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Date: Wed, 26 Sep 2018 16:14:19 +0000
From: Christopher Lameter <cl@linux.com>
Subject: Re: [PATCH] mm/slub: disallow obj's allocation on page with mismatched
 pfmemalloc purpose
In-Reply-To: <1537944728-18036-1-git-send-email-kernelfans@gmail.com>
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Sender: owner-linux-mm@kvack.org
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To: Pingfan Liu <kernelfans@gmail.com>
Cc: linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Andrew Morton <akpm@linux-foundation.org>

On Wed, 26 Sep 2018, Pingfan Liu wrote:

> -
>  	if (unlikely(!freelist)) {
>  		slab_out_of_memory(s, gfpflags, node);
>  		return NULL;
>  	}
>
> +	VM_BUG_ON(!pfmemalloc_match(page, gfpflags));
>  	page = c->page;
> -	if (likely(!kmem_cache_debug(s) && pfmemalloc_match(page, gfpflags)))
> +	if (likely(!kmem_cache_debug(s))
>  		goto load_freelist;
>
>  	/* Only entered in the debug case */
> -	if (kmem_cache_debug(s) &&
> -			!alloc_debug_processing(s, page, freelist, addr))
> +	if (!alloc_debug_processing(s, page, freelist, addr))
>  		goto new_slab;	/* Slab failed checks. Next slab needed */
> -
> -	deactivate_slab(s, page, get_freepointer(s, freelist), c);

In the debug case the slab needs to be deactivated. Otherwise the
slowpath will not be used and debug checks on the following objects will
not be done.

> -	return freelist;
> +	else
> +		goto load_freelist;
>  }
>
>  /*
>