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Date: Mon, 15 Jun 2015 23:18:16 +0200
From: Michal Hocko <mhocko@suse.cz>
To: Pali =?iso-8859-1?Q?Roh=E1r?= <pali.rohar@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>, Darren Hart <dvhart@infradead.org>,
        Ben Skeggs <bskeggs@redhat.com>, Stuart Hayes <stuart_hayes@dell.com>,
        Matthew Garrett <mjg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: Possible broken MM code in dell-laptop.c?
Message-ID: <20150615211816.GC16138@dhcp22.suse.cz>
References: <201506141105.07171@pali>
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On Sun 14-06-15 11:05:07, Pali Rohár wrote:
> Hello,
> 
> in drivers/platform/x86/dell-laptop.c is this part of code:
> 
> static int __init dell_init(void)
> {
> ...
> 	/*
> 	 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
> 	 * is passed to SMI handler.
> 	 */
> 	bufferpage = alloc_page(GFP_KERNEL | GFP_DMA32);
[...]
> 	buffer = page_address(bufferpage);
[...]
> fail_rfkill:
> 	free_page((unsigned long)bufferpage);

This one should be __free_page because it consumes struct page* and it
is the proper counter part for alloc_page. free_page, just to make it
confusing, consumes an address which has to be translated to a struct
page.

I have no idea why the API has been done this way and yeah, it is really
confusing.

[...]
> static void __exit dell_exit(void)
> {
> ...
> 	free_page((unsigned long)buffer);


-- 
Michal Hocko
SUSE Labs