From ab108d992b1248adfb7c13c1136cab59c944a98c Mon Sep 17 00:00:00 2001 From: David Sterba Date: Wed, 1 Jul 2020 20:45:04 +0200 Subject: 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: Johannes Thumshirn Signed-off-by: David Sterba --- fs/btrfs/file-item.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/btrfs/file-item.c') diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c index 816f57d52fc9..81a318a92418 100644 --- a/fs/btrfs/file-item.c +++ b/fs/btrfs/file-item.c @@ -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); -- cgit v1.2.3