md: set rotational bit

if all disks in an array are non-rotational, set the array
non-rotational.

This only works for array with all disks populated at startup. Support
for disk hotadd/hotremove could be added later if necessary.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 457b53863117..eac84d8ff724 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5297,6 +5297,21 @@ int md_run(struct mddev *mddev)
                 return err;
         }
         if (mddev->queue) {
+                bool nonrot = true;
+
+                rdev_for_each(rdev, mddev) {
+                        if (rdev->raid_disk >= 0 &&
+                            !blk_queue_nonrot(bdev_get_queue(rdev->bdev))) {
+                                nonrot = false;
+                                break;
+                        }
+                }
+                if (mddev->degraded)
+                        nonrot = false;
+                if (nonrot)
+                        queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mddev->queue);
+                else
+                        queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, mddev->queue);
                 mddev->queue->backing_dev_info.congested_data = mddev;
                 mddev->queue->backing_dev_info.congested_fn = md_congested;
         }