From: Frank Sorenson <sorenson@xxxxxxxxxx> Subject: fat: create a function to calculate the timezone offest 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@xxxxxxxxxx Signed-off-by: Frank Sorenson <sorenson@xxxxxxxxxx> Acked-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/fat/misc.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) --- a/fs/fat/misc.c~fat-create-a-function-to-calculate-the-timezone-offest +++ a/fs/fat/misc.c @@ -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_i + 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_i __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) { _
