Btrfs: fix uncheck memory allocations

To make Btrfs code more robust, several return value checks where memory
allocation can fail are introduced. I use BUG_ON where I don't know how
to handle the error properly, which increases the number of using the
notorious BUG_ON, though.

Signed-off-by: Yoshinori Sano <yoshinori.sano@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 4d2110e..992a4b9 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -340,6 +340,8 @@
 
 	WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
 	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
+	if (!cb)
+		return -ENOMEM;
 	atomic_set(&cb->pending_bios, 0);
 	cb->errors = 0;
 	cb->inode = inode;
@@ -354,6 +356,10 @@
 	bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
 
 	bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
+	if(!bio) {
+		kfree(cb);
+		return -ENOMEM;
+	}
 	bio->bi_private = cb;
 	bio->bi_end_io = end_compressed_bio_write;
 	atomic_inc(&cb->pending_bios);