Bug 641258

Summary: fix split_huge_page error like mapcount 3 page_mapcount 2 [rhel-6.0.z]
Product: Red Hat Enterprise Linux 6 Reporter: RHEL Program Management <pm-rhel>
Component: kernelAssignee: Frantisek Hrbata <fhrbata>
Status: CLOSED ERRATA QA Contact: Zhang Kexin <kzhang>
Severity: urgent Docs Contact:
Priority: urgent    
Version: 6.0CC: aarcange, dhoward, jpirko, kzhang, mjenner, pm-eus, qcai, syeghiay, tburke, wenliu
Target Milestone: rcKeywords: ZStream
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: kernel-2.6.32-71.4.1.el6 Doc Type: Bug Fix
Doc Text:
The fork() system call led to an rmap walk finding the parent huge-pmd twice instead of once, thus causing a discrepancy between the mapcount and page_mapcount check, which could have led to erratic page counts for subpages. This fix ensures that that the rmap walk is accurate when a process is forked, thus resolving the issue.
Story Points: ---
Clone Of: Environment:
Last Closed: 2010-11-10 19:10:47 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On: 640611    
Bug Blocks:    

Description RHEL Program Management 2010-10-08 07:44:55 UTC
This bug has been copied from bug #640611 and has been proposed
to be backported to 6.0 z-stream (EUS).

Comment 2 Frantisek Hrbata 2010-10-12 18:53:23 UTC
in kernel-2.6.32-71.4.1.el6

Comment 7 errata-xmlrpc 2010-11-10 19:10:47 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 therefore 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-2010-0842.html

Comment 8 Martin Prpič 2010-11-11 11:56:40 UTC
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
The fork() system call led to an rmap walk finding the parent huge-pmd twice instead of once, thus causing a discrepancy between the mapcount and page_mapcount check, which could have led to erratic page counts for subpages. This fix ensures that that the rmap walk is accurate when a process is forked, thus resolving the issue.