** Also affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Also affects: zfs-linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu)
Status: New => Invalid
** Changed in: linux (Ubuntu Bionic)
Status: New => Fix Committed
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https://bugs.launchpad.net/bugs/1772412
Title:
zfs 0.7.9 fixes a bug (https://github.com/zfsonlinux/zfs/pull/7343)
that hangs the system completely
Status in linux package in Ubuntu:
Invalid
Status in zfs-linux package in Ubuntu:
In Progress
Status in linux source package in Bionic:
Fix Committed
Status in zfs-linux source package in Bionic:
New
Bug description:
SRU Bionic
== SRU Justification ==
Intensive I/O such as performed by ZFS send/receive can cause hangs because
of monopolization of the global system_taskq. The outcome is that z_zvol hung
tasks occur and I/O gets blocked.
== Fix ==
Upstream ZFS commit 77d8a0f1a4d0b2f59cee63088f7987cb38e66538 ("Fix
hung z_zvol tasks during 'zfs receive'") fixes this issue, it adds a
dedicated per-pool prefetch taskq that prevents the traverse code from
monopolizing the global (and limited) system_taskq by inappropriately
scheduling long running tasks on it. This fixes the z_zvol hung tasks.
A trivial backport is required for Bionic ZFS.
== Testcase ==
Perform large send/receives. Occasionally they lock up. With the fix,
this issue is addressed and no more lockups occur. Also must pass the
full ZFS ubuntu autotest tests to prove no regressions occur.
== Regression Potential ==
This fix adds more per-pool prefetch taskq's so we have more kernel
resources being used. There is therefore a very small risk that this
may impact ZFS running on memory and CPU constrained systems.
However, the fix is small, has been upstream for a while and is in
Cosmic+ releases and has not caused any regressions, so I think this
is a relatively safe fix.
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I have experienced the problems fixed by this commit
https://github.com/zfsonlinux/zfs/pull/7343 a few times on my NAS. The
system hangs completely when it occurs. It looks like 0.7.9 brings
other interesting bug fixes that potentially freeze the system.
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