linux-kernel - Re: [PATCH V3 2/2] mm/mmap: Drop generic protection

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Message-ID: <7c72a97f-d7d4-db27-faa5-fec01673cca7@arm.com>
Date:   Fri, 17 Jun 2022 08:59:12 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     "hch@...radead.org" <hch@...radead.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel test robot <lkp@...el.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH V3 2/2] mm/mmap: Drop generic protection_map[] array



On 6/16/22 11:42, hch@...radead.org wrote:
> On Thu, Jun 16, 2022 at 05:45:39AM +0000, Christophe Leroy wrote:
>>> +/* Note due to the way vm flags are laid out, the bits are XWR */
>>> +pgprot_t protection_map[16] = {
>>
>> Was const previously, now back to non const ? Maybe due to a conflict 
>> with linux/mm.h ? At least it should be __ro_after_init.
> 
> Maybe we just need to duplicate vm_get_page_prot in all the
> architectures and thus avoid making protection_map global in a
> common header entirely.  That certainly seems like the cleaner
> interface.

Agreed, also it does free up the platforms to provide any appropriate
qualifiers for the protection_map[] array i.e __ro_after_init, const
etc without impacting generic declaration used in a generic function.