linux-kernel - Re: [PATCH] vm/agp: remove private page protection map

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Date:	Thu, 27 Jul 2006 00:24:27 +0100 (IST)
From:	Dave Airlie <airlied@...ux.ie>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Andrew Morton <akpm@...l.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] vm/agp: remove private page protection map

>
> I'm happy with the intent of your vm_get_page_prot() patch (and would
> like to extend it to other places after, minimizing references to the
> protection_map[]).  But there's a few aspects which distress me - the
> u8 type nowhere else in mm, the requirement that caller mask the arg,
> agp_convert_mmap_flags still using its own conversion from PROT_ to VM_
> while there's an inline in mm.h (though why someone thought to optimize
> and so obscure that version puzzles me!).  Would you be happy to insert
> your Sign-off in the replacement below?

No worries, I think davej can drop my one from his tree as well and take 
this..

Thanks for looking at this..

Dave.

>
>
> AGP keeps its own copy of the protection_map, upcoming DRM changes will
> also require access to this map from modules.
>
> Signed-off-by: Hugh Dickins <hugh@...itas.com>

Signed-of-by: Dave Airlie <airlied@...ux.ie>

> ---
>
> drivers/char/agp/frontend.c |   27 ++-------------------------
> include/linux/mm.h          |    1 +
> mm/mmap.c                   |    7 +++++++
> 3 files changed, 10 insertions(+), 25 deletions(-)
>
> --- 2.6.18-rc2-git6/drivers/char/agp/frontend.c	2006-07-16 00:17:07.000000000 +0100
> +++ linux/drivers/char/agp/frontend.c	2006-07-26 20:32:10.000000000 +0100
> @@ -151,35 +151,12 @@ static void agp_add_seg_to_client(struct
> 	client->segments = seg;
> }
>
> -/* Originally taken from linux/mm/mmap.c from the array
> - * protection_map.
> - * The original really should be exported to modules, or
> - * some routine which does the conversion for you
> - */
> -
> -static const pgprot_t my_protect_map[16] =
> -{
> -	__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
> -	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
> -};
> -
> static pgprot_t agp_convert_mmap_flags(int prot)
> {
> -#define _trans(x,bit1,bit2) \
> -((bit1==bit2)?(x&bit1):(x&bit1)?bit2:0)
> -
> 	unsigned long prot_bits;
> -	pgprot_t temp;
> -
> -	prot_bits = _trans(prot, PROT_READ, VM_READ) |
> -	    _trans(prot, PROT_WRITE, VM_WRITE) |
> -	    _trans(prot, PROT_EXEC, VM_EXEC);
> -
> -	prot_bits |= VM_SHARED;
>
> -	temp = my_protect_map[prot_bits & 0x0000000f];
> -
> -	return temp;
> +	prot_bits = calc_vm_prot_bits(prot) | VM_SHARED;
> +	return vm_get_page_prot(prot_bits);
> }
>
> static int agp_create_segment(struct agp_client *client, struct agp_region *region)
> --- 2.6.18-rc2-git6/include/linux/mm.h	2006-07-16 00:17:31.000000000 +0100
> +++ linux/include/linux/mm.h	2006-07-26 20:33:59.000000000 +0100
> @@ -1012,6 +1012,7 @@ static inline unsigned long vma_pages(st
> 	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> }
>
> +pgprot_t vm_get_page_prot(unsigned long vm_flags);
> struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
> struct page *vmalloc_to_page(void *addr);
> unsigned long vmalloc_to_pfn(void *addr);
> --- 2.6.18-rc2-git6/mm/mmap.c	2006-07-16 00:17:39.000000000 +0100
> +++ linux/mm/mmap.c	2006-07-26 20:40:12.000000000 +0100
> @@ -60,6 +60,13 @@ pgprot_t protection_map[16] = {
> 	__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
> };
>
> +pgprot_t vm_get_page_prot(unsigned long vm_flags)
> +{
> +	return protection_map[vm_flags &
> +				(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
> +}
> +EXPORT_SYMBOL(vm_get_page_prot);
> +
> int sysctl_overcommit_memory = OVERCOMMIT_GUESS;  /* heuristic overcommit */
> int sysctl_overcommit_ratio = 50;	/* default is 50% */
> int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
>

-- 
David Airlie, Software Engineer
http://www.skynet.ie/~airlied / airlied at skynet.ie
Linux kernel - DRI, VAX / pam_smb / ILUG

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