lib/raid6: Optimize raid6_select_algo to ensure

index 799e0e5eac26..c21e3ad99d97 100644
@@ -152,8 +152,32 @@ static inline const struct raid6_recov_calls *raid6_choose_recov(void)
 	return best;
 }
 
-static inline const struct raid6_calls *raid6_choose_gen(
-	void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
+/* Quick selection: select the highest priority valid algorithm. */
+static inline int raid6_choose_gen_fast(void)
+{
+	int ret = 0;
+	const struct raid6_calls *const *algo;
+	const struct raid6_calls *best = NULL;
+
+	for (best = NULL, algo = raid6_algos; *algo; algo++)
+		if (!best || (*algo)->priority > best->priority)
+			if (!(*algo)->valid || (*algo)->valid())
+				best = *algo;
+
+	if (best) {
+		raid6_call = *best;
+		pr_info("raid6: skipped pq benchmark and selected %s\n",
+				best->name);
+	} else {
+		pr_err("raid6: No valid algorithm found even for fast selection!\n");
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static inline const struct raid6_calls *raid6_gen_benchmark(
+		void *(*const dptrs)[RAID6_TEST_DISKS], const int disks)
 {
 	unsigned long perf, bestgenperf, j0, j1;
 	int start = (disks>>1)-1, stop = disks-3;	/* work on the second half of the disks */

@@ -165,11 +189,6 @@ static inline const struct raid6_calls *raid6_choose_gen(
 			if ((*algo)->valid && !(*algo)->valid())
 				continue;
 
-			if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
-				best = *algo;
-				break;
-			}
-
 			perf = 0;
 
 			preempt_disable();

@@ -200,12 +219,6 @@ static inline const struct raid6_calls *raid6_choose_gen(
 
 	raid6_call = *best;
 
-	if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK)) {
-		pr_info("raid6: skipped pq benchmark and selected %s\n",
-			best->name);
-		goto out;
-	}
-
 	pr_info("raid6: using algorithm %s gen() %ld MB/s\n",
 		best->name,
 		(bestgenperf * HZ * (disks - 2)) >>

@@ -239,15 +252,13 @@ static inline const struct raid6_calls *raid6_choose_gen(
 /* Try to pick the best algorithm */
 /* This code uses the gfmul table as convenient data set to abuse */
 
-int __init raid6_select_algo(void)
+static int raid6_choose_gen_benmark(void)
 {
 	const int disks = RAID6_TEST_DISKS;
-
 	const struct raid6_calls *gen_best;
-	const struct raid6_recov_calls *rec_best;
 	char *disk_ptr, *p;
 	void *dptrs[RAID6_TEST_DISKS];
-	int i, cycle;
+	int i, cycle, ret = 0;
 
 	/* prepare the buffer and fill it circularly with gfmul table */
 	disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER);

@@ -269,15 +280,36 @@ int __init raid6_select_algo(void)
 	if ((disks - 2) * PAGE_SIZE % 65536)
 		memcpy(p, raid6_gfmul, (disks - 2) * PAGE_SIZE % 65536);
 
-	/* select raid gen_syndrome function */
-	gen_best = raid6_choose_gen(&dptrs, disks);
+	gen_best = raid6_gen_benchmark(&dptrs, disks);
+	if (!gen_best)
+		ret = -EINVAL;
+
+	free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
+
+	return ret;
+}
+
+int __init raid6_select_algo(void)
+{
+	int ret = 0;
+	const struct raid6_recov_calls *rec_best = NULL;
+
+	/* select raid gen_syndrome functions */
+	if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK))
+		ret = raid6_choose_gen_fast();
+	else
+		ret = raid6_choose_gen_benmark();
+
+	if (ret < 0)
+		goto out;
 
 	/* select raid recover functions */
 	rec_best = raid6_choose_recov();
+	if (!rec_best)
+		ret = -EINVAL;
 
-	free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
-
-	return gen_best && rec_best ? 0 : -EINVAL;
+out:
+	return ret;
 }
 
 static void raid6_exit(void)

index c21e3ad99d97..b8b5515ac7a6 100644
@@ -12,6 +12,7 @@
  */
 
 #include <linux/raid/pq.h>
+#include <linux/workqueue.h>
 #ifndef __KERNEL__
 #include <sys/mman.h>
 #include <stdio.h>

@@ -166,7 +167,7 @@ static inline int raid6_choose_gen_fast(void)
 
 	if (best) {
 		raid6_call = *best;
-		pr_info("raid6: skipped pq benchmark and selected %s\n",
+		pr_info("raid6: raid6: fast selected %s, async benchmark pending\n",
 				best->name);
 	} else {
 		pr_err("raid6: No valid algorithm found even for fast selection!\n");

@@ -213,7 +214,7 @@ static inline const struct raid6_calls *raid6_gen_benchmark(
 	}
 
 	if (!best) {
-		pr_err("raid6: Yikes! No algorithm found!\n");
+		pr_warn("raid6: async benchmark failed to find any algorithm\n");
 		goto out;
 	}
 

@@ -289,24 +290,33 @@ static int raid6_choose_gen_benmark(void)
 	return ret;
 }
 
+static struct work_struct raid6_benchmark_work;
+
+static void benchmark_work_func(struct work_struct *work)
+{
+	raid6_choose_gen_benmark();
+}
+
 int __init raid6_select_algo(void)
 {
 	int ret = 0;
 	const struct raid6_recov_calls *rec_best = NULL;
 
-	/* select raid gen_syndrome functions */
-	if (!IS_ENABLED(CONFIG_RAID6_PQ_BENCHMARK))
-		ret = raid6_choose_gen_fast();
-	else
-		ret = raid6_choose_gen_benmark();
-
+	/* phase 1: synchronous fast selection generation algorithm */
+	ret = raid6_choose_gen_fast();
 	if (ret < 0)
 		goto out;
 
 	/* select raid recover functions */
 	rec_best = raid6_choose_recov();
-	if (!rec_best)
+	if (!rec_best) {
 		ret = -EINVAL;
+		goto out;
+	}
+
+	/* phase 2: asynchronous performance benchmarking */
+	INIT_WORK(&raid6_benchmark_work, benchmark_work_func);
+	schedule_work(&raid6_benchmark_work);
 
 out:
 	return ret;

@@ -314,7 +324,7 @@ int __init raid6_select_algo(void)
 
 static void raid6_exit(void)
 {
-	do { } while (0);
+	cancel_work_sync(&raid6_benchmark_work);
 }
 
 subsys_initcall(raid6_select_algo);