Update mmp_delay on sync or skipped, failed write

When an MMP write is skipped, or fails, and time since
mts->mmp_last_write is already greater than mts->mmp_delay, increase
mts->mmp_delay.  The original code only updated mts->mmp_delay when a
write succeeded, but this results in the write(s) after delays and
failed write(s) reporting an ub_mmp_delay which is too low.

Update mmp_last_write and mmp_delay if a txg sync was successful.  At
least one uberblock was written, thus extending the time we can be sure
the pool will not be imported by another host.

Do not allow mmp_delay to go below (MSEC2NSEC(zfs_multihost_interval) /
vdev_count_leaves()) so that a period of frequent successful MMP writes,
e.g. due to frequent txg syncs, does not result in an import activity
check so short it is not reliable based on mmp thread writes alone.

Remove unnecessary local variable, start.  We do not use the start time
of the loop iteration.

Add a debug message in spa_activity_check() to allow verification of the
import_delay value and to prove the activity check occurred.

Alter the tests that import pools and attempt to detect an activity
check.  Calculate the expected duration of spa_activity_check() based on
module parameters at the time the import is performed, rather than a
fixed time set in mmp.cfg.  The fixed time may be wrong.  Also, use the
default zfs_multihost_interval value so the activity check is longer and
easier to recognize.

Reviewed-by: Tony Hutter <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Signed-off-by: Olaf Faaland <[email protected]>
Closes #7330 

3 files changed, 25 insertions, 6 deletions

diff --git a/tests/zfs-tests/tests/functional/mmp/mmp.cfg b/tests/zfs-tests/tests/functional/mmp/mmp.cfg
index 36f995443..52680c275 100644
--- a/tests/zfs-tests/tests/functional/mmp/mmp.cfg
+++ b/tests/zfs-tests/tests/functional/mmp/mmp.cfg
@@ -38,5 +38,3 @@ export MMP_HISTORY_OFF=0
 export MMP_INTERVAL_HOUR=$((60*60*1000))
 export MMP_INTERVAL_DEFAULT=1000
 export MMP_INTERVAL_MIN=100
-
-export ZPOOL_IMPORT_DURATION=9
diff --git a/tests/zfs-tests/tests/functional/mmp/mmp.kshlib b/tests/zfs-tests/tests/functional/mmp/mmp.kshlib
index 571affe89..e74f04a5b 100644
--- a/tests/zfs-tests/tests/functional/mmp/mmp.kshlib
+++ b/tests/zfs-tests/tests/functional/mmp/mmp.kshlib
@@ -163,17 +163,32 @@ function mmp_pool_set_hostid # pool hostid
 	return 0
 }
 
+# Return the number of seconds the activity check portion of the import process
+# will take.  Does not include the time to find devices and assemble the
+# preliminary pool configuration passed into the kernel.
+function seconds_mmp_waits_for_activity
+{
+	typeset import_intervals=$(get_tunable zfs_multihost_import_intervals)
+	typeset interval=$(get_tunable zfs_multihost_interval)
+	typeset seconds=$((interval*import_intervals/1000))
+
+	echo $seconds
+}
+
 function import_no_activity_check # pool opts
 {
 	typeset pool=$1
 	typeset opts=$2
 
+	typeset max_duration=$(seconds_mmp_waits_for_activity)
+
 	SECONDS=0
 	zpool import $opts $pool
 	typeset rc=$?
 
-	if [[ $SECONDS -gt $ZPOOL_IMPORT_DURATION ]]; then
-		log_fail "unexpected activity check (${SECONDS}s)"
+	if [[ $SECONDS -gt $max_duration ]]; then
+		log_fail "unexpected activity check (${SECONDS}s gt \
+$max_duration)"
 	fi
 
 	return $rc
@@ -184,12 +199,15 @@ function import_activity_check # pool opts
 	typeset pool=$1
 	typeset opts=$2
 
+	typeset min_duration=$(seconds_mmp_waits_for_activity)
+
 	SECONDS=0
 	zpool import $opts $pool
 	typeset rc=$?
 
-	if [[ $SECONDS -le $ZPOOL_IMPORT_DURATION ]]; then
-		log_fail "expected activity check (${SECONDS}s)"
+	if [[ $SECONDS -le $min_duration ]]; then
+		log_fail "expected activity check (${SECONDS}s le \
+$min_duration)"
 	fi
 
 	return $rc
diff --git a/tests/zfs-tests/tests/functional/mmp/mmp_active_import.ksh b/tests/zfs-tests/tests/functional/mmp/mmp_active_import.ksh
index 035264fe0..e39c5ab30 100755
--- a/tests/zfs-tests/tests/functional/mmp/mmp_active_import.ksh
+++ b/tests/zfs-tests/tests/functional/mmp/mmp_active_import.ksh
@@ -103,6 +103,9 @@ MMP_IMPORTED_MSG="pool was previously in use from another system."
 log_must try_pool_import $MMP_POOL "-d $MMP_DIR" "$MMP_IMPORTED_MSG"
 
 # 7. Verify 'zpool import -f $MMP_POOL' can now import the pool.
+# Default interval results in minimum activity test 10s which
+# makes detection of the activity test reliable.
+log_must set_tunable64 zfs_multihost_interval $MMP_INTERVAL_DEFAULT
 log_must import_activity_check $MMP_POOL "-f -d $MMP_DIR"
 
 # 8 Verify pool may be exported/imported without -f argument.