Bug 1369456

Summary: [RFE] libdevmapper: Provide support for deferred device removal cancellation
Product: Red Hat Enterprise Linux 7 Reporter: Vivek Goyal <vgoyal>
Component: lvm2Assignee: LVM and device-mapper development team <lvm-team>
lvm2 sub component: libdevmapper QA Contact: cluster-qe <cluster-qe>
Status: CLOSED CURRENTRELEASE Docs Contact:
Severity: medium    
Priority: unspecified CC: agk, heinzm, jbrassow, msnitzer, prajnoha, zkabelac
Version: 7.3Keywords: FutureFeature
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2020-11-18 18:15:50 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:

Description Vivek Goyal 2016-08-23 13:03:03 UTC 
Description of problem:

Docker can schedule deferred device removal and can cancel the removal later if need be. That is deferred removal can be cancelled before device is actually removed.

libdevmapper removes the symlink to device node when deferred removal is scheduled. But if removal is cancelled, that symlink never reappears. And that means device is no more accessible.

Opening this bug to take care of deferred device removal cancellation case.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:
Comment 1 Peter Rajnoha 2016-08-23 13:17:49 UTC 
For now, this is not documented well, but it's actually:

   dmsetup message <dm_name> 0 "@cancel_deferred_remove"

Works fine if we use DM_UDEV_DISABLE_LIBRARY_FALLBACK flag for DM cookies (passed in as part of dm_task_set_cookie call).

Still needs better device node handling in case we don't rely on udev fully and we still have the fallback code that checks udev enabled. In this case, we need to put the device node back if previous "deferred remove" operation removed the node already (as part of the libdm fallback code).
Comment 4 Alasdair Kergon 2016-08-24 20:50:37 UTC 
It should be a built-in command, just like the removal itself is, and that should revert the /dev node changes in the specific case mentioned.
Comment 8 Zdenek Kabelac 2020-11-18 18:15:50 UTC 
dmsetup support --deferred with version of  1.02.89 
(goes with lvm2 2.02.110)