Re: [PATCH] fat/vfat: optionally ignore system timezone offset when reading/writingtimestamps

From: Hiroyuki Machida
Date: Mon Mar 26 2007 - 00:20:30 EST

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HI OGAWA-san and Paul-san,

Sorry late response,

I'm not famillar with recent fat code, but code itself looks good for
just turn on/off time adjusting. On the other hand, I feel we need more
consideration on use cases/requirements. I feel that turning off
time adjustment is a just ad-hoc solution to issues like Paul san
brought up.

Thanks,
Hiroyuki

OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> wrote on 2007/03/19 23:31:06:
> 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->cd
> ate);
> > - 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->cd
> ate,
> > + 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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Next message: Nicolas Boichat: "Re: [BUG] Patch "CPU hotplug: call check_tsc_sync_source() with irqsoff" breaks some drivers"
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Next in thread: OGAWA Hirofumi: "Re: [PATCH] fat/vfat: optionally ignore system timezone offset when reading/writing timestamps"
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