Whamcloud Community JIRA https://jira.whamcloud.com This file is an XML representation of an issue en-us 9.4.14 940014 05-12-2023 [LU-12079] lockless IO stucks if client has other lock already https://jira.whamcloud.com/browse/LU-12079 Lustre <p>lockless write IO may stuck if client has other lock on the same page, e.g. PR lock from previous READ or GLIMPSE requests. WRITE IO cause blocking AST from server for that PR lock which tries to discard pages on client and stuck on cl_page_own() forever if that page is involved in lockless WRITE already.</p> <p>At first sign it seems that any lockless write must find and cancel all client locks on write range before IO is started. Though can be not enough because some other concurrent lock can be taken while lockless IO is being issued.</p> LU-12079 lockless IO stucks if client has other lock already Bug Major Resolved Duplicate Patrick Farrell Mikhail Pershin Sun, 17 Mar 2019 09:17:56 +0000 Fri, 9 Jul 2021 20:04:59 +0000 Fri, 9 Jul 2021 20:04:59 +0000 0 2 <p>I have found that while testing lock contention mechanism for DOM, which switches locks to lockless locks, but that is also true for normal files. That can be seen with hard lock contention settings with <tt>ns_contended_locks=0</tt> and <tt>ns_max_nolock_size=some_big_value</tt>. Running <tt>fsx</tt> reveals such bug quite quickly.</p> <p> Interesting that <tt>ns_max_nolock_size</tt> default value is <tt>0</tt>. That means the lockless IO is always turned off in Lustre by default</p> <p>Ahh, I thought lockless i/o was off by default, because I never saw it turn on when working on shared file contention...  It's good to know why.</p> <p>yes, I was thinking that lockless IO is good benefit when there is lock contention on server and client switches to using of server locks temporarily because there is no sense in lock caching and constant ping-pong with lock enqueue - lock cancel. But it is not working at all until ns_contended_locks will be set to some value and even being enabled it is not reliable because of possible deadlocks.</p> <p>Duplicated/resolved by removal in <a href="https://jira.whamcloud.com/browse/LU-14838" title="Remove old lockless code: Truncate &amp; contention based lockless i/o" class="issue-link" data-issue-key="LU-14838"><del>LU-14838</del></a></p> Related LU-11435 Development Rank 1|i00dfz: Rank (Obsolete) 9223372036854775807 Severity