smb3 client: fix return code mapping of remap_file_range

We were returning -EOPNOTSUPP for various remap_file_range cases
but for some of these the copy_file_range_syscall() requires -EINVAL
to be returned (e.g. where source and target file ranges overlap when
source and target are the same file). This fixes xfstest generic/157
which was expecting EINVAL for that (and also e.g. for when the src
offset is beyond end of file).

Cc: stable@vger.kernel.org
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: smfrench

fs/smb/client/cifsfs.c

@@ -1358,6 +1358,20 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 			truncate_setsize(target_inode, new_size);
 			fscache_resize_cookie(cifs_inode_cookie(target_inode),
 					      new_size);
+		} else if (rc == -EOPNOTSUPP) {
+			/*
+			 * copy_file_range syscall man page indicates EINVAL
+			 * is returned e.g when "fd_in and fd_out refer to the
+			 * same file and the source and target ranges overlap."
+			 * Test generic/157 was what showed these cases where
+			 * we need to remap EOPNOTSUPP to EINVAL
+			 */
+			if (off >= src_inode->i_size) {
+				rc = -EINVAL;
+			} else if (src_inode == target_inode) {
+				if (off + len > destoff)
+					rc = -EINVAL;
+			}
 		}
 		if (rc == 0 && new_size > target_cifsi->netfs.zero_point)
 			target_cifsi->netfs.zero_point = new_size;