fat: create a function to calculate the timezone offest (d9f4d942) · Commits · 戴 / test

Patch series "fat: timestamp updates", v5. fat/msdos timestamps are stored on-disk with several different granularities, some of them lower resolution than timespec64_trunc() can provide. In addition, they are only truncated as they are written to disk, so the timestamps in-memory for new or modified files/directories may be different from the same timestamps after a remount, as the now-truncated times are re-read from the on-disk format. These patches allow finer granularity for the timestamps where possible and add fat-specific ->update_time inode operation and fat_truncate_time functions to truncate each timestamp correctly, giving consistent times across remounts. This patch (of 4): Move the calculation of the number of seconds in the timezone offset to a common function. Link: http://lkml.kernel.org/r/3671ff8cff5eeedbb85ebda5e4de0728920db4f6.1538363961.git.sorenson@redhat.com Signed-off-by:

Frank Sorenson <sorenson@redhat.com> Acked-by:

OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/fat/misc.c

+9 −7

Original line number	Diff line number	Diff line
		@@ -185,6 +185,13 @@ static long days_in_year[] = {
		0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
		};

		static inline int fat_tz_offset(struct msdos_sb_info *sbi)
		{
		return (sbi->options.tz_set ?
		-sbi->options.time_offset :
		sys_tz.tz_minuteswest) * SECS_PER_MIN;
		}

		/* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
		void fat_time_fat2unix(struct msdos_sb_info sbi, struct timespec64 ts,
		__le16 __time, __le16 __date, u8 time_cs)
		@@ -210,10 +217,7 @@ void fat_time_fat2unix(struct msdos_sb_info sbi, struct timespec64 ts,
		+ days_in_year[month] + day
		+ DAYS_DELTA) * SECS_PER_DAY;

		if (!sbi->options.tz_set)
		second += sys_tz.tz_minuteswest * SECS_PER_MIN;
		else
		second -= sbi->options.time_offset * SECS_PER_MIN;
		second += fat_tz_offset(sbi);

		if (time_cs) {
		ts->tv_sec = second + (time_cs / 100);
		@@ -229,9 +233,7 @@ void fat_time_unix2fat(struct msdos_sb_info sbi, struct timespec64 ts,
		__le16 time, __le16 date, u8 *time_cs)
		{
		struct tm tm;
		time64_to_tm(ts->tv_sec,
		(sbi->options.tz_set ? sbi->options.time_offset :
		-sys_tz.tz_minuteswest) * SECS_PER_MIN, &tm);
		time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);

		/* FAT can only support year between 1980 to 2107 */
		if (tm.tm_year < 1980 - 1900) {

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