md/plug: optionally use plugger to unplug an array during resync/recovery.

If an array doesn't have a 'queue' then md_do_sync cannot
unplug it.
In that case it will have a 'plugger', so make that available
to the mddev, and use it to unplug the array if needed.

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

3 files changed, 15 insertions, 3 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index eec75f130708..03c64e9735fb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4693,6 +4693,7 @@ static void md_clean(mddev_t *mddev)
         mddev->bitmap_info.chunksize = 0;
         mddev->bitmap_info.daemon_sleep = 0;
         mddev->bitmap_info.max_write_behind = 0;
+        mddev->plug = NULL;
 }
 
 void md_stop_writes(mddev_t *mddev)
@@ -6626,6 +6627,14 @@ int md_allow_write(mddev_t *mddev)
 }
 EXPORT_SYMBOL_GPL(md_allow_write);
 
+static void md_unplug(mddev_t *mddev)
+{
+        if (mddev->queue)
+                blk_unplug(mddev->queue);
+        if (mddev->plug)
+                mddev->plug->unplug_fn(mddev->plug);
+}
+
 #define SYNC_MARKS      10
 #define SYNC_MARK_STEP  (3*HZ)
 void md_do_sync(mddev_t *mddev)
@@ -6804,7 +6813,7 @@ void md_do_sync(mddev_t *mddev)
                      >= mddev->resync_max - mddev->curr_resync_completed
                             )) {
                         /* time to update curr_resync_completed */
-                        blk_unplug(mddev->queue);
+                        md_unplug(mddev);
                         wait_event(mddev->recovery_wait,
                                    atomic_read(&mddev->recovery_active) == 0);
                         mddev->curr_resync_completed =
@@ -6882,7 +6891,7 @@ void md_do_sync(mddev_t *mddev)
                  * about not overloading the IO subsystem. (things like an
                  * e2fsck being done on the RAID array should execute fast)
                  */
-                blk_unplug(mddev->queue);
+                md_unplug(mddev);
                 cond_resched();
 
                 currspeed = ((unsigned long)(io_sectors-mddev->resync_mark_cnt))/2
@@ -6901,7 +6910,7 @@ void md_do_sync(mddev_t *mddev)
          * this also signals 'finished resyncing' to md_stop
          */
  out:
-        blk_unplug(mddev->queue);
+        md_unplug(mddev);
 
         wait_event(mddev->recovery_wait, !atomic_read(&mddev->recovery_active));
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 5be0d6921b9d..57eb864a8249 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -328,6 +328,8 @@ struct mddev_s
         struct list_head                all_mddevs;
 
         struct attribute_group          *to_remove;
+        struct plug_handle              *plug; /* if used by personality */
+
         /* Generic barrier handling.
          * If there is a pending barrier request, all other
          * writes are blocked while the devices are flushed.
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 84bb9aec2211..0a8173e650bb 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5189,6 +5189,7 @@ static int run(mddev_t *mddev)
         md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
 
         plugger_init(&conf->plug, raid5_unplug);
+        mddev->plug = &conf->plug;
         if (mddev->queue) {
                 /* read-ahead size must cover two whole stripes, which
                  * is 2 * (datadisks) * chunksize where 'n' is the