linux-ext4 - [PATCH] ext4: fix extra time handling for >32bit timestamps

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Message-ID: <CANghDUV1xUMkcTcKUs9eu6PuwaG-WRtMVFM9vosPWaHV-Fo68A@mail.gmail.com>
Date:	Mon, 1 Aug 2011 13:37:28 -0400
From:	David Jeffery <dhjeffery@...il.com>
To:	linux-ext4@...r.kernel.org
Subject: [PATCH] ext4: fix extra time handling for >32bit timestamps

On 64bit systems, using ext4 to store inode times for after the 32bit
time rollover doesn't work as expected.  Setting a date with a time
too big for 32bits can still result in time wrapping around when read
back from disk.  This is do to the sign extension performed in
EXT4_INODE_GET_XTIME().  The sign extension causes any time with
the 32nd bit set to be sign extended and have a time before 1970.

For the case where there isn't any extra time storage area, this patch
leaves the sign extension as is.  In the event there is the >32 bit
time bits in the inode, the ext4_decode_extra_time() is patched to
clear the upper 32 time bits, set the extra time bits, and perform a
sign extension if needed.

The patch also alters ext4_encode_extra_time() for 32bit systems.
Previously, the extra time bits were never set on 32bit system.  The
patch now sets them so that times will remain the same when migrating
an ext4 filesystem from a 32bit system to a 64bit system.

Signed-off-by: David Jeffery <dhjeffery@...il.com>
---
diffstat ext4_extra_time_fix.patch
ext4.h |   13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

Download attachment "ext4_extra_time_fix.patch" of type "application/octet-stream" (1211 bytes)