Commit ab108d99 authored by David Sterba's avatar David Sterba
Browse files

btrfs: use precalculated sectorsize_bits from fs_info 



We do a lot of calculations where we divide or multiply by sectorsize.
We also know and make sure that sectorsize is a power of two, so this
means all divisions can be turned to shifts and avoid eg. expensive
u64/u32 divisions.

The type is u32 as it's more register friendly on x86_64 compared to u8
and the resulting assembly is smaller (movzbl vs movl).

There's also superblock s_blocksize_bits but it's usually one more
pointer dereference farther than fs_info.

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e940e9a7

fs/btrfs/ctree.h

+2 −0
Original line number Diff line number Diff line
@@ -935,6 +935,8 @@ struct btrfs_fs_info { 
	/* Cached block sizes */

	u32 nodesize;

	u32 sectorsize;

	/* ilog2 of sectorsize, use to avoid 64bit division */

	u32 sectorsize_bits;

	u32 stripesize;



	/* Block groups and devices containing active swapfiles. */

fs/btrfs/disk-io.c

+2 −0
Original line number Diff line number Diff line
@@ -2814,6 +2814,7 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info) 
	/* Usable values until the real ones are cached from the superblock */

	fs_info->nodesize = 4096;

	fs_info->sectorsize = 4096;

	fs_info->sectorsize_bits = ilog2(4096);

	fs_info->stripesize = 4096;



	spin_lock_init(&fs_info->swapfile_pins_lock);
@@ -3078,6 +3079,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device 
	/* Cache block sizes */

	fs_info->nodesize = nodesize;

	fs_info->sectorsize = sectorsize;

	fs_info->sectorsize_bits = ilog2(sectorsize);

	fs_info->stripesize = stripesize;



	/*

fs/btrfs/extent-tree.c

+1 −1
Original line number Diff line number Diff line
@@ -2145,7 +2145,7 @@ u64 btrfs_csum_bytes_to_leaves(struct btrfs_fs_info *fs_info, u64 csum_bytes) 
	csum_size = BTRFS_MAX_ITEM_SIZE(fs_info);

	num_csums_per_leaf = div64_u64(csum_size,

			(u64)btrfs_super_csum_size(fs_info->super_copy));

	num_csums = div64_u64(csum_bytes, fs_info->sectorsize);

	num_csums = csum_bytes >> fs_info->sectorsize_bits;

	num_csums += num_csums_per_leaf - 1;

	num_csums = div64_u64(num_csums, num_csums_per_leaf);

	return num_csums;

fs/btrfs/file-item.c

+1 −1
Original line number Diff line number Diff line
@@ -369,7 +369,7 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, 
		 * a single leaf so it will also fit inside a u32

		 */

		diff = disk_bytenr - item_start_offset;

		diff = diff / fs_info->sectorsize;

		diff = diff >> fs_info->sectorsize_bits;

		diff = diff * csum_size;

		count = min_t(int, nblocks, (item_last_offset - disk_bytenr) >>

					    inode->i_sb->s_blocksize_bits);

fs/btrfs/free-space-tree.c

+3 −3
Original line number Diff line number Diff line
@@ -416,7 +416,7 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans, 
	btrfs_mark_buffer_dirty(leaf);

	btrfs_release_path(path);



	nrbits = div_u64(block_group->length, block_group->fs_info->sectorsize);

	nrbits = block_group->length >> block_group->fs_info->sectorsize_bits;

	start_bit = find_next_bit_le(bitmap, nrbits, 0);



	while (start_bit < nrbits) {
@@ -540,8 +540,8 @@ static void free_space_set_bits(struct btrfs_block_group *block_group, 
		end = found_end;



	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);

	first = div_u64(*start - found_start, fs_info->sectorsize);

	last = div_u64(end - found_start, fs_info->sectorsize);

	first = (*start - found_start) >> fs_info->sectorsize_bits;

	last = (end - found_start) >> fs_info->sectorsize_bits;

	if (bit)

		extent_buffer_bitmap_set(leaf, ptr, first, last - first);

	else