linux-kernel - Re: [PATCH 3/5] mm/vmalloc: Initialize VA's list node after unlink

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Date:   Wed, 8 Jun 2022 11:19:39 +0800
From:   Baoquan He <bhe@...hat.com>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>
Subject: Re: [PATCH 3/5] mm/vmalloc: Initialize VA's list node after unlink

On 06/07/22 at 11:34am, Uladzislau Rezki (Sony) wrote:
> A vmap_area can travel between different places. For example
> attached/detached to/from different rb-trees. In order to
> prevent fancy bugs, initialize a VA's list node after it is
> removed from the list, so it pairs with VA's rb_node which
> is also initialized.
> 
> There is no functional change as a result of this patch.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  mm/vmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 745e89eb6ca1..82771e555273 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -978,7 +978,7 @@ __unlink_va(struct vmap_area *va, struct rb_root *root, bool augment)
>  	else
>  		rb_erase(&va->rb_node, root);
>  
> -	list_del(&va->list);
> +	list_del_init(&va->list);

Don't object this change, while list_del poison members, which is also
not bad?

static inline void list_del(struct list_head *entry)                                     
{                                                                                        
        __list_del_entry(entry);                                                         
        entry->next = LIST_POISON1;                                                      
        entry->prev = LIST_POISON2;                                                      
}   


>  	RB_CLEAR_NODE(&va->rb_node);
>  }
>  
> -- 
> 2.30.2
> 
>