[PATCH 004 of 006] raid5: Move read completion copies to a workqueue

[Dan Williams]

This patch moves the data copying portion of satisfying read requests
into the work queue. It adds a 'read' (past tense) pointer to the r5dev
structure to to track reads that have been offloaded to the work queue.
When the copy operation is complete the 'read' pointer is reused as the
return_bi for the bi_end_io() call.

Signed-off-by: Dan Williams <dan.j.willams@xxxxxxxxx>

 drivers/md/raid5.c         |   94 ++++++++++++++++++++++++++++++++-------------
 include/linux/raid/raid5.h |    6 +-
 2 files changed, 71 insertions(+), 29 deletions(-)

===================================================================
Index: linux-2.6-raid/drivers/md/raid5.c
===================================================================
--- linux-2.6-raid.orig/drivers/md/raid5.c	2006-06-28 10:35:31.000000000 -0700
+++ linux-2.6-raid/drivers/md/raid5.c	2006-06-28 10:35:40.000000000 -0700
@@ -213,11 +213,11 @@
 	for (i = sh->disks; i--; ) {
 		struct r5dev *dev = &sh->dev[i];
 
-		if (dev->toread || dev->towrite || dev->written ||
+		if (dev->toread || dev->read || dev->towrite || dev->written ||
 		    test_bit(R5_LOCKED, &dev->flags)) {
-			printk("sector=%llx i=%d %p %p %p %d\n",
+			printk("sector=%llx i=%d %p %p %p %p %d\n",
 			       (unsigned long long)sh->sector, i, dev->toread,
-			       dev->towrite, dev->written,
+			       dev->read, dev->towrite, dev->written,
 			       test_bit(R5_LOCKED, &dev->flags));
 			BUG();
 		}
@@ -1490,6 +1490,35 @@
 	ops_state_orig = ops_state = sh->ops.state;
 	spin_unlock(&sh->lock);
 
+	if (test_bit(STRIPE_OP_BIOFILL, &state)) {
+		raid5_conf_t *conf = sh->raid_conf;
+		struct bio *return_bi=NULL;
+		PRINTK("%s: stripe %llu STRIPE_OP_BIOFILL op_state: %lx\n",
+			__FUNCTION__, (unsigned long long)sh->sector,
+			ops_state);
+
+		for (i=disks ; i-- ;) {
+			struct r5dev *dev = &sh->dev[i];
+			struct bio *rbi, *rbi2;
+			rbi = dev->read;
+			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;
+				dev->read = return_bi;
+			}
+		}
+
+		work++;
+		set_bit(STRIPE_OP_BIOFILL_Done, &ops_state);
+	}
+
 	if (test_bit(STRIPE_OP_COMPUTE, &state)) {
 		for (i=disks ; i-- ;) {
 			struct r5dev *dev = &sh->dev[i];
@@ -1725,6 +1754,7 @@
 	int i;
 	int syncing, expanding, expanded;
 	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
+	int fill_complete=0, to_fill=0;
 	int non_overwrite = 0;
 	int failed_num=0;
 	struct r5dev *dev;
@@ -1740,45 +1770,49 @@
 	syncing = test_bit(STRIPE_SYNCING, &sh->state);
 	expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state);
 	expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
-	/* Now to look around and see what can be done */
+	if (test_bit(STRIPE_OP_BIOFILL, &sh->state) &&
+		test_bit(STRIPE_OP_BIOFILL_Done, &sh->ops.state)) {
+			clear_bit(STRIPE_OP_BIOFILL, &sh->state);
+			clear_bit(STRIPE_OP_BIOFILL_Done, &sh->ops.state);
+			fill_complete++;
+	}
 
+	/* Now to look around and see what can be done */
 	rcu_read_lock();
 	for (i=disks; i--; ) {
 		mdk_rdev_t *rdev;
 		dev = &sh->dev[i];
 		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);
+		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 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;
+		if (dev->read && fill_complete) {
+			return_bi = dev->read;
+			dev->read = NULL;
+		}
+
+		/* maybe we can start a biofill operation */
+		if (dev->toread) {
+			if (test_bit(R5_UPTODATE, &dev->flags)) {
+				if (!test_bit(STRIPE_OP_BIOFILL, &sh->state)) {
+					BUG_ON(dev->read);
+					spin_lock_irq(&conf->device_lock);
+					dev->read = 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);
+					to_fill++;
 				}
-				spin_unlock_irq(&conf->device_lock);
-				rbi = rbi2;
-			}
+			} else
+				to_read++;
 		}
 
 		/* now count some things */
 		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
 		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
 
-		
-		if (dev->toread) to_read++;
 		if (dev->towrite) {
 			to_write++;
 			if (!test_bit(R5_OVERWRITE, &dev->flags))
@@ -1799,6 +1833,12 @@
 			set_bit(R5_Insync, &dev->flags);
 	}
 	rcu_read_unlock();
+
+	if (to_fill) {
+		set_bit(STRIPE_OP_BIOFILL, &sh->state);
+		sh->ops.pending++;
+	}
+
 	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);
Index: linux-2.6-raid/include/linux/raid/raid5.h
===================================================================
--- linux-2.6-raid.orig/include/linux/raid/raid5.h	2006-06-28 10:35:31.000000000 -0700
+++ linux-2.6-raid/include/linux/raid/raid5.h	2006-06-28 10:35:40.000000000 -0700
@@ -160,7 +160,7 @@
 		struct bio	req;
 		struct bio_vec	vec;
 		struct page	*page;
-		struct bio	*toread, *towrite, *written;
+		struct bio	*toread, *read, *towrite, *written;
 		sector_t	sector;			/* sector of this page */
 		unsigned long	flags;
 	} dev[1]; /* allocated with extra space depending of RAID geometry */
@@ -240,6 +240,7 @@
 #define	STRIPE_OP_COMPUTE_End		16
 #define	STRIPE_OP_COMPUTE_Done		17
 #define	STRIPE_OP_COMPUTE_Recover	18
+#define	STRIPE_OP_BIOFILL_Done		19
 
 /*
  * Bit mask for status bits not to be cleared by the work queue thread
@@ -249,7 +250,8 @@
 						1 << STRIPE_OP_CHECK_Done |\
 						1 << STRIPE_OP_CHECK_IsZero |\
 						1 << STRIPE_OP_COMPUTE_Done |\
-						1 << STRIPE_OP_COMPUTE_Recover)
+						1 << STRIPE_OP_COMPUTE_Recover |\
+						1 << STRIPE_OP_BIOFILL_Done)
 /*
  * Plugging:
  *
-
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