On 08.08.19 09:18, Chuhong Yuan wrote:
> Reference counters are preferred to use refcount_t instead of
> atomic_t.
> This is because the implementation of refcount_t can prevent
> overflows and detect possible use-after-free.
> So convert atomic_t ref counters to refcount_t.
>
> Signed-off-by: Chuhong Yuan <hslester96@xxxxxxxxx>
> ---
> arch/s390/include/asm/gmap.h | 4 +++-
> arch/s390/mm/gmap.c | 10 +++++-----
> 2 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/arch/s390/include/asm/gmap.h b/arch/s390/include/asm/gmap.h
> index fcbd638fb9f4..37f96b6f0e61 100644
> --- a/arch/s390/include/asm/gmap.h
> +++ b/arch/s390/include/asm/gmap.h
> @@ -9,6 +9,8 @@
> #ifndef _ASM_S390_GMAP_H
> #define _ASM_S390_GMAP_H
>
> +#include <linux/refcount.h>
> +
> /* Generic bits for GMAP notification on DAT table entry changes. */
> #define GMAP_NOTIFY_SHADOW 0x2
> #define GMAP_NOTIFY_MPROT 0x1
> @@ -46,7 +48,7 @@ struct gmap {
> struct radix_tree_root guest_to_host;
> struct radix_tree_root host_to_guest;
> spinlock_t guest_table_lock;
> - atomic_t ref_count;
> + refcount_t ref_count;
> unsigned long *table;
> unsigned long asce;
> unsigned long asce_end;
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 39c3a6e3d262..cd8e03f04d6d 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -67,7 +67,7 @@ static struct gmap *gmap_alloc(unsigned long limit)
> INIT_RADIX_TREE(&gmap->host_to_rmap, GFP_ATOMIC);
> spin_lock_init(&gmap->guest_table_lock);
> spin_lock_init(&gmap->shadow_lock);
> - atomic_set(&gmap->ref_count, 1);
> + refcount_set(&gmap->ref_count, 1);
> page = alloc_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
> if (!page)
> goto out_free;
> @@ -214,7 +214,7 @@ static void gmap_free(struct gmap *gmap)
> */
> struct gmap *gmap_get(struct gmap *gmap)
> {
> - atomic_inc(&gmap->ref_count);
> + refcount_inc(&gmap->ref_count);
> return gmap;
> }
> EXPORT_SYMBOL_GPL(gmap_get);
> @@ -227,7 +227,7 @@ EXPORT_SYMBOL_GPL(gmap_get);
> */
> void gmap_put(struct gmap *gmap)
> {
> - if (atomic_dec_return(&gmap->ref_count) == 0)
> + if (refcount_dec_and_test(&gmap->ref_count))
> gmap_free(gmap);
> }
> EXPORT_SYMBOL_GPL(gmap_put);
> @@ -1594,7 +1594,7 @@ static struct gmap *gmap_find_shadow(struct gmap *parent, unsigned long asce,
> continue;
> if (!sg->initialized)
> return ERR_PTR(-EAGAIN);
> - atomic_inc(&sg->ref_count);
> + refcount_inc(&sg->ref_count);
> return sg;
> }
> return NULL;
> @@ -1682,7 +1682,7 @@ struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
> }
> }
> }
> - atomic_set(&new->ref_count, 2);
> + refcount_set(&new->ref_count, 2);
> list_add(&new->list, &parent->children);
> if (asce & _ASCE_REAL_SPACE) {
> /* nothing to protect, return right away */
>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
