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>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d45f52e..9f0ff71 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -339,6 +339,29 @@
return mddev_congested(mddev, bits);
}
+static int md_mergeable_bvec(struct request_queue *q,
+ struct bvec_merge_data *bvm,
+ struct bio_vec *biovec)
+{
+ struct mddev *mddev = q->queuedata;
+ int ret;
+ rcu_read_lock();
+ if (mddev->suspended) {
+ /* Must always allow one vec */
+ if (bvm->bi_size == 0)
+ ret = biovec->bv_len;
+ else
+ ret = 0;
+ } else {
+ struct md_personality *pers = mddev->pers;
+ if (pers && pers->mergeable_bvec)
+ ret = pers->mergeable_bvec(mddev, bvm, biovec);
+ else
+ ret = biovec->bv_len;
+ }
+ rcu_read_unlock();
+ return ret;
+}
/*
* Generic flush handling for md
*/
@@ -4925,6 +4948,7 @@
if (mddev->queue) {
mddev->queue->backing_dev_info.congested_data = mddev;
mddev->queue->backing_dev_info.congested_fn = md_congested;
+ blk_queue_merge_bvec(mddev->queue, md_mergeable_bvec);
}
if (mddev->pers->sync_request) {
if (mddev->kobj.sd &&