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Date: Mon, 14 Sep 2026 12:16:32 +0200
From: Florian Westphal <fw@strlen.de>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: kadlec@netfilter.org, linux-crypto@vger.kernel.org
Subject: Re: [v5 PATCH] rhashtable: Add rhashtable_flush_and_free helper
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In-Reply-To: <aqYQJlrjbxEgp4Y4@gondor.apana.org.au>

Herbert Xu <herbert@gondor.apana.org.au> wrote:
> v5 makes the following changes:
> 
> - Add bucket_table dying flag to fix walker race.

Thanks, I rebased the ipset rhashtable conversion patches
on top of this; all tests pass.

> Once rehashes are completely gone, ht->nelems is reset to zero,
> and the new table is installed.

Wrt. to this, you could do:

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 63129a8e223b..c5a3c15b3f7e 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -1265,6 +1265,8 @@ static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
 {
        struct rhlist_head *list;

+       atomic_dec(&ht->nelems);
+
        if (!ht->rhlist) {
                free_fn(rht_obj(ht, obj), arg);
                return;


To avoid the need for an 'atomic_set'.  That said, I don't mind the
NULL-plus-concurrent-insertions-drop behaviour, its not an issue for
ipset.