linux-kernel - Re: [PATCH v3 1/2] io_uring: Move from hlist to io_wq_work

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Message-ID: <Y/iJiCW+HmWZofgs@gmail.com>
Date:   Fri, 24 Feb 2023 01:55:20 -0800
From:   Breno Leitao <leitao@...ian.org>
To:     Gabriel Krisman Bertazi <krisman@...e.de>
Cc:     axboe@...nel.dk, asml.silence@...il.com, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, gustavold@...a.com, leit@...a.com,
        kasan-dev@...glegroups.com
Subject: Re: [PATCH v3 1/2] io_uring: Move from hlist to io_wq_work_node

Hello Krisman, thanks for the review

On Thu, Feb 23, 2023 at 04:02:25PM -0300, Gabriel Krisman Bertazi wrote:
> Breno Leitao <leitao@...ian.org> writes:

> >  static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
> >  {
> > -	if (!hlist_empty(&cache->list)) {
> > -		struct hlist_node *node = cache->list.first;
> > +	if (cache->list.next) {
> > +		struct io_cache_entry *entry;
> >  
> > -		hlist_del(node);
> > -		return container_of(node, struct io_cache_entry, node);
> > +		entry = container_of(cache->list.next, struct io_cache_entry, node);
> > +		cache->list.next = cache->list.next->next;
> > +		return entry;
> >  	}
> 
> From a quick look, I think you could use wq_stack_extract() here

True, we can use wq_stack_extract() in this patch, but, we would need to
revert to back to this code in the next patch. Remember that
wq_stack_extract() touches the stack->next->next, which will be
poisoned, causing a KASAN warning.

Here is relevant part of the code:

	struct io_wq_work_node *wq_stack_extract(struct io_wq_work_node *stack)
	{
		struct io_wq_work_node *node = stack->next;
		stack->next = node->next;