Merge branch 'rhashtable-test-enhancements'

Phil Sutter says:

====================
improve fault-tolerance of rhashtable runtime-test

The following series aims to improve lib/test_rhashtable in different
situations:

Patch 1 allows the kernel to reschedule so the test does not block too
        long on slow systems.
Patch 2 fixes behaviour under pressure, retrying inserts in non-permanent
        error case (-EBUSY).
Patch 3 auto-adjusts the upper table size limit according to the number
        of threads (in concurrency test). In fact, the current default is
	already too small.
Patch 4 makes it possible to retry inserts even in supposedly permanent
        error case (-ENOMEM) to expose rhashtable's remaining problem of
	-ENOMEM being not as permanent as it is expected to be.

Changes since v1:
- Introduce insert_retry() which is then used in single-threaded test as
  well.
- Do not retry inserts by default if -ENOMEM was returned.
- Rename the retry counter to be a bit more verbose about what it
  contains.
- Add patch 4 as a debugging aid.
====================
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

lib/test_rhashtable.c

@@ -36,9 +36,9 @@ static int runs = 4;
 module_param(runs, int, 0);
 MODULE_PARM_DESC(runs, "Number of test runs per variant (default: 4)");
 
-static int max_size = 65536;
+static int max_size = 0;
 module_param(max_size, int, 0);
-MODULE_PARM_DESC(runs, "Maximum table size (default: 65536)");
+MODULE_PARM_DESC(runs, "Maximum table size (default: calculated)");
 
 static bool shrinking = false;
 module_param(shrinking, bool, 0);
@@ -52,6 +52,10 @@ static int tcount = 10;
 module_param(tcount, int, 0);
 MODULE_PARM_DESC(tcount, "Number of threads to spawn (default: 10)");
 
+static bool enomem_retry = false;
+module_param(enomem_retry, bool, 0);
+MODULE_PARM_DESC(enomem_retry, "Retry insert even if -ENOMEM was returned (default: off)");
+
 struct test_obj {
 	int			value;
 	struct rhash_head	node;
@@ -76,6 +80,28 @@ static struct rhashtable_params test_rht_params = {
 static struct semaphore prestart_sem;
 static struct semaphore startup_sem = __SEMAPHORE_INITIALIZER(startup_sem, 0);
 
+static int insert_retry(struct rhashtable *ht, struct rhash_head *obj,
+                        const struct rhashtable_params params)
+{
+	int err, retries = -1, enomem_retries = 0;
+
+	do {
+		retries++;
+		cond_resched();
+		err = rhashtable_insert_fast(ht, obj, params);
+		if (err == -ENOMEM && enomem_retry) {
+			enomem_retries++;
+			err = -EBUSY;
+		}
+	} while (err == -EBUSY);
+
+	if (enomem_retries)
+		pr_info(" %u insertions retried after -ENOMEM\n",
+			enomem_retries);
+
+	return err ? : retries;
+}
+
 static int __init test_rht_lookup(struct rhashtable *ht)
 {
 	unsigned int i;
@@ -157,7 +183,7 @@ static s64 __init test_rhashtable(struct rhashtable *ht)
 {
 	struct test_obj *obj;
 	int err;
-	unsigned int i, insert_fails = 0;
+	unsigned int i, insert_retries = 0;
 	s64 start, end;
 
 	/*
@@ -170,22 +196,16 @@ static s64 __init test_rhashtable(struct rhashtable *ht)
 		struct test_obj *obj = &array[i];
 
 		obj->value = i * 2;
-
-		err = rhashtable_insert_fast(ht, &obj->node, test_rht_params);
-		if (err == -ENOMEM || err == -EBUSY) {
-			/* Mark failed inserts but continue */
-			obj->value = TEST_INSERT_FAIL;
-			insert_fails++;
-		} else if (err) {
+		err = insert_retry(ht, &obj->node, test_rht_params);
+		if (err > 0)
+			insert_retries += err;
+		else if (err)
 			return err;
-		}
-
-		cond_resched();
 	}
 
-	if (insert_fails)
-		pr_info("  %u insertions failed due to memory pressure\n",
-			insert_fails);
+	if (insert_retries)
+		pr_info("  %u insertions retried due to memory pressure\n",
+			insert_retries);
 
 	test_bucket_stats(ht);
 	rcu_read_lock();
@@ -236,13 +256,15 @@ static int thread_lookup_test(struct thread_data *tdata)
 			       obj->value, key);
 			err++;
 		}
+
+		cond_resched();
 	}
 	return err;
 }
 
 static int threadfunc(void *data)
 {
-	int i, step, err = 0, insert_fails = 0;
+	int i, step, err = 0, insert_retries = 0;
 	struct thread_data *tdata = data;
 
 	up(&prestart_sem);
@@ -251,20 +273,18 @@ static int threadfunc(void *data)
 
 	for (i = 0; i < entries; i++) {
 		tdata->objs[i].value = (tdata->id << 16) | i;
-		err = rhashtable_insert_fast(&ht, &tdata->objs[i].node,
-		                             test_rht_params);
-		if (err == -ENOMEM || err == -EBUSY) {
-			tdata->objs[i].value = TEST_INSERT_FAIL;
-			insert_fails++;
+		err = insert_retry(&ht, &tdata->objs[i].node, test_rht_params);
+		if (err > 0) {
+			insert_retries += err;
 		} else if (err) {
 			pr_err("  thread[%d]: rhashtable_insert_fast failed\n",
 			       tdata->id);
 			goto out;
 		}
 	}
-	if (insert_fails)
-		pr_info("  thread[%d]: %d insert failures\n",
-		        tdata->id, insert_fails);
+	if (insert_retries)
+		pr_info("  thread[%d]: %u insertions retried due to memory pressure\n",
+			tdata->id, insert_retries);
 
 	err = thread_lookup_test(tdata);
 	if (err) {
@@ -285,6 +305,8 @@ static int threadfunc(void *data)
 				goto out;
 			}
 			tdata->objs[i].value = TEST_INSERT_FAIL;
+
+			cond_resched();
 		}
 		err = thread_lookup_test(tdata);
 		if (err) {
@@ -311,7 +333,7 @@ static int __init test_rht_init(void)
 	entries = min(entries, MAX_ENTRIES);
 
 	test_rht_params.automatic_shrinking = shrinking;
-	test_rht_params.max_size = max_size;
+	test_rht_params.max_size = max_size ? : roundup_pow_of_two(entries);
 	test_rht_params.nelem_hint = size;
 
 	pr_info("Running rhashtable test nelem=%d, max_size=%d, shrinking=%d\n",
@@ -357,6 +379,8 @@ static int __init test_rht_init(void)
 		return -ENOMEM;
 	}
 
+	test_rht_params.max_size = max_size ? :
+	                           roundup_pow_of_two(tcount * entries);
 	err = rhashtable_init(&ht, &test_rht_params);
 	if (err < 0) {
 		pr_warn("Test failed: Unable to initialize hashtable: %d\n",