md: make merge_bvec_fn more robust in face of personality changes.

There is no locking around calls to merge_bvec_fn(), so
it is possible that calls which coincide with a level (or personality)
change could go wrong.

So create a central dispatch point for these functions and use
rcu_read_lock().
If the array is suspended, reject any merge that can be rejected.
If not, we know it is safe to call the function.

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

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 4b521eac5b69..3770c9675b17 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -350,17 +350,16 @@ static struct md_rdev *map_sector(struct mddev *mddev, struct strip_zone *zone,
 
 /**
  *      raid0_mergeable_bvec -- tell bio layer if two requests can be merged
- *      @q: request queue
+ *      @mddev: the md device
  *      @bvm: properties of new bio
  *      @biovec: the request that could be merged to it.
  *
  *      Return amount of bytes we can accept at this offset
  */
-static int raid0_mergeable_bvec(struct request_queue *q,
+static int raid0_mergeable_bvec(struct mddev *mddev,
                                 struct bvec_merge_data *bvm,
                                 struct bio_vec *biovec)
 {
-        struct mddev *mddev = q->queuedata;
         struct r0conf *conf = mddev->private;
         sector_t sector = bvm->bi_sector + get_start_sect(bvm->bi_bdev);
         sector_t sector_offset = sector;
@@ -465,7 +464,6 @@ static int raid0_run(struct mddev *mddev)
                         mddev->queue->backing_dev_info.ra_pages = 2* stripe;
         }
 
-        blk_queue_merge_bvec(mddev->queue, raid0_mergeable_bvec);
         dump_zones(mddev);
 
         ret = md_integrity_register(mddev);
@@ -724,6 +722,7 @@ static struct md_personality raid0_personality=
         .takeover       = raid0_takeover,
         .quiesce        = raid0_quiesce,
         .congested      = raid0_congested,
+        .mergeable_bvec = raid0_mergeable_bvec,
 };
 
 static int __init raid0_init (void)