Commit 451cbaa1c328082832a8fbcc427cd4416c602c5a
Committed by
Linus Torvalds
Linus Torvalds
1 parent
4e57b68178
Exists in
master
and in
4 other branches
[PATCH] fat: cleanup and optimization of checksum
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Showing 3 changed files with 14 additions and 10 deletions Side-by-side Diff
fs/fat/dir.c
| ... | ... | @@ -263,7 +263,6 @@ |
| 263 | 263 | unsigned char id; |
| 264 | 264 | unsigned char slot; |
| 265 | 265 | unsigned char slots; |
| 266 | - unsigned char sum; | |
| 267 | 266 | unsigned char alias_checksum; |
| 268 | 267 | |
| 269 | 268 | if (!unicode) { |
| ... | ... | @@ -317,9 +316,7 @@ |
| 317 | 316 | goto parse_long; |
| 318 | 317 | if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME)) |
| 319 | 318 | continue; |
| 320 | - for (sum = 0, i = 0; i < 11; i++) | |
| 321 | - sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i]; | |
| 322 | - if (sum != alias_checksum) | |
| 319 | + if (fat_checksum(de->name) != alias_checksum) | |
| 323 | 320 | nr_slots = 0; |
| 324 | 321 | } |
| 325 | 322 | |
| ... | ... | @@ -479,7 +476,6 @@ |
| 479 | 476 | unsigned char id; |
| 480 | 477 | unsigned char slot; |
| 481 | 478 | unsigned char slots; |
| 482 | - unsigned char sum; | |
| 483 | 479 | unsigned char alias_checksum; |
| 484 | 480 | |
| 485 | 481 | if (!unicode) { |
| ... | ... | @@ -534,9 +530,7 @@ |
| 534 | 530 | goto ParseLong; |
| 535 | 531 | if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME)) |
| 536 | 532 | goto RecEnd; |
| 537 | - for (sum = 0, i = 0; i < 11; i++) | |
| 538 | - sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i]; | |
| 539 | - if (sum != alias_checksum) | |
| 533 | + if (fat_checksum(de->name) != alias_checksum) | |
| 540 | 534 | long_slots = 0; |
| 541 | 535 | } |
| 542 | 536 |
fs/vfat/namei.c
| ... | ... | @@ -621,8 +621,7 @@ |
| 621 | 621 | } |
| 622 | 622 | |
| 623 | 623 | /* build the entry of long file name */ |
| 624 | - for (cksum = i = 0; i < 11; i++) | |
| 625 | - cksum = (((cksum&1)<<7)|((cksum&0xfe)>>1)) + msdos_name[i]; | |
| 624 | + cksum = fat_checksum(msdos_name); | |
| 626 | 625 | |
| 627 | 626 | *nr_slots = usize / 13; |
| 628 | 627 | for (ps = slots, i = *nr_slots; i > 0; i--, ps++) { |
include/linux/msdos_fs.h
| ... | ... | @@ -282,6 +282,17 @@ |
| 282 | 282 | MSDOS_I(inode)->i_attrs; |
| 283 | 283 | } |
| 284 | 284 | |
| 285 | +static inline unsigned char fat_checksum(const __u8 *name) | |
| 286 | +{ | |
| 287 | + unsigned char s = name[0]; | |
| 288 | + s = (s<<7) + (s>>1) + name[1]; s = (s<<7) + (s>>1) + name[2]; | |
| 289 | + s = (s<<7) + (s>>1) + name[3]; s = (s<<7) + (s>>1) + name[4]; | |
| 290 | + s = (s<<7) + (s>>1) + name[5]; s = (s<<7) + (s>>1) + name[6]; | |
| 291 | + s = (s<<7) + (s>>1) + name[7]; s = (s<<7) + (s>>1) + name[8]; | |
| 292 | + s = (s<<7) + (s>>1) + name[9]; s = (s<<7) + (s>>1) + name[10]; | |
| 293 | + return s; | |
| 294 | +} | |
| 295 | + | |
| 285 | 296 | static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus) |
| 286 | 297 | { |
| 287 | 298 | return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus |