@@ -142,27 +142,20 @@ void btrfs_set_token_##bits(struct btrfs_map_token *token, \
void btrfs_set_##bits(struct extent_buffer *eb, void *ptr, \
unsigned long off, u##bits val) \
{ \
- unsigned long part_offset = (unsigned long)ptr; \
- unsigned long offset = part_offset + off; \
- void *p; \
- int err; \
- char *kaddr; \
- unsigned long map_start; \
- unsigned long map_len; \
- int size = sizeof(u##bits); \
+ const unsigned long member_offset = (unsigned long)ptr + off; \
+ const unsigned long oip = offset_in_page(member_offset); \
+ const int size = sizeof(u##bits); \
+ __le##bits leres; \
\
ASSERT(check_setget_bounds(eb, ptr, off, size)); \
- err = map_private_extent_buffer(eb, offset, size, \
- &kaddr, &map_start, &map_len); \
- if (err) { \
- __le##bits val2; \
- \
- val2 = cpu_to_le##bits(val); \
- write_extent_buffer(eb, &val2, offset, size); \
+ if (oip + size <= PAGE_SIZE) { \
+ const unsigned long idx = member_offset >> PAGE_SHIFT; \
+ char *kaddr = page_address(eb->pages[idx]); \
+ put_unaligned_le##bits(val, kaddr + oip); \
return; \
} \
- p = kaddr + part_offset - map_start; \
- put_unaligned_le##bits(val, p + off); \
+ leres = cpu_to_le##bits(val); \
+ write_extent_buffer(eb, &leres, member_offset, size); \
}
DEFINE_BTRFS_SETGET_BITS(8)
The helpers unconditionally call map_private_extent_buffer to get the address of page containing the requested offset plus the mapping start and length. Depending on the return value, the fast path uses unaligned put to write data within a page, or fall back to write_extent_buffer that can handle writes spanning more pages. This is all wasteful. We know the number of bytes to read, 1/2/4/8 and can find out the page. Then simply check if it's contained or the fallback is needed. This saves one function call to map_private_extent_buffer and several unnecessary temporary variables. Signed-off-by: David Sterba <dsterba@suse.com> --- fs/btrfs/struct-funcs.c | 27 ++++++++++----------------- 1 file changed, 10 insertions(+), 17 deletions(-)