diff --git a/block/bio.c b/block/bio.c
index 2a00d349cd6883cba32d9fd477251889a1c58081..d6e5ba3399f0ae151ea040e2ec1fd1df1c3dba6a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1831,8 +1831,9 @@ EXPORT_SYMBOL(bio_endio);
  * Allocates and returns a new bio which represents @sectors from the start of
  * @bio, and updates @bio to represent the remaining sectors.
  *
- * The newly allocated bio will point to @bio's bi_io_vec; it is the caller's
- * responsibility to ensure that @bio is not freed before the split.
+ * Unless this is a discard request the newly allocated bio will point
+ * to @bio's bi_io_vec; it is the caller's responsibility to ensure that
+ * @bio is not freed before the split.
  */
 struct bio *bio_split(struct bio *bio, int sectors,
 		      gfp_t gfp, struct bio_set *bs)
@@ -1842,7 +1843,15 @@ struct bio *bio_split(struct bio *bio, int sectors,
 	BUG_ON(sectors <= 0);
 	BUG_ON(sectors >= bio_sectors(bio));
 
-	split = bio_clone_fast(bio, gfp, bs);
+	/*
+	 * Discards need a mutable bio_vec to accommodate the payload
+	 * required by the DSM TRIM and UNMAP commands.
+	 */
+	if (bio->bi_rw & REQ_DISCARD)
+		split = bio_clone_bioset(bio, gfp, bs);
+	else
+		split = bio_clone_fast(bio, gfp, bs);
+
 	if (!split)
 		return NULL;
 
@@ -2009,6 +2018,7 @@ int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
 	bio->bi_css = blkcg_css;
 	return 0;
 }
+EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
  * bio_associate_current - associate a bio with %current
@@ -2039,6 +2049,7 @@ int bio_associate_current(struct bio *bio)
 	bio->bi_css = task_get_css(current, blkio_cgrp_id);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(bio_associate_current);
 
 /**
  * bio_disassociate_task - undo bio_associate_current()
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9da02c021ebe2ed296cbdf8560d5bbf2ecd1c48f..d6283b3f5db50674d18ae485970f1e24ed44569d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -718,8 +718,12 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		return -EINVAL;
 
 	disk = get_gendisk(MKDEV(major, minor), &part);
-	if (!disk || part)
+	if (!disk)
 		return -EINVAL;
+	if (part) {
+		put_disk(disk);
+		return -EINVAL;
+	}
 
 	rcu_read_lock();
 	spin_lock_irq(disk->queue->queue_lock);
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 69de41a87b74311b2b7478fb0226b8bc253c6ebc..3177b245d2bdf63e821a12a4c0f18cbab1b16229 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -240,19 +240,19 @@ static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
 	while ((entry = llist_del_all(&cq->list)) != NULL) {
 		entry = llist_reverse_order(entry);
 		do {
+			struct request_queue *q = NULL;
+
 			cmd = container_of(entry, struct nullb_cmd, ll_list);
 			entry = entry->next;
+			if (cmd->rq)
+				q = cmd->rq->q;
 			end_cmd(cmd);
 
-			if (cmd->rq) {
-				struct request_queue *q = cmd->rq->q;
-
-				if (!q->mq_ops && blk_queue_stopped(q)) {
-					spin_lock(q->queue_lock);
-					if (blk_queue_stopped(q))
-						blk_start_queue(q);
-					spin_unlock(q->queue_lock);
-				}
+			if (q && !q->mq_ops && blk_queue_stopped(q)) {
+				spin_lock(q->queue_lock);
+				if (blk_queue_stopped(q))
+					blk_start_queue(q);
+				spin_unlock(q->queue_lock);
 			}
 		} while (entry);
 	}
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f0520bcf209442914eff0ed60d380fb3d2c66402..518c6294bf6c0ef965e9f56baa4e11d2eccc0165 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -702,6 +702,7 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page,
 	else
 		wbc->wb_tcand_bytes -= min(bytes, wbc->wb_tcand_bytes);
 }
+EXPORT_SYMBOL_GPL(wbc_account_io);
 
 /**
  * inode_congested - test whether an inode is congested