fs: make the pipe_buf_operations ->confirm operation optional

Just return 0 for success if it is not present.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/pipe.c

@@ -200,22 +200,6 @@ bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 }
 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
@@ -232,7 +216,6 @@ void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 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

@@ -156,7 +156,6 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 }
 
 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,
@@ -331,7 +330,6 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 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,
@@ -339,7 +337,6 @@ const struct pipe_buf_operations default_pipe_buf_ops = {
 
 /* 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

@@ -82,7 +82,7 @@ struct pipe_buf_operations {
 	 * 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 *);
 
@@ -195,6 +195,8 @@ static inline void pipe_buf_release(struct pipe_inode_info *pipe,
 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);
 }
 
@@ -232,7 +234,6 @@ void free_pipe_info(struct pipe_inode_info *);
 
 /* 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

@@ -1177,7 +1177,6 @@ static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
 }
 
 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

@@ -7574,7 +7574,6 @@ static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
 
 /* 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

@@ -130,7 +130,6 @@ static void smc_rx_pipe_buf_release(struct pipe_inode_info *pipe,
 }
 
 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
 };