Btrfs: Only do async bio submission for pdflush

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/disk-io.c

@@ -381,6 +381,13 @@ int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
 {
 	struct async_submit_bio *async;
 
+	/*
+	 * inline writerback should stay inline, only hop to the async
+	 * queue if we're pdflush
+	 */
+	if (!current_is_pdflush())
+		return submit_bio_hook(inode, rw, bio, mirror_num);
+
 	async = kmalloc(sizeof(*async), GFP_NOFS);
 	if (!async)
 		return -ENOMEM;