linux-kernel - Re: [Regression]: mm: nommu: Memory leak introduced with commit "mm/nommu: use alloc_pages_exact() rather than its own implementation"

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Date:	Mon, 16 Feb 2015 12:45:24 +0100
From:	Maxime Coquelin <mcoquelin.stm32@...il.com>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Regression]: mm: nommu: Memory leak introduced with commit
 "mm/nommu: use alloc_pages_exact() rather than its own implementation"

Hello Joonsoo,

2015-02-16 5:43 GMT+01:00 Joonsoo Kim <js1304@...il.com>:
>
> Hello,
>
> Sorry for my mistake.
> Problem happens because when we allocate memory through
> __get_free_pages(), refcount of each pages is not 1 except
> head page. Below modification will fix your problem. Could you
> test it, please?

I just tested it, and confirm it fixes the regression.

You can add my:
Tested-by: Maxime Coquelin <mcoquelin.stm32@...il.com>

Thanks for the quick fix!
Maxime

>
> Thanks.
>
> ------------>8-------------
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 28bd8c4..ff6c1e2 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -1189,11 +1189,9 @@ static int do_mmap_private(struct vm_area_struct *vma,
>         if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages) {
>                 total = point;
>                 kdebug("try to alloc exact %lu pages", total);
> -               base = alloc_pages_exact(len, GFP_KERNEL);
> -       } else {
> -               base = (void *)__get_free_pages(GFP_KERNEL, order);
>         }
>
> +       base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
>         if (!base)
>                 goto enomem;
--
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