Red Hat Bugzilla – Bug 145976
Sub-second mtime changes without modifying file
Last modified: 2007-11-30 17:07:15 EST
*** This bug has been split off bug 139884 ***
------- Original comment by Patrick J. LoPresti on 2004.11.18 12:05 -------
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Description of problem:
The 2.6 kernel's buffer cache has sub-second resolution for file
times. The ext3 file system does not. Consequently, the observable
mtime for a file changes unpredictably.
This is causing problems for us while compiling our product, because
"make" relies on file modification times to determine what to compile.
But the bug is easily observed without running make; see the steps below.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. touch /tmp/foo
2. ls -l --full-time /tmp/foo
3. (reboot system)
4. ls -l --full-time /tmp/foo
Actual Results: The visible file modification time changes (gets
rounded down) as a result of the reboot. The rounding down happens
whenever the kernel's buffer cache for the file gets flushed, which on
an active system is essentially random.
Expected Results: The file modification time should not change for a
file which is not modified.
This was discussed on the linux-kernel mailing list back in April, but
as far as I can tell it was never resolved:
And now it is causing a real problem for us. This is clearly a kernel
bug; a file's modification time should not change unless the file is
Created attachment 110123 [details]
Upstream 2.6 patch to implement fs-specific timestamp granularities
*** Bug 155406 has been marked as a duplicate of this bug. ***
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.