btrfs: Perform locking/unlocking in btrfs_remap_file_range()

Move code to make it more readable, so as locking and unlocking is
done in the same function. The generic checks that are now performed in
the locked section are unaffected.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3950,16 +3950,10 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in,
 			return -EXDEV;
 	}
 
-	if (same_inode)
-		inode_lock(inode_in);
-	else
-		lock_two_nondirectories(inode_in, inode_out);
-
 	/* don't make the dst file partly checksummed */
 	if ((BTRFS_I(inode_in)->flags & BTRFS_INODE_NODATASUM) !=
 	    (BTRFS_I(inode_out)->flags & BTRFS_INODE_NODATASUM)) {
-		ret = -EINVAL;
-		goto out_unlock;
+		return -EINVAL;
 	}
 
 	/*
@@ -3993,26 +3987,14 @@ static int btrfs_remap_file_range_prep(struct file *file_in, loff_t pos_in,
 	ret = btrfs_wait_ordered_range(inode_in, ALIGN_DOWN(pos_in, bs),
 				       wb_len);
 	if (ret < 0)
-		goto out_unlock;
+		return ret;
 	ret = btrfs_wait_ordered_range(inode_out, ALIGN_DOWN(pos_out, bs),
 				       wb_len);
 	if (ret < 0)
-		goto out_unlock;
+		return ret;
 
-	ret = generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
+	return generic_remap_file_range_prep(file_in, pos_in, file_out, pos_out,
 					    len, remap_flags);
-	if (ret < 0 || *len == 0)
-		goto out_unlock;
-
-	return 0;
-
- out_unlock:
-	if (same_inode)
-		inode_unlock(inode_in);
-	else
-		unlock_two_nondirectories(inode_in, inode_out);
-
-	return ret;
 }
 
 loff_t btrfs_remap_file_range(struct file *src_file, loff_t off,
@@ -4027,16 +4009,22 @@ loff_t btrfs_remap_file_range(struct file *src_file, loff_t off,
 	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
 		return -EINVAL;
 
+	if (same_inode)
+		inode_lock(src_inode);
+	else
+		lock_two_nondirectories(src_inode, dst_inode);
+
 	ret = btrfs_remap_file_range_prep(src_file, off, dst_file, destoff,
 					  &len, remap_flags);
 	if (ret < 0 || len == 0)
-		return ret;
+		goto out_unlock;
 
 	if (remap_flags & REMAP_FILE_DEDUP)
 		ret = btrfs_extent_same(src_inode, off, len, dst_inode, destoff);
 	else
 		ret = btrfs_clone_files(dst_file, src_file, off, len, destoff);
 
+out_unlock:
 	if (same_inode)
 		inode_unlock(src_inode);
 	else