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Commit 451cbaa1 authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Linus Torvalds
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[PATCH] fat: cleanup and optimization of checksum 



Signed-off-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4e57b681

fs/fat/dir.c

+2 −8
Original line number Diff line number Diff line
@@ -263,7 +263,6 @@ int fat_search_long(struct inode *inode, const unsigned char *name, 
			unsigned char id;

			unsigned char slot;

			unsigned char slots;

			unsigned char sum;

			unsigned char alias_checksum;



			if (!unicode) {
@@ -317,9 +316,7 @@ int fat_search_long(struct inode *inode, const unsigned char *name, 
				goto parse_long;

			if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))

				continue;

			for (sum = 0, i = 0; i < 11; i++)

				sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];

			if (sum != alias_checksum)

			if (fat_checksum(de->name) != alias_checksum)

				nr_slots = 0;

		}
@@ -479,7 +476,6 @@ static int fat_readdirx(struct inode *inode, struct file *filp, void *dirent, 
		unsigned char id;

		unsigned char slot;

		unsigned char slots;

		unsigned char sum;

		unsigned char alias_checksum;



		if (!unicode) {
@@ -534,9 +530,7 @@ static int fat_readdirx(struct inode *inode, struct file *filp, void *dirent, 
			goto ParseLong;

		if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))

			goto RecEnd;

		for (sum = 0, i = 0; i < 11; i++)

			sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];

		if (sum != alias_checksum)

		if (fat_checksum(de->name) != alias_checksum)

			long_slots = 0;

	}

fs/vfat/namei.c

+1 −2
Original line number Diff line number Diff line
@@ -621,8 +621,7 @@ static int vfat_build_slots(struct inode *dir, const unsigned char *name, 
	}



	/* build the entry of long file name */

	for (cksum = i = 0; i < 11; i++)

		cksum = (((cksum&1)<<7)|((cksum&0xfe)>>1)) + msdos_name[i];

	cksum = fat_checksum(msdos_name);



	*nr_slots = usize / 13;

	for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {

include/linux/msdos_fs.h

+11 −0
Original line number Diff line number Diff line
@@ -282,6 +282,17 @@ static inline u8 fat_attr(struct inode *inode) 
		MSDOS_I(inode)->i_attrs;

}



static inline unsigned char fat_checksum(const __u8 *name)

{

	unsigned char s = name[0];

	s = (s<<7) + (s>>1) + name[1];	s = (s<<7) + (s>>1) + name[2];

	s = (s<<7) + (s>>1) + name[3];	s = (s<<7) + (s>>1) + name[4];

	s = (s<<7) + (s>>1) + name[5];	s = (s<<7) + (s>>1) + name[6];

	s = (s<<7) + (s>>1) + name[7];	s = (s<<7) + (s>>1) + name[8];

	s = (s<<7) + (s>>1) + name[9];	s = (s<<7) + (s>>1) + name[10];

	return s;

}



static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus)

{

	return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus