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Bug 150162

Summary:	msync(..., ..., MS_SYNC) returning before data written to disk
Product:	Red Hat Enterprise Linux 2.1	Reporter:	Jim Paradis <jparadis>
Component:	kernel	Assignee:	Jim Paradis <jparadis>
Status:	CLOSED ERRATA	QA Contact:	Brian Brock <bbrock>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	2.1	CC:	peterm, riel
Target Milestone:	---
Target Release:	---
Hardware:	i386
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2005-04-28 15:05:55 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Jim Paradis 2005-03-03 04:10:52 UTC

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]

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

How reproducible:
Always

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.

Comment 1 Jim Paradis 2005-03-03 04:11:36 UTC

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).

Comment 2 John Flanagan 2005-04-28 15:05:55 UTC

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.

http://rhn.redhat.com/errata/RHSA-2005-283.html