2 files changed, 18 insertions, 7 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 14a8fe0349c7..a8bc93d6ff63 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -154,7 +154,7 @@ static void put_all_bios(conf_t *conf, r1bio_t *r1_bio)
 
         for (i = 0; i < conf->raid_disks; i++) {
                 struct bio **bio = r1_bio->bios + i;
-                if (*bio)
+                if (*bio && *bio != IO_BLOCKED)
                         bio_put(*bio);
                 *bio = NULL;
         }
@@ -419,11 +419,13 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
                 new_disk = 0;
 
                 for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
+                     r1_bio->bios[new_disk] == IO_BLOCKED ||
                      !rdev || !test_bit(In_sync, &rdev->flags)
                              || test_bit(WriteMostly, &rdev->flags);
                      rdev = rcu_dereference(conf->mirrors[++new_disk].rdev)) {
 
-                        if (rdev && test_bit(In_sync, &rdev->flags))
+                        if (rdev && test_bit(In_sync, &rdev->flags) &&
+                                r1_bio->bios[new_disk] != IO_BLOCKED)
                                 wonly_disk = new_disk;
 
                         if (new_disk == conf->raid_disks - 1) {
@@ -437,11 +439,13 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
 
         /* make sure the disk is operational */
         for (rdev = rcu_dereference(conf->mirrors[new_disk].rdev);
+             r1_bio->bios[new_disk] == IO_BLOCKED ||
              !rdev || !test_bit(In_sync, &rdev->flags) ||
                      test_bit(WriteMostly, &rdev->flags);
              rdev = rcu_dereference(conf->mirrors[new_disk].rdev)) {
 
-                if (rdev && test_bit(In_sync, &rdev->flags))
+                if (rdev && test_bit(In_sync, &rdev->flags) &&
+                    r1_bio->bios[new_disk] != IO_BLOCKED)
                         wonly_disk = new_disk;
 
                 if (new_disk <= 0)
@@ -478,7 +482,7 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
 
                 rdev = rcu_dereference(conf->mirrors[disk].rdev);
 
-                if (!rdev ||
+                if (!rdev || r1_bio->bios[disk] == IO_BLOCKED ||
                     !test_bit(In_sync, &rdev->flags) ||
                     test_bit(WriteMostly, &rdev->flags))
                         continue;
@@ -1335,7 +1339,7 @@ static void raid1d(mddev_t *mddev)
                         sector_t sect = r1_bio->sector;
                         int sectors = r1_bio->sectors;
                         freeze_array(conf);
-                        while(sectors) {
+                        if (mddev->ro == 0) while(sectors) {
                                 int s = sectors;
                                 int d = r1_bio->read_disk;
                                 int success = 0;
@@ -1388,7 +1392,6 @@ static void raid1d(mddev_t *mddev)
                                 sect += s;
                         }
 
-
                         unfreeze_array(conf);
 
                         bio = r1_bio->bios[r1_bio->read_disk];
@@ -1399,7 +1402,8 @@ static void raid1d(mddev_t *mddev)
                                        (unsigned long long)r1_bio->sector);
                                 raid_end_bio_io(r1_bio);
                         } else {
-                                r1_bio->bios[r1_bio->read_disk] = NULL;
+                                r1_bio->bios[r1_bio->read_disk] =
+                                        mddev->ro ? IO_BLOCKED : NULL;
                                 r1_bio->read_disk = disk;
                                 bio_put(bio);
                                 bio = bio_clone(r1_bio->master_bio, GFP_NOIO);
diff --git a/include/linux/raid/raid1.h b/include/linux/raid/raid1.h
index cbe4238d3f9f..9d5494aaac0f 100644
--- a/include/linux/raid/raid1.h
+++ b/include/linux/raid/raid1.h
@@ -109,6 +109,13 @@ struct r1bio_s {
         /* DO NOT PUT ANY NEW FIELDS HERE - bios array is contiguously alloced*/
 };
 
+/* when we get a read error on a read-only array, we redirect to another
+ * device without failing the first device, or trying to over-write to
+ * correct the read error.  To keep track of bad blocks on a per-bio
+ * level, we store IO_BLOCKED in the appropriate 'bios' pointer
+ */
+#define IO_BLOCKED ((struct bio*)1)
+
 /* bits for r1bio.state */
 #define R1BIO_Uptodate  0
 #define R1BIO_IsSync    1