Re: [PATCH] mm: don't rely on flags coincidence

[Wu Fengguang <fengguang.wu@intel.com>]

On Tue, Jun 23, 2009 at 08:52:49PM +0800, Hugh Dickins wrote:
> Indeed FOLL_WRITE matches FAULT_FLAG_WRITE, matches GUP_FLAGS_WRITE,
> and it's tempting to devise a set of Grand Unified Paging flags;
> but not today.  So until then, let's rely upon the compiler to spot
> the coincidence, "rather than have that subtle dependency and a
> comment for it" - as you remarked in another context yesterday.
> 
> Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>

Acked-by: Wu Fengguang <fengguang.wu@intel.com>

> ---
> 
>  mm/memory.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> --- 2.6.30-git20/mm/memory.c	2009-06-23 11:06:25.000000000 +0100
> +++ linux/mm/memory.c	2009-06-23 13:07:57.000000000 +0100
> @@ -1311,8 +1311,10 @@ int __get_user_pages(struct task_struct
>  			while (!(page = follow_page(vma, start, foll_flags))) {
>  				int ret;
>  
> -				/* FOLL_WRITE matches FAULT_FLAG_WRITE! */
> -				ret = handle_mm_fault(mm, vma, start, foll_flags & FOLL_WRITE);
> +				ret = handle_mm_fault(mm, vma, start,
> +					(foll_flags & FOLL_WRITE) ?
> +					FAULT_FLAG_WRITE : 0);
> +
>  				if (ret & VM_FAULT_ERROR) {
>  					if (ret & VM_FAULT_OOM)
>  						return i ? i : -ENOMEM;

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