Commit 77be4b13 authored by Shuah Khan's avatar Shuah Khan Committed by Pekka Enberg
Browse files

mm/slab: restructure kmem_cache_create() debug checks 

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



[akpm@linux-foundation.org: fix build, cleanup]
Signed-off-by: default avatarShuah Khan <shuah.khan@hp.com>
Acked-by: default avatarChristoph Lameter <cl@linux.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent b920536a

mm/slab_common.c

+48 −49
Original line number Diff line number Diff line
@@ -23,6 +23,52 @@ 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;



	if (!name || in_interrupt() || size < sizeof(void *) ||

		size > KMALLOC_MAX_SIZE) {

		pr_err("kmem_cache_create(%s) integrity check failed\n", name);

		return -EINVAL;

	}



	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.
@@ -53,60 +99,13 @@ 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);

		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) == 0)

		s = __kmem_cache_create(name, size, align, flags, ctor);



#ifdef CONFIG_DEBUG_VM

oops:

#endif

	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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