raid5: Don't set read-ahead when there is no queue

dm-raid456 does not provide a 'queue' for raid5 to use,
so we must make raid5 stop depending on the queue.

First: read_ahead
dm handles read-ahead adjustment fully in userspace, so
simply don't do any readahead adjustments if there is
no queue.

Also re-arrange code slightly so all the accesses to ->queue are
together.

Finally, move the blk_queue_merge_bvec function into the 'if' as
the ->split_io setting in dm-raid456 has the same effect.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 17 insertions, 15 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 6fa60e416a09..9c462f6659c3 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5161,16 +5161,6 @@ static int run(mddev_t *mddev)
                                                         "reshape");
         }
 
-        /* read-ahead size must cover two whole stripes, which is
-         * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
-         */
-        {
-                int data_disks = conf->previous_raid_disks - conf->max_degraded;
-                int stripe = data_disks *
-                        ((mddev->chunk_sectors << 9) / PAGE_SIZE);
-                if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
-                        mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
-        }
 
         /* Ok, everything is just fine now */
         if (mddev->to_remove == &raid5_attrs_group)
@@ -5178,8 +5168,23 @@ static int run(mddev_t *mddev)
         else if (mddev->kobj.sd &&
             sysfs_create_group(&mddev->kobj, &raid5_attrs_group))
                 printk(KERN_WARNING
-                       "md/raid:%s: failed to create sysfs attributes.\n",
+                       "raid5: failed to create sysfs attributes for %s\n",
                        mdname(mddev));
+        md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
+
+        if (mddev->queue) {
+                /* read-ahead size must cover two whole stripes, which
+                 * is 2 * (datadisks) * chunksize where 'n' is the
+                 * number of raid devices
+                 */
+                int data_disks = conf->previous_raid_disks - conf->max_degraded;
+                int stripe = data_disks *
+                        ((mddev->chunk_sectors << 9) / PAGE_SIZE);
+                if (mddev->queue->backing_dev_info.ra_pages < 2 * stripe)
+                        mddev->queue->backing_dev_info.ra_pages = 2 * stripe;
+
+                blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
+        }
 
         mddev->queue->queue_lock = &conf->device_lock;
 
@@ -5187,9 +5192,6 @@ static int run(mddev_t *mddev)
         mddev->queue->backing_dev_info.congested_data = mddev;
         mddev->queue->backing_dev_info.congested_fn = raid5_congested;
 
-        md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
-
-        blk_queue_merge_bvec(mddev->queue, raid5_mergeable_bvec);
         chunk_size = mddev->chunk_sectors << 9;
         blk_queue_io_min(mddev->queue, chunk_size);
         blk_queue_io_opt(mddev->queue, chunk_size *
@@ -5618,7 +5620,7 @@ static void end_reshape(raid5_conf_t *conf)
                 /* read-ahead size must cover two whole stripes, which is
                  * 2 * (datadisks) * chunksize where 'n' is the number of raid devices
                  */
-                {
+                if (conf->mddev->queue) {
                         int data_disks = conf->raid_disks - conf->max_degraded;
                         int stripe = data_disks * ((conf->chunk_sectors << 9)
                                                    / PAGE_SIZE);