From: David Sterba Date: Thu, 30 Apr 2020 15:57:55 +0000 (+0200) Subject: btrfs: optimize split page read in btrfs_get_##bits X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=84da071f3df5a9c0df0352d1c52b0c36ddb1c53f;p=linux.git btrfs: optimize split page read in btrfs_get_##bits The helper read_extent_buffer is called to do read of the data spanning two extent buffer pages. As the size is known, we can do the read directly in two steps. This removes one function call and compiler can optimize memcpy as the sizes are known at compile time. Reviewed-by: Johannes Thumshirn Signed-off-by: David Sterba --- diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c index 0b23aa0a32d5c..46a7269bee075 100644 --- a/fs/btrfs/struct-funcs.c +++ b/fs/btrfs/struct-funcs.c @@ -90,17 +90,20 @@ u##bits btrfs_get_##bits(const struct extent_buffer *eb, \ { \ const unsigned long member_offset = (unsigned long)ptr + off; \ const unsigned long oip = offset_in_page(member_offset); \ + const unsigned long idx = member_offset >> PAGE_SHIFT; \ + char *kaddr = page_address(eb->pages[idx]); \ const int size = sizeof(u##bits); \ - __le##bits leres; \ + const int part = PAGE_SIZE - oip; \ + u8 lebytes[sizeof(u##bits)]; \ \ ASSERT(check_setget_bounds(eb, ptr, off, size)); \ - if (oip + size <= PAGE_SIZE) { \ - const unsigned long idx = member_offset >> PAGE_SHIFT; \ - const char *kaddr = page_address(eb->pages[idx]); \ + if (oip + size <= PAGE_SIZE) \ return get_unaligned_le##bits(kaddr + oip); \ - } \ - read_extent_buffer(eb, &leres, member_offset, size); \ - return le##bits##_to_cpu(leres); \ + \ + memcpy(lebytes, kaddr + oip, part); \ + kaddr = page_address(eb->pages[idx + 1]); \ + memcpy(lebytes + part, kaddr, size - part); \ + return get_unaligned_le##bits(lebytes); \ } \ void btrfs_set_token_##bits(struct btrfs_map_token *token, \ const void *ptr, unsigned long off, \