Re: [PATCH 08/30] mm: serialize access to min_free_kbytes

Pekka Enberg
2008-07-30T12:36:16Z

On Thu, 2008-07-24 at 16:00 +0200, Peter Zijlstra wrote:
> plain text document attachment (mm-setup_per_zone_pages_min.patch)
> There is a small race between the procfs caller and the memory hotplug caller
> of setup_per_zone_pages_min(). Not a big deal, but the next patch will add yet
> another caller. Time to close the gap.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

Looks good to me.

Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>

> ---
> mm/page_alloc.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -118,6 +118,7 @@ static char * const zone_names[MAX_NR_ZO
> "Movable",
> };
>
> +static DEFINE_SPINLOCK(min_free_lock);
> int min_free_kbytes = 1024;
>
> unsigned long __meminitdata nr_kernel_pages;
> @@ -4333,12 +4334,12 @@ static void setup_per_zone_lowmem_reserv
> }
>
> /**
> - * setup_per_zone_pages_min - called when min_free_kbytes changes.
> + * __setup_per_zone_pages_min - called when min_free_kbytes changes.
> *
> * Ensures that the pages_{min,low,high} values for each zone are set correctly
> * with respect to min_free_kbytes.
> */
> -void setup_per_zone_pages_min(void)
> +static void __setup_per_zone_pages_min(void)
> {
> unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
> unsigned long lowmem_pages = 0;
> @@ -4433,6 +4434,15 @@ void setup_per_zone_inactive_ratio(void)
> }
> }
>
> +void setup_per_zone_pages_min(void)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&min_free_lock, flags);
> + __setup_per_zone_pages_min();
> + spin_unlock_irqrestore(&min_free_lock, flags);
> +}
> +
> /*
> * Initialise min_free_kbytes.
> *
> @@ -4468,7 +4478,7 @@ static int __init init_per_zone_pages_mi
> min_free_kbytes = 128;
> if (min_free_kbytes > 65536)
> min_free_kbytes = 65536;
> - setup_per_zone_pages_min();
> + __setup_per_zone_pages_min();
> setup_per_zone_lowmem_reserve();
> setup_per_zone_inactive_ratio();
> return 0;
>