Btrfs: Optimizations for the extent_buffer code
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c4b8298..30fbbd7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -22,6 +22,7 @@
#include <linux/fs.h>
#include <linux/workqueue.h>
#include <linux/completion.h>
+#include <asm/kmap_types.h>
#include "bit-radix.h"
#include "extent_map.h"
@@ -431,15 +432,52 @@
static inline u##bits btrfs_##name(struct extent_buffer *eb, \
type *s) \
{ \
- __le##bits res; \
- read_eb_member(eb, s, type, member, &res); \
- return le##bits##_to_cpu(res); \
+ int err; \
+ char *map_token; \
+ char *kaddr; \
+ unsigned long map_start; \
+ unsigned long map_len; \
+ unsigned long offset = (unsigned long)s + \
+ offsetof(type, member); \
+ err = map_extent_buffer(eb, offset, \
+ sizeof(((type *)0)->member), \
+ &map_token, &kaddr, \
+ &map_start, &map_len, KM_USER0); \
+ if (!err) { \
+ __le##bits *tmp = (__le##bits *)(kaddr + offset - \
+ map_start); \
+ u##bits res = le##bits##_to_cpu(*tmp); \
+ unmap_extent_buffer(eb, map_token, KM_USER0); \
+ return res; \
+ } else { \
+ __le##bits res; \
+ read_eb_member(eb, s, type, member, &res); \
+ return le##bits##_to_cpu(res); \
+ } \
} \
static inline void btrfs_set_##name(struct extent_buffer *eb, \
type *s, u##bits val) \
{ \
- val = cpu_to_le##bits(val); \
- write_eb_member(eb, s, type, member, &val); \
+ int err; \
+ char *map_token; \
+ char *kaddr; \
+ unsigned long map_start; \
+ unsigned long map_len; \
+ unsigned long offset = (unsigned long)s + \
+ offsetof(type, member); \
+ err = map_extent_buffer(eb, offset, \
+ sizeof(((type *)0)->member), \
+ &map_token, &kaddr, \
+ &map_start, &map_len, KM_USER0); \
+ if (!err) { \
+ __le##bits *tmp = (__le##bits *)(kaddr + offset - \
+ map_start); \
+ *tmp = cpu_to_le##bits(val); \
+ unmap_extent_buffer(eb, map_token, KM_USER0); \
+ } else { \
+ val = cpu_to_le##bits(val); \
+ write_eb_member(eb, s, type, member, &val); \
+ } \
}
#define BTRFS_SETGET_HEADER_FUNCS(name, type, member, bits) \