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Dangling reference from dmu_objset_upgrade 

After porting the fix for https://github.com/openzfs/zfs/issues/5295
over to illumos, we started hitting an assertion failure when running
the testsuite:

	assertion failed: rc->rc_count == number, file: .../refcount.c

and the unexpected hold has this stack:

	dsl_dataset_long_hold+0x59 dmu_objset_upgrade+0x73
dmu_objset_id_quota_upgrade+0x15 dmu_objset_own+0x14f

The simplest reproducer for this in illumos is

    zpool create -f -O version=1 testpool c3t0d0; zpool destroy testpool

which is run as part of the zpool_create_tempname test, but I can't get
this to trigger on FreeBSD. This appears to be because of the call to
txg_wait_synced() in dmu_objset_upgrade_stop() (which was missing in
illumos), slows down dmu_objset_disown() enough to avoid the condition.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Andy Fiddaman <andy@omnios.org>
Closes #11368
This commit is contained in:
Andy Fiddaman 2020-12-21 18:13:23 +00:00 committed by GitHub
parent 6152014d1a
commit 39372fa25b
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1 changed files with 8 additions and 1 deletions
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9
module/zfs/dmu_objset.c
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@ -1428,10 +1428,15 @@ dmu_objset_upgrade_task_cb(void *data)
mutex_enter(&os->os_upgrade_lock);
os->os_upgrade_status = EINTR;
if (!os->os_upgrade_exit) {
int status;
mutex_exit(&os->os_upgrade_lock);
os->os_upgrade_status = os->os_upgrade_cb(os);
status = os->os_upgrade_cb(os);
mutex_enter(&os->os_upgrade_lock);
os->os_upgrade_status = status;
}
os->os_upgrade_exit = B_TRUE;
os->os_upgrade_id = 0;
@ -1459,6 +1464,8 @@ dmu_objset_upgrade(objset_t *os, dmu_objset_upgrade_cb_t cb)
dsl_dataset_long_rele(dmu_objset_ds(os), upgrade_tag);
os->os_upgrade_status = ENOMEM;
}
} else {
dsl_dataset_long_rele(dmu_objset_ds(os), upgrade_tag);
}
mutex_exit(&os->os_upgrade_lock);
}