2020년 6월 14일 (일) 오후 9:39, Muchun Song <songmuchun@xxxxxxxxxxxxx>님이 작성:
>
> The slabs_node() always return zero when CONFIG_SLUB_DEBUG is disabled.
> But some codes determine whether slab is empty by checking the return
> value of slabs_node(). As you know, the result is not correct. This
> problem can be reproduce by the follow code(and boot system with the
> cmdline of "slub_nomerge"):
>
> void *objs[32];
> struct kmem_cache *cache = kmem_cache_create("kmem-test", 128, 0,
> 0, 0);
>
> if (cache) {
> int i;
>
> /* Make a full slab */
> for (i = 0; i < ARRAY_SIZE(objs); i++)
> objs[i] = kmem_cache_alloc(cache, GFP_KERNEL_ACCOUNT);
>
> /*
> * This really should fail because the slab cache still has
> * objects. But we did destroy the @cache because of zero
> * returned by slabs_node().
> */
> kmem_cache_destroy(cache);
> }
>
> To fix it, we can move the nr_slabs of kmem_cache_node out of the
> CONFIG_SLUB_DEBUG. So we can get the corrent value returned by the
> slabs_node().
>
> With this patch applied, we will get a warning message and stack
> trace in the dmesg.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> mm/slab.h | 2 +-
> mm/slub.c | 80 +++++++++++++++++++++++++++++++++------------------------------
> 2 files changed, 43 insertions(+), 39 deletions(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 0b91f2a7b033..062d4542b7e2 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -619,8 +619,8 @@ struct kmem_cache_node {
> #ifdef CONFIG_SLUB
> unsigned long nr_partial;
> struct list_head partial;
> -#ifdef CONFIG_SLUB_DEBUG
> atomic_long_t nr_slabs;
> +#ifdef CONFIG_SLUB_DEBUG
> atomic_long_t total_objects;
> struct list_head full;
> #endif
> diff --git a/mm/slub.c b/mm/slub.c
> index 49b5cb7da318..1a3e6a5b7287 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
Hello,
You also need to initialize nr_slabs in init_kmem_cache_node()
on !CONFIG_SLUB_DEBUG.
Otherwise, looks good to me.
Thanks.
