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SubjectRe: [PATCH 1/1] mm/vmalloc: convert vmap_lazy_nr to atomic_long_t
On Thu 31-01-19 17:24:52, Uladzislau Rezki (Sony) wrote:
> vmap_lazy_nr variable has atomic_t type that is 4 bytes integer
> value on both 32 and 64 bit systems. lazy_max_pages() deals with
> "unsigned long" that is 8 bytes on 64 bit system, thus vmap_lazy_nr
> should be 8 bytes on 64 bit as well.

But do we really need 64b number of _pages_? I have hard time imagine
that we would have that many lazy pages to accumulate.

>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> ---
> mm/vmalloc.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index abe83f885069..755b02983d8d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -632,7 +632,7 @@ static unsigned long lazy_max_pages(void)
> return log * (32UL * 1024 * 1024 / PAGE_SIZE);
> }
>
> -static atomic_t vmap_lazy_nr = ATOMIC_INIT(0);
> +static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0);
>
> /*
> * Serialize vmap purging. There is no actual criticial section protected
> @@ -650,7 +650,7 @@ static void purge_fragmented_blocks_allcpus(void);
> */
> void set_iounmap_nonlazy(void)
> {
> - atomic_set(&vmap_lazy_nr, lazy_max_pages()+1);
> + atomic_long_set(&vmap_lazy_nr, lazy_max_pages()+1);
> }
>
> /*
> @@ -658,10 +658,10 @@ void set_iounmap_nonlazy(void)
> */
> static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
> {
> + unsigned long resched_threshold;
> struct llist_node *valist;
> struct vmap_area *va;
> struct vmap_area *n_va;
> - int resched_threshold;
>
> lockdep_assert_held(&vmap_purge_lock);
>
> @@ -681,16 +681,16 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
> }
>
> flush_tlb_kernel_range(start, end);
> - resched_threshold = (int) lazy_max_pages() << 1;
> + resched_threshold = lazy_max_pages() << 1;
>
> spin_lock(&vmap_area_lock);
> llist_for_each_entry_safe(va, n_va, valist, purge_list) {
> - int nr = (va->va_end - va->va_start) >> PAGE_SHIFT;
> + unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT;
>
> __free_vmap_area(va);
> - atomic_sub(nr, &vmap_lazy_nr);
> + atomic_long_sub(nr, &vmap_lazy_nr);
>
> - if (atomic_read(&vmap_lazy_nr) < resched_threshold)
> + if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)
> cond_resched_lock(&vmap_area_lock);
> }
> spin_unlock(&vmap_area_lock);
> @@ -727,10 +727,10 @@ static void purge_vmap_area_lazy(void)
> */
> static void free_vmap_area_noflush(struct vmap_area *va)
> {
> - int nr_lazy;
> + unsigned long nr_lazy;
>
> - nr_lazy = atomic_add_return((va->va_end - va->va_start) >> PAGE_SHIFT,
> - &vmap_lazy_nr);
> + nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >>
> + PAGE_SHIFT, &vmap_lazy_nr);
>
> /* After this point, we may free va at any time */
> llist_add(&va->purge_list, &vmap_purge_list);
> --
> 2.11.0
>

--
Michal Hocko
SUSE Labs

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