[LU-17463] enable/disable page cache shrinker for mlocked pages on OSC layer

• Type: Bug
• Resolution: Unresolved
• Priority: Minor
• Severity: 3
• Assignee: Qian Yingjin
• Reporter: Qian Yingjin

Description

Those pages mapped into VM_LOCKED [mlock()ed] VMAs should be unevictable pages:
i.e. mlocked pages via mlock() or mlockall() (see the URL for details: https://www.kernel.org/doc/html/v4.19/vm/unevictable-lru.html).

However, OSC page cache shrinker treats all cached page equally even some of them are unelectable. It may evict the mlocked pages wrongly.

We should disable page cache shrinker to avoid it evicting mlocked pages.

Issue Links

• is related to: LU-18397 mmap reads may not correctly update LDLM extent lock usage
• is related to: LU-18226 sanity: test_600b Error: 'unevict_mb is 99, expected 100'

Comments

[Andreas Dilger]

Patch https://review.whamcloud.com/56637 "LU-18226 tests: allow small margin for unevicted pages" was landed as v2_16_0-RC2-2-gfda0fb235a to address the intermittent failures in test_600a.

[Andreas Dilger]

The new sanity test_600a added by patch https://review.whamcloud.com/53826 "LU-17463 osc: add support for unevictable mlock()ed pages" is failing intermittently with "unevict_mb is 99, expected 100" :
https://testing.whamcloud.com/search?status%5B%5D=FAIL&test_set_script_id=f9516376-32bc-11e0-aaee-52540025f9ae&sub_test_script_id=80fa812e-ebde-494c-9b7a-25ad76267630&start_date=2024-08-21&end_date=2024-09-02&source=sub_tests#redirect

so it looks like the test is a bit flakey and needs to be fixed.

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/53826/
Subject: LU-17463 osc: add support for unevictable mlock()ed pages
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 2a3ec2fea384355901e7888d1e043e82416518cb

[Gerrit Updater]

"Qian Yingjin <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/c/fs/lustre-release/+/55469
Subject: LU-17463 llite: add a tunable parameter for mlocked page checking
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 0232e134b474d137212990fe307858f655358341

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/c/fs/lustre-release/+/53795/
Subject: LU-17463 osc: add option to disable page cache shrinker
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: d90ce0aab10ee8856140720cd71935da6877a5ab