Btrfs: check the nodatasum flag when writing compressed files

If mounting with nodatasum option, we won't csum file data for
general write or direct-io write, and this rule should also be
applied when writing compressed files.

Signed-off-by: Li Zefan <[e-mail]>
Signed-off-by: Chris Mason <[e-mail]>

fs/btrfs/compression.c

···
 	u64 first_byte = disk_start;
 	struct block_device *bdev;
 	int ret;
+	int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 
 	WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
 	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
···
 			ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
 			BUG_ON(ret);
 
-			ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
-			BUG_ON(ret);
+			if (!skip_sum) {
+				ret = btrfs_csum_one_bio(root, inode, bio,
+							 start, 1);
+				BUG_ON(ret);
+			}
 
 			ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
 			BUG_ON(ret);
···
 	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
 	BUG_ON(ret);
 
-	ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
-	BUG_ON(ret);
+	if (!skip_sum) {
+		ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
+		BUG_ON(ret);
+	}
 
 	ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
 	BUG_ON(ret);