self-hosting hang/deadlock (zpool on zvol) #4694
Comments
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is is reproducible |
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@nigoroll actually on Solaris-ish systems this isn't 100% safe either and may deadlock. It just happens to be much much more likely with ZoL due to a greater degree of concurrency allowed in the Linux block layer. But your definitely right this can deadlock and should be resolved, patches welcome. :) |
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@behlendorf yes, you are right, and I've experienced a similar thing shortly after logging this issue: https://www.illumos.org/issues/6994 |
behlendorf
added
Bug
Component: Test Suite
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disagree, the deadlocks are below the volume interface (in ZFS module), not above it. So changing the wiring above the volume interface makes no difference. |
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Yeah, I've had it hang via a VirtualBox and iSCSI (physical disk->ZFS->ZVolume->iSCSI->Network->Physical Machine->VirtualBox VM->ZFS on VM disks). |
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@kpande no it's not a regression, this has never been 100% safe. Over the years we'd addressed some of the possible deadlocks bet we never got all of them. |
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@kpande nothing comes to mind. But if you wanted to add such as thing all you'd need to do is update |
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@behlendorf @kpande's description of his problem in IRC is the ZFS stacking problem where a zvol is the backing device for another device that is the vdev of another pool. @nigoroll Would you try reproducing with this patch applied and the parallel open explicitly disabled? Either we disabled parallel vdev open and things deadlocked anyway, or our detection code for disabling it failed to realize the device is a zvol due to the symlink. It is somewhat hard to read the stack traces without kernel debug symbols, but my guess is that the problem is one of those two. If the symlink caused the problem, then it should be an easy fix. |
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Closing as duplicate of #3484. |
and others
On solaris-ish systems, zfs is capabable of self hosting / creating zpools within other zpools
For me, this leads to a hang/deadlock:
debian 8.4Linux haggis 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt25-2 (2016-04-08) x86_64 GNU/Linuxzfs-dkms 0.6.5.7-8-jessieNote that this case is different from #2469
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