Bug 1369456 - [RFE] libdevmapper: Provide support for deferred device removal cancellation
Summary: [RFE] libdevmapper: Provide support for deferred device removal cancellation
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: lvm2
Version: 7.3
Hardware: Unspecified
OS: Unspecified
unspecified
medium
Target Milestone: rc
: ---
Assignee: LVM and device-mapper development team
QA Contact: cluster-qe@redhat.com
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2016-08-23 13:03 UTC by Vivek Goyal
Modified: 2021-09-03 12:41 UTC (History)
6 users (show)

Fixed In Version:
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Environment:
Last Closed: 2020-11-18 18:15:50 UTC
Target Upstream Version:


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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):


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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)


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