Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
"Four smaller fixes for the current series. This contains:

- A fix for clones of discard bio's, that can cause data corruption.
From Martin.

- A fix for null_blk, where in certain queue modes it could access a
request after it had been freed. From Mike Krinkin.

- An error handling leak fix for blkcg, from Tejun.

- Also from Tejun, export of the functions that a file system needs
to implement cgroup writeback support"

* 'for-linus' of git://git.kernel.dk/linux-block:
block: Do a full clone when splitting discard bios
block: export bio_associate_*() and wbc_account_io()
blkcg: fix gendisk reference leak in blkg_conf_prep()
null_blk: fix use-after-free problem

block/bio.c

···
  * 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)
···
 	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;
 
···
 	bio->bi_css = blkcg_css;
 	return 0;
 }
+EXPORT_SYMBOL_GPL(bio_associate_blkcg);
 
 /**
  * bio_associate_current - associate a bio with %current
···
 	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()

block/blk-cgroup.c

···
 		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);

drivers/block/null_blk.c

···
 	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);
 	}

fs/fs-writeback.c

···
 	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