linux-kernel - [PATCH 04/11] pipe: add pipe_buf

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Date:   Wed, 14 Sep 2016 10:37:09 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 04/11] pipe: add pipe_buf_steal() helper

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 drivers/char/virtio_console.c |  2 +-
 fs/fuse/dev.c                 |  2 +-
 include/linux/pipe_fs_i.h     | 11 +++++++++++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 5da47e26a012..8114744bf30c 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -889,7 +889,7 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 		return 0;
 
 	/* Try lock this page */
-	if (buf->ops->steal(pipe, buf) == 0) {
+	if (pipe_buf_steal(pipe, buf) == 0) {
 		/* Get reference and unlock page for moving */
 		get_page(buf->page);
 		unlock_page(buf->page);
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 9aa757f283e5..6830b3ca1bbb 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -841,7 +841,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 	if (cs->len != PAGE_SIZE)
 		goto out_fallback;
 
-	if (buf->ops->steal(cs->pipe, buf) != 0)
+	if (pipe_buf_steal(cs->pipe, buf) != 0)
 		goto out_fallback;
 
 	newpage = buf->page;
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 654413334537..bddccf0159bb 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -151,6 +151,17 @@ static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
 	return buf->ops->confirm(pipe, buf);
 }
 
+/**
+ * pipe_buf_steal - attempt to take ownership of a pipe_buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer to attempt to steal
+ */
+static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
+				 struct pipe_buffer *buf)
+{
+	return buf->ops->steal(pipe, buf);
+}
+
 /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
    memory allocation, whereas PIPE_BUF makes atomicity guarantees.  */
 #define PIPE_SIZE		PAGE_SIZE
-- 
2.5.5