On Wed, Jun 10, 2020 at 06:31:33PM +0200, Vlastimil Babka wrote:
> There are few places that call kmem_cache_debug(s) (which tests if any of debug
> flags are enabled for a cache) immediatelly followed by a test for a specific
> flag. The compiler can probably eliminate the extra check, but we can make the
> code nicer by introducing kmem_cache_debug_flags() that works like
> kmem_cache_debug() (including the static key check) but tests for specifig
> flag(s). The next patches will add more users.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/slub.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
Acked-by: Roman Gushchin <guro@xxxxxx>
One small nit below.
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 24d3e5f832aa..c8e8b4ae2451 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -122,18 +122,28 @@ DEFINE_STATIC_KEY_FALSE(slub_debug_enabled);
> #endif
> #endif
>
> -static inline int kmem_cache_debug(struct kmem_cache *s)
> +/*
> + * Returns true if any of the specified slub_debug flags is enabled for the
> + * cache. Use only for flags parsed by setup_slub_debug() as it also enables
> + * the static key.
Maybe adding VM_WARN_ON_ONCE(!(flags & SLAB_DEBUG_FLAGS)) to make sure the flags
argument is valid?
> + */
> +static inline int kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t flags)
> {
> #ifdef CONFIG_SLUB_DEBUG
> if (static_branch_unlikely(&slub_debug_enabled))
> - return s->flags & SLAB_DEBUG_FLAGS;
> + return s->flags & flags;
> #endif
> return 0;
> }
>
> +static inline int kmem_cache_debug(struct kmem_cache *s)
> +{
> + return kmem_cache_debug_flags(s, SLAB_DEBUG_FLAGS);
> +}
> +
> void *fixup_red_left(struct kmem_cache *s, void *p)
> {
> - if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE)
> + if (kmem_cache_debug_flags(s, SLAB_RED_ZONE))
> p += s->red_left_pad;
>
> return p;
> @@ -4076,7 +4086,7 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
> offset = (ptr - page_address(page)) % s->size;
>
> /* Adjust for redzone and reject if within the redzone. */
> - if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
> + if (kmem_cache_debug_flags(s, SLAB_RED_ZONE)) {
> if (offset < s->red_left_pad)
> usercopy_abort("SLUB object in left red zone",
> s->name, to_user, offset, n);
> --
> 2.26.2
>
