[PATCH 10/16] md: satisfy raid5 read requests via raid5_run_ops

[Dan Williams <dan.j.williams@intel.com>]

Use raid5_run_ops to carry out the memory copies for a raid5 read request.

Changelog:
* cleanup to_read and to_fill accounting
* do not fail reads that have reached the cache

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---

 drivers/md/raid5.c |   61 ++++++++++++++++++++++++++--------------------------
 1 files changed, 30 insertions(+), 31 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f8a4522..6bde174 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1998,7 +1998,7 @@ static void handle_stripe5(struct stripe_head *sh)
 	int i;
 	int syncing, expanding, expanded;
 	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
-	int compute=0, req_compute=0, non_overwrite=0;
+	int to_fill=0, compute=0, req_compute=0, non_overwrite=0;
 	int failed_num=0;
 	struct r5dev *dev;
 	unsigned long pending=0;
@@ -2022,37 +2022,29 @@ static void handle_stripe5(struct stripe_head *sh)
 		dev = &sh->dev[i];
 		clear_bit(R5_Insync, &dev->flags);
 
-		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
-			i, dev->flags, dev->toread, dev->towrite, dev->written);
-		/* maybe we can reply to a read */
-		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
-			struct bio *rbi, *rbi2;
-			PRINTK("Return read for disc %d\n", i);
-			spin_lock_irq(&conf->device_lock);
-			rbi = dev->toread;
-			dev->toread = NULL;
-			if (test_and_clear_bit(R5_Overlap, &dev->flags))
-				wake_up(&conf->wait_for_overlap);
-			spin_unlock_irq(&conf->device_lock);
-			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
-				copy_data(0, rbi, dev->page, dev->sector);
-				rbi2 = r5_next_bio(rbi, dev->sector);
-				spin_lock_irq(&conf->device_lock);
-				if (--rbi->bi_phys_segments == 0) {
-					rbi->bi_next = return_bi;
-					return_bi = rbi;
-				}
-				spin_unlock_irq(&conf->device_lock);
-				rbi = rbi2;
-			}
-		}
+		PRINTK("check %d: state 0x%lx toread %p read %p write %p written %p\n",
+		i, dev->flags, dev->toread, dev->read, dev->towrite, dev->written);
+
+		/* maybe we can request a biofill operation
+		 *
+		 * new wantfill requests are only permitted while
+		 * STRIPE_OP_BIOFILL is clear
+		 */
+		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread &&
+			!test_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
+			set_bit(R5_Wantfill, &dev->flags);
 
 		/* now count some things */
 		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
 		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
+
+		if (test_bit(R5_Wantfill, &dev->flags))
+			to_fill++;
+		else if (dev->toread)
+			to_read++;
+
 		if (test_bit(R5_Wantcompute, &dev->flags)) BUG_ON(++compute > 1);
 
-		if (dev->toread) to_read++;
 		if (dev->towrite) {
 			to_write++;
 			if (!test_bit(R5_OVERWRITE, &dev->flags))
@@ -2073,9 +2065,13 @@ static void handle_stripe5(struct stripe_head *sh)
 			set_bit(R5_Insync, &dev->flags);
 	}
 	rcu_read_unlock();
+
+	if (to_fill && !test_and_set_bit(STRIPE_OP_BIOFILL, &sh->ops.pending))
+		sh->ops.count++;
+
 	PRINTK("locked=%d uptodate=%d to_read=%d"
-		" to_write=%d failed=%d failed_num=%d\n",
-		locked, uptodate, to_read, to_write, failed, failed_num);
+		" to_write=%d to_fill=%d failed=%d failed_num=%d\n",
+		locked, uptodate, to_read, to_write, to_fill, failed, failed_num);
 	/* check if the array has lost two devices and, if so, some requests might
 	 * need to be failed
 	 */
@@ -2127,9 +2123,12 @@ static void handle_stripe5(struct stripe_head *sh)
 				bi = bi2;
 			}
 
-			/* fail any reads if this device is non-operational */
-			if (!test_bit(R5_Insync, &sh->dev[i].flags) ||
-			    test_bit(R5_ReadError, &sh->dev[i].flags)) {
+			/* fail any reads if this device is non-operational and
+			 * the data has not reached the cache yet.
+			 */
+			if (!test_bit(R5_Wantfill, &sh->dev[i].flags) &&
+			    (!test_bit(R5_Insync, &sh->dev[i].flags) ||
+			      test_bit(R5_ReadError, &sh->dev[i].flags))) {
 				bi = sh->dev[i].toread;
 				sh->dev[i].toread = NULL;
 				if (test_and_clear_bit(R5_Overlap, &sh->dev[i].flags))
-
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