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-3209 Lustre <p>When swapping layouts between two files f0 and f1, if f1 has no striping then the layout gen of f0 is not incremented. This can be used to create layout gen collisions and cache inconsistencies:</p> <div class="preformatted panel" style="border-width: 1px;"><div class="preformattedContent panelContent"> <pre># cd ~/lustre-release # git describe 2.3.64-30-g5b91c09 # MOUNT_2=y llmount.sh ... # cd /mnt/lustre # touch f0 # multiop f1 m # lfs swap_layouts /mnt/lustre2/f0 /mnt/lustre2/f1 # echo HI &gt; /mnt/lustre2/f0 # cat f0 # cat /mnt/lustre2/f0 HI </pre> </div></div> <div class="preformatted panel" style="border-width: 1px;"><div class="preformattedContent panelContent"> <pre># MOUNT_2=y llmount.sh ... # cd /mnt/lustre # echo OLD &gt; f0 # echo NEW &gt; f1 # multiop f2 m ## mknod # lfs getstripe f0 f0 lmm_stripe_count: 1 lmm_stripe_size: 1048576 lmm_layout_gen: 0 lmm_stripe_offset: 1 obdidx objid objid group 1 2 0x2 0 # lfs swap_layouts /mnt/lustre2/f0 /mnt/lustre2/f2 # lfs swap_layouts /mnt/lustre2/f0 /mnt/lustre2/f1 # lfs getstripe f0 f0 lmm_stripe_count: 1 lmm_stripe_size: 1048576 lmm_layout_gen: 0 lmm_stripe_offset: 0 obdidx objid objid group 0 2 0x2 0 # cat f0 OLD # cat /mnt/lustre2/f0 NEW # cat f0 OLD # cat /mnt/lustre2/f0 NEW </pre> </div></div> <div class="preformatted panel" style="border-width: 1px;"><div class="preformattedContent panelContent"> <pre># MOUNT_2=y llmount.sh ... # cd /mnt/lustre # touch f0 # multiop f1 m # lfs swap_layouts /mnt/lustre2/f0 /mnt/lustre2/f1 # echo &gt; /mnt/lustre2/f0 # # stat f0 File: `f0' Size: 0 Blocks: 0 IO Block: 4194304 regular empty file Device: 2c54f966h/743766374d Inode: 144115205255725134 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2013-04-23 12:04:26.000000000 -0500 Modify: 2013-04-23 12:04:26.000000000 -0500 Change: 2013-04-23 12:04:26.000000000 -0500 # stat f1 stat: cannot stat `f1': Input/output error </pre> </div></div> LU-3209

layout swap with stripeless files allows layout gen collisions

Bug Minor Closed Won't Fix John Hammond John Hammond hsm mdd Tue, 23 Apr 2013 17:28:47 +0000 Fri, 11 Mar 2022 15:23:36 +0000 Fri, 11 Mar 2022 15:23:36 +0000 Lustre 2.4.0 0 4 <p>The problem is there is nowhere to store generation for an empty layout file. The only thing we can do is to hope customers won't run this test cases <img class="emoticon" src="https://jira.whamcloud.com/images/icons/emoticons/wink.png" height="16" width="16" align="absmiddle" alt="" border="0"/></p> <p>We can forbid swap or transform the empty file into a released file before swaping</p> <p>Hmm, doesn't layout swap preserve the layout version on each file? I thought that was part of the original patch. That would make sense since the layout version only makes sense for the file that was being modified.</p> <p>layout swap increases each generation number, the issue with stripeless file is that we have no place to store it, or we have to transform it to a released layout</p> <p>For HSM, the layout would be LOV_PATTERN_RELEASED, so it will have a place to store the layout generation. For stripeless files, I'm not sure whether there is a real-world issue or not, since I don't see any valid case of swapping the an empty layout and then keeping the empty file.</p> <p>"For HSM, the layout would be LOV_PATTERN_RELEASED, so it will have a place to store the layout generation. For stripeless files, I'm not sure whether there is a real-world issue or not, since I don't see any valid case of swapping the an empty layout and then keeping the empty file."</p> <p>This sounds reasonable. There should be no this kind of issue in real world.</p> <p>If we do not see any use case, the best is to forbid it so no risk of side effects</p> <p>In that case, let me work out a patch.</p> Development Rank 1|hzvosf: Rank (Obsolete) 7841 Severity