1 files changed, 31 insertions, 3 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index fb96c0c2db40..d9869f25aa75 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -497,9 +497,11 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
         const sector_t this_sector = r1_bio->sector;
         int sectors;
         int best_good_sectors;
-        int best_disk;
+        int best_disk, best_dist_disk, best_pending_disk;
+        int has_nonrot_disk;
         int disk;
         sector_t best_dist;
+        unsigned int min_pending;
         struct md_rdev *rdev;
         int choose_first;
 
@@ -512,8 +514,12 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
  retry:
         sectors = r1_bio->sectors;
         best_disk = -1;
+        best_dist_disk = -1;
         best_dist = MaxSector;
+        best_pending_disk = -1;
+        min_pending = UINT_MAX;
         best_good_sectors = 0;
+        has_nonrot_disk = 0;
 
         if (conf->mddev->recovery_cp < MaxSector &&
             (this_sector + sectors >= conf->next_resync))
@@ -525,6 +531,7 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
                 sector_t dist;
                 sector_t first_bad;
                 int bad_sectors;
+                unsigned int pending;
 
                 rdev = rcu_dereference(conf->mirrors[disk].rdev);
                 if (r1_bio->bios[disk] == IO_BLOCKED
@@ -583,22 +590,43 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
                 } else
                         best_good_sectors = sectors;
 
+                has_nonrot_disk |= blk_queue_nonrot(bdev_get_queue(rdev->bdev));
+                pending = atomic_read(&rdev->nr_pending);
                 dist = abs(this_sector - conf->mirrors[disk].head_position);
                 if (choose_first
                     /* Don't change to another disk for sequential reads */
                     || conf->mirrors[disk].next_seq_sect == this_sector
                     || dist == 0
                     /* If device is idle, use it */
-                    || atomic_read(&rdev->nr_pending) == 0) {
+                    || pending == 0) {
                         best_disk = disk;
                         break;
                 }
+
+                if (min_pending > pending) {
+                        min_pending = pending;
+                        best_pending_disk = disk;
+                }
+
                 if (dist < best_dist) {
                         best_dist = dist;
-                        best_disk = disk;
+                        best_dist_disk = disk;
                 }
         }
 
+        /*
+         * If all disks are rotational, choose the closest disk. If any disk is
+         * non-rotational, choose the disk with less pending request even the
+         * disk is rotational, which might/might not be optimal for raids with
+         * mixed ratation/non-rotational disks depending on workload.
+         */
+        if (best_disk == -1) {
+                if (has_nonrot_disk)
+                        best_disk = best_pending_disk;
+                else
+                        best_disk = best_dist_disk;
+        }
+
         if (best_disk >= 0) {
                 rdev = rcu_dereference(conf->mirrors[best_disk].rdev);
                 if (!rdev)