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btrfs: speed up and simplify generic_bin_search

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The bin search jumps over the extent buffer item keys, comparing
directly the bytes if the key is in one page, or storing it in a
temporary buffer in case it spans two pages.

The mapping start and length are obtained from map_private_extent_buffer,
which is heavy weight compared to what we need. We know the key size and
can find out the eb page in a simple way.  For keys spanning two pages
the fallback read_extent_buffer is used.

The temporary variables are reduced and moved to the scope of use.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
David Sterba 2020-04-29 23:23:37 +02:00
parent ce7afe8782
commit 5cd17f343b
1 changed files with 15 additions and 28 deletions
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43
fs/btrfs/ctree.c
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@ -1668,15 +1668,8 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
{
int low = 0;
int high = max;
int mid;
int ret;
struct btrfs_disk_key *tmp = NULL;
struct btrfs_disk_key unaligned;
unsigned long offset;
char *kaddr = NULL;
unsigned long map_start = 0;
unsigned long map_len = 0;
int err;
const int key_size = sizeof(struct btrfs_disk_key);
if (low > high) {
btrfs_err(eb->fs_info,
@ -1687,32 +1680,26 @@ static noinline int generic_bin_search(struct extent_buffer *eb,
}
while (low < high) {
unsigned long oip;
unsigned long offset;
struct btrfs_disk_key *tmp;
struct btrfs_disk_key unaligned;
int mid;
mid = (low + high) / 2;
offset = p + mid * item_size;
oip = offset_in_page(offset);
if (!kaddr || offset < map_start ||
(offset + sizeof(struct btrfs_disk_key)) >
map_start + map_len) {
err = map_private_extent_buffer(eb, offset,
sizeof(struct btrfs_disk_key),
&kaddr, &map_start, &map_len);
if (!err) {
tmp = (struct btrfs_disk_key *)(kaddr + offset -
map_start);
} else if (err == 1) {
read_extent_buffer(eb, &unaligned,
offset, sizeof(unaligned));
tmp = &unaligned;
} else {
return err;
}
if (oip + key_size <= PAGE_SIZE) {
const unsigned long idx = offset >> PAGE_SHIFT;
char *kaddr = page_address(eb->pages[idx]);
tmp = (struct btrfs_disk_key *)(kaddr + oip);
} else {
tmp = (struct btrfs_disk_key *)(kaddr + offset -
map_start);
read_extent_buffer(eb, &unaligned, offset, key_size);
tmp = &unaligned;
}
ret = comp_keys(tmp, key);
if (ret < 0)