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| author |   David Sterba <dsterba@suse.com> | 2020-04-30 17:57:55 +0200 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-05-25 11:25:34 +0200 |
| commit | 84da071f3df5a9c0df0352d1c52b0c36ddb1c53f (patch) | |
| tree | 9afe4d666d6c5c7ce55f2b07602f514a38866f9b /fs/btrfs | |
| parent | btrfs: drop unnecessary offset_in_page in extent buffer helpers (diff) | |
| download | wireguard-linux-84da071f3df5a9c0df0352d1c52b0c36ddb1c53f.tar.xz wireguard-linux-84da071f3df5a9c0df0352d1c52b0c36ddb1c53f.zip | |
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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/struct-funcs.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/fs/btrfs/struct-funcs.c b/fs/btrfs/struct-funcs.c index 0b23aa0a32d5..46a7269bee07 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, \ |