Btrfs: Avoid memcpy where possible in extent_buffers
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 30fbbd7..aed0861 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -483,15 +483,50 @@
#define BTRFS_SETGET_HEADER_FUNCS(name, type, member, bits) \
static inline u##bits btrfs_##name(struct extent_buffer *eb) \
{ \
- __le##bits res; \
- read_eb_member(eb, NULL, 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 = 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, NULL, type, member, &res); \
+ return le##bits##_to_cpu(res); \
+ } \
} \
static inline void btrfs_set_##name(struct extent_buffer *eb, \
u##bits val) \
{ \
- val = cpu_to_le##bits(val); \
- write_eb_member(eb, NULL, type, member, &val); \
+ int err; \
+ char *map_token; \
+ char *kaddr; \
+ unsigned long map_start; \
+ unsigned long map_len; \
+ unsigned long offset = 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, NULL, type, member, &val); \
+ } \
}
#define BTRFS_SETGET_STACK_FUNCS(name, type, member, bits) \