[LU-20] patchless server kernel

• Type: Improvement
• Resolution: Fixed
• Priority: Critical
• Affects Version/s: Lustre 2.4.0
• Labels: cea llnl
• Bugzilla ID: 21,524
• Assignee: Oleg Drokin
• Reporter: nasf (Inactive)

Description

Remove Lustre kernel patches to allow Lustre servers to be more easily ported to new kernels, and to be built against vendor kernels without changing the vendor kernel RPMs. There are a number of different patches, each one needs to use equivalent functionality which already exists in the kernel, or work to get the patch accepted upstream.

Corresponding to bugzilla link:
https://bugzilla.lustre.org/show_bug.cgi?id=21524

Issue Links

• is blocked by: LU-8685 Fix JBD2 issue in EL7 Kernels
• is blocking: LU-9761 Add ldiskfs support to dkms for patchless kernel
• is related to: LU-8729 conf-sanity test_84: FAIL: /dev/mapper/mds1_flakey failed to initialize!
• is related to: LU-9339 fix RHEL 7.2 project quota build error
• is related to: LU-2442 metadata performance degradation on current master
• is related to: LU-9698 osd-ldiskfs: unknown symbol error on patched kernel
• is related to: LU-7643 Remove kernel version string from Lustre release field
• is related to: LU-2473 ldiskfs RHEL6.4 support
• is related to: LU-9111 update osd-ldiskfs to not depend on dev_readonly patches
• is related to: LUDOC-83 Patchless Server Doc Changes
• is related to: LU-3406 Submit raid5-mmp-unplug-dev patch upstream
• is related to: LU-433 remove jbd2-jcberr patch from kernel

Comments

[Andreas Dilger]

All of the kernels can run patchless now, and our testing has moved over to dm-flakey so the dev_readonly patches are no longer needed (and have been removed from 4.x kernels).

[Peter Jones]

I don't think that we can fully close out this ticket until servers only run on distros with kernels that include the project quotas patches. However, the option remains for those who prefer to use patchless servers rather than project quotas.

[Bob Glossman (Inactive)]

James,
Even if not technically supported there's still a lot of el6 of various vintages out in the field. If we break it I'm sure we will be making a lot of our users unhappy. I don't think we should.

[James A Simmons]

Technically rhel6 server side is no longer supported. Testing of rhel6 server should have been stopped by now.

[Bob Glossman (Inactive)]

The recent landing of 'LU-20 osd-ldiskfs: Make readonly patches optional', https://review.whamcloud.com/27549 has broken lustre on el6. This mod added calls to kallsyms_lookup_name(), a kernel API not previously used. On el6 this API isn't globally visible to kernel modules, it has no EXPORT() statement. This leads to install time errors like:

WARNING: /lib/modules/2.6.32-696.3.2.el6_lustre.x86_64/extra/lustre-osd-ldiskfs/fs/osd_ldiskfs.ko needs unknown symbol kallsyms_lookup_name
WARNING: /lib/modules/2.6.32-696.3.1.el6_lustre.x86_64/weak-updates/lustre-osd-ldiskfs/fs/osd_ldiskfs.ko needs unknown symbol kallsyms_lookup_name
WARNING: /lib/modules/2.6.32-696.3.2.el6_lustre.x86_64/extra/lustre-osd-ldiskfs/fs/osd_ldiskfs.ko needs unknown symbol kallsyms_lookup_name
WARNING: /lib/modules/2.6.32-696.3.2.el6.x86_64/weak-updates/lustre-osd-ldiskfs/fs/osd_ldiskfs.ko needs unknown symbol kallsyms_lookup_name

and runtime errors like:

osd_ldiskfs: Unknown symbol kallsyms_lookup_name (err 0)
LustreError: 158-c: Can't load module 'osd-ldiskfs'

This flaw blocks any use of ldiskfs on el6
It's a pretty serious regression.

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/27549/
Subject: LU-20 osd-ldiskfs: Make readonly patches optional
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 0f0a43b4ba6660a88f7922aadaba1a69c297142c

[Gerrit Updater]

Oleg Drokin ([e-mail]) uploaded a new patch: https://review.whamcloud.com/27549
Subject: LU-20 osd-ldiskfs: Make readonly patches optional
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: aface21135cc936be2cf72fc2e092a4784fbecc0

[Andreas Dilger]

All of the recovery-* tests depend on this functionality to some extent, to allow clients to submit writes to the server that are dropped deterministically before the server restarts.

Note there is no reason that the presence of the dev-rdonly patch in our kernel prevents people from building patchless kernels. We need that for the testing ldiskfs, but it is not needed for production with either ldiskfs or ZFS. Note that if you want project quota support for ldiskfs then kernel patches are needed regardless (project quota for ZFS will similarly need ZFS to be patched).

[Christopher Morrone (Inactive)]

How many tests actually use the dev_rdonly/dm-flakey functionality?

If it is small, perhaps the best path forward is to simply disable those tests until LU-684 is complete. That would allow us to unblock this ticket, LU-20.

[Minh Diep]

yup, just found that out too. Thanks. this is great news!