[V4,0/4] fat: timestamp updates

Message

Frank Sorenson Sept. 26, 2018, 10:43 p.m. UTC

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.


V4 changes
  corrected to use fat_truncate_time() and keep mark_inode_dirty()
  set s_time_gran to 1ns unconditionally
  add i_version support to update_time()
  fix atime bug with localtime


Frank Sorenson (4):
  fat: create a function to calculate the timezone offest
  fat: add functions to update and truncate timestamps appropriately
  fat: change timestamp updates to use fat_truncate_time
  fat: truncate inode timestamp updates in setattr

 fs/fat/dir.c         |  2 +-
 fs/fat/fat.h         |  2 ++
 fs/fat/file.c        | 17 ++++++++--
 fs/fat/inode.c       |  9 ++++--
 fs/fat/misc.c        | 91 ++++++++++++++++++++++++++++++++++++++++++++++++----
 fs/fat/namei_msdos.c | 17 +++++-----
 fs/fat/namei_vfat.c  | 15 +++++----
 7 files changed, 126 insertions(+), 27 deletions(-)