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exfat: using ffs instead of internal logic

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Replaced the internal table lookup algorithm with ffs of
the bitops library with better performance.

Use it to increase the single processing length of the
exfat_find_free_bitmap function, from single-byte search to long type.

Signed-off-by: John Sanpe <sanpeqf@gmail.com>
Acked-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
John Sanpe 2023-12-08 07:47:01 +08:00 committed by Namjae Jeon
parent 7423546040
commit 34939ae005
2 changed files with 16 additions and 28 deletions
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41
fs/exfat/balloc.c
View File

@ -14,29 +14,15 @@
#if BITS_PER_LONG == 32
#define __le_long __le32
#define lel_to_cpu(A) le32_to_cpu(A)
#define cpu_to_lel(A) cpu_to_le32(A)
#elif BITS_PER_LONG == 64
#define __le_long __le64
#define lel_to_cpu(A) le64_to_cpu(A)
#define cpu_to_lel(A) cpu_to_le64(A)
#else
#error "BITS_PER_LONG not 32 or 64"
#endif
static const unsigned char free_bit[] = {
0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/* 0 ~ 19*/
0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3,/* 20 ~ 39*/
0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/* 40 ~ 59*/
0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/* 60 ~ 79*/
0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2,/* 80 ~ 99*/
0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3,/*100 ~ 119*/
0, 1, 0, 2, 0, 1, 0, 7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/*120 ~ 139*/
0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5,/*140 ~ 159*/
0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/*160 ~ 179*/
0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3,/*180 ~ 199*/
0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/*200 ~ 219*/
0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/*220 ~ 239*/
0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0 /*240 ~ 254*/
};
/*
* Allocation Bitmap Management Functions
*/
@ -195,32 +181,35 @@ unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu)
{
unsigned int i, map_i, map_b, ent_idx;
unsigned int clu_base, clu_free;
unsigned char k, clu_mask;
unsigned long clu_bits, clu_mask;
struct exfat_sb_info *sbi = EXFAT_SB(sb);
__le_long bitval;
WARN_ON(clu < EXFAT_FIRST_CLUSTER);
ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
clu_base = BITMAP_ENT_TO_CLUSTER(ent_idx & ~(BITS_PER_BYTE_MASK));
ent_idx = ALIGN_DOWN(CLUSTER_TO_BITMAP_ENT(clu), BITS_PER_LONG);
clu_base = BITMAP_ENT_TO_CLUSTER(ent_idx);
clu_mask = IGNORED_BITS_REMAINED(clu, clu_base);
map_i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
map_b = BITMAP_OFFSET_BYTE_IN_SECTOR(sb, ent_idx);
for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters;
i += BITS_PER_BYTE) {
k = *(sbi->vol_amap[map_i]->b_data + map_b);
i += BITS_PER_LONG) {
bitval = *(__le_long *)(sbi->vol_amap[map_i]->b_data + map_b);
if (clu_mask > 0) {
k |= clu_mask;
bitval |= cpu_to_lel(clu_mask);
clu_mask = 0;
}
if (k < 0xFF) {
clu_free = clu_base + free_bit[k];
if (lel_to_cpu(bitval) != ULONG_MAX) {
clu_bits = lel_to_cpu(bitval);
clu_free = clu_base + ffz(clu_bits);
if (clu_free < sbi->num_clusters)
return clu_free;
}
clu_base += BITS_PER_BYTE;
clu_base += BITS_PER_LONG;
map_b += sizeof(long);
if (++map_b >= sb->s_blocksize ||
if (map_b >= sb->s_blocksize ||
clu_base >= sbi->num_clusters) {
if (++map_i >= sbi->map_sectors) {
clu_base = EXFAT_FIRST_CLUSTER;

3
fs/exfat/exfat_fs.h
View File

@ -135,8 +135,7 @@ enum {
#define BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent) (ent & BITS_PER_SECTOR_MASK(sb))
#define BITMAP_OFFSET_BYTE_IN_SECTOR(sb, ent) \
((ent / BITS_PER_BYTE) & ((sb)->s_blocksize - 1))
#define BITS_PER_BYTE_MASK 0x7
#define IGNORED_BITS_REMAINED(clu, clu_base) ((1 << ((clu) - (clu_base))) - 1)
#define IGNORED_BITS_REMAINED(clu, clu_base) ((1UL << ((clu) - (clu_base))) - 1)
#define ES_ENTRY_NUM(name_len) (ES_IDX_LAST_FILENAME(name_len) + 1)
/* 19 entries = 1 file entry + 1 stream entry + 17 filename entries */