Re: [PATCH] fat/vfat: optionally ignore system timezone offset when reading/writing timestamps
From: OGAWA Hirofumi
Date: Mon Mar 19 2007 - 10:31:32 EST
Paul Collins <paul@xxxxxxxxxxxxxxxxxxx> writes:
> Hello,
Hello,
> Here is a patch that adds a mount option named "posixtime" that, when
> enabled, causes the fat/vfat code to not adjust timestamps as they are
> read/written to/from disk. The intent of the adjustment as performed
> by the existing code appears to be to present correct timestamps to
> Windows and friends, which treat the timestamp values as local time.
>
> However, the systems that I use to update my FAT32 filesystems are all
> running Linux, and as such will process POSIX timestamps correctly.
> (The filesystems are on disks in digital audio players, which do not
> process timestamps except to check if they have changed.) Due to the
> aforementioned adjustment on read/write, after a Daylight Savings
> transition I must update the file timestamps on the filesystems so
> that rsync does not needlessly re-copy files.
>
> Please review and consider applying this patch.
Thanks. Looks good to me as start. IIRC, Machida-san did this few
years ago. Machida-san, do you have any comment?
> diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> index c16af24..d6c0a7f 100644
> --- a/fs/fat/dir.c
> +++ b/fs/fat/dir.c
> @@ -1064,7 +1064,7 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
> goto error_free;
> }
>
> - fat_date_unix2dos(ts->tv_sec, &time, &date);
> + fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.adjust);
>
> de = (struct msdos_dir_entry *)bhs[0]->b_data;
> /* filling the new directory slots ("." and ".." entries) */
> diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> index a9e4688..02d9225 100644
> --- a/fs/fat/inode.c
> +++ b/fs/fat/inode.c
> @@ -374,17 +374,20 @@ static int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
> inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
> & ~((loff_t)sbi->cluster_size - 1)) >> 9;
> inode->i_mtime.tv_sec =
> - date_dos2unix(le16_to_cpu(de->time), le16_to_cpu(de->date));
> + date_dos2unix(le16_to_cpu(de->time), le16_to_cpu(de->date),
> + sbi->options.adjust);
> inode->i_mtime.tv_nsec = 0;
> if (sbi->options.isvfat) {
> int secs = de->ctime_cs / 100;
> int csecs = de->ctime_cs % 100;
> inode->i_ctime.tv_sec =
> date_dos2unix(le16_to_cpu(de->ctime),
> - le16_to_cpu(de->cdate)) + secs;
> + le16_to_cpu(de->cdate),
> + sbi->options.adjust) + secs;
> inode->i_ctime.tv_nsec = csecs * 10000000;
> inode->i_atime.tv_sec =
> - date_dos2unix(0, le16_to_cpu(de->adate));
> + date_dos2unix(0, le16_to_cpu(de->adate),
> + sbi->options.adjust);
> inode->i_atime.tv_nsec = 0;
> } else
> inode->i_ctime = inode->i_atime = inode->i_mtime;
> @@ -592,11 +595,14 @@ retry:
> raw_entry->attr = fat_attr(inode);
> raw_entry->start = cpu_to_le16(MSDOS_I(inode)->i_logstart);
> raw_entry->starthi = cpu_to_le16(MSDOS_I(inode)->i_logstart >> 16);
> - fat_date_unix2dos(inode->i_mtime.tv_sec, &raw_entry->time, &raw_entry->date);
> + fat_date_unix2dos(inode->i_mtime.tv_sec, &raw_entry->time, &raw_entry->date,
> + sbi->options.adjust);
> if (sbi->options.isvfat) {
> __le16 atime;
> - fat_date_unix2dos(inode->i_ctime.tv_sec,&raw_entry->ctime,&raw_entry->cdate);
> - fat_date_unix2dos(inode->i_atime.tv_sec,&atime,&raw_entry->adate);
> + fat_date_unix2dos(inode->i_ctime.tv_sec,&raw_entry->ctime,&raw_entry->cdate,
> + sbi->options.adjust);
> + fat_date_unix2dos(inode->i_atime.tv_sec,&atime,&raw_entry->adate,
> + sbi->options.adjust);
> raw_entry->ctime_cs = (inode->i_ctime.tv_sec & 1) * 100 +
> inode->i_ctime.tv_nsec / 10000000;
> }
> @@ -854,7 +860,7 @@ enum {
> Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
> Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
> Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
> - Opt_obsolate, Opt_flush, Opt_err,
> + Opt_obsolate, Opt_flush, Opt_posixtime, Opt_err,
> };
>
> static match_table_t fat_tokens = {
> @@ -887,6 +893,7 @@ static match_table_t fat_tokens = {
> {Opt_obsolate, "cvf_options=%100s"},
> {Opt_obsolate, "posix"},
> {Opt_flush, "flush"},
> + {Opt_posixtime, "posixtime"},
> {Opt_err, NULL},
> };
> static match_table_t msdos_tokens = {
> @@ -950,6 +957,7 @@ static int parse_options(char *options, int is_vfat, int silent, int *debug,
> opts->utf8 = opts->unicode_xlate = 0;
> opts->numtail = 1;
> opts->nocase = 0;
> + opts->adjust = 1;
> *debug = 0;
>
> if (!options)
> @@ -1032,6 +1040,10 @@ static int parse_options(char *options, int is_vfat, int silent, int *debug,
> opts->flush = 1;
> break;
>
> + case Opt_posixtime:
> + opts->adjust = 0;
> + break;
> +
> /* msdos specific */
> case Opt_dots:
> opts->dotsOK = 1;
> diff --git a/fs/fat/misc.c b/fs/fat/misc.c
> index 308f2b6..72a1a29 100644
> --- a/fs/fat/misc.c
> +++ b/fs/fat/misc.c
> @@ -143,7 +143,7 @@ static int day_n[] = {
> };
>
> /* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
> -int date_dos2unix(unsigned short time, unsigned short date)
> +int date_dos2unix(unsigned short time, unsigned short date, int adjust)
> {
> int month, year, secs;
>
> @@ -157,16 +157,18 @@ int date_dos2unix(unsigned short time, unsigned short date)
> ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
> month < 2 ? 1 : 0)+3653);
> /* days since 1.1.70 plus 80's leap day */
> - secs += sys_tz.tz_minuteswest*60;
> + if (adjust)
> + secs += sys_tz.tz_minuteswest*60;
> return secs;
> }
>
> /* Convert linear UNIX date to a MS-DOS time/date pair. */
> -void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date)
> +void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date, int adjust)
> {
> int day, year, nl_day, month;
>
> - unix_date -= sys_tz.tz_minuteswest*60;
> + if (adjust)
> + unix_date -= sys_tz.tz_minuteswest*60;
>
> /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
> if (unix_date < 315532800)
> diff --git a/fs/vfat/namei.c b/fs/vfat/namei.c
> index 0afd745..7e5487b 100644
> --- a/fs/vfat/namei.c
> +++ b/fs/vfat/namei.c
> @@ -626,7 +626,7 @@ shortname:
> memcpy(de->name, msdos_name, MSDOS_NAME);
> de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
> de->lcase = lcase;
> - fat_date_unix2dos(ts->tv_sec, &time, &date);
> + fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.adjust);
> de->time = de->ctime = time;
> de->date = de->cdate = de->adate = date;
> de->ctime_cs = 0;
> diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
> index 24a9ef1..b3eeec8 100644
> --- a/include/linux/msdos_fs.h
> +++ b/include/linux/msdos_fs.h
> @@ -205,7 +205,8 @@ struct fat_mount_options {
> numtail:1, /* Does first alias have a numeric '~1' type tail? */
> atari:1, /* Use Atari GEMDOS variation of MS-DOS fs */
> flush:1, /* write things quickly */
> - nocase:1; /* Does this need case conversion? 0=need case conversion*/
> + nocase:1, /* Does this need case conversion? 0=need case conversion*/
> + adjust:1; /* Adjust time and date based on sys_tz?*/
> };
>
> #define FAT_HASH_BITS 8
> @@ -421,8 +422,8 @@ extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
> extern void fat_fs_panic(struct super_block *s, const char *fmt, ...);
> extern void fat_clusters_flush(struct super_block *sb);
> extern int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster);
> -extern int date_dos2unix(unsigned short time, unsigned short date);
> -extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date);
> +extern int date_dos2unix(unsigned short time, unsigned short date, int adjust);
> +extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date, int adjust);
> extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
>
> int fat_cache_init(void);
--
OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
-
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