Commit 5cd17f34 authored by David Sterba's avatar David Sterba
Browse files

btrfs: speed up and simplify generic_bin_search 



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: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent ce7afe87

fs/btrfs/ctree.c

+15 −28
Original line number Diff line number Diff line
@@ -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 (oip + key_size <= PAGE_SIZE) {

			const unsigned long idx = offset >> PAGE_SHIFT;

			char *kaddr = page_address(eb->pages[idx]);



			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;

			tmp = (struct btrfs_disk_key *)(kaddr + oip);

		} else {

				return err;

			read_extent_buffer(eb, &unaligned, offset, key_size);

			tmp = &unaligned;

		}



		} else {

			tmp = (struct btrfs_disk_key *)(kaddr + offset -

							map_start);

		}

		ret = comp_keys(tmp, key);



		if (ret < 0)