diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index f1b749c..872bf94 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -191,12 +191,6 @@
 {
 	conf_t *conf = r10_bio->mddev->private;
 
-	/*
-	 * Wake up any possible resync thread that waits for the device
-	 * to go idle.
-	 */
-	allow_barrier(conf);
-
 	put_all_bios(conf, r10_bio);
 	mempool_free(r10_bio, conf->r10bio_pool);
 }
@@ -235,9 +229,27 @@
 static void raid_end_bio_io(r10bio_t *r10_bio)
 {
 	struct bio *bio = r10_bio->master_bio;
+	int done;
+	conf_t *conf = r10_bio->mddev->private;
 
-	bio_endio(bio,
-		test_bit(R10BIO_Uptodate, &r10_bio->state) ? 0 : -EIO);
+	if (bio->bi_phys_segments) {
+		unsigned long flags;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		bio->bi_phys_segments--;
+		done = (bio->bi_phys_segments == 0);
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+	} else
+		done = 1;
+	if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
+		clear_bit(BIO_UPTODATE, &bio->bi_flags);
+	if (done) {
+		bio_endio(bio, 0);
+		/*
+		 * Wake up any possible resync thread that waits for the device
+		 * to go idle.
+		 */
+		allow_barrier(conf);
+	}
 	free_r10bio(r10_bio);
 }
 
@@ -307,6 +319,7 @@
 				   mdname(conf->mddev),
 				   bdevname(conf->mirrors[dev].rdev->bdev, b),
 				   (unsigned long long)r10_bio->sector);
+		set_bit(R10BIO_ReadError, &r10_bio->state);
 		reschedule_retry(r10_bio);
 	}
 }
@@ -505,11 +518,12 @@
  * FIXME: possibly should rethink readbalancing and do it differently
  * depending on near_copies / far_copies geometry.
  */
-static int read_balance(conf_t *conf, r10bio_t *r10_bio)
+static int read_balance(conf_t *conf, r10bio_t *r10_bio, int *max_sectors)
 {
 	const sector_t this_sector = r10_bio->sector;
 	int disk, slot;
-	const int sectors = r10_bio->sectors;
+	int sectors = r10_bio->sectors;
+	int best_good_sectors;
 	sector_t new_distance, best_dist;
 	mdk_rdev_t *rdev;
 	int do_balance;
@@ -518,8 +532,10 @@
 	raid10_find_phys(conf, r10_bio);
 	rcu_read_lock();
 retry:
+	sectors = r10_bio->sectors;
 	best_slot = -1;
 	best_dist = MaxSector;
+	best_good_sectors = 0;
 	do_balance = 1;
 	/*
 	 * Check if we can balance. We can balance on the whole
@@ -532,6 +548,10 @@
 		do_balance = 0;
 
 	for (slot = 0; slot < conf->copies ; slot++) {
+		sector_t first_bad;
+		int bad_sectors;
+		sector_t dev_sector;
+
 		if (r10_bio->devs[slot].bio == IO_BLOCKED)
 			continue;
 		disk = r10_bio->devs[slot].devnum;
@@ -541,6 +561,37 @@
 		if (!test_bit(In_sync, &rdev->flags))
 			continue;
 
+		dev_sector = r10_bio->devs[slot].addr;
+		if (is_badblock(rdev, dev_sector, sectors,
+				&first_bad, &bad_sectors)) {
+			if (best_dist < MaxSector)
+				/* Already have a better slot */
+				continue;
+			if (first_bad <= dev_sector) {
+				/* Cannot read here.  If this is the
+				 * 'primary' device, then we must not read
+				 * beyond 'bad_sectors' from another device.
+				 */
+				bad_sectors -= (dev_sector - first_bad);
+				if (!do_balance && sectors > bad_sectors)
+					sectors = bad_sectors;
+				if (best_good_sectors > sectors)
+					best_good_sectors = sectors;
+			} else {
+				sector_t good_sectors =
+					first_bad - dev_sector;
+				if (good_sectors > best_good_sectors) {
+					best_good_sectors = good_sectors;
+					best_slot = slot;
+				}
+				if (!do_balance)
+					/* Must read from here */
+					break;
+			}
+			continue;
+		} else
+			best_good_sectors = sectors;
+
 		if (!do_balance)
 			break;
 
@@ -582,6 +633,7 @@
 	} else
 		disk = -1;
 	rcu_read_unlock();
+	*max_sectors = best_good_sectors;
 
 	return disk;
 }
@@ -829,12 +881,27 @@
 	r10_bio->sector = bio->bi_sector;
 	r10_bio->state = 0;
 
+	/* We might need to issue multiple reads to different
+	 * devices if there are bad blocks around, so we keep
+	 * track of the number of reads in bio->bi_phys_segments.
+	 * If this is 0, there is only one r10_bio and no locking
+	 * will be needed when the request completes.  If it is
+	 * non-zero, then it is the number of not-completed requests.
+	 */
+	bio->bi_phys_segments = 0;
+	clear_bit(BIO_SEG_VALID, &bio->bi_flags);
+
 	if (rw == READ) {
 		/*
 		 * read balancing logic:
 		 */
-		int disk = read_balance(conf, r10_bio);
-		int slot = r10_bio->read_slot;
+		int max_sectors;
+		int disk;
+		int slot;
+
+read_again:
+		disk = read_balance(conf, r10_bio, &max_sectors);
+		slot = r10_bio->read_slot;
 		if (disk < 0) {
 			raid_end_bio_io(r10_bio);
 			return 0;
@@ -842,6 +909,8 @@
 		mirror = conf->mirrors + disk;
 
 		read_bio = bio_clone_mddev(bio, GFP_NOIO, mddev);
+		md_trim_bio(read_bio, r10_bio->sector - bio->bi_sector,
+			    max_sectors);
 
 		r10_bio->devs[slot].bio = read_bio;
 
@@ -852,7 +921,39 @@
 		read_bio->bi_rw = READ | do_sync;
 		read_bio->bi_private = r10_bio;
 
-		generic_make_request(read_bio);
+		if (max_sectors < r10_bio->sectors) {
+			/* Could not read all from this device, so we will
+			 * need another r10_bio.
+			 */
+			int sectors_handled;
+
+			sectors_handled = (r10_bio->sectors + max_sectors
+					   - bio->bi_sector);
+			r10_bio->sectors = max_sectors;
+			spin_lock_irq(&conf->device_lock);
+			if (bio->bi_phys_segments == 0)
+				bio->bi_phys_segments = 2;
+			else
+				bio->bi_phys_segments++;
+			spin_unlock(&conf->device_lock);
+			/* Cannot call generic_make_request directly
+			 * as that will be queued in __generic_make_request
+			 * and subsequent mempool_alloc might block
+			 * waiting for it.  so hand bio over to raid10d.
+			 */
+			reschedule_retry(r10_bio);
+
+			r10_bio = mempool_alloc(conf->r10bio_pool, GFP_NOIO);
+
+			r10_bio->master_bio = bio;
+			r10_bio->sectors = ((bio->bi_size >> 9)
+					    - sectors_handled);
+			r10_bio->state = 0;
+			r10_bio->mddev = mddev;
+			r10_bio->sector = bio->bi_sector + sectors_handled;
+			goto read_again;
+		} else
+			generic_make_request(read_bio);
 		return 0;
 	}
 
@@ -1627,6 +1728,7 @@
 	mdk_rdev_t *rdev;
 	char b[BDEVNAME_SIZE];
 	unsigned long do_sync;
+	int max_sectors;
 
 	/* we got a read error. Maybe the drive is bad.  Maybe just
 	 * the block and we can fix it.
@@ -1646,8 +1748,8 @@
 	bio = r10_bio->devs[slot].bio;
 	r10_bio->devs[slot].bio =
 		mddev->ro ? IO_BLOCKED : NULL;
-	mirror = read_balance(conf, r10_bio);
-	if (mirror == -1) {
+	mirror = read_balance(conf, r10_bio, &max_sectors);
+	if (mirror == -1 || max_sectors < r10_bio->sectors) {
 		printk(KERN_ALERT "md/raid10:%s: %s: unrecoverable I/O"
 		       " read error for block %llu\n",
 		       mdname(mddev),
@@ -1712,8 +1814,15 @@
 			sync_request_write(mddev, r10_bio);
 		else if (test_bit(R10BIO_IsRecover, &r10_bio->state))
 			recovery_request_write(mddev, r10_bio);
-		else
+		else if (test_bit(R10BIO_ReadError, &r10_bio->state))
 			handle_read_error(mddev, r10_bio);
+		else {
+			/* just a partial read to be scheduled from a
+			 * separate context
+			 */
+			int slot = r10_bio->read_slot;
+			generic_make_request(r10_bio->devs[slot].bio);
+		}
 
 		cond_resched();
 		if (mddev->flags & ~(1<<MD_CHANGE_PENDING))
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index a485914..c646152 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -124,4 +124,8 @@
 #define	R10BIO_IsSync	1
 #define	R10BIO_IsRecover 2
 #define	R10BIO_Degraded 3
+/* Set ReadError on bios that experience a read error
+ * so that raid10d knows what to do with them.
+ */
+#define	R10BIO_ReadError 4
 #endif