[LU-15156] Back port upstream patch for rwsem issue

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.15.0
• Assignee: Yang Sheng
• Reporter: Yang Sheng

Description

We need back port patch from upstream to fix some rwsem issue.

From 5c1ec49b60cdb31e51010f8a647f3189b774bddf Mon Sep 17 00:00:00 2001
From: Waiman Long <[e-mail]>
Date: Mon, 20 May 2019 16:59:01 -0400
Subject: [PATCH] locking/rwsem: Remove rwsem_wake() wakeup optimization

After the following commit:

  59aabfc7e959 ("locking/rwsem: Reduce spinlock contention in wakeup after up_read()/up_write()")

the rwsem_wake() forgoes doing a wakeup if the wait_lock cannot be directly
acquired and an optimistic spinning locker is present.  This can help performance
by avoiding spinning on the wait_lock when it is contended.

With the later commit:

  133e89ef5ef3 ("locking/rwsem: Enable lockless waiter wakeup(s)")

the performance advantage of the above optimization diminishes as the average
wait_lock hold time become much shorter.

With a later patch that supports rwsem lock handoff, we can no
longer relies on the fact that the presence of an optimistic spinning
locker will ensure that the lock will be acquired by a task soon and
rwsem_wake() will be called later on to wake up waiters. This can lead
to missed wakeup and application hang.

So the original 59aabfc7e959 commit has to be reverted.

Issue Links

• is related to: LU-10678 LBUG: osd_handler.c:2353:osd_read_lock()) ASSERTION( obj->oo_owner == ((void *)0) ) failed:
• is related to: LU-12508 (llite_mmap.c:71:our_vma()) ASSERTION( !down_write_trylock(&mm->mmap_sem) ) failed when writing in multiple threads

Comments

[Peter Jones]

Landed for 2.15

[Gerrit Updater]

"Oleg Drokin <[e-mail]>" merged in patch https://review.whamcloud.com/45383/
Subject: LU-15156 kernel: back port patch for rwsem issue
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 85362faed8f5ee94ffee1f3f6330beee57ea9284

[Gerrit Updater]

"Yang Sheng <[e-mail]>" uploaded a new patch: https://review.whamcloud.com/45383
Subject: LU-15156 kernel: back port patch for resem issue
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: b4a103d6a6ec09e74654f422a8956ec21f5bbef0