linux-kernel - [PATCH] UTC timestamp option for FAT filesystems

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Message-ID: <4861D685.4070308@skyrush.com>
Date:	Tue, 24 Jun 2008 23:24:21 -0600
From:	Joe Peterson <joe@...rush.com>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH] UTC timestamp option for FAT filesystems

(This patch is based on one submitted last year by Paul Collins, but it
is updated to work with current source, and it uses a different option
name.)

Attached is a patch to provide a new mount option ("utc") for DOS
(vfat/msdos) filesystems, allowing timestamps to be in universal
coordinated time (UTC) rather than local time in applications where
doing this is advantageous.

Since DOS filesystems do not contain time zone information, and
timestamps are typically in local time, a file written in one time
zone will be wrong when read in a different time zone.  When interacting
with filesystems written or read in Windows, using local time is
often necessary, but there are other situations in which the
problems with using local time can be avoided.

Many digital cameras and other portable devices use vfat, and when
traveling across time zones it is inconvenient and confusing to
change the clock setting, but downloading files to a computer in
a different time zone will result in erroneous timestamps.  Also,
it is often necessary to remember to manually change the clock at
daylight saving time changes.  Forgetting to do this also results
in incorrect timestamps.

Setting the clock to UTC is an obvious solution, eliminating
these issues, but Linux is currently hard-coded to always offset the
timestamps by sys_tz.tz_minuteswest in order to interpret them as
local time only.  The new mount option removed this limitation.

						-Joe

View attachment "utc-timestamp-option-for-fat-filesystems.patch" of type "text/x-patch" (7511 bytes)