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btrfs: simplify eb checksum verification in btrfs_validate_metadata_buffer 

The verification copies the calculated checksum bytes to a temporary
buffer but this is not necessary. We can map the eb header on the first
page and use the checksum bytes directly.

This saves at least one function call and boundary checks so it could
lead to a minor performance improvement.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2020-09-21 22:07:14 +02:00
parent ff14aa7987
commit dfd29eed4a
1 changed files with 5 additions and 5 deletions
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10
fs/btrfs/disk-io.c
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@ -584,6 +584,7 @@ static int validate_extent_buffer(struct extent_buffer *eb)
const u32 csum_size = fs_info->csum_size;
u8 found_level;
u8 result[BTRFS_CSUM_SIZE];
const u8 *header_csum;
int ret = 0;
found_start = btrfs_header_bytenr(eb);
@ -608,15 +609,14 @@ static int validate_extent_buffer(struct extent_buffer *eb)
}
csum_tree_block(eb, result);
header_csum = page_address(eb->pages[0]) +
get_eb_offset_in_page(eb, offsetof(struct btrfs_header, csum));
if (memcmp_extent_buffer(eb, result, 0, csum_size)) {
u8 val[BTRFS_CSUM_SIZE] = { 0 };
read_extent_buffer(eb, &val, 0, csum_size);
if (memcmp(result, header_csum, csum_size) != 0) {
btrfs_warn_rl(fs_info,
"checksum verify failed on %llu wanted " CSUM_FMT " found " CSUM_FMT " level %d",
eb->start,
CSUM_FMT_VALUE(csum_size, val),
CSUM_FMT_VALUE(csum_size, header_csum),
CSUM_FMT_VALUE(csum_size, result),
btrfs_header_level(eb));
ret = -EUCLEAN;