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Bug 1400491

Summary: rescan-scsi-bus.sh removes devices after their revision changes
Product: Red Hat Enterprise Linux 7 Reporter: Andreas Bleischwitz <ableisch>
Component: sg3_utilsAssignee: Gris Ge <fge>
Status: CLOSED ERRATA QA Contact: zguo <zguo>
Severity: high Docs Contact:
Priority: high    
Version: 7.3CC: ableisch, coughlan, djez, dkutalek, fge, loberman, ovasik
Target Milestone: rcKeywords: Reopened
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: sg3_utils-1.37-14.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2018-10-30 10:54:34 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1420851, 1473612, 1546181    
Attachments:
Description Flags
scsi_debug code with rev change patch none

Description Andreas Bleischwitz 2016-12-01 11:27:30 UTC 
Description of problem:
"rescan-scsi-bus.sh -r" currently removes and re-adds scsi-disk after their SCSI-Revision changed which could render a system unusable.

Version-Release number of selected component (if applicable):
sg3_utils-1.37-5.el7.x86_64

How reproducible:
Always after SCSI-revision change

Steps to Reproduce:
1. Create virtual machine on a host running qemu-2.4 or lower
2. live migrate that machine to a host running qemu-2.5+
3. issue a "rescan-scsi-bus.sh -r" on the quest

Actual results:
System detects a SCSI-revision change and removes the old-disk and re-adds the disk with the updated revision - which renders the system unusable.

Expected results:
System detects SCSI-revision change and issues a "rescan" to reflect any updates or simply ignores the revision change.

Additional info:
The issue is caused by a revision change of a existing SCSI-disk. This also affects disks which may be presented by a storage-system which gets a firmware upgrade - yes this is possible doing online without interruption of the disk.
Comment 4 Andreas Bleischwitz 2017-02-10 09:48:25 UTC 
In case that rescan-scsi-bus.sh with option "-r" can not be changed in the behavior, we should at least remark that this could be a very dangerous action as system-devices could be removed and render the system unusable.

This should be reflected in the output of "--help" and in the manpage at least.

Raised the priority for given reason.
Comment 6 Gris Ge 2017-03-07 14:30:43 UTC 
Hi Andreas Bleischwitz,

Changing "-r" behaviour is too risky, I am intend to:

 1. Add new option like '--ignore-rev-change' to skip remove/readd on disks with
    rev change only.
 2. Mark '-r' option as 'DANGEROUS'.

How's that sounds to you?
Comment 7 Andreas Bleischwitz 2017-03-07 14:33:45 UTC 
Hi Gris,

sounds reasonable. I'm fine with a opt-out for the "-r" parameter and that this will be marked as potentially dangerous.
That way we would not change current behaviour - which may be intentionally remove devices on revision-changes.
/Andreas
Comment 8 Gris Ge 2017-03-10 10:00:09 UTC 
Patch send to upstream for review.

https://github.com/hreinecke/sg3_utils/pull/13

I didn't mark '-r' as dangerous as 'remove' seems already contain dangerous in it.
Comment 9 Gris Ge 2017-03-10 10:20:06 UTC 
Hi Andreas Bleischwitz,

I have no idea how to do a live migrate VM.

Could try these rpms in your system for `sudo rescan-scsi-bus.sh -r --ignore-rev`
command:
    http://people.redhat.com/fge/BZ_1400491/

Thank you very much.
Comment 12 Tom Coughlan 2017-04-27 16:32:21 UTC 
Not accepted upstream yet.
Comment 14 Red Hat Bugzilla Rules Engine 2017-11-03 13:46:56 UTC 
Development Management has reviewed and declined this request. You may appeal this decision by reopening this request.
Comment 19 Gris Ge 2018-04-17 13:08:14 UTC 
Created attachment 1423018 [details]
scsi_debug code with rev change patch

Reproduce steps:

 * Download attached tarball and extract it.
 * cd scsi_debug-el7-bz-1400491 && sudo make
 * sudo insmod scsi_debug.ko
 * To change revision: 
   echo -n '0001' | sudo tee /sys/module/scsi_debug/parameters/inq_rev
 * To check current revision:
   sg_inq /dev/sdb
Comment 22 Gris Ge 2018-06-12 12:32:10 UTC 
`--ignore-rec` option has been added to `rescan-scsi-bus.sh` command.
Comment 27 errata-xmlrpc 2018-10-30 10:54:34 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:3181