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-8915 Lustre <p>As the upstream client looks like move out of staging issues are being brought up that need to be addressed. One issue is that the lnet selftest utility uses and passes linux kernel link list as arguments. A new proper user land interface has to be developed do we can stop using linux link list arguments as ioctl parameters.</p> LU-8915

Don't use linux list structure as user land arguments for lnet selftest

Bug Major Reopened Unresolved James A Simmons James A Simmons Wed, 7 Dec 2016 14:25:44 +0000 Thu, 19 Jan 2023 20:48:49 +0000 Lustre 2.10.0 Lustre 2.16.0 0 11 <p>Thanks James</p> <p>Before I go changing user land API's Doug, Amir and the rest of the LNet guys need to chime in for what the API should looks like.</p> <p>I was looking at this today in the context of patch <a href="https://review.whamcloud.com/38105" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/38105</a> "<tt><a href="https://jira.whamcloud.com/browse/LU-13344" title="Support for linux 5.6 clients" class="issue-link" data-issue-key="LU-13344"><del>LU-13344</del></a> lnet: stop using struct timeval</tt>" and came to the conclusion that we aren't <em>really</em> using "<tt>struct list_head</tt>" in the userspace interface, even though it looks that way.</p> <p>What is actually being done is that <tt>stuct list_head</tt> is being used in userspace to generate a linked list of reply buffers for requests, and the kernel is essentially using the "<tt>.next</tt>" field in <tt>lstcon_rpc_trans_interpreter()</tt> as a way of passing a series of userspace pointers to the kernel. The somewhat confusing part is that this is done within a <tt>list_for_each_entry()</tt> loop in the kernel, but that is actually walking a <b>different</b> list, which is OK.</p> <p>For the "<tt>head_up</tt>" pointer passed from userspace, each one has the "<tt>struct lstcon_rpc_ent</tt>" copied properly from userspace, but only the <tt>.next</tt> field is used from "<tt>struct list_head rpe_link</tt>" to point to the next "<tt>struct lstcon_rpc_ent</tt>" structure. The fact that all of these functions pass "<tt>struct list_head __user *head_up</tt>" as an argument is misleading and makes it look like they could be using <tt>list_for_each()</tt> in the kernel on this list, but that never happens. Also, since "<tt>rpe_link</tt>" is the first field in the structure, passing the "<tt>head_up</tt>" pointer (named <tt>result_up</tt> in the caller) as the function argument is really the same as passing the pointer to "<tt>struct lstcon_rpc_ent</tt>" itself.</p> <p>I think it would be possible to change all of these functions and structs in <tt>lnet/include/uapi/linux/lnet/lnetst.h</tt> from passing "<tt>struct list_head __user *</tt>" to passing "<tt>struct lstcon_rpc_ent __user *</tt>" as the argument with no functional difference in the code (even binary compatibility), since all of these pointers end up down in <tt>lstcon_rpc_trans_interpreter()</tt> at the end. Inside <tt>lstcon_rpc_trans_interpreter()</tt> instead of "<tt>ent = list_entry()</tt>" it would use "<tt>ent = container_of()</tt>" (which <tt>list_entry()</tt> uses internally these days anyway) to make it clear that it isn't treating this as a <tt>list_head</tt>. The <tt>rpe_link.next</tt> field is treated as a 64-bit field that holds a userspace pointer to the next "<tt>struct lstcon_rpc_ent</tt>", which is only ever accessed via <tt>copy_to_user()</tt> or compared against itself, which is fine.</p> <p>In summary, I think we can remove the use of "<tt>struct list&#95;head</tt>" for from the <tt>lnetst.h</tt> user/kernel interface without even compatibility issues.</p> <p>James Simmons (jsimmons@infradead.org) uploaded a new patch: <a href="https://review.whamcloud.com/43298" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/43298</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-8915" title="Don&#39;t use linux list structure as user land arguments for lnet selftest" class="issue-link" data-issue-key="LU-8915">LU-8915</a> lnet: migrate LNet selftest session handling to Netlink<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 3d1631ed0561651bdef83b138f086864f54c6a5d</p> <p>"Oleg Drokin &lt;green@whamcloud.com&gt;" merged in patch <a href="https://review.whamcloud.com/c/fs/lustre-release/+/43298/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/43298/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-8915" title="Don&#39;t use linux list structure as user land arguments for lnet selftest" class="issue-link" data-issue-key="LU-8915">LU-8915</a> lnet: migrate LNet selftest session handling to Netlink<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: 15c82ae3d31969afd866ca825c2f6ab11ae36a8f</p> <p>Only patch seems to have landed for 2.16. Should reopen if more is to come</p> <p>More patches coming.</p> <p>"James Simmons &lt;jsimmons@infradead.org&gt;" uploaded a new patch: <a href="https://review.whamcloud.com/c/fs/lustre-release/+/49314" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/49314</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-8915" title="Don&#39;t use linux list structure as user land arguments for lnet selftest" class="issue-link" data-issue-key="LU-8915">LU-8915</a> lnet: migrate LNet selftest group handling to Netlink<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 3a0d2dda2cdcb491f11b0ea4977a8ccb11bcf37e</p> <p>"Oleg Drokin &lt;green@whamcloud.com&gt;" merged in patch <a href="https://review.whamcloud.com/c/fs/lustre-release/+/49314/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/49314/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-8915" title="Don&#39;t use linux list structure as user land arguments for lnet selftest" class="issue-link" data-issue-key="LU-8915">LU-8915</a> lnet: migrate LNet selftest group handling to Netlink<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: a6c2d277d09ce9b33d5407dd08da7ffc42066de0</p> <p>Still more to come?</p> <p>yes</p> Related LU-10975 LU-9680 LU-10391 Development Rank 1|hzyxpr: Rank (Obsolete) 9223372036854775807 Severity