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From:   Davidlohr Bueso <dave@stgolabs.net>
To:     akpm@linux-foundation.org
Cc:     herbert@gondor.apana.org.au, tgraf@suug.ch,
        linux-kernel@vger.kernel.org, dave@stgolabs.net,
        Davidlohr Bueso <dbueso@suse.de>
Subject: [PATCH] lib/rhashtable: consider param->min_size when setting initial table size
Date:   Fri, 13 Jul 2018 23:25:16 -0700
Message-Id: <20180714062516.30433-1-dave@stgolabs.net>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

rhashtable_init() currently does not take into account the user-passed
min_size parameter unless param->nelem_hint is set as well. As such,
the default size (number of buckets) will always be HASH_DEFAULT_SIZE
even if the smallest allowed size is larger than that. Remediate this
by unconditionally calling into rounded_hashtable_size() and handling
things accordingly.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 lib/rhashtable.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 411c4041ce83..89c3cfc8334d 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -962,8 +962,16 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
 
 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
 {
-	return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
-		   (unsigned long)params->min_size);
+	size_t retsize;
+
+	if (params->nelem_hint)
+		retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
+			      (unsigned long)params->min_size);
+	else
+		retsize = max(HASH_DEFAULT_SIZE,
+			      (unsigned long)params->min_size);
+
+	return retsize;
 }
 
 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
@@ -1020,8 +1028,6 @@ int rhashtable_init(struct rhashtable *ht,
 	struct bucket_table *tbl;
 	size_t size;
 
-	size = HASH_DEFAULT_SIZE;
-
 	if ((!params->key_len && !params->obj_hashfn) ||
 	    (params->obj_hashfn && !params->obj_cmpfn))
 		return -EINVAL;
@@ -1048,8 +1054,7 @@ int rhashtable_init(struct rhashtable *ht,
 
 	ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
 
-	if (params->nelem_hint)
-		size = rounded_hashtable_size(&ht->p);
+	size = rounded_hashtable_size(&ht->p);
 
 	if (params->locks_mul)
 		ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
-- 
2.16.4