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Subject: Re: [PATCH v2 sl-b 2/5] mm: Make mem_dump_obj() handle NULL and
 zero-sized pointers
To:     paulmck@kernel.org, rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org,
        jiangshanlai@gmail.com, akpm@linux-foundation.org,
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        oleg@redhat.com, joel@joelfernandes.org, iamjoonsoo.kim@lge.com,
        andrii@kernel.org, Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>, linux-mm@kvack.org
References: <20201209011124.GA31164@paulmck-ThinkPad-P72>
 <20201209011303.32737-2-paulmck@kernel.org>
From:   Vlastimil Babka <vbabka@suse.cz>
Message-ID: <462f135a-f8e4-6291-6c1c-4fdd2e415462@suse.cz>
Date:   Wed, 9 Dec 2020 18:48:47 +0100
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On 12/9/20 2:13 AM, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
> 
> This commit makes mem_dump_obj() call out NULL and zero-sized pointers
> specially instead of classifying them as non-paged memory.
> 
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: <linux-mm@kvack.org>
> Reported-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/util.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/util.c b/mm/util.c
> index d0e60d2..8c2449f 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -985,7 +985,12 @@ int __weak memcmp_pages(struct page *page1, struct page *page2)
>  void mem_dump_obj(void *object)
>  {
>  	if (!virt_addr_valid(object)) {
> -		pr_cont(" non-paged (local) memory.\n");
> +		if (object == NULL)
> +			pr_cont(" NULL pointer.\n");
> +		else if (object == ZERO_SIZE_PTR)
> +			pr_cont(" zero-size pointer.\n");
> +		else
> +			pr_cont(" non-paged (local) memory.\n");
>  		return;
>  	}
>  	if (kmem_valid_obj(object)) {
>