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Date: Mon, 1 Jun 2020 21:20:26 +0900
From: "Sungjong Seo" <sj1557.seo@...sung.com>
To: "'Tetsuhiro Kohada'" <kohada.t2@...il.com>
Cc: <kohada.tetsuhiro@...mitsubishielectric.co.jp>,
<mori.takahiro@...mitsubishielectric.co.jp>,
<motai.hirotaka@...mitsubishielectric.co.jp>,
"'Namjae Jeon'" <namjae.jeon@...sung.com>,
<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 4/4 v3] exfat: standardize checksum calculation
> To clarify that it is a 16-bit checksum, the parts related to the 16-bit
> checksum are renamed and change type to u16.
> Furthermore, replace checksum calculation in exfat_load_upcase_table()
> with exfat_calc_checksum32().
>
> Signed-off-by: Tetsuhiro Kohada <kohada.t2@...il.com>
Reviewed-by: Sungjong Seo <sj1557.seo@...sung.com>
> ---
> Changes in v2:
> - rebase with patch 'optimize dir-cache' applied Changes in v3:
> - based on '[PATCH 2/4 v3] exfat: separate the boot sector analysis'
>
> fs/exfat/dir.c | 12 ++++++------
> fs/exfat/exfat_fs.h | 5 ++---
> fs/exfat/misc.c | 10 ++++------
> fs/exfat/nls.c | 19 +++++++------------
> 4 files changed, 19 insertions(+), 27 deletions(-)
>
> diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index
> 2902d285bf20..de43534aa299 100644
> --- a/fs/exfat/dir.c
> +++ b/fs/exfat/dir.c
> @@ -491,7 +491,7 @@ int exfat_update_dir_chksum(struct inode *inode,
> struct exfat_chain *p_dir,
> int ret = 0;
> int i, num_entries;
> sector_t sector;
> - unsigned short chksum;
> + u16 chksum;
> struct exfat_dentry *ep, *fep;
> struct buffer_head *fbh, *bh;
>
> @@ -500,7 +500,7 @@ int exfat_update_dir_chksum(struct inode *inode,
> struct exfat_chain *p_dir,
> return -EIO;
>
> num_entries = fep->dentry.file.num_ext + 1;
> - chksum = exfat_calc_chksum_2byte(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);
> + chksum = exfat_calc_chksum16(fep, DENTRY_SIZE, 0, CS_DIR_ENTRY);
>
> for (i = 1; i < num_entries; i++) {
> ep = exfat_get_dentry(sb, p_dir, entry + i, &bh, NULL); @@ -
> 508,7 +508,7 @@ int exfat_update_dir_chksum(struct inode *inode, struct
> exfat_chain *p_dir,
> ret = -EIO;
> goto release_fbh;
> }
> - chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,
> + chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
> CS_DEFAULT);
> brelse(bh);
> }
> @@ -593,8 +593,8 @@ void exfat_update_dir_chksum_with_entry_set(struct
> exfat_entry_set_cache *es)
>
> for (i = 0; i < es->num_entries; i++) {
> ep = exfat_get_dentry_cached(es, i);
> - chksum = exfat_calc_chksum_2byte(ep, DENTRY_SIZE, chksum,
> - chksum_type);
> + chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
> + chksum_type);
> chksum_type = CS_DEFAULT;
> }
> ep = exfat_get_dentry_cached(es, 0);
> @@ -1000,7 +1000,7 @@ int exfat_find_dir_entry(struct super_block *sb,
> struct exfat_inode_info *ei,
> }
>
> if (entry_type == TYPE_STREAM) {
> - unsigned short name_hash;
> + u16 name_hash;
>
> if (step != DIRENT_STEP_STRM) {
> step = DIRENT_STEP_FILE;
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index
> eebbe5a84b2b..9188985694f0 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -137,7 +137,7 @@ struct exfat_dentry_namebuf { struct exfat_uni_name {
> /* +3 for null and for converting */
> unsigned short name[MAX_NAME_LENGTH + 3];
> - unsigned short name_hash;
> + u16 name_hash;
> unsigned char name_len;
> };
>
> @@ -512,8 +512,7 @@ void exfat_get_entry_time(struct exfat_sb_info *sbi,
> struct timespec64 *ts, void exfat_truncate_atime(struct timespec64 *ts);
> void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64
*ts,
> u8 *tz, __le16 *time, __le16 *date, u8 *time_cs); -unsigned
> short exfat_calc_chksum_2byte(void *data, int len,
> - unsigned short chksum, int type);
> +u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type);
> u32 exfat_calc_chksum32(void *data, int len, u32 chksum, int type); void
> exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync);
> void exfat_chain_set(struct exfat_chain *ec, unsigned int dir, diff --git
> a/fs/exfat/misc.c b/fs/exfat/misc.c index b82d2dd5bd7c..17d41f3d3709
> 100644
> --- a/fs/exfat/misc.c
> +++ b/fs/exfat/misc.c
> @@ -136,17 +136,15 @@ void exfat_truncate_atime(struct timespec64 *ts)
> ts->tv_nsec = 0;
> }
>
> -unsigned short exfat_calc_chksum_2byte(void *data, int len,
> - unsigned short chksum, int type)
> +u16 exfat_calc_chksum16(void *data, int len, u16 chksum, int type)
> {
> int i;
> - unsigned char *c = (unsigned char *)data;
> + u8 *c = (u8 *)data;
>
> for (i = 0; i < len; i++, c++) {
> - if (((i == 2) || (i == 3)) && (type == CS_DIR_ENTRY))
> + if (unlikely(type == CS_DIR_ENTRY && (i == 2 || i == 3)))
> continue;
> - chksum = (((chksum & 1) << 15) | ((chksum & 0xFFFE) >> 1)) +
> - (unsigned short)*c;
> + chksum = ((chksum << 15) | (chksum >> 1)) + *c;
> }
> return chksum;
> }
> diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c index
> 1ebda90cbdd7..19321773dd07 100644
> --- a/fs/exfat/nls.c
> +++ b/fs/exfat/nls.c
> @@ -527,7 +527,7 @@ static int exfat_utf8_to_utf16(struct super_block *sb,
>
> *uniname = '\0';
> p_uniname->name_len = unilen;
> - p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1,
> 0,
> + p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,
> CS_DEFAULT);
>
> if (p_lossy)
> @@ -623,7 +623,7 @@ static int exfat_nls_to_ucs2(struct super_block *sb,
>
> *uniname = '\0';
> p_uniname->name_len = unilen;
> - p_uniname->name_hash = exfat_calc_chksum_2byte(upname, unilen << 1,
> 0,
> + p_uniname->name_hash = exfat_calc_chksum16(upname, unilen << 1, 0,
> CS_DEFAULT);
>
> if (p_lossy)
> @@ -655,7 +655,8 @@ static int exfat_load_upcase_table(struct super_block
> *sb, {
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
> unsigned int sect_size = sb->s_blocksize;
> - unsigned int i, index = 0, checksum = 0;
> + unsigned int i, index = 0;
> + u32 chksum = 0;
> int ret;
> unsigned char skip = false;
> unsigned short *upcase_table;
> @@ -681,13 +682,6 @@ static int exfat_load_upcase_table(struct super_block
> *sb,
> for (i = 0; i < sect_size && index <= 0xFFFF; i += 2) {
> unsigned short uni = get_unaligned_le16(bh->b_data +
> i);
>
> - checksum = ((checksum & 1) ? 0x80000000 : 0) +
> - (checksum >> 1) +
> - *(((unsigned char *)bh->b_data) + i);
> - checksum = ((checksum & 1) ? 0x80000000 : 0) +
> - (checksum >> 1) +
> - *(((unsigned char *)bh->b_data) + (i + 1));
> -
> if (skip) {
> index += uni;
> skip = false;
> @@ -701,13 +695,14 @@ static int exfat_load_upcase_table(struct
> super_block *sb,
> }
> }
> brelse(bh);
> + chksum = exfat_calc_chksum32(bh->b_data, i, chksum,
> CS_DEFAULT);
> }
>
> - if (index >= 0xFFFF && utbl_checksum == checksum)
> + if (index >= 0xFFFF && utbl_checksum == chksum)
> return 0;
>
> exfat_err(sb, "failed to load upcase table (idx : 0x%08x, chksum :
> 0x%08x, utbl_chksum : 0x%08x)",
> - index, checksum, utbl_checksum);
> + index, chksum, utbl_checksum);
> ret = -EINVAL;
> free_table:
> exfat_free_upcase_table(sbi);
> --
> 2.25.1
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