1 files changed, 62 insertions, 7 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 516baf4..b443cd2 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -532,13 +532,21 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
 			bi->bi_end_io = raid5_end_read_request;
 
 		rcu_read_lock();
-		rdev = rcu_dereference(conf->disks[i].rdev);
 		rrdev = rcu_dereference(conf->disks[i].replacement);
+		smp_mb(); /* Ensure that if rrdev is NULL, rdev won't be */
+		rdev = rcu_dereference(conf->disks[i].rdev);
+		if (!rdev) {
+			rdev = rrdev;
+			rrdev = NULL;
+		}
 		if (rw & WRITE) {
 			if (replace_only)
 				rdev = NULL;
+			if (rdev == rrdev)
+				/* We raced and saw duplicates */
+				rrdev = NULL;
 		} else {
-			if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+			if (test_bit(R5_ReadRepl, &sh->dev[i].flags) && rrdev)
 				rdev = rrdev;
 			rrdev = NULL;
 		}
@@ -1640,7 +1648,7 @@ static void raid5_end_read_request(struct bio * bi, int error)
 	int disks = sh->disks, i;
 	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
 	char b[BDEVNAME_SIZE];
-	struct md_rdev *rdev;
+	struct md_rdev *rdev = NULL;
 
 
 	for (i=0 ; i<disks; i++)
@@ -1655,8 +1663,13 @@ static void raid5_end_read_request(struct bio * bi, int error)
 		return;
 	}
 	if (test_bit(R5_ReadRepl, &sh->dev[i].flags))
+		/* If replacement finished while this request was outstanding,
+		 * 'replacement' might be NULL already.
+		 * In that case it moved down to 'rdev'.
+		 * rdev is not removed until all requests are finished.
+		 */
 		rdev = conf->disks[i].replacement;
-	else
+	if (!rdev)
 		rdev = conf->disks[i].rdev;
 
 	if (uptodate) {
@@ -1753,7 +1766,14 @@ static void raid5_end_write_request(struct bio *bi, int error)
 		}
 		if (bi == &sh->dev[i].rreq) {
 			rdev = conf->disks[i].replacement;
-			replacement = 1;
+			if (rdev)
+				replacement = 1;
+			else
+				/* rdev was removed and 'replacement'
+				 * replaced it.  rdev is not removed
+				 * until all requests are finished.
+				 */
+				rdev = conf->disks[i].rdev;
 			break;
 		}
 	}
@@ -3539,6 +3559,9 @@ finish:
 			}
 			if (test_and_clear_bit(R5_MadeGoodRepl, &dev->flags)) {
 				rdev = conf->disks[i].replacement;
+				if (!rdev)
+					/* rdev have been moved down */
+					rdev = conf->disks[i].rdev;
 				rdev_clear_badblocks(rdev, sh->sector,
 						     STRIPE_SECTORS);
 				rdev_dec_pending(rdev, conf->mddev);
@@ -5204,7 +5227,25 @@ static int raid5_spare_active(struct mddev *mddev)
 
 	for (i = 0; i < conf->raid_disks; i++) {
 		tmp = conf->disks + i;
-		if (tmp->rdev
+		if (tmp->replacement
+		    && tmp->replacement->recovery_offset == MaxSector
+		    && !test_bit(Faulty, &tmp->replacement->flags)
+		    && !test_and_set_bit(In_sync, &tmp->replacement->flags)) {
+			/* Replacement has just become active. */
+			if (!tmp->rdev
+			    || !test_and_clear_bit(In_sync, &tmp->rdev->flags))
+				count++;
+			if (tmp->rdev) {
+				/* Replaced device not technically faulty,
+				 * but we need to be sure it gets removed
+				 * and never re-added.
+				 */
+				set_bit(Faulty, &tmp->rdev->flags);
+				sysfs_notify_dirent_safe(
+					tmp->rdev->sysfs_state);
+			}
+			sysfs_notify_dirent_safe(tmp->replacement->sysfs_state);
+		} else if (tmp->rdev
 		    && tmp->rdev->recovery_offset == MaxSector
 		    && !test_bit(Faulty, &tmp->rdev->flags)
 		    && !test_and_set_bit(In_sync, &tmp->rdev->flags)) {
@@ -5250,6 +5291,7 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 	if (!test_bit(Faulty, &rdev->flags) &&
 	    mddev->recovery_disabled != conf->recovery_disabled &&
 	    !has_failed(conf) &&
+	    (!p->replacement || p->replacement == rdev) &&
 	    number < conf->raid_disks) {
 		err = -EBUSY;
 		goto abort;
@@ -5260,7 +5302,20 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 		/* lost the race, try later */
 		err = -EBUSY;
 		*rdevp = rdev;
-	}
+	} else if (p->replacement) {
+		/* We must have just cleared 'rdev' */
+		p->rdev = p->replacement;
+		clear_bit(Replacement, &p->replacement->flags);
+		smp_mb(); /* Make sure other CPUs may see both as identical
+			   * but will never see neither - if they are careful
+			   */
+		p->replacement = NULL;
+		clear_bit(WantReplacement, &rdev->flags);
+	} else
+		/* We might have just removed the Replacement as faulty-
+		 * clear the bit just in case
+		 */
+		clear_bit(WantReplacement, &rdev->flags);
 abort:
 
 	print_raid5_conf(conf);