fs: make the pipe_buf_operations ->steal operation optional

Just return 1 for failure if it is not present.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/splice.c

@@ -337,17 +337,10 @@ const struct pipe_buf_operations default_pipe_buf_ops = {
 	.get = generic_pipe_buf_get,
 };
 
-int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
-			     struct pipe_buffer *buf)
-{
-	return 1;
-}
-
 /* 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,
-	.steal = generic_pipe_buf_nosteal,
 	.get = generic_pipe_buf_get,
 };
 EXPORT_SYMBOL(nosteal_pipe_buf_ops);

include/linux/pipe_fs_i.h

@@ -206,6 +206,8 @@ static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
 				 struct pipe_buffer *buf)
 {
+	if (!buf->ops->steal)
+		return 1;
 	return buf->ops->steal(pipe, buf);
 }
 
@@ -232,7 +234,6 @@ void free_pipe_info(struct pipe_inode_info *);
 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 *);
-int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
 void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
 
 extern const struct pipe_buf_operations nosteal_pipe_buf_ops;

kernel/trace/trace.c

@@ -7576,7 +7576,6 @@ static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
 static const struct pipe_buf_operations buffer_pipe_buf_ops = {
 	.confirm		= generic_pipe_buf_confirm,
 	.release		= buffer_pipe_buf_release,
-	.steal			= generic_pipe_buf_nosteal,
 	.get			= buffer_pipe_buf_get,
 };
 

net/smc/smc_rx.c

@@ -129,16 +129,9 @@ static void smc_rx_pipe_buf_release(struct pipe_inode_info *pipe,
 	sock_put(sk);
 }
 
-static int smc_rx_pipe_buf_nosteal(struct pipe_inode_info *pipe,
-				   struct pipe_buffer *buf)
-{
-	return 1;
-}
-
 static const struct pipe_buf_operations smc_pipe_ops = {
 	.confirm = generic_pipe_buf_confirm,
 	.release = smc_rx_pipe_buf_release,
-	.steal = smc_rx_pipe_buf_nosteal,
 	.get = generic_pipe_buf_get
 };