fs: make the pipe_buf_operations ->confirm operation optional

Just return 0 for success if it is not present.

Signed-off-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/pipe.c

···
 EXPORT_SYMBOL(generic_pipe_buf_get);
 
 /**
- * generic_pipe_buf_confirm - verify contents of the pipe buffer
- * @info:	the pipe that the buffer belongs to
- * @buf:	the buffer to confirm
- *
- * Description:
- *	This function does nothing, because the generic pipe code uses
- *	pages that are always good when inserted into the pipe.
- */
-int generic_pipe_buf_confirm(struct pipe_inode_info *info,
-			     struct pipe_buffer *buf)
-{
-	return 0;
-}
-EXPORT_SYMBOL(generic_pipe_buf_confirm);
-
-/**
  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
  * @pipe:	the pipe that the buffer belongs to
  * @buf:	the buffer to put a reference to
···
 EXPORT_SYMBOL(generic_pipe_buf_release);
 
 static const struct pipe_buf_operations anon_pipe_buf_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = anon_pipe_buf_release,
 	.steal = anon_pipe_buf_steal,
 	.get = generic_pipe_buf_get,

fs/splice.c

···
 }
 
 static const struct pipe_buf_operations user_page_pipe_buf_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = page_cache_pipe_buf_release,
 	.steal = user_page_pipe_buf_steal,
 	.get = generic_pipe_buf_get,
···
 EXPORT_SYMBOL(generic_file_splice_read);
 
 const struct pipe_buf_operations default_pipe_buf_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = generic_pipe_buf_release,
 	.steal = generic_pipe_buf_steal,
 	.get = generic_pipe_buf_get,
···
 
 /* Pipe buffer operations for a socket and similar. */
 const struct pipe_buf_operations nosteal_pipe_buf_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = generic_pipe_buf_release,
 	.get = generic_pipe_buf_get,
 };

include/linux/pipe_fs_i.h

···
 	 * and that the contents are good. If the pages in the pipe belong
 	 * to a file system, we may need to wait for IO completion in this
 	 * hook. Returns 0 for good, or a negative error value in case of
-	 * error.
+	 * error.  If not present all pages are considered good.
 	 */
 	int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
 
···
 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 				   struct pipe_buffer *buf)
 {
+	if (!buf->ops->confirm)
+		return 0;
 	return buf->ops->confirm(pipe, buf);
 }
 
···
 
 /* Generic pipe buffer ops functions */
 bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
-int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 

kernel/relay.c

···
 }
 
 static const struct pipe_buf_operations relay_pipe_buf_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = relay_pipe_buf_release,
 	.steal = generic_pipe_buf_steal,
 	.get = generic_pipe_buf_get,

kernel/trace/trace.c

···
 
 /* Pipe buffer operations for a buffer. */
 static const struct pipe_buf_operations buffer_pipe_buf_ops = {
-	.confirm		= generic_pipe_buf_confirm,
 	.release		= buffer_pipe_buf_release,
 	.get			= buffer_pipe_buf_get,
 };

net/smc/smc_rx.c

···
 }
 
 static const struct pipe_buf_operations smc_pipe_ops = {
-	.confirm = generic_pipe_buf_confirm,
 	.release = smc_rx_pipe_buf_release,
 	.get = generic_pipe_buf_get
 };