Add export-lookup-evict-race test

Add a test that creates races between fh_to_dentry and eviction
triggered by lock invalidation.

Signed-off-by: Zach Brown <zab@versity.com>

tests/sequence

@@ -13,6 +13,7 @@ lock-refleak.sh
 lock-shrink-consistency.sh
 lock-pr-cw-conflict.sh
 lock-revoke-getcwd.sh
+export-lookup-evict-race.sh
 createmany-parallel.sh
 createmany-large-names.sh
 createmany-rename-large-dir.sh

tests/tests/export-lookup-evict-race.sh

@@ -0,0 +1,32 @@
+#
+# test racing fh_to_dentry with evict from lock invalidation.   We've
+# had deadlocks between the ordering of iget and evict when they acquire
+# cluster locks.
+# 
+
+t_require_commands touch stat handle_cat
+t_require_mounts 2
+
+CPUS=$(getconf _NPROCESSORS_ONLN)
+NR=$((CPUS * 4))
+END=$((SECONDS + 30))
+
+touch "$T_D0/file"
+ino=$(stat -c "%i" "$T_D0/file")
+
+while test $SECONDS -lt $END; do
+	for i in $(seq 1 $NR); do
+		fs=$((RANDOM % T_NR_MOUNTS))
+		eval dir="\$T_D${fs}"
+		write=$((RANDOM & 1))
+
+		if [ "$write" == 1 ]; then
+			touch "$dir/file" &
+		else
+			handle_cat "$dir" "$ino" &
+		fi
+	done
+	wait
+done
+
+t_pass