releases/2.6.23.6/md-raid5-not-raid6-fix-clearing-of-biofill-operations.patch

From stable-bounces@linux.kernel.org Mon Oct 22 20:45:44 2007
From: Dan Williams <dan.j.williams@intel.com>
Date: Mon, 22 Oct 2007 20:45:11 -0700
Subject: md: raid5: fix clearing of biofill operations
To: torvalds@linux-foundation.org
Cc: joel.bertrand@systella.fr, neilb@suse.de, akpm@linux-foundation.org, dan.j.williams@intel.com, stable@kernel.org
Message-ID: <200710230345.l9N3jC2M030292@imap1.linux-foundation.org>

From: Dan Williams <dan.j.williams@intel.com>

raid5: fix clearing of biofill operations

This is the correct merge of the two upstream patches for this issue (it
was mis-merged...)

ops_complete_biofill() runs outside of spin_lock(&sh->lock) and clears the
'pending' and 'ack' bits.  Since the test_and_ack_op() macro only checks
against 'complete' it can get an inconsistent snapshot of pending work.

Move the clearing of these bits to handle_stripe5(), under the lock.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Joel Bertrand <joel.bertrand@systella.fr>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/md/raid5.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -377,7 +377,12 @@ static unsigned long get_stripe_work(str
 		ack++;
 
 	sh->ops.count -= ack;
-	BUG_ON(sh->ops.count < 0);
+	if (unlikely(sh->ops.count < 0)) {
+		printk(KERN_ERR "pending: %#lx ops.pending: %#lx ops.ack: %#lx "
+			"ops.complete: %#lx\n", pending, sh->ops.pending,
+			sh->ops.ack, sh->ops.complete);
+		BUG();
+	}
 
 	return pending;
 }
@@ -551,8 +556,7 @@ static void ops_complete_biofill(void *s
 			}
 		}
 	}
-	clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
-	clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
+	set_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
 
 	return_io(return_bi);
 
@@ -2630,6 +2634,13 @@ static void handle_stripe5(struct stripe
 	s.expanded = test_bit(STRIPE_EXPAND_READY, &sh->state);
 	/* Now to look around and see what can be done */
 
+	/* clean-up completed biofill operations */
+	if (test_bit(STRIPE_OP_BIOFILL, &sh->ops.complete)) {
+		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.pending);
+		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.ack);
+		clear_bit(STRIPE_OP_BIOFILL, &sh->ops.complete);
+	}
+
 	rcu_read_lock();
 	for (i=disks; i--; ) {
 		mdk_rdev_t *rdev;