Btrfs: check return value of bio_alloc() properly

bio_alloc() has the possibility of returning NULL.
So, it is necessary to check the return value.

Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index c9a2c1a..60f0e28 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -1044,6 +1044,8 @@
 
 		BUG_ON(!page->page);
 		bio = bio_alloc(GFP_NOFS, 1);
+		if (!bio)
+			return -EIO;
 		bio->bi_bdev = page->bdev;
 		bio->bi_sector = page->physical >> 9;
 		bio->bi_end_io = scrub_complete_bio_end_io;
@@ -1172,6 +1174,8 @@
 		DECLARE_COMPLETION_ONSTACK(complete);
 
 		bio = bio_alloc(GFP_NOFS, 1);
+		if (!bio)
+			return -EIO;
 		bio->bi_bdev = page_bad->bdev;
 		bio->bi_sector = page_bad->physical >> 9;
 		bio->bi_end_io = scrub_complete_bio_end_io;