https://jira.whamcloud.com This file is an XML representation of an issue en-us 9.4.14 940014 05-12-2023 https://jira.whamcloud.com/browse/LU-7829 Lustre <p> A deadlock is possible during ccc_prep_size()-&gt;ldlm_lock_match() vs<br/> cl_io_lock() which is waiting for a matched lock and conflicts with<br/> already taken lock before ccc_prep_size().</p> <p> It is better to send an aditional lock request to avoid deadlock.</p> LU-7829

Glimpse lock shouldn't match not granted locks

Bug Minor Resolved Fixed WC Triage Andriy Skulysh patch Tue, 1 Mar 2016 14:01:36 +0000 Fri, 13 May 2016 05:02:39 +0000 Wed, 23 Mar 2016 15:36:27 +0000 Lustre 2.9.0 0 9 <p>Andriy Skulysh (andriy.skulysh@seagate.com) uploaded a new patch: <a href="http://review.whamcloud.com/18738" class="external-link" target="_blank" rel="nofollow noopener">http://review.whamcloud.com/18738</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-7829" title="Glimpse lock shouldn&#39;t match not granted locks" class="issue-link" data-issue-key="LU-7829"><del>LU-7829</del></a> osc: glimpse lock should match only with granted locks<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 12ca5348a93485a3f2112e82095b83aad02e77ea</p> <p>I am pulling Jinshan into this ticket.</p> <p>I am not happy about the current matching behavior either, but I think this was discussed a few years ago and there were some compelling reasons to do it too. Possibly they went away with clio simplification, but I want to be sure that is fine now.</p> <p>Hi Andriy,</p> <p>Can you please describe the deadlock issue in detail? In my understanding, the cl_io_lock() should have finished before doing ccc_prep_size() in the same I/O.</p> <p>yes, we have obtained a lock in cl_io_lock() and call ccc_prep_size() which matches not granted lock from another I/O. The second lock can't be granted because it conflicts with lock from first I/O. It can be obtained for some limited range but ccc_prep_size() needs <span class="error">&#91;0..EOF&#93;</span></p> <p>We have an instance of this:</p> <p>crash&gt; bt 7141<br/> PID: 7141 TASK: ffff8808360a9800 CPU: 2 COMMAND: "wc"<br/> #0 <span class="error">&#91;ffff8807ccf87668&#93;</span> schedule at ffffffff8141c637<br/> #1 <span class="error">&#91;ffff8807ccf877d0&#93;</span> schedule_timeout at ffffffff8141d0e0<br/> #2 <span class="error">&#91;ffff8807ccf87870&#93;</span> ldlm_lock_match at ffffffffa0474b01 <span class="error">&#91;ptlrpc&#93;</span><br/> #3 <span class="error">&#91;ffff8807ccf87950&#93;</span> osc_enqueue_base at ffffffffa06e9970 <span class="error">&#91;osc&#93;</span><br/> #4 <span class="error">&#91;ffff8807ccf879e0&#93;</span> osc_lock_enqueue at ffffffffa0704576 <span class="error">&#91;osc&#93;</span><br/> #5 <span class="error">&#91;ffff8807ccf87a70&#93;</span> cl_enqueue_try at ffffffffa037c6eb <span class="error">&#91;obdclass&#93;</span><br/> #6 <span class="error">&#91;ffff8807ccf87ac0&#93;</span> lov_lock_enqueue at ffffffffa0799f02 <span class="error">&#91;lov&#93;</span><br/> #7 <span class="error">&#91;ffff8807ccf87b60&#93;</span> cl_enqueue_try at ffffffffa037c6eb <span class="error">&#91;obdclass&#93;</span><br/> #8 <span class="error">&#91;ffff8807ccf87bb0&#93;</span> cl_enqueue_locked at ffffffffa037d0ff <span class="error">&#91;obdclass&#93;</span><br/> #9 <span class="error">&#91;ffff8807ccf87bf0&#93;</span> cl_lock_request at ffffffffa037dd1e <span class="error">&#91;obdclass&#93;</span><br/> #10 <span class="error">&#91;ffff8807ccf87c50&#93;</span> cl_glimpse_lock at ffffffffa0869bff <span class="error">&#91;lustre&#93;</span><br/> #11 <span class="error">&#91;ffff8807ccf87cb0&#93;</span> ccc_prep_size at ffffffffa086bc3e <span class="error">&#91;lustre&#93;</span><br/> #12 <span class="error">&#91;ffff8807ccf87d10&#93;</span> vvp_io_read_start at ffffffffa087457a <span class="error">&#91;lustre&#93;</span><br/> #13 <span class="error">&#91;ffff8807ccf87d80&#93;</span> cl_io_start at ffffffffa037f4d2 <span class="error">&#91;obdclass&#93;</span><br/> #14 <span class="error">&#91;ffff8807ccf87db0&#93;</span> cl_io_loop at ffffffffa0383054 <span class="error">&#91;obdclass&#93;</span><br/> #15 <span class="error">&#91;ffff8807ccf87de0&#93;</span> ll_file_io_generic at ffffffffa0815f02 <span class="error">&#91;lustre&#93;</span><br/> #16 <span class="error">&#91;ffff8807ccf87e60&#93;</span> ll_file_aio_read at ffffffffa081669b <span class="error">&#91;lustre&#93;</span><br/> #17 <span class="error">&#91;ffff8807ccf87eb0&#93;</span> ll_file_read at ffffffffa081700a <span class="error">&#91;lustre&#93;</span><br/> #18 <span class="error">&#91;ffff8807ccf87f10&#93;</span> vfs_read at ffffffff8115c048<br/> #19 <span class="error">&#91;ffff8807ccf87f40&#93;</span> sys_read at ffffffff8115c205<br/> #20 <span class="error">&#91;ffff8807ccf87f80&#93;</span> system_call_fastpath at ffffffff81426aab<br/> RIP: 00002aaaaad9db90 RSP: 00007fffffff2f60 RFLAGS: 00000206<br/> RAX: 0000000000000000 RBX: ffffffff81426aab RCX: 0000000000000002<br/> RDX: 0000000000004000 RSI: 00007fffffff2fd0 RDI: 0000000000000003<br/> RBP: 0000000000000000 R8: 00007fffffff6a82 R9: 0000000000000001<br/> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000021ec000<br/> R13: 0000000000000003 R14: 00007fffffff2fd0 R15: 0000000000004000<br/> ORIG_RAX: 0000000000000000 CS: 0033 SS: 002b<br/> crash&gt; </p> <p>The lock matched is conflicting with the lock it held in cl_io_lock before coming to this point. And also because this deadlock the lock couldn't be canceled for blocking AST and the client eventually got evicted by the server.</p> <p>The dump of the instance is on ftp.cray.com:/outbound/835240-logs-021116.tar.bz2. The client is Lustre 2.5.</p> <p>Oleg Drokin (oleg.drokin@intel.com) merged in patch <a href="http://review.whamcloud.com/18738/" class="external-link" target="_blank" rel="nofollow noopener">http://review.whamcloud.com/18738/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-7829" title="Glimpse lock shouldn&#39;t match not granted locks" class="issue-link" data-issue-key="LU-7829"><del>LU-7829</del></a> osc: glimpse lock should match only with granted locks<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: a9b3317360261b9a694a445e4dac1d3fa61664fd</p> <p>Landed for 2.9.0</p> Development Rank 1|hzy37z: Rank (Obsolete) 9223372036854775807 Severity