[PATCH] vmsplice: restrict stealing a little more

Apply the same rules as the anon pipe pages, only allow stealing
if no one else is using the page.

Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/fs/pipe.c b/fs/pipe.c
index 3941a7f..5acd895 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -184,8 +184,8 @@
 		kunmap(buf->page);
 }
 
-static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
-			       struct pipe_buffer *buf)
+int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
+			   struct pipe_buffer *buf)
 {
 	struct page *page = buf->page;
 
@@ -213,7 +213,7 @@
 	.unmap = generic_pipe_buf_unmap,
 	.pin = generic_pipe_buf_pin,
 	.release = anon_pipe_buf_release,
-	.steal = anon_pipe_buf_steal,
+	.steal = generic_pipe_buf_steal,
 	.get = generic_pipe_buf_get,
 };