From 1d8dc3d3c8f1d8ee1da9d54c5d7c8694419ade42 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Thu, 23 Apr 2015 16:38:43 +0200 Subject: [PATCH] rhashtable: don't attempt to grow when at max_size The conversion of mac80211's station table to rhashtable had a bug that I found by accident in code review, that hadn't been found as rhashtable apparently managed to have a maximum hash chain length of one (!) in all our testing. In order to test the bug and verify the fix I set my rhashtable's max_size very low (4) in order to force getting hash collisions. At that point, rhashtable WARNed in rhashtable_insert_rehash() but didn't actually reject the hash table insertion. This caused it to lose insertions - my master list of stations would have 9 entries, but the rhashtable only had 5. This may warrant a deeper look, but that WARN_ON() just shouldn't happen. Fix this by not returning true from rht_grow_above_100() when the rhashtable's max_size has been reached - in this case the user is explicitly configuring it to be at most that big, so even if it's now above 100% it shouldn't attempt to resize. This fixes the "lost insertion" issue and consequently allows my code to display its error (and verify my fix for it.) Signed-off-by: Johannes Berg Acked-by: Thomas Graf Signed-off-by: David S. Miller --- include/linux/rhashtable.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/rhashtable.h b/include/linux/rhashtable.h index e23d242..dbcbcc5 100644 --- a/include/linux/rhashtable.h +++ b/include/linux/rhashtable.h @@ -282,7 +282,8 @@ static inline bool rht_shrink_below_30(const struct rhashtable *ht, static inline bool rht_grow_above_100(const struct rhashtable *ht, const struct bucket_table *tbl) { - return atomic_read(&ht->nelems) > tbl->size; + return atomic_read(&ht->nelems) > tbl->size && + (!ht->p.max_size || tbl->size < ht->p.max_size); } /* The bucket lock is selected based on the hash and protects mutations -- 2.7.4