There are two codepaths than can dirty final TXGs:
1) If calling spa_export_common()->spa_unload()->
spa_unload_log_sm_flush_all() after the spa_final_txg is set, then
spa_sync()->spa_flush_metaslabs() may end up dirtying the final
TXGs. Then we have the following panic:
Call Trace:
<TASK>
dump_stack_lvl+0x46/0x62
spl_panic+0xea/0x102 [spl]
dbuf_dirty+0xcd6/0x11b0 [zfs]
zap_lockdir_impl+0x321/0x590 [zfs]
zap_lockdir+0xed/0x150 [zfs]
zap_update+0x69/0x250 [zfs]
feature_sync+0x5f/0x190 [zfs]
space_map_alloc+0x83/0xc0 [zfs]
spa_generate_syncing_log_sm+0x10b/0x2f0 [zfs]
spa_flush_metaslabs+0xb2/0x350 [zfs]
spa_sync_iterate_to_convergence+0x15a/0x320 [zfs]
spa_sync+0x2e0/0x840 [zfs]
txg_sync_thread+0x2b1/0x3f0 [zfs]
thread_generic_wrapper+0x62/0xa0 [spl]
kthread+0x127/0x150
ret_from_fork+0x22/0x30
</TASK>
2) Calling vdev_*_stop_all() for a second time in spa_unload() after
spa_export_common() unnecessarily delays the final TXGs beyond what
spa_final_txg is set at.
Fix this by performing the check and call for
spa_unload_log_sm_flush_all() before the spa_final_txg is set in
spa_export_common(). Also check if the spa_final_txg has already been
set in spa_unload() and skip those calls in this case.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Amanakis <gamanakis@gmail.com>
External-issue: https://www.illumos.org/issues/9081Closes#13048Closes#13098
George Amanakis
6c6153e5b8