Bug 689551
| Summary: | cfq-iosched: Fix a potential crash upon frequent group weight change | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Vivek Goyal <vgoyal> |
| Component: | kernel | Assignee: | Vivek Goyal <vgoyal> |
| Status: | CLOSED ERRATA | QA Contact: | Red Hat Kernel QE team <kernel-qe> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 6.1 | ||
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | kernel-2.6.32-130.el6 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-05-19 12:35:58 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: | |||
This request was evaluated by Red Hat Product Management for inclusion in the current release of Red Hat Enterprise Linux. Because the affected component is not scheduled to be updated in the current release, Red Hat is unfortunately unable to address this request at this time. Red Hat invites you to ask your support representative to propose this request, if appropriate and relevant, in the next release of Red Hat Enterprise Linux. If you would like it considered as an exception in the current release, please ask your support representative. This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release. Patch(es) available on kernel-2.6.32-130.el6 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-2011-0542.html |
Description of problem: It was reported that CFQ has the potential to crash if group weights are changed frequently. It can happen because if weights are changed, they are directly updated in a group (which group is on service tree), leaving the the service tree in an inconsistent state once group is removed from tree. Fix it by incorporating the weight changes only at certain points like queuing the group where it is safe to do so. Backport from commit from Jens's tree. commit 8184f93eced1e304721c2a55c00d87d5a14f8907 Author: Justin TerAvest <teravest> Date: Thu Mar 17 16:12:36 2011 +0100 cfq-iosched: Don't update group weights when on service tree Version 3 is updated to apply to for-2.6.39/core. For version 2, I took Vivek's advice and made sure we update the group weight from cfq_group_service_tree_add(). If a weight was updated while a group is on the service tree, the calculation for the total weight of the service tree can be adjusted improperly, which either leads to bad service tree weights, or potentially crashes (if total_weight becomes 0). This patch defers updates to the weight until a group is off the service tree. Signed-off-by: Justin TerAvest <teravest> Acked-by: Vivek Goyal <vgoyal> Signed-off-by: Jens Axboe <jaxboe> Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: