linux-kernel - Re: [PATCH 1/2] maple_tree: Use kfree_rcu in ma_free

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tbm6emntje2lcwmg5xa6whlhsghwflbyb6p7m4y72dffenttqz@g2hftzczixxx>
Date: Wed, 6 Aug 2025 11:20:19 +0100
From: Pedro Falcato <pfalcato@...e.de>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <willy@...radead.org>, 
	maple-tree@...ts.infradead.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] maple_tree: Use kfree_rcu in ma_free_rcu

On Tue, Aug 05, 2025 at 09:25:13PM -0400, Liam R. Howlett wrote:
> * Pedro Falcato <pfalcato@...e.de> [250718 13:21]:
> > kfree_rcu is an optimized version of call_rcu + kfree. It used to not be
> > possible to call it on non-kmalloc objects, but this restriction was
> > lifted ever since SLOB was dropped from the kernel, and since commit
> > 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()").
> > 
> > Thus, replace call_rcu + mt_free_rcu with kfree_rcu.
> [snip]
> >  static void mt_set_height(struct maple_tree *mt, unsigned char height)
> > @@ -5281,7 +5274,7 @@ static void mt_free_walk(struct rcu_head *head)
> >  	mt_free_bulk(node->slot_len, slots);
> >  
> >  free_leaf:
> > -	mt_free_rcu(&node->rcu);
> > +	mt_free_one(node);
> 
> Why are we still using mt_free_one()?  Couldn't this also be dropped in
> favour of kfree() or does kfree() not work for kmem_cache?

kfree() also works (since SLOB was dropped). I thought you wanted mt_free_one
for style points, but I can replace all calls with a direct kfree() if you prefer.

-- 
Pedro