Note: This bug is displayed in read-only format because the product is no longer active in Red Hat Bugzilla.

RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

Description of problem:

See https://github.com/rear/rear/pull/2034

When a system has many multipath devices (547 disks, 272 x 2 paths), creating the ReaR rescue takes several hours. This is due to:

* the `get_device_name()` function to scan all multipath devices multiple times without caching the information (legacy code, when kernel has no `/sys/block/<dev>/dm/name` node)
* the `get_device_name()` function to scan the multipath devices even if there is no need for that
* the collect of unused `/sys/class/fc_transport` information


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

rear-2.00 and rear-2.4.2


How reproducible:

Always with tons of multipath devices


Actual results:

ReaR rescue takes several hours


Expected results:

ReaR rescue takes a couple of minutes

Is there a way to reproduce without multipath devices? Would the problem show up with hundreds of non-multipath disks? I suppose that the fact that multipath devices use device-mapper is the key. Would another device-mapper type trigger the problem (e.g. if one had hundreds of logical volumes instead)?

AFAICT, the issue will show up only on kernels which do not have /sys/block/<dev>/dm/name. How old must the kernel be for that?

> AFAICT, the issue will show up only on kernels which do not have /sys/block/<dev>/dm/name. How old must the kernel be for that?

No, the current code is broken and as soon as the raw device (e.g. "/dev/sda") has to be resolved through get_device_name(), the code goes through scanning all multipath devices, because /dev/sda is no device mapper.

this will need a RHEL 8 clone, right? Otherwise we will have a regression in 8 compared to 7.y.z.

indeed

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-2019:2273