On Mon, 2012-08-06 at 15:13 -0600, Shuah Khan wrote:
> kmem_cache_create() does cache integrity checks when CONFIG_DEBUG_VM
> is defined. These checks interspersed with the regular code path has
> lead to compile time warnings when compiled without CONFIG_DEBUG_VM
> defined. Restructuring the code to move the integrity checks in to a new
> function would eliminate the current compile warning problem and also
> will allow for future changes to the debug only code to evolve without
> introducing new warnings in the regular path. This restructuring work
> is based on the discussion in the following thread:
>
> https://lkml.org/lkml/2012/7/13/424
Comments, questions. Does this patch look good?
Thanks,
-- Shuah
>
> Signed-off-by: Shuah Khan <shuah.k...@hp.com>
> ---
> mm/slab_common.c | 79
> +++++++++++++++++++++++++++++-------------------------
> 1 file changed, 43 insertions(+), 36 deletions(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 12637ce..67409f7 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -23,6 +23,46 @@ enum slab_state slab_state;
> LIST_HEAD(slab_caches);
> DEFINE_MUTEX(slab_mutex);
>
> +#ifdef CONFIG_DEBUG_VM
> +static int kmem_cache_sanity_check(const char *name, size_t size)
> +{
> + struct kmem_cache *s = NULL;
> +
> + list_for_each_entry(s, &slab_caches, list) {
> + char tmp;
> + int res;
> +
> + /*
> + * This happens when the module gets unloaded and doesn't
> + * destroy its slab cache and no-one else reuses the vmalloc
> + * area of the module. Print a warning.
> + */
> + res = probe_kernel_address(s->name, tmp);
> + if (res) {
> + pr_err("Slab cache with size %d has lost its name\n",
> + s->object_size);
> + continue;
> + }
> +
> + if (!strcmp(s->name, name)) {
> + pr_err("%s (%s): Cache name already exists.\n",
> + __func__, name);
> + dump_stack();
> + s = NULL;
> + return -EINVAL;
> + }
> + }
> +
> + WARN_ON(strchr(name, ' ')); /* It confuses parsers */
> + return 0;
> +}
> +#else
> +static inline int kmem_cache_sanity_check(const char *name, size_t size)
> +{
> + return 0;
> +}
> +#endif
> +
> /*
> * kmem_cache_create - Create a cache.
> * @name: A string which is used in /proc/slabinfo to identify this cache.
> @@ -53,48 +93,17 @@ struct kmem_cache *kmem_cache_create(const char *name,
> size_t size, size_t align
> {
> struct kmem_cache *s = NULL;
>
> -#ifdef CONFIG_DEBUG_VM
> if (!name || in_interrupt() || size < sizeof(void *) ||
> size > KMALLOC_MAX_SIZE) {
> - printk(KERN_ERR "kmem_cache_create(%s) integrity check"
> - " failed\n", name);
> + pr_err("kmem_cache_create(%s) integrity check failed\n", name);
> goto out;
> }
> -#endif
>
> get_online_cpus();
> mutex_lock(&slab_mutex);
>
> -#ifdef CONFIG_DEBUG_VM
> - list_for_each_entry(s, &slab_caches, list) {
> - char tmp;
> - int res;
> -
> - /*
> - * This happens when the module gets unloaded and doesn't
> - * destroy its slab cache and no-one else reuses the vmalloc
> - * area of the module. Print a warning.
> - */
> - res = probe_kernel_address(s->name, tmp);
> - if (res) {
> - printk(KERN_ERR
> - "Slab cache with size %d has lost its name\n",
> - s->object_size);
> - continue;
> - }
> -
> - if (!strcmp(s->name, name)) {
> - printk(KERN_ERR "kmem_cache_create(%s): Cache name"
> - " already exists.\n",
> - name);
> - dump_stack();
> - s = NULL;
> - goto oops;
> - }
> - }
> -
> - WARN_ON(strchr(name, ' ')); /* It confuses parsers */
> -#endif
> + if (kmem_cache_sanity_check(name, size))
> + goto oops;
>
> s = __kmem_cache_create(name, size, align, flags, ctor);
>
> @@ -102,9 +111,7 @@ oops:
> mutex_unlock(&slab_mutex);
> put_online_cpus();
>
> -#ifdef CONFIG_DEBUG_VM
> out:
> -#endif
> if (!s && (flags & SLAB_PANIC))
> panic("kmem_cache_create: Failed to create slab '%s'\n", name);
>
--
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