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-16695 Lustre <p>Usage of O_DIRECT and O_APPEND from file-&gt;f_flags to make decisions about IO exposes us to races with fcntl.  The upstream kernel fixed this in 2015 by mirroring them in to the IOCB flags.  Let's use these.</p> LU-16695

switch Lustre to use IOCB_APPEND and IOCB_DIRECT instead of file flags

Improvement Minor Resolved Fixed Patrick Farrell Patrick Farrell Fri, 31 Mar 2023 21:15:22 +0000 Wed, 13 Dec 2023 15:05:09 +0000 Wed, 13 Dec 2023 15:05:09 +0000 Lustre 2.16.0 0 4 <p>Note: I'm not aware of any actual issues here, but there is a theoretical problem and this is also required for switching buffered IO to direct IO inside the kernel, because we need to play with these flags and we can't safely do that on the actual file flags.</p> <p>"Patrick Farrell &lt;pfarrell@whamcloud.com&gt;" uploaded a new patch: <a href="https://review.whamcloud.com/c/fs/lustre-release/+/50493" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/50493</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-16695" title="switch Lustre to use IOCB_APPEND and IOCB_DIRECT instead of file flags" class="issue-link" data-issue-key="LU-16695"><del>LU-16695</del></a> llite: switch to ki_flags from f_flags<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 6d057bbfe727f4372e19326ea225e2b7736d23cb</p> <p>We ran into an issue when using loop devices in direct I/O to manage file systems backed on files in Lustre. I have opened a ticket before I found this one... <a href="https://jira.whamcloud.com/browse/LU-17116" class="external-link" rel="nofollow">https://jira.whamcloud.com/browse/LU-17116</a></p> <p>I'm happy to close it if it is considered to be a duplicate. Worst case scenario, on master the client can crash during a read (see the ticket for more details). We ran into the issue in 2.12 initially where we only got an Input/Output error in this case. On master, the client would crash right after the losetup has finished because a read was triggered on the loop device.</p> <p>I will try to see if your patch fixes the issue. I think we should at least add a test to check whether losetup --direct-io=on can be used successfully.</p> <p>The patch seems to fix the issue.</p> <p>Guillaume,</p> <p>Thanks for your report in <a href="https://jira.whamcloud.com/browse/LU-17116" title="losetup --direct-io=on trigger LASSERT(ll_dio_aio) in ll_file_io_generic" class="issue-link" data-issue-key="LU-17116"><del>LU-17116</del></a> - I was aware of this more as a compatibility issue and a small theoretical issue with someone changing those flags.  I wasn't aware we'd ever see IOCB_DIRECT without O_DIRECT.  That's a very good catch.  And I can work on getting this patch actually merged, because previously it was just in the (lengthy) backlog.</p> <p>Guillaume,</p> <p>Actually, since you generated a patch in <a href="https://jira.whamcloud.com/browse/LU-17116" title="losetup --direct-io=on trigger LASSERT(ll_dio_aio) in ll_file_io_generic" class="issue-link" data-issue-key="LU-17116"><del>LU-17116</del></a>, would you be able to rebase and clean up the patch for <a href="https://jira.whamcloud.com/browse/LU-16695" title="switch Lustre to use IOCB_APPEND and IOCB_DIRECT instead of file flags" class="issue-link" data-issue-key="LU-16695"><del>LU-16695</del></a>?  It's tough for me to find time for that right now.  I can help if you have questions or issues.</p> <p>I will look into it.</p> <p>"Etienne AUJAMES &lt;eaujames@ddn.com&gt;" uploaded a new patch: <a href="https://review.whamcloud.com/c/fs/lustre-release/+/53248" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/53248</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-16695" title="switch Lustre to use IOCB_APPEND and IOCB_DIRECT instead of file flags" class="issue-link" data-issue-key="LU-16695"><del>LU-16695</del></a> llite: switch to ki_flags from f_flags<br/> Project: fs/lustre-release<br/> Branch: b2_15<br/> Current Patch Set: 1<br/> Commit: 9795cdb4f4230ae654990ccae5a2803ad850954e</p> <p>"Oleg Drokin &lt;green@whamcloud.com&gt;" merged in patch <a href="https://review.whamcloud.com/c/fs/lustre-release/+/50493/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/50493/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-16695" title="switch Lustre to use IOCB_APPEND and IOCB_DIRECT instead of file flags" class="issue-link" data-issue-key="LU-16695"><del>LU-16695</del></a> llite: switch to ki_flags from f_flags<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: dad7079dfd9d1e17af15a2df67e76605db677e84</p> <p>Landed for 2.16</p> Related LU-17116 Development Rank 1|i03hsf: Rank (Obsolete) 9223372036854775807