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/disk-io.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs/btrfs/disk-io.c') diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index ad526aa5312a..25889a2362e2 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -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; /* -- cgit v1.2.3