd_idx;
+        int qd_idx = sh->qd_idx;
+        int i;
 
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
 
         for (i = disks; i--; ) {
                 struct r5dev *dev = &sh->dev[i];
-                if (dev->written || i == pd_idx)
+
+                if (dev->written || i == pd_idx || i == qd_idx)
                         set_bit(R5_UPTODATE, &dev->flags);
         }
 
@@ -770,12 +990,12 @@ static void ops_complete_postxor(void *stripe_head_ref)
 }
 
 static void
-ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
+ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
+                     struct dma_async_tx_descriptor *tx)
 {
-        /* kernel stack size limits the total number of disks */
         int disks = sh->disks;
-        struct page *xor_srcs[disks];
-
+        struct page **xor_srcs = percpu->scribble;
+        struct async_submit_ctl submit;
         int count = 0, pd_idx = sh->pd_idx, i;
         struct page *xor_dest;
         int prexor = 0;
@@ -809,18 +1029,36 @@ ops_run_postxor(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
          * 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 |
+        flags = 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, ops_complete_postxor, sh);
-        } else
-                tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
-                        flags, tx, ops_complete_postxor, sh);
+        init_async_submit(&submit, flags, tx, ops_complete_reconstruct, sh,
+                          to_addr_conv(sh, percpu));
+        if (unlikely(count == 1))
+                tx = async_memcpy(xor_dest, xor_srcs[0], 0, 0, STRIPE_SIZE, &submit);
+        else
+                tx = async_xor(xor_dest, xor_srcs, 0, count, STRIPE_SIZE, &submit);
+}
+
+static void
+ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
+                     struct dma_async_tx_descriptor *tx)
+{
+        struct async_submit_ctl submit;
+        struct page **blocks = percpu->scribble;
+        int count;
+
+        pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
+
+        count = set_syndrome_sources(blocks, sh);
+
+        atomic_inc(&sh->count);
+
+        init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_reconstruct,
+                          sh, to_addr_conv(sh, percpu));
+        async_gen_syndrome(blocks, 0, count+2, STRIPE_SIZE,  &submit);
 }
 
 static void ops_complete_check(void *stripe_head_ref)
@@ -835,63 +1073,115 @@ static void ops_complete_check(void *stripe_head_ref)
         release_stripe(sh);
 }
 
-static void ops_run_check(struct stripe_head *sh)
+static void ops_run_check_p(struct stripe_head *sh, struct raid5_percpu *percpu)
 {
-        /* kernel stack size limits the total number of disks */
         int disks = sh->disks;
-        struct page *xor_srcs[disks];
+        int pd_idx = sh->pd_idx;
+        int qd_idx = sh->qd_idx;
+        struct page *xor_dest;
+        struct page **xor_srcs = percpu->scribble;
         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;
+        struct async_submit_ctl submit;
+        int count;
+        int i;
 
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
 
+        count = 0;
+        xor_dest = sh->dev[pd_idx].page;
+        xor_srcs[count++] = xor_dest;
         for (i = disks; i--; ) {
-                struct r5dev *dev = &sh->dev[i];
-                if (i != pd_idx)
-                        xor_srcs[count++] = dev->page;
+                if (i == pd_idx || i == qd_idx)
+                        continue;
+                xor_srcs[count++] = sh->dev[i].page;
         }
 
-        tx = async_xor_zero_sum(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
-                &sh->ops.zero_sum_result, 0, NULL, NULL, NULL);
+        init_async_submit(&submit, 0, NULL, NULL, NULL,
+                          to_addr_conv(sh, percpu));
+        tx = async_xor_val(xor_dest, xor_srcs, 0, count, STRIPE_SIZE,
+                           &sh->ops.zero_sum_result, &submit);
+
+        atomic_inc(&sh->count);
+        init_async_submit(&submit, ASYNC_TX_ACK, tx, ops_complete_check, sh, NULL);
+        tx = async_trigger_callback(&submit);
+}
+
+static void ops_run_check_pq(struct stripe_head *sh, struct raid5_percpu *percpu, int checkp)
+{
+        struct page **srcs = percpu->scribble;
+        struct async_submit_ctl submit;
+        int count;
+
+        pr_debug("%s: stripe %llu checkp: %d\n", __func__,
+                (unsigned long long)sh->sector, checkp);
+
+        count = set_syndrome_sources(srcs, sh);
+        if (!checkp)
+                srcs[count] = NULL;
 
         atomic_inc(&sh->count);
-        tx = async_trigger_callback(ASYNC_TX_DEP_ACK | ASYNC_TX_ACK, tx,
-                ops_complete_check, sh);
+        init_async_submit(&submit, ASYNC_TX_ACK, NULL, ops_complete_check,
+                          sh, to_addr_conv(sh, percpu));
+        async_syndrome_val(srcs, 0, count+2, STRIPE_SIZE,
+                           &sh->ops.zero_sum_result, percpu->spare_page, &submit);
 }
 
-static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
+static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
 {
         int overlap_clear = 0, i, disks = sh->disks;
         struct dma_async_tx_descriptor *tx = NULL;
+        raid5_conf_t *conf = sh->raid_conf;
+        int level = conf->level;
+        struct raid5_percpu *percpu;
+        unsigned long cpu;
 
+        cpu = get_cpu();
+        percpu = per_cpu_ptr(conf->percpu, cpu);
         if (test_bit(STRIPE_OP_BIOFILL, &ops_request)) {
                 ops_run_biofill(sh);
                 overlap_clear++;
         }
 
         if (test_bit(STRIPE_OP_COMPUTE_BLK, &ops_request)) {
-                tx = ops_run_compute5(sh);
-                /* terminate the chain if postxor is not set to be run */
-                if (tx && !test_bit(STRIPE_OP_POSTXOR, &ops_request))
+                if (level < 6)
+                        tx = ops_run_compute5(sh, percpu);
+                else {
+                        if (sh->ops.target2 < 0 || sh->ops.target < 0)
+                                tx = ops_run_compute6_1(sh, percpu);
+                        else
+                                tx = ops_run_compute6_2(sh, percpu);
+                }
+                /* terminate the chain if reconstruct is not set to be run */
+                if (tx && !test_bit(STRIPE_OP_RECONSTRUCT, &ops_request))
                         async_tx_ack(tx);
         }
 
         if (test_bit(STRIPE_OP_PREXOR, &ops_request))
-                tx = ops_run_prexor(sh, tx);
+                tx = ops_run_prexor(sh, percpu, tx);
 
         if (test_bit(STRIPE_OP_BIODRAIN, &ops_request)) {
                 tx = ops_run_biodrain(sh, tx);
                 overlap_clear++;
         }
 
-        if (test_bit(STRIPE_OP_POSTXOR, &ops_request))
-                ops_run_postxor(sh, tx);
+        if (test_bit(STRIPE_OP_RECONSTRUCT, &ops_request)) {
+                if (level < 6)
+                        ops_run_reconstruct5(sh, percpu, tx);
+                else
+                        ops_run_reconstruct6(sh, percpu, tx);
+        }
 
-        if (test_bit(STRIPE_OP_CHECK, &ops_request))
-                ops_run_check(sh);
+        if (test_bit(STRIPE_OP_CHECK, &ops_request)) {
+                if (sh->check_state == check_state_run)
+                        ops_run_check_p(sh, percpu);
+                else if (sh->check_state == check_state_run_q)
+                        ops_run_check_pq(sh, percpu, 0);
+                else if (sh->check_state == check_state_run_pq)
+                        ops_run_check_pq(sh, percpu, 1);
+                else
+                        BUG();
+        }
 
         if (overlap_clear)
                 for (i = disks; i--; ) {
@@ -899,6 +1189,7 @@ static void raid5_run_ops(struct stripe_head *sh, unsigned long ops_request)
                         if (test_and_clear_bit(R5_Overlap, &dev->flags))
                                 wake_up(&sh->raid_conf->wait_for_overlap);
                 }
+        put_cpu();
 }
 
 static int grow_one_stripe(raid5_conf_t *conf)
@@ -948,6 +1239,28 @@ static int grow_stripes(raid5_conf_t *conf, int num)
         return 0;
 }
 
+/**
+ * scribble_len - return the required size of the scribble region
+ * @num - total number of disks in the array
+ *
+ * The size must be enough to contain:
+ * 1/ a struct page pointer for each device in the array +2
+ * 2/ room to convert each entry in (1) to its corresponding dma
+ *    (dma_map_page()) or page (page_address()) address.
+ *
+ * Note: the +2 is for the destination buffers of the ddf/raid6 case where we
+ * calculate over all devices (not just the data blocks), using zeros in place
+ * of the P and Q blocks.
+ */
+static size_t scribble_len(int num)
+{
+        size_t len;
+
+        len = sizeof(struct page *) * (num+2) + sizeof(addr_conv_t) * (num+2);
+
+        return len;
+}
+
 static int resize_stripes(raid5_conf_t *conf, int newsize)
 {
         /* Make all the stripes able to hold 'newsize' devices.
@@ -976,6 +1289,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
         struct stripe_head *osh, *nsh;
         LIST_HEAD(newstripes);
         struct disk_info *ndisks;
+        unsigned long cpu;
         int err;
         struct kmem_cache *sc;
         int i;
@@ -1041,7 +1355,7 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
         /* Step 3.
          * At this point, we are holding all the stripes so the array
          * is completely stalled, so now is a good time to resize
-         * conf->disks.
+         * conf->disks and the scribble region
          */
         ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
         if (ndisks) {
@@ -1052,10 +1366,30 @@ static int resize_stripes(raid5_conf_t *conf, int newsize)
         } else
                 err = -ENOMEM;
 
+        get_online_cpus();
+        conf->scribble_len = scribble_len(newsize);
+        for_each_present_cpu(cpu) {
+                struct raid5_percpu *percpu;
+                void *scribble;
+
+                percpu = per_cpu_ptr(conf->percpu, cpu);
+                scribble = kmalloc(conf->scribble_len, GFP_NOIO);
+
+                if (scribble) {
+                        kfree(percpu->scribble);
+                        percpu->scribble = scribble;
+                } else {
+                        err = -ENOMEM;
+                        break;
+                }
+        }
+        put_online_cpus();
+
         /* Step 4, return new stripes to service */
         while(!list_empty(&newstripes)) {
                 nsh = list_entry(newstripes.next, struct stripe_head, lru);
                 list_del_init(&nsh->lru);
+
                 for (i=conf->raid_disks; i < newsize; i++)
                         if (nsh->dev[i].page == NULL) {
                                 struct page *p = alloc_page(GFP_NOIO);
@@ -1594,258 +1928,13 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous)
 }
 
 
-
-/*
- * Copy data between a page in the stripe cache, and one or more bion
- * The page could align with the middle of the bio, or there could be
- * several bion, each with several bio_vecs, which cover part of the page
- * Multiple bion are linked together on bi_next.  There may be extras
- * at the end of this list.  We ignore them.
- */
-static void copy_data(int frombio, struct bio *bio,
-                     struct page *page,
-                     sector_t sector)
-{
-        char *pa = page_address(page);
-        struct bio_vec *bvl;
-        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) {
-                        char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
-                        if (frombio)
-                                memcpy(pa+page_offset, ba+b_offset, clen);
-                        else
-                                memcpy(ba+b_offset, pa+page_offset, clen);
-                        __bio_kunmap_atomic(ba, KM_USER0);
-                }
-                if (clen < len) /* hit end of page */
-                        break;
-                page_offset +=  len;
-        }
-}
-
-#define check_xor()     do {                                              \
-                                if (count == MAX_XOR_BLOCKS) {            \
-                                xor_blocks(count, STRIPE_SIZE, dest, ptr);\
-                                count = 0;                                \
-                           }                                              \
-                        } while(0)
-
-static void compute_parity6(struct stripe_head *sh, int method)
-{
-        raid5_conf_t *conf = sh->raid_conf;
-        int i, pd_idx, qd_idx, d0_idx, disks = sh->disks, count;
-        int syndrome_disks = sh->ddf_layout ? disks : (disks - 2);
-        struct bio *chosen;
-        /**** FIX THIS: This could be very bad if disks is close to 256 ****/
-        void *ptrs[syndrome_disks+2];
-
-        pd_idx = sh->pd_idx;
-        qd_idx = sh->qd_idx;
-        d0_idx = raid6_d0(sh);
-
-        pr_debug("compute_parity, stripe %llu, method %d\n",
-                (unsigned long long)sh->sector, method);
-
-        switch(method) {
-        case READ_MODIFY_WRITE:
-                BUG();          /* READ_MODIFY_WRITE N/A for RAID-6 */
-        case RECONSTRUCT_WRITE:
-                for (i= disks; i-- ;)
-                        if ( i != pd_idx && i != qd_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:
-                BUG();          /* Not implemented yet */
-        }
-
-        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);
-                }
-
-        /* Note that unlike RAID-5, the ordering of the disks matters greatly.*/
-
-        for (i = 0; i < disks; i++)
-                ptrs[i] = (void *)raid6_empty_zero_page;
-
-        count = 0;
-        i = d0_idx;
-        do {
-                int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
-
-                ptrs[slot] = page_address(sh->dev[i].page);
-                if (slot < syndrome_disks &&
-                    !test_bit(R5_UPTODATE, &sh->dev[i].flags)) {
-                        printk(KERN_ERR "block %d/%d not uptodate "
-                               "on parity calc\n", i, count);
-                        BUG();
-                }
-
-                i = raid6_next_disk(i, disks);
-        } while (i != d0_idx);
-        BUG_ON(count != syndrome_disks);
-
-        raid6_call.gen_syndrome(syndrome_disks+2, STRIPE_SIZE, ptrs);
-
-        switch(method) {
-        case RECONSTRUCT_WRITE:
-                set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-                set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
-                set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
-                set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
-                break;
-        case UPDATE_PARITY:
-                set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
-                set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
-                break;
-        }
-}
-
-
-/* Compute one missing block */
-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], *dest, *p;
-        int qd_idx = sh->qd_idx;
-
-        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 {
-                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;
-                        p = page_address(sh->dev[i].page);
-                        if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
-                                ptr[count++] = p;
-                        else
-                                printk("compute_block() %d, stripe %llu, %d"
-                                       " not present\n", dd_idx,
-                                       (unsigned long long)sh->sector, i);
-
-                        check_xor();
-                }
-                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);
-        }
-}
-
-/* Compute two missing blocks */
-static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
-{
-        int i, count, disks = sh->disks;
-        int syndrome_disks = sh->ddf_layout ? disks : disks-2;
-        int d0_idx = raid6_d0(sh);
-        int faila = -1, failb = -1;
-        /**** FIX THIS: This could be very bad if disks is close to 256 ****/
-        void *ptrs[syndrome_disks+2];
-
-        for (i = 0; i < disks ; i++)
-                ptrs[i] = (void *)raid6_empty_zero_page;
-        count = 0;
-        i = d0_idx;
-        do {
-                int slot = raid6_idx_to_slot(i, sh, &count, syndrome_disks);
-
-                ptrs[slot] = page_address(sh->dev[i].page);
-
-                if (i == dd_idx1)
-                        faila = slot;
-                if (i == dd_idx2)
-                        failb = slot;
-                i = raid6_next_disk(i, disks);
-        } while (i != d0_idx);
-        BUG_ON(count != syndrome_disks);
-
-        BUG_ON(faila == failb);
-        if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
-
-        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 == syndrome_disks+1) {
-                /* Q disk is one of the missing disks */
-                if (faila == syndrome_disks) {
-                        /* Missing P+Q, just recompute */
-                        compute_parity6(sh, UPDATE_PARITY);
-                        return;
-                } else {
-                        /* We're missing D+Q; recompute D from P */
-                        compute_block_1(sh, ((dd_idx1 == sh->qd_idx) ?
-                                             dd_idx2 : dd_idx1),
-                                        0);
-                        compute_parity6(sh, UPDATE_PARITY); /* Is this necessary? */
-                        return;
-                }
-        }
-
-        /* We're missing D+P or D+D; */
-        if (failb == syndrome_disks) {
-                /* We're missing D+P. */
-                raid6_datap_recov(syndrome_disks+2, STRIPE_SIZE, faila, ptrs);
-        } else {
-                /* We're missing D+D. */
-                raid6_2data_recov(syndrome_disks+2, STRIPE_SIZE, faila, failb,
-                                  ptrs);
-        }
-
-        /* Both the above update both missing blocks */
-        set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
-        set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
-}
-
 static void
-schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
+schedule_reconstruction(struct stripe_head *sh, struct stripe_head_state *s,
                          int rcw, int expand)
 {
         int i, pd_idx = sh->pd_idx, disks = sh->disks;
+        raid5_conf_t *conf = sh->raid_conf;
+        int level = conf->level;
 
         if (rcw) {
                 /* if we are not expanding this is a proper write request, and
@@ -1858,7 +1947,7 @@ schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
                 } else
                         sh->reconstruct_state = reconstruct_state_run;
 
-                set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
+                set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
 
                 for (i = disks; i--; ) {
                         struct r5dev *dev = &sh->dev[i];
@@ -1871,17 +1960,18 @@ schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
                                 s->locked++;
                         }
                 }
-                if (s->locked + 1 == disks)
+                if (s->locked + conf->max_degraded == disks)
                         if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
-                                atomic_inc(&sh->raid_conf->pending_full_writes);
+                                atomic_inc(&conf->pending_full_writes);
         } else {
+                BUG_ON(level == 6);
                 BUG_ON(!(test_bit(R5_UPTODATE, &sh->dev[pd_idx].flags) ||
                         test_bit(R5_Wantcompute, &sh->dev[pd_idx].flags)));
 
                 sh->reconstruct_state = reconstruct_state_prexor_drain_run;
                 set_bit(STRIPE_OP_PREXOR, &s->ops_request);
                 set_bit(STRIPE_OP_BIODRAIN, &s->ops_request);
-                set_bit(STRIPE_OP_POSTXOR, &s->ops_request);
+                set_bit(STRIPE_OP_RECONSTRUCT, &s->ops_request);
 
                 for (i = disks; i--; ) {
                         struct r5dev *dev = &sh->dev[i];
@@ -1899,13 +1989,22 @@ schedule_reconstruction5(struct stripe_head *sh, struct stripe_head_state *s,
                 }
         }
 
-        /* keep the parity disk locked while asynchronous operations
+        /* keep the parity disk(s) 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);
         s->locked++;
 
+        if (level == 6) {
+                int qd_idx = sh->qd_idx;
+                struct r5dev *dev = &sh->dev[qd_idx];
+
+                set_bit(R5_LOCKED, &dev->flags);
+                clear_bit(R5_UPTODATE, &dev->flags);
+                s->locked++;
+        }
+
         pr_debug("%s: stripe %llu locked: %d ops_request: %lx\n",
                 __func__, (unsigned long long)sh->sector,
                 s->locked, s->ops_request);
@@ -1986,13 +2085,6 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
 
 static void end_reshape(raid5_conf_t *conf);
 
-static int page_is_zero(struct page *p)
-{
-        char *a = page_address(p);
-        return ((*(u32*)a) == 0 &&
-                memcmp(a, a+4, STRIPE_SIZE-4)==0);
-}
-
 static void stripe_set_idx(sector_t stripe, raid5_conf_t *conf, int previous,
                             struct stripe_head *sh)
 {
@@ -2133,9 +2225,10 @@ static int fetch_block5(struct stripe_head *sh, struct stripe_head_state *s,
                         set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
                         set_bit(R5_Wantcompute, &dev->flags);
                         sh->ops.target = disk_idx;
+                        sh->ops.target2 = -1;
                         s->req_compute = 1;
                         /* Careful: from this point on 'uptodate' is in the eye
-                         * of raid5_run_ops which services 'compute' operations
+                         * of raid_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.
@@ -2174,61 +2267,104 @@ static void handle_stripe_fill5(struct stripe_head *sh,
         set_bit(STRIPE_HANDLE, &sh->state);
 }
 
-static void handle_stripe_fill6(struct stripe_head *sh,
-                        struct stripe_head_state *s, struct r6_state *r6s,
-                        int disks)
+/* fetch_block6 - checks the given member device to see if its data needs
+ * to be read or computed to satisfy a request.
+ *
+ * Returns 1 when no more member devices need to be checked, otherwise returns
+ * 0 to tell the loop in handle_stripe_fill6 to continue
+ */
+static int fetch_block6(struct stripe_head *sh, struct stripe_head_state *s,
+                         struct r6_state *r6s, int disk_idx, 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
+        struct r5dev *dev = &sh->dev[disk_idx];
+        struct r5dev *fdev[2] = { &sh->dev[r6s->failed_num[0]],
+                                  &sh->dev[r6s->failed_num[1]] };
+
+        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 &&
+              (fdev[0]->toread || s->to_write)) ||
+             (s->failed >= 2 &&
+              (fdev[1]->toread || s->to_write)))) {
+                /* we would like to get this block, possibly by computing it,
+                 * otherwise read it if the backing disk is insync
+                 */
+                BUG_ON(test_bit(R5_Wantcompute, &dev->flags));
+                BUG_ON(test_bit(R5_Wantread, &dev->flags));
+                if ((s->uptodate == disks - 1) &&
+                    (s->failed && (disk_idx == r6s->failed_num[0] ||
+                                   disk_idx == r6s->failed_num[1]))) {
+                        /* have disk failed, and we're requested to fetch it;
+                         * do compute it
                          */
-                        if ((s->uptodate == disks - 1) &&
-                            (s->failed && (i == r6s->failed_num[0] ||
-                                           i == r6s->failed_num[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);
+                        pr_debug("Computing stripe %llu block %d\n",
+                               (unsigned long long)sh->sector, disk_idx);
+                        set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+                        set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+                        set_bit(R5_Wantcompute, &dev->flags);
+                        sh->ops.target = disk_idx;
+                        sh->ops.target2 = -1; /* no 2nd target */
+                        s->req_compute = 1;
+                        s->uptodate++;
+                        return 1;
+                } 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 == disk_idx)
+                                        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,
+                               disk_idx, other);
+                        set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+                        set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+                        set_bit(R5_Wantcompute, &sh->dev[disk_idx].flags);
+                        set_bit(R5_Wantcompute, &sh->dev[other].flags);
+                        sh->ops.target = disk_idx;
+                        sh->ops.target2 = other;
+                        s->uptodate += 2;
+                        s->req_compute = 1;
+                        return 1;
+                } 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",
+                                disk_idx, s->syncing);
                 }
         }
+
+        return 0;
+}
+
+/**
+ * handle_stripe_fill6 - read or compute data to satisfy pending requests.
+ */
+static void handle_stripe_fill6(struct stripe_head *sh,
+                        struct stripe_head_state *s, struct r6_state *r6s,
+                        int disks)
+{
+        int i;
+
+        /* 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_COMPUTE_RUN, &sh->state) && !sh->check_state &&
+            !sh->reconstruct_state)
+                for (i = disks; i--; )
+                        if (fetch_block6(sh, s, r6s, i, disks))
+                                break;
         set_bit(STRIPE_HANDLE, &sh->state);
 }
 
@@ -2362,114 +2498,61 @@ static void handle_stripe_dirtying5(raid5_conf_t *conf,
          */
         /* 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
+         * subsequent call wants to start a write request.  raid_run_ops only
+         * handles the case where compute block and reconstruct 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_COMPUTE_RUN, &sh->state)) &&
             (s->locked == 0 && (rcw == 0 || rmw == 0) &&
             !test_bit(STRIPE_BIT_DELAY, &sh->state)))
-                schedule_reconstruction5(sh, s, rcw == 0, 0);
+                schedule_reconstruction(sh, s, rcw == 0, 0);
 }
 
 static void handle_stripe_dirtying6(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 rcw = 0, pd_idx = sh->pd_idx, i;
         int qd_idx = sh->qd_idx;
+
+        set_bit(STRIPE_HANDLE, &sh->state);
         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++;
+                /* check if we haven't enough data */
+                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) ||
+                      test_bit(R5_Wantcompute, &dev->flags))) {
+                        rcw++;
+                        if (!test_bit(R5_Insync, &dev->flags))
+                                continue; /* it's a failed drive */
+
+                        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);
                         }
                 }
         }
-        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 &&
+        if ((s->req_compute || !test_bit(STRIPE_COMPUTE_RUN, &sh->state)) &&
+            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);
-                        }
-                if (s->locked == disks)
-                        if (!test_and_set_bit(STRIPE_FULL_WRITE, &sh->state))
-                                atomic_inc(&conf->pending_full_writes);
-                /* 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);
-                }
+                schedule_reconstruction(sh, s, 1, 0);
         }
 }
 
@@ -2528,7 +2611,7 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
                  * we are done.  Otherwise update the mismatch count and repair
                  * parity if !MD_RECOVERY_CHECK
                  */
-                if (sh->ops.zero_sum_result == 0)
+                if ((sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) == 0)
                         /* parity is correct (on disc,
                          * not in buffer any more)
                          */
@@ -2545,6 +2628,7 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
                                 set_bit(R5_Wantcompute,
                                         &sh->dev[sh->pd_idx].flags);
                                 sh->ops.target = sh->pd_idx;
+                                sh->ops.target2 = -1;
                                 s->uptodate++;
                         }
                 }
@@ -2561,67 +2645,74 @@ static void handle_parity_checks5(raid5_conf_t *conf, struct stripe_head *sh,
 
 
 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)
+                                  struct stripe_head_state *s,
+                                  struct r6_state *r6s, int disks)
 {
-        int update_p = 0, update_q = 0;
-        struct r5dev *dev;
         int pd_idx = sh->pd_idx;
         int qd_idx = sh->qd_idx;
+        struct r5dev *dev;
 
         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) {
+        switch (sh->check_state) {
+        case check_state_idle:
+                /* start a new check operation if there are < 2 failures */
                 if (s->failed == r6s->q_failed) {
-                        /* The only possible failed device holds 'Q', so it
+                        /* 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;
-                        }
+                        sh->check_state = check_state_run;
                 }
                 if (!r6s->q_failed && s->failed < 2) {
-                        /* q is not failed, and we didn't use it to generate
+                        /* 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 (sh->check_state == check_state_run)
+                                sh->check_state = check_state_run_pq;
+                        else
+                                sh->check_state = check_state_run_q;
                 }
-                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;
+
+                /* discard potentially stale zero_sum_result */
+                sh->ops.zero_sum_result = 0;
+
+                if (sh->check_state == check_state_run) {
+                        /* async_xor_zero_sum destroys the contents of P */
+                        clear_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+                        s->uptodate--;
                 }
+                if (sh->check_state >= check_state_run &&
+                    sh->check_state <= check_state_run_pq) {
+                        /* async_syndrome_zero_sum preserves P and Q, so
+                         * no need to mark them !uptodate here
+                         */
+                        set_bit(STRIPE_OP_CHECK, &s->ops_request);
+                        break;
+                }
+
+                /* we have 2-disk failure */
+                BUG_ON(s->failed != 2);
+                /* fall through */
+        case check_state_compute_result:
+                sh->check_state = check_state_idle;
+
+                /* check that a write has not made the stripe insync */
+                if (test_bit(STRIPE_INSYNC, &sh->state))
+                        break;
 
                 /* now write out any block on a failed drive,
-                 * or P or Q if they need it
+                 * or P or Q if they were recomputed
                  */
-
+                BUG_ON(s->uptodate < disks - 1); /* We don't need Q to recover */
                 if (s->failed == 2) {
                         dev = &sh->dev[r6s->failed_num[1]];
                         s->locked++;
@@ -2634,14 +2725,13 @@ static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
                         set_bit(R5_LOCKED, &dev->flags);
                         set_bit(R5_Wantwrite, &dev->flags);
                 }
-
-                if (update_p) {
+                if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
                         dev = &sh->dev[pd_idx];
                         s->locked++;
                         set_bit(R5_LOCKED, &dev->flags);
                         set_bit(R5_Wantwrite, &dev->flags);
                 }
-                if (update_q) {
+                if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
                         dev = &sh->dev[qd_idx];
                         s->locked++;
                         set_bit(R5_LOCKED, &dev->flags);
@@ -2650,6 +2740,70 @@ static void handle_parity_checks6(raid5_conf_t *conf, struct stripe_head *sh,
                 clear_bit(STRIPE_DEGRADED, &sh->state);
 
                 set_bit(STRIPE_INSYNC, &sh->state);
+                break;
+        case check_state_run:
+        case check_state_run_q:
+        case check_state_run_pq:
+                break; /* we will be called again upon completion */
+        case check_state_check_result:
+                sh->check_state = check_state_idle;
+
+                /* handle a successful check operation, if parity is correct
+                 * we are done.  Otherwise update the mismatch count and repair
+                 * parity if !MD_RECOVERY_CHECK
+                 */
+                if (sh->ops.zero_sum_result == 0) {
+                        /* both parities are correct */
+                        if (!s->failed)
+                                set_bit(STRIPE_INSYNC, &sh->state);
+                        else {
+                                /* in contrast to the raid5 case we can validate
+                                 * parity, but still have a failure to write
+                                 * back
+                                 */
+                                sh->check_state = check_state_compute_result;
+                                /* Returning at this point means that we may go
+                                 * off and bring p and/or q uptodate again so
+                                 * we make sure to check zero_sum_result again
+                                 * to verify if p or q need writeback
+                                 */
+                        }
+                } 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 {
+                                int *target = &sh->ops.target;
+
+                                sh->ops.target = -1;
+                                sh->ops.target2 = -1;
+                                sh->check_state = check_state_compute_run;
+                                set_bit(STRIPE_COMPUTE_RUN, &sh->state);
+                                set_bit(STRIPE_OP_COMPUTE_BLK, &s->ops_request);
+                                if (sh->ops.zero_sum_result & SUM_CHECK_P_RESULT) {
+                                        set_bit(R5_Wantcompute,
+                                                &sh->dev[pd_idx].flags);
+                                        *target = pd_idx;
+                                        target = &sh->ops.target2;
+                                        s->uptodate++;
+                                }
+                                if (sh->ops.zero_sum_result & SUM_CHECK_Q_RESULT) {
+                                        set_bit(R5_Wantcompute,
+                                                &sh->dev[qd_idx].flags);
+                                        *target = qd_idx;
+                                        s->uptodate++;
+                                }
+                        }
+                }
+                break;
+        case check_state_compute_run:
+                break;
+        default:
+                printk(KERN_ERR "%s: unknown check_state: %d sector: %llu\n",
+                       __func__, sh->check_state,
+                       (unsigned long long) sh->sector);
+                BUG();
         }
 }
 
@@ -2667,6 +2821,7 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
                 if (i != sh->pd_idx && i != sh->qd_idx) {
                         int dd_idx, j;
                         struct stripe_head *sh2;
+                        struct async_submit_ctl submit;
 
                         sector_t bn = compute_blocknr(sh, i, 1);
                         sector_t s = raid5_compute_sector(conf, bn, 0,
@@ -2686,9 +2841,10 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
                         }
 
                         /* place all the copies on one channel */
+                        init_async_submit(&submit, 0, tx, NULL, NULL, NULL);
                         tx = async_memcpy(sh2->dev[dd_idx].page,
-                                sh->dev[i].page, 0, 0, STRIPE_SIZE,
-                                ASYNC_TX_DEP_ACK, tx, NULL, NULL);
+                                          sh->dev[i].page, 0, 0, STRIPE_SIZE,
+                                          &submit);
 
                         set_bit(R5_Expanded, &sh2->dev[dd_idx].flags);
                         set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
@@ -2974,7 +3130,7 @@ static bool handle_stripe5(struct stripe_head *sh)
                 /* Need to write out all blocks after computing parity */
                 sh->disks = conf->raid_disks;
                 stripe_set_idx(sh->sector, conf, 0, sh);
-                schedule_reconstruction5(sh, &s, 1, 1);
+                schedule_reconstruction(sh, &s, 1, 1);
         } else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
                 clear_bit(STRIPE_EXPAND_READY, &sh->state);
                 atomic_dec(&conf->reshape_stripes);
@@ -2994,7 +3150,7 @@ static bool handle_stripe5(struct stripe_head *sh)
                 md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
 
         if (s.ops_request)
-                raid5_run_ops(sh, s.ops_request);
+                raid_run_ops(sh, s.ops_request);
 
         ops_run_io(sh, &s);
 
@@ -3003,7 +3159,7 @@ static bool handle_stripe5(struct stripe_head *sh)
         return blocked_rdev == NULL;
 }
 
-static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
+static bool handle_stripe6(struct stripe_head *sh)
 {
         raid5_conf_t *conf = sh->raid_conf;
         int disks = sh->disks;
@@ -3015,9 +3171,10 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         mdk_rdev_t *blocked_rdev = NULL;
 
         pr_debug("handling stripe %llu, state=%#lx cnt=%d, "
-                "pd_idx=%d, qd_idx=%d\n",
+                "pd_idx=%d, qd_idx=%d\n, check:%d, reconstruct:%d\n",
                (unsigned long long)sh->sector, sh->state,
-               atomic_read(&sh->count), pd_idx, qd_idx);
+               atomic_read(&sh->count), pd_idx, qd_idx,
+               sh->check_state, sh->reconstruct_state);
         memset(&s, 0, sizeof(s));
 
         spin_lock(&sh->lock);
@@ -3037,35 +3194,24 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 
                 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;
-                        pr_debug("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 (!raid5_dec_bi_phys_segments(rbi)) {
-                                        rbi->bi_next = return_bi;
-                                        return_bi = rbi;
-                                }
-                                spin_unlock_irq(&conf->device_lock);
-                                rbi = rbi2;
-                        }
-                }
+                /* maybe we can reply to a read
+                 *
+                 * new wantfill requests are only permitted while
+                 * ops_complete_biofill is guaranteed to be inactive
+                 */
+                if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
+                    !test_bit(STRIPE_BIOFILL_RUN, &sh->state))
+                        set_bit(R5_Wantfill, &dev->flags);
 
                 /* 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))
+                        BUG_ON(++s.compute > 2);
 
-
-                if (dev->toread)
+                if (test_bit(R5_Wantfill, &dev->flags)) {
+                        s.to_fill++;
+                } else if (dev->toread)
                         s.to_read++;
                 if (dev->towrite) {
                         s.to_write++;
@@ -3106,6 +3252,11 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                 blocked_rdev = NULL;
         }
 
+        if (s.to_fill && !test_bit(STRIPE_BIOFILL_RUN, &sh->state)) {
+                set_bit(STRIPE_OP_BIOFILL, &s.ops_request);
+                set_bit(STRIPE_BIOFILL_RUN, &sh->state);
+        }
+
         pr_debug("locked=%d uptodate=%d to_read=%d"
                " to_write=%d failed=%d failed_num=%d,%d\n",
                s.locked, s.uptodate, s.to_read, s.to_write, s.failed,
@@ -3146,19 +3297,62 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
          * or to load a block that is being partially written.
          */
         if (s.to_read || s.non_overwrite || (s.to_write && s.failed) ||
-            (s.syncing && (s.uptodate < disks)) || s.expanding)
+            (s.syncing && (s.uptodate + s.compute < disks)) || s.expanding)
                 handle_stripe_fill6(sh, &s, &r6s, disks);
 
-        /* now to consider writing and what else, if anything should be read */
-        if (s.to_write)
+        /* Now we check to see if any write operations have recently
+         * completed
+         */
+        if (sh->reconstruct_state == reconstruct_state_drain_result) {
+                int qd_idx = sh->qd_idx;
+
+                sh->reconstruct_state = reconstruct_state_idle;
+                /* All the 'written' buffers and the parity blocks are ready to
+                 * be written back to disk
+                 */
+                BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[sh->pd_idx].flags));
+                BUG_ON(!test_bit(R5_UPTODATE, &sh->dev[qd_idx].flags));
+                for (i = disks; i--; ) {
+                        dev = &sh->dev[i];
+                        if (test_bit(R5_LOCKED, &dev->flags) &&
+                            (i == sh->pd_idx || i == qd_idx ||
+                             dev->written)) {
+                                pr_debug("Writing block %d\n", i);
+                                BUG_ON(!test_bit(R5_UPTODATE, &dev->flags));
+                                set_bit(R5_Wantwrite, &dev->flags);
+                                if (!test_bit(R5_Insync, &dev->flags) ||
+                                    ((i == sh->pd_idx || i == qd_idx) &&
+                                      s.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);
+                }
+        }
+
+        /* 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+gen_syndrome) is already in flight.
+         * 2/ A 'check' operation is in flight, as it may clobber the parity
+         *    block.
+         */
+        if (s.to_write && !sh->reconstruct_state && !sh->check_state)
                 handle_stripe_dirtying6(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
+         * 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_INSYNC, &sh->state))
-                handle_parity_checks6(conf, sh, &s, &r6s, tmp_page, disks);
+        if (sh->check_state ||
+            (s.syncing && s.locked == 0 &&
+             !test_bit(STRIPE_COMPUTE_RUN, &sh->state) &&
+             !test_bit(STRIPE_INSYNC, &sh->state)))
+                handle_parity_checks6(conf, sh, &s, &r6s, disks);
 
         if (s.syncing && s.locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
                 md_done_sync(conf->mddev, STRIPE_SECTORS,1);
@@ -3179,15 +3373,29 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                                         set_bit(R5_Wantwrite, &dev->flags);
                                         set_bit(R5_ReWrite, &dev->flags);
                                         set_bit(R5_LOCKED, &dev->flags);
+                                        s.locked++;
                                 } else {
                                         /* let's read it back */
                                         set_bit(R5_Wantread, &dev->flags);
                                         set_bit(R5_LOCKED, &dev->flags);
+                                        s.locked++;
                                 }
                         }
                 }
 
-        if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state)) {
+        /* Finish reconstruct operations initiated by the expansion process */
+        if (sh->reconstruct_state == reconstruct_state_result) {
+                sh->reconstruct_state = reconstruct_state_idle;
+                clear_bit(STRIPE_EXPANDING, &sh->state);
+                for (i = conf->raid_disks; i--; ) {
+                        set_bit(R5_Wantwrite, &sh->dev[i].flags);
+                        set_bit(R5_LOCKED, &sh->dev[i].flags);
+                        s.locked++;
+                }
+        }
+
+        if (s.expanded && test_bit(STRIPE_EXPANDING, &sh->state) &&
+            !sh->reconstruct_state) {
                 struct stripe_head *sh2
                         = get_active_stripe(conf, sh->sector, 1, 1, 1);
                 if (sh2 && test_bit(STRIPE_EXPAND_SOURCE, &sh2->state)) {
@@ -3208,14 +3416,8 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                 /* Need to write out all blocks after computing P&Q */
                 sh->disks = conf->raid_disks;
                 stripe_set_idx(sh->sector, conf, 0, sh);
-                compute_parity6(sh, RECONSTRUCT_WRITE);
-                for (i = conf->raid_disks ; i-- ;  ) {
-                        set_bit(R5_LOCKED, &sh->dev[i].flags);
-                        s.locked++;
-                        set_bit(R5_Wantwrite, &sh->dev[i].flags);
-                }
-                clear_bit(STRIPE_EXPANDING, &sh->state);
-        } else if (s.expanded) {
+                schedule_reconstruction(sh, &s, 1, 1);
+        } else if (s.expanded && !sh->reconstruct_state && s.locked == 0) {
                 clear_bit(STRIPE_EXPAND_READY, &sh->state);
                 atomic_dec(&conf->reshape_stripes);
                 wake_up(&conf->wait_for_overlap);
@@ -3233,6 +3435,9 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
         if (unlikely(blocked_rdev))
                 md_wait_for_blocked_rdev(blocked_rdev, conf->mddev);
 
+        if (s.ops_request)
+                raid_run_ops(sh, s.ops_request);
+
         ops_run_io(sh, &s);
 
         return_io(return_bi);
@@ -3241,16 +3446,14 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
 }
 
 /* returns true if the stripe was handled */
-static bool handle_stripe(struct stripe_head *sh, struct page *tmp_page)
+static bool handle_stripe(struct stripe_head *sh)
 {
         if (sh->raid_conf->level == 6)
-                return handle_stripe6(sh, tmp_page);
+                return handle_stripe6(sh);
         else
                 return handle_stripe5(sh);
 }
 
-
-
 static void raid5_activate_delayed(raid5_conf_t *conf)
 {
         if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
@@ -4046,7 +4249,7 @@ static inline sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *ski
         spin_unlock(&sh->lock);
 
         /* wait for any blocked device to be handled */
-        while(unlikely(!handle_stripe(sh, NULL)))
+        while (unlikely(!handle_stripe(sh)))
                 ;
         release_stripe(sh);
 
@@ -4103,7 +4306,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                         return handled;
                 }
 
-                handle_stripe(sh, NULL);
+                handle_stripe(sh);
                 release_stripe(sh);
                 handled++;
         }
@@ -4117,6 +4320,36 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
         return handled;
 }
 
+#ifdef CONFIG_MULTICORE_RAID456
+static void __process_stripe(void *param, async_cookie_t cookie)
+{
+        struct stripe_head *sh = param;
+
+        handle_stripe(sh);
+        release_stripe(sh);
+}
+
+static void process_stripe(struct stripe_head *sh, struct list_head *domain)
+{
+        async_schedule_domain(__process_stripe, sh, domain);
+}
+
+static void synchronize_stripe_processing(struct list_head *domain)
+{
+        async_synchronize_full_domain(domain);
+}
+#else
+static void process_stripe(struct stripe_head *sh, struct list_head *domain)
+{
+        handle_stripe(sh);
+        release_stripe(sh);
+        cond_resched();
+}
+
+static void synchronize_stripe_processing(struct list_head *domain)
+{
+}
+#endif
 
 
 /*
@@ -4131,6 +4364,7 @@ static void raid5d(mddev_t *mddev)
         struct stripe_head *sh;
         raid5_conf_t *conf = mddev_to_conf(mddev);
         int handled;
+        LIST_HEAD(raid_domain);
 
         pr_debug("+++ raid5d active\n");
 
@@ -4167,8 +4401,7 @@ static void raid5d(mddev_t *mddev)
                 spin_unlock_irq(&conf->device_lock);
                 
                 handled++;
-                handle_stripe(sh, conf->spare_page);
-                release_stripe(sh);
+                process_stripe(sh, &raid_domain);
 
                 spin_lock_irq(&conf->device_lock);
         }
@@ -4176,6 +4409,7 @@ static void raid5d(mddev_t *mddev)
 
         spin_unlock_irq(&conf->device_lock);
 
+        synchronize_stripe_processing(&raid_domain);
         async_tx_issue_pending_all();
         unplug_slaves(mddev);
 
@@ -4308,6 +4542,118 @@ raid5_size(mddev_t *mddev, sector_t sectors, int raid_disks)
         return sectors * (raid_disks - conf->max_degraded);
 }
 
+static void raid5_free_percpu(raid5_conf_t *conf)
+{
+        struct raid5_percpu *percpu;
+        unsigned long cpu;
+
+        if (!conf->percpu)
+                return;
+
+        get_online_cpus();
+        for_each_possible_cpu(cpu) {
+                percpu = per_cpu_ptr(conf->percpu, cpu);
+                safe_put_page(percpu->spare_page);
+                kfree(percpu->scribble);
+        }
+#ifdef CONFIG_HOTPLUG_CPU
+        unregister_cpu_notifier(&conf->cpu_notify);
+#endif
+        put_online_cpus();
+
+        free_percpu(conf->percpu);
+}
+
+static void free_conf(raid5_conf_t *conf)
+{
+        shrink_stripes(conf);
+        raid5_free_percpu(conf);
+        kfree(conf->disks);
+        kfree(conf->stripe_hashtbl);
+        kfree(conf);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int raid456_cpu_notify(struct notifier_block *nfb, unsigned long action,
+                              void *hcpu)
+{
+        raid5_conf_t *conf = container_of(nfb, raid5_conf_t, cpu_notify);
+        long cpu = (long)hcpu;
+        struct raid5_percpu *percpu = per_cpu_ptr(conf->percpu, cpu);
+
+        switch (action) {
+        case CPU_UP_PREPARE:
+        case CPU_UP_PREPARE_FROZEN:
+                if (conf->level == 6 && !percpu->spare_page)
+                        percpu->spare_page = alloc_page(GFP_KERNEL);
+                if (!percpu->scribble)
+                        percpu->scribble = kmalloc(conf->scribble_len, GFP_KERNEL);
+
+                if (!percpu->scribble ||
+                    (conf->level == 6 && !percpu->spare_page)) {
+                        safe_put_page(percpu->spare_page);
+                        kfree(percpu->scribble);
+                        pr_err("%s: failed memory allocation for cpu%ld\n",
+                               __func__, cpu);
+                        return NOTIFY_BAD;
+                }
+                break;
+        case CPU_DEAD:
+        case CPU_DEAD_FROZEN:
+                safe_put_page(percpu->spare_page);
+                kfree(percpu->scribble);
+                percpu->spare_page = NULL;
+                percpu->scribble = NULL;
+                break;
+        default:
+                break;
+        }
+        return NOTIFY_OK;
+}
+#endif
+
+static int raid5_alloc_percpu(raid5_conf_t *conf)
+{
+        unsigned long cpu;
+        struct page *spare_page;
+        struct raid5_percpu *allcpus;
+        void *scribble;
+        int err;
+
+        allcpus = alloc_percpu(struct raid5_percpu);
+        if (!allcpus)
+                return -ENOMEM;
+        conf->percpu = allcpus;
+
+        get_online_cpus();
+        err = 0;
+        for_each_present_cpu(cpu) {
+                if (conf->level == 6) {
+                        spare_page = alloc_page(GFP_KERNEL);
+                        if (!spare_page) {
+                                err = -ENOMEM;
+                                break;
+                        }
+                        per_cpu_ptr(conf->percpu, cpu)->spare_page = spare_page;
+                }
+                scribble = kmalloc(scribble_len(conf->raid_disks), GFP_KERNEL);
+                if (!scribble) {
+                        err = -ENOMEM;
+                        break;
+                }
+                per_cpu_ptr(conf->percpu, cpu)->scribble = scribble;
+        }
+#ifdef CONFIG_HOTPLUG_CPU
+        conf->cpu_notify.notifier_call = raid456_cpu_notify;
+        conf->cpu_notify.priority = 0;
+        if (err == 0)
+                err = register_cpu_notifier(&conf->cpu_notify);
+#endif
+        put_online_cpus();
+
+        return err;
+}
+
 static raid5_conf_t *setup_conf(mddev_t *mddev)
 {
         raid5_conf_t *conf;
@@ -4347,6 +4693,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
                 goto abort;
 
         conf->raid_disks = mddev->raid_disks;
+        conf->scribble_len = scribble_len(conf->raid_disks);
         if (mddev->reshape_position == MaxSector)
                 conf->previous_raid_disks = mddev->raid_disks;
         else
@@ -4362,11 +4709,10 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
         if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
                 goto abort;
 
-        if (mddev->new_level == 6) {
-                conf->spare_page = alloc_page(GFP_KERNEL);
-                if (!conf->spare_page)
-                        goto abort;
-        }
+        conf->level = mddev->new_level;
+        if (raid5_alloc_percpu(conf) != 0)
+                goto abort;
+
         spin_lock_init(&conf->device_lock);
         init_waitqueue_head(&conf->wait_for_stripe);
         init_waitqueue_head(&conf->wait_for_overlap);
@@ -4402,7 +4748,6 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
         }
 
         conf->chunk_size = mddev->new_chunk;
-        conf->level = mddev->new_level;
         if (conf->level == 6)
                 conf->max_degraded = 2;
         else
@@ -4437,11 +4782,7 @@ static raid5_conf_t *setup_conf(mddev_t *mddev)
 
  abort:
         if (conf) {
-                shrink_stripes(conf);
-                safe_put_page(conf->spare_page);
-                kfree(conf->disks);
-                kfree(conf->stripe_hashtbl);
-                kfree(conf);
+                free_conf(conf);
                 return ERR_PTR(-EIO);
         } else
                 return ERR_PTR(-ENOMEM);
@@ -4607,12 +4948,8 @@ abort:
         md_unregister_thread(mddev->thread);
         mddev->thread = NULL;
         if (conf) {
-                shrink_stripes(conf);
                 print_raid5_conf(conf);
-                safe_put_page(conf->spare_page);
-                kfree(conf->disks);
-                kfree(conf->stripe_hashtbl);
-                kfree(conf);
+                free_conf(conf);
         }
         mddev->private = NULL;
         printk(KERN_ALERT "raid5: failed to run raid set %s\n", mdname(mddev));
@@ -4627,13 +4964,10 @@ static int stop(mddev_t *mddev)
 
         md_unregister_thread(mddev->thread);
         mddev->thread = NULL;
-        shrink_stripes(conf);
-        kfree(conf->stripe_hashtbl);
         mddev->queue->backing_dev_info.congested_fn = NULL;
         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
         sysfs_remove_group(&mddev->kobj, &raid5_attrs_group);
-        kfree(conf->disks);
-        kfree(conf);
+        free_conf(conf);
         mddev->private = NULL;
         return 0;
 }