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<p class="MsoNormal"><span style="font-size:11.0pt">Neil, James,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It looks like the patch we landed as:<o:p></o:p></span></p>
<pre style="background:#F4F5F7"><span style="font-size:9.0pt;color:#172B4D">LU-8130 ptlrpc: convert conn_hash to rhashtable<o:p></o:p></span></pre>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">Linux has a resizeable hashtable implementation in lib,<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">so we should use that instead of having one in libcfs.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">This patch converts the ptlrpc conn_hash to use rhashtable.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">In the process we gain lockless lookup.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">As connections are never deleted until the hash table is destroyed,<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">there is no need to count the reference in the hash table. There<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">is also no need to enable automatic_shrinking.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="background:#F4F5F7"><span style="font-size:9.0pt;font-family:"Courier New";color:#172B4D">Linux-commit: ac2370ac2bc5215daf78546cd8d925510065bb7f<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Introduced a bug. Ihara-san opened something to track it here:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://jira.whamcloud.com/browse/LU-11624">https://jira.whamcloud.com/browse/LU-11624</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It’s a null pointer in nid_hash(); there are some more d</span><span style="font-size:11.0pt">etails at that link.</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">We’re seeing it at Cray as well, when testing the current WhamCloud branch.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Basically, when we fail over an MDS(/MDT) under load (ie with real activity on the file system) we hit this panic about 30-50% of the time right now. I assume it’s possible on OSSes as well but we haven’t
seen it there.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">I haven’t done any detailed investigation, but I thought I’d bring it to your attention. Per Ihara-san in LU-11624, the crash does not happen without the commit listed above.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Patrick<o:p></o:p></span></li></ul>
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