[PATCH] pipe: introduce ->pin() buffer operation
The ->map() function is really expensive on highmem machines right now,
since it has to use the slower kmap() instead of kmap_atomic(). Splice
rarely needs to access the virtual address of a page, so it's a waste
of time doing it.
Introduce ->pin() to take over the responsibility of making sure the
page data is valid. ->map() is then reduced to just kmap(). That way we
can also share a most of the pipe buffer ops between pipe.c and splice.c
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 3130977..b8aae1f 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -14,10 +14,23 @@
unsigned int flags;
};
+/*
+ * Note on the nesting of these functions:
+ *
+ * ->pin()
+ * ->steal()
+ * ...
+ * ->map()
+ * ...
+ * ->unmap()
+ *
+ * That is, ->map() must be called on a pinned buffer, same goes for ->steal().
+ */
struct pipe_buf_operations {
int can_merge;
- void * (*map)(struct file *, struct pipe_inode_info *, struct pipe_buffer *);
+ void * (*map)(struct pipe_inode_info *, struct pipe_buffer *);
void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *);
+ int (*pin)(struct pipe_inode_info *, struct pipe_buffer *);
void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
@@ -50,6 +63,12 @@
void free_pipe_info(struct inode * inode);
void __free_pipe_info(struct pipe_inode_info *);
+/* Generic pipe buffer ops functions */
+void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *);
+void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *);
+void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
+int generic_pipe_buf_pin(struct pipe_inode_info *, struct pipe_buffer *);
+
/*
* splice is tied to pipes as a transport (at least for now), so we'll just
* add the splice flags here.