[PATCH 1/3] fs: add 'nonblock' parameter to pipe_buf_confirm() and fops method

[Jens Axboe <axboe@xxxxxxxxx>]

In preparation for being able to do a nonblocking confirm attempt of a
pipe buffer, plumb a parameter through the stack to indicate if this is
a nonblocking attempt or not.

Each caller is passing down 'false' right now, but the only confirm
method in the tree, page_cache_pipe_buf_confirm(), is converted to do a
trylock_page() if nonblock == true.

Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
 fs/fuse/dev.c             |  4 ++--
 fs/pipe.c                 |  4 ++--
 fs/splice.c               | 11 +++++++----
 include/linux/pipe_fs_i.h |  7 ++++---
 4 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index eb4f88e3dc97..0bd1b0870f2d 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -700,7 +700,7 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 		struct pipe_buffer *buf = cs->pipebufs;
 
 		if (!cs->write) {
-			err = pipe_buf_confirm(cs->pipe, buf);
+			err = pipe_buf_confirm(cs->pipe, buf, false);
 			if (err)
 				return err;
 
@@ -800,7 +800,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 
 	fuse_copy_finish(cs);
 
-	err = pipe_buf_confirm(cs->pipe, buf);
+	err = pipe_buf_confirm(cs->pipe, buf, false);
 	if (err)
 		goto out_put_old;
 
diff --git a/fs/pipe.c b/fs/pipe.c
index 42c7ff41c2db..340f253913a2 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -297,7 +297,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 				chars = total_len;
 			}
 
-			error = pipe_buf_confirm(pipe, buf);
+			error = pipe_buf_confirm(pipe, buf, false);
 			if (error) {
 				if (!ret)
 					ret = error;
@@ -461,7 +461,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
 
 		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
 		    offset + chars <= PAGE_SIZE) {
-			ret = pipe_buf_confirm(pipe, buf);
+			ret = pipe_buf_confirm(pipe, buf, false);
 			if (ret)
 				goto out;
 
diff --git a/fs/splice.c b/fs/splice.c
index 2e76dbb81a8f..5ae6b4a202df 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -100,13 +100,16 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  * is a page cache page, IO may be in flight.
  */
 static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
-				       struct pipe_buffer *buf)
+				       struct pipe_buffer *buf, bool nonblock)
 {
 	struct page *page = buf->page;
 	int err;
 
 	if (!PageUptodate(page)) {
-		lock_page(page);
+		if (nonblock && !trylock_page(page))
+			return -EAGAIN;
+		else
+			lock_page(page);
 
 		/*
 		 * Page got truncated/unhashed. This will cause a 0-byte
@@ -498,7 +501,7 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des
 		if (sd->len > sd->total_len)
 			sd->len = sd->total_len;
 
-		ret = pipe_buf_confirm(pipe, buf);
+		ret = pipe_buf_confirm(pipe, buf, false);
 		if (unlikely(ret)) {
 			if (ret == -ENODATA)
 				ret = 0;
@@ -761,7 +764,7 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 				continue;
 			this_len = min(this_len, left);
 
-			ret = pipe_buf_confirm(pipe, buf);
+			ret = pipe_buf_confirm(pipe, buf, false);
 			if (unlikely(ret)) {
 				if (ret == -ENODATA)
 					ret = 0;
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index d2c3f16cf6b1..d63278bb0797 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -100,7 +100,8 @@ struct pipe_buf_operations {
 	 * hook. Returns 0 for good, or a negative error value in case of
 	 * error.  If not present all pages are considered good.
 	 */
-	int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
+	int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *,
+			bool nonblock);
 
 	/*
 	 * When the contents of this pipe buffer has been completely
@@ -209,11 +210,11 @@ static inline void pipe_buf_release(struct pipe_inode_info *pipe,
  * @buf:	the buffer to confirm
  */
 static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
-				   struct pipe_buffer *buf)
+				   struct pipe_buffer *buf, bool nonblock)
 {
 	if (!buf->ops->confirm)
 		return 0;
-	return buf->ops->confirm(pipe, buf);
+	return buf->ops->confirm(pipe, buf, nonblock);
 }
 
 /**
-- 
2.39.2