From ba8a9a0537770df69d9dc38c11312c9b0f840cf2 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 30 Apr 2020 17:57:55 +0200 Subject: [PATCH] btrfs: optimize split page read in btrfs_get_token_##bits The fallback path calls helper read_extent_buffer 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. The cached token address is set to the second page. Reviewed-by: Johannes Thumshirn Signed-off-by: David Sterba --- fs/btrfs/struct-funcs.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c index 46a7269bee07..63cab91507f8 100644 --- a/fs/btrfs/struct-funcs.c +++ b/fs/btrfs/struct-funcs.c @@ -66,7 +66,8 @@ u##bits btrfs_get_token_##bits(struct btrfs_map_token *token, \ const unsigned long idx = member_offset >> PAGE_SHIFT; \ const unsigned long oip = offset_in_page(member_offset); \ const int size = sizeof(u##bits); \ - __le##bits leres; \ + u8 lebytes[sizeof(u##bits)]; \ + const int part = PAGE_SIZE - oip; \ \ ASSERT(token); \ ASSERT(token->kaddr); \ @@ -75,15 +76,16 @@ u##bits btrfs_get_token_##bits(struct btrfs_map_token *token, \ member_offset + size <= token->offset + PAGE_SIZE) { \ return get_unaligned_le##bits(token->kaddr + oip); \ } \ - if (oip + size <= PAGE_SIZE) { \ - token->kaddr = page_address(token->eb->pages[idx]); \ - token->offset = idx << PAGE_SHIFT; \ + token->kaddr = page_address(token->eb->pages[idx]); \ + token->offset = idx << PAGE_SHIFT; \ + if (oip + size <= PAGE_SIZE) \ return get_unaligned_le##bits(token->kaddr + oip); \ - } \ + \ + memcpy(lebytes, token->kaddr + oip, part); \ token->kaddr = page_address(token->eb->pages[idx + 1]); \ token->offset = (idx + 1) << PAGE_SHIFT; \ - read_extent_buffer(token->eb, &leres, member_offset, size); \ - return le##bits##_to_cpu(leres); \ + memcpy(lebytes + part, token->kaddr, size - part); \ + return get_unaligned_le##bits(lebytes); \ } \ u##bits btrfs_get_##bits(const struct extent_buffer *eb, \ const void *ptr, unsigned long off) \ -- 2.39.5