2 files changed, 115 insertions, 36 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index d9521aa69461..42439a4c1c51 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2077,36 +2077,101 @@ handle_requests_to_failed_array(raid5_conf_t *conf, struct stripe_head *sh,
 
 }
 
+/* __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;
-        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 && (sh->dev[s->failed_num].toread ||
-                        (sh->dev[s->failed_num].towrite &&
-                        !test_bit(R5_OVERWRITE, &sh->dev[s->failed_num].flags))
-                      )))) {
-                        /* 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 block %d\n", i);
-                                compute_block(sh, i);
-                                s->uptodate++;
-                        } 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);
-                        }
-                }
+
+        /* 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);
 }
@@ -2223,7 +2288,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                 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_UPTODATE, &dev->flags) ||
+                      test_bit(R5_Wantcompute, &dev->flags))) {
                         if (test_bit(R5_Insync, &dev->flags))
                                 rmw++;
                         else
@@ -2232,9 +2298,9 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                 /* 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++;
+                    !(test_bit(R5_UPTODATE, &dev->flags) ||
+                    test_bit(R5_Wantcompute, &dev->flags))) {
+                        if (test_bit(R5_Insync, &dev->flags)) rcw++;
                         else
                                 rcw += 2*disks;
                 }
@@ -2248,7 +2314,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                         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_UPTODATE, &dev->flags) ||
+                            test_bit(R5_Wantcompute, &dev->flags)) &&
                             test_bit(R5_Insync, &dev->flags)) {
                                 if (
                                   test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
@@ -2270,7 +2337,8 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
                         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_UPTODATE, &dev->flags) ||
+                            test_bit(R5_Wantcompute, &dev->flags)) &&
                             test_bit(R5_Insync, &dev->flags)) {
                                 if (
                                   test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
@@ -2288,8 +2356,17 @@ static void handle_issuing_new_write_requests5(raid5_conf_t *conf,
         /* now if nothing is locked, and if we have enough data,
          * we can start a write request
          */
-        if (s->locked == 0 && (rcw == 0 || rmw == 0) &&
-            !test_bit(STRIPE_BIT_DELAY, &sh->state))
+        /* 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);
 }
 
@@ -2650,6 +2727,7 @@ static void handle_stripe5(struct stripe_head *sh)
                 /* 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 (dev->toread)
                         s.to_read++;
@@ -2706,7 +2784,8 @@ static void handle_stripe5(struct stripe_head *sh)
          * or to load a block that is being partially written.
          */
         if (s.to_read || s.non_overwrite ||
-                (s.syncing && (s.uptodate < disks)) || s.expanding)
+            (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
diff --git a/include/linux/raid/raid5.h b/include/linux/raid/raid5.h
index 6fb9d94e6f2e..2293015de1d5 100644
--- a/include/linux/raid/raid5.h
+++ b/include/linux/raid/raid5.h
@@ -200,7 +200,7 @@ struct stripe_head {
 struct stripe_head_state {
         int syncing, expanding, expanded;
         int locked, uptodate, to_read, to_write, failed, written;
-        int non_overwrite;
+        int compute, req_compute, non_overwrite;
         int failed_num;
 };