Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA

[KOSAKI Motohiro]

>  struct anon_vma *page_lock_anon_vma(struct page *page)
>  {
> @@ -294,14 +309,24 @@ struct anon_vma *page_lock_anon_vma(struct page *page)
>  	unsigned long anon_mapping;
>  
>  	rcu_read_lock();
> -	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
> +	anon_mapping = (unsigned long)rcu_dereference(page->mapping);
>  	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
>  		goto out;
> -	if (!page_mapped(page))
> -		goto out;
>  
>  	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
>  	spin_lock(&anon_vma->lock);

Does anon->lock dereference is guranteed if page->_mapcount==-1?
It can be freed miliseconds ago, rcu_read_lock() doesn't provide such
gurantee.

perhaps, I'm missing your point.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/