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 <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b1b6d9a..2bfad19 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -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. */

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ad526aa..25889a2 100644 (file)
--- 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;
 
        /*

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index bac1eb1..14d5aaa 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -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;

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 816f57d..81a318a 100644 (file)
--- 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);

diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
index 6b9faf3..84eb1a3 100644 (file)
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -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

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 87bac9e..c6534da 100644 (file)
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -868,7 +868,6 @@ int btrfs_find_ordered_sum(struct btrfs_inode *inode, u64 offset,
        struct btrfs_ordered_inode_tree *tree = &inode->ordered_tree;
        unsigned long num_sectors;
        unsigned long i;
-       u32 sectorsize = btrfs_inode_sectorsize(inode);
        const u8 blocksize_bits = inode->vfs_inode.i_sb->s_blocksize_bits;
        const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
        int index = 0;
@@ -890,7 +889,7 @@ int btrfs_find_ordered_sum(struct btrfs_inode *inode, u64 offset,
                        index += (int)num_sectors * csum_size;
                        if (index == len)
                                goto out;
-                       disk_bytenr += num_sectors * sectorsize;
+                       disk_bytenr += num_sectors * fs_info->sectorsize;
                }
        }
 out:

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 04351b5..c307f25 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2300,7 +2300,7 @@ static inline void __scrub_mark_bitmap(struct scrub_parity *sparity,
        u64 offset;
        u64 nsectors64;
        u32 nsectors;
-       int sectorsize = sparity->sctx->fs_info->sectorsize;
+       u32 sectorsize_bits = sparity->sctx->fs_info->sectorsize_bits;
 
        if (len >= sparity->stripe_len) {
                bitmap_set(bitmap, 0, sparity->nsectors);
@@ -2309,8 +2309,8 @@ static inline void __scrub_mark_bitmap(struct scrub_parity *sparity,
 
        start -= sparity->logic_start;
        start = div64_u64_rem(start, sparity->stripe_len, &offset);
-       offset = div_u64(offset, sectorsize);
-       nsectors64 = div_u64(len, sectorsize);
+       offset = offset >> sectorsize_bits;
+       nsectors64 = len >> sectorsize_bits;
 
        ASSERT(nsectors64 < UINT_MAX);
        nsectors = (u32)nsectors64;
@@ -2386,10 +2386,10 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u8 *csum)
        if (!sum)
                return 0;
 
-       index = div_u64(logical - sum->bytenr, sctx->fs_info->sectorsize);
+       index = (logical - sum->bytenr) >> sctx->fs_info->sectorsize_bits;
        ASSERT(index < UINT_MAX);
 
-       num_sectors = sum->len / sctx->fs_info->sectorsize;
+       num_sectors = sum->len >> sctx->fs_info->sectorsize_bits;
        memcpy(csum, sum->sums + index * sctx->csum_size, sctx->csum_size);
        if (index == num_sectors - 1) {
                list_del(&sum->list);
@@ -2776,7 +2776,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
        int extent_mirror_num;
        int stop_loop = 0;
 
-       nsectors = div_u64(map->stripe_len, fs_info->sectorsize);
+       nsectors = map->stripe_len >> fs_info->sectorsize_bits;
        bitmap_len = scrub_calc_parity_bitmap_len(nsectors);
        sparity = kzalloc(sizeof(struct scrub_parity) + 2 * bitmap_len,
                          GFP_NOFS);

diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c
index 999c14e..b36e887 100644 (file)
--- a/fs/btrfs/tests/btrfs-tests.c
+++ b/fs/btrfs/tests/btrfs-tests.c
@@ -134,6 +134,7 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize)
 
        fs_info->nodesize = nodesize;
        fs_info->sectorsize = sectorsize;
+       fs_info->sectorsize_bits = ilog2(sectorsize);
        set_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);
 
        test_mnt->mnt_sb->s_fs_info = fs_info;