[kernel-hardening] Re: [PATCH v2 04/13] mm: Track NR_KERNEL_STACK in KiB instead of number of stacks

[Michal Hocko <mhocko@kernel.org>]

On Fri 17-06-16 13:00:40, Andy Lutomirski wrote:
> Currently, NR_KERNEL_STACK tracks the number of kernel stacks in a
> zone.  This only makes sense if each kernel stack exists entirely in
> one zone, and allowing vmapped stacks could break this assumption.
> 
> Since frv has THREAD_SIZE < PAGE_SIZE, we need to track kernel stack
> allocations in a unit that divides both THREAD_SIZE and PAGE_SIZE on
> all architectures.  Keep it simple and use KiB.
> 
> Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: linux-mm@kvack.org
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

Makes sense to me.
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  drivers/base/node.c    | 3 +--
>  fs/proc/meminfo.c      | 2 +-
>  include/linux/mmzone.h | 2 +-
>  kernel/fork.c          | 3 ++-
>  mm/page_alloc.c        | 3 +--
>  5 files changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 560751bad294..27dc68a0ed2d 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -121,8 +121,7 @@ static ssize_t node_read_meminfo(struct device *dev,
>  		       nid, K(node_page_state(nid, NR_FILE_MAPPED)),
>  		       nid, K(node_page_state(nid, NR_ANON_PAGES)),
>  		       nid, K(i.sharedram),
> -		       nid, node_page_state(nid, NR_KERNEL_STACK) *
> -				THREAD_SIZE / 1024,
> +		       nid, node_page_state(nid, NR_KERNEL_STACK_KB),
>  		       nid, K(node_page_state(nid, NR_PAGETABLE)),
>  		       nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
>  		       nid, K(node_page_state(nid, NR_BOUNCE)),
> diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
> index 83720460c5bc..239b5a06cee0 100644
> --- a/fs/proc/meminfo.c
> +++ b/fs/proc/meminfo.c
> @@ -145,7 +145,7 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
>  				global_page_state(NR_SLAB_UNRECLAIMABLE)),
>  		K(global_page_state(NR_SLAB_RECLAIMABLE)),
>  		K(global_page_state(NR_SLAB_UNRECLAIMABLE)),
> -		global_page_state(NR_KERNEL_STACK) * THREAD_SIZE / 1024,
> +		global_page_state(NR_KERNEL_STACK_KB),
>  		K(global_page_state(NR_PAGETABLE)),
>  #ifdef CONFIG_QUICKLIST
>  		K(quicklist_total_size()),
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 02069c23486d..63f05a7efb54 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -127,7 +127,7 @@ enum zone_stat_item {
>  	NR_SLAB_RECLAIMABLE,
>  	NR_SLAB_UNRECLAIMABLE,
>  	NR_PAGETABLE,		/* used for pagetables */
> -	NR_KERNEL_STACK,
> +	NR_KERNEL_STACK_KB,	/* measured in KiB */
>  	/* Second 128 byte cacheline */
>  	NR_UNSTABLE_NFS,	/* NFS unstable pages */
>  	NR_BOUNCE,
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 5c2c355aa97f..be7f006af727 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -225,7 +225,8 @@ static void account_kernel_stack(struct thread_info *ti, int account)
>  {
>  	struct zone *zone = page_zone(virt_to_page(ti));
>  
> -	mod_zone_page_state(zone, NR_KERNEL_STACK, account);
> +	mod_zone_page_state(zone, NR_KERNEL_STACK_KB,
> +			    THREAD_SIZE / 1024 * account);
>  }
>  
>  void free_task(struct task_struct *tsk)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6903b695ebae..a277dea926c9 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4457,8 +4457,7 @@ void show_free_areas(unsigned int filter)
>  			K(zone_page_state(zone, NR_SHMEM)),
>  			K(zone_page_state(zone, NR_SLAB_RECLAIMABLE)),
>  			K(zone_page_state(zone, NR_SLAB_UNRECLAIMABLE)),
> -			zone_page_state(zone, NR_KERNEL_STACK) *
> -				THREAD_SIZE / 1024,
> +			zone_page_state(zone, NR_KERNEL_STACK_KB),
>  			K(zone_page_state(zone, NR_PAGETABLE)),
>  			K(zone_page_state(zone, NR_UNSTABLE_NFS)),
>  			K(zone_page_state(zone, NR_BOUNCE)),
> -- 
> 2.5.5

-- 
Michal Hocko
SUSE Labs