Red Hat Bugzilla – Bug 150162
msync(..., ..., MS_SYNC) returning before data written to disk
Last modified: 2013-08-05 21:12:52 EDT
This bug is to track the RHEL2.1 variant of Bug 147969.
From that bug report:
Description of problem:
Calling msync(p, size, MS_SYNC) on a memory mapped file is not waiting for the
data to be flushed to disk [eg a 128Mb chunk of data is claiming to be flushed
in 1-2ms : cf 2.4.21-15 / 2.6.8-1.521 where the same test code takes 2-3s to do
This means that there is no way for code to know that the data it has just
written to a memory mapped file has actually made it to disk.
Version-Release number of selected component (if applicable):
kernel-2.4.21-20.EL and kernel-2.4.21-27.0.2.EL
Steps to Reproduce:
1.mmap a (large-ish) file
2.write some data into the memory region
3.call msync with the MS_SYNC option
4.reboot the PC by hitting the power switch once msync has completed... [or time
how long it takes to sync the data]
5.look at the contents of the file
Actual Results: Data missing from file on disk (was present in file (ie disk
buffers) prior to hitting power)
Expected Results: msync should wait for the data to be written to disk when the
MS_SYNC flag is used.
A fix for this problem has just been committed to the RHEL2.1 U7
patch pool this evening (in kernel version 2.4.9-61).
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.