pipe: allow passing around of ops private pointer

relay needs this for proper consumption handling, and the network
receive support needs it as well to lookup the sk_buff on pipe
release.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/splice.c

@@ -185,6 +185,7 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 			buf->page = spd->pages[page_nr];
 			buf->offset = spd->partial[page_nr].offset;
 			buf->len = spd->partial[page_nr].len;
+			buf->private = spd->partial[page_nr].private;
 			buf->ops = spd->ops;
 			if (spd->flags & SPLICE_F_GIFT)
 				buf->flags |= PIPE_BUF_FLAG_GIFT;

include/linux/pipe_fs_i.h

@@ -14,6 +14,7 @@ struct pipe_buffer {
 	unsigned int offset, len;
 	const struct pipe_buf_operations *ops;
 	unsigned int flags;
+	unsigned long private;
 };
 
 struct pipe_inode_info {

include/linux/splice.h

@@ -41,6 +41,7 @@ struct splice_desc {
 struct partial_page {
 	unsigned int offset;
 	unsigned int len;
+	unsigned long private;
 };
 
 /*