From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 38642] New: ext4 timestamp format unable to uniquely represent
times
Date: Fri, 1 Jul 2011 15:05:38 GMT
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https://bugzilla.kernel.org/show_bug.cgi?id=38642
Summary: ext4 timestamp format unable to uniquely represent
times
Product: File System
Version: 2.5
Kernel Version: all
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext4
AssignedTo: fs_ext4@kernel-bugs.osdl.org
ReportedBy: ersmith.nospam@totalspectrum.ca
Regression: No
The presence of the extra bits in the ext4 timestamps implies a desire to
represent file times to sub-second accuracy. Unfortunately, standard posix
timestamps are not uniformly 1 SI second long, due to the presence of leap
seconds. For example, the Posix timestamp 1230768000 corresponds to the UTC
times "2008-12-31 23:59:60" and "2009-01-01 00:00:00".
Since there are only 30 bits in the nanosecond field, ext4 cannot accurately
keep track of file times during a leap second.
One possible solution would be to add another bit to the nanosecond field,
allowing nanoseconds to range from 0 to 1999999999 and hence allowing
sufficient range to keep accurate time even during "long" posix timestamps.
Another would be to specify that the seconds fields of ext4 time stamps should
hold actual SI seconds elapsed, rather than POSIX timestamps; this would be
considerably more complicated, though.
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