Re: [PATCH v17 03/14] shmem: Implement splice-read

[David Howells]

Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> But please at least stop doing the
> 
>      get_page(buf->page);
> 
> on the zero-page (which includes using no-op .get and .put functions
> in  zero_pipe_buf_ops().

I'll make the attached change.  It seems to work.

David
---
diff --git a/mm/shmem.c b/mm/shmem.c
index 3cbec1d56112..d9b60ab556fe 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2719,6 +2719,17 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	return retval ? retval : error;
 }
 
+static bool zero_pipe_buf_get(struct pipe_inode_info *pipe,
+			      struct pipe_buffer *buf)
+{
+	return true;
+}
+
+static void zero_pipe_buf_release(struct pipe_inode_info *pipe,
+				  struct pipe_buffer *buf)
+{
+}
+
 static bool zero_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 				    struct pipe_buffer *buf)
 {
@@ -2726,9 +2737,9 @@ static bool zero_pipe_buf_try_steal(struct pipe_inode_info *pipe,
 }
 
 static const struct pipe_buf_operations zero_pipe_buf_ops = {
-	.release	= generic_pipe_buf_release,
+	.release	= zero_pipe_buf_release,
 	.try_steal	= zero_pipe_buf_try_steal,
-	.get		= generic_pipe_buf_get,
+	.get		= zero_pipe_buf_get,
 };
 
 static size_t splice_zeropage_into_pipe(struct pipe_inode_info *pipe,