Re: 2.6.15-rc1-git crashes in kswapd

[Rohit Seth <rohit.seth@intel.com>]

On Thu, 2005-11-17 at 13:02 -0800, Andrew Morton wrote:
> Jens Axboe <axboe@suse.de> wrote:
> >
> > does zonelist->zones change further down the path
> > and we need the revalidation before after restarting?
> > 
> 
> err, yeah.   Like this, I think?
> 
> 

Good catch Jens.  The zone variables (and their initialization) got
slightly changed because we moved the zone_statistics part from
_alloc_pages to get_page_from_freelist function.

Andrew's patch below is the right fix.

-rohit
> 
> We modify local variable `z' while walking across the zones.  So we need to
> restore it if we do the `goto restart' thing in the rare case where the
> oom-killer was called.
> 
> 
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> ---
> 
>  mm/page_alloc.c |    9 ++++-----
>  1 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff -puN mm/page_alloc.c~alloc_pages-oops-fix mm/page_alloc.c
> --- 25/mm/page_alloc.c~alloc_pages-oops-fix	Thu Nov 17 12:58:38 2005
> +++ 25-akpm/mm/page_alloc.c	Thu Nov 17 12:59:19 2005
> @@ -845,13 +845,12 @@ __alloc_pages(gfp_t gfp_mask, unsigned i
>  
>  	might_sleep_if(wait);
>  
> -	z = zonelist->zones;  /* the list of zones suitable for gfp_mask */
> +restart:
> +	z = zonelist->zones;	  /* the list of zones suitable for gfp_mask */
>  
> -	if (unlikely(*z == NULL)) {
> -		/* Should this ever happen?? */
> +	if (unlikely(*z == NULL)) /* Should this ever happen?? */
>  		return NULL;
> -	}
> -restart:
> +
>  	page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, order,
>  				zonelist, ALLOC_CPUSET);
>  	if (page)
> _
>