mm, sl[aou]b: Use a common mutex definition

Use the mutex definition from SLAB and make it the common way to take a sleeping lock.

This has the effect of using a mutex instead of a rw semaphore for SLUB.

SLOB gains the use of a mutex for kmem_cache_create serialization.
Not needed now but SLOB may acquire some more features later (like slabinfo
/ sysfs support) through the expansion of the common code that will
need this.

Reviewed-by: Glauber Costa <glommer@parallels.com>
Reviewed-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

4 files changed, 82 insertions, 86 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 59a466b85b0f..fd7dac67c26e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -68,7 +68,7 @@
  * Further notes from the original documentation:
  *
  * 11 April '97.  Started multi-threading - markhe
- *      The global cache-chain is protected by the mutex 'cache_chain_mutex'.
+ *      The global cache-chain is protected by the mutex 'slab_mutex'.
  *      The sem is only needed when accessing/extending the cache-chain, which
  *      can never happen inside an interrupt (kmem_cache_create(),
  *      kmem_cache_shrink() and kmem_cache_reap()).
@@ -671,12 +671,6 @@ static void slab_set_debugobj_lock_classes(struct kmem_cache *cachep)
 }
 #endif
 
-/*
- * Guard access to the cache-chain.
- */
-static DEFINE_MUTEX(cache_chain_mutex);
-static struct list_head cache_chain;
-
 static DEFINE_PER_CPU(struct delayed_work, slab_reap_work);
 
 static inline struct array_cache *cpu_cache_get(struct kmem_cache *cachep)
@@ -1100,7 +1094,7 @@ static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
  * When hotplugging memory or a cpu, existing nodelists are not replaced if
  * already in use.
  *
- * Must hold cache_chain_mutex.
+ * Must hold slab_mutex.
  */
 static int init_cache_nodelists_node(int node)
 {
@@ -1108,7 +1102,7 @@ static int init_cache_nodelists_node(int node)
         struct kmem_list3 *l3;
         const int memsize = sizeof(struct kmem_list3);
 
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 /*
                  * Set up the size64 kmemlist for cpu before we can
                  * begin anything. Make sure some other cpu on this
@@ -1124,7 +1118,7 @@ static int init_cache_nodelists_node(int node)
 
                         /*
                          * The l3s don't come and go as CPUs come and
-                         * go.  cache_chain_mutex is sufficient
+                         * go.  slab_mutex is sufficient
                          * protection here.
                          */
                         cachep->nodelists[node] = l3;
@@ -1146,7 +1140,7 @@ static void __cpuinit cpuup_canceled(long cpu)
         int node = cpu_to_mem(cpu);
         const struct cpumask *mask = cpumask_of_node(node);
 
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 struct array_cache *nc;
                 struct array_cache *shared;
                 struct array_cache **alien;
@@ -1196,7 +1190,7 @@ free_array_cache:
          * the respective cache's slabs,  now we can go ahead and
          * shrink each nodelist to its limit.
          */
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 l3 = cachep->nodelists[node];
                 if (!l3)
                         continue;
@@ -1225,7 +1219,7 @@ static int __cpuinit cpuup_prepare(long cpu)
          * Now we can go ahead with allocating the shared arrays and
          * array caches
          */
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 struct array_cache *nc;
                 struct array_cache *shared = NULL;
                 struct array_cache **alien = NULL;
@@ -1293,9 +1287,9 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
         switch (action) {
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
                 err = cpuup_prepare(cpu);
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 break;
         case CPU_ONLINE:
         case CPU_ONLINE_FROZEN:
@@ -1305,7 +1299,7 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
         case CPU_DOWN_PREPARE:
         case CPU_DOWN_PREPARE_FROZEN:
                 /*
-                 * Shutdown cache reaper. Note that the cache_chain_mutex is
+                 * Shutdown cache reaper. Note that the slab_mutex is
                  * held so that if cache_reap() is invoked it cannot do
                  * anything expensive but will only modify reap_work
                  * and reschedule the timer.
@@ -1332,9 +1326,9 @@ static int __cpuinit cpuup_callback(struct notifier_block *nfb,
 #endif
         case CPU_UP_CANCELED:
         case CPU_UP_CANCELED_FROZEN:
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
                 cpuup_canceled(cpu);
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 break;
         }
         return notifier_from_errno(err);
@@ -1350,14 +1344,14 @@ static struct notifier_block __cpuinitdata cpucache_notifier = {
  * Returns -EBUSY if all objects cannot be drained so that the node is not
  * removed.
  *
- * Must hold cache_chain_mutex.
+ * Must hold slab_mutex.
  */
 static int __meminit drain_cache_nodelists_node(int node)
 {
         struct kmem_cache *cachep;
         int ret = 0;
 
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 struct kmem_list3 *l3;
 
                 l3 = cachep->nodelists[node];
@@ -1388,14 +1382,14 @@ static int __meminit slab_memory_callback(struct notifier_block *self,
 
         switch (action) {
         case MEM_GOING_ONLINE:
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
                 ret = init_cache_nodelists_node(nid);
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 break;
         case MEM_GOING_OFFLINE:
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
                 ret = drain_cache_nodelists_node(nid);
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 break;
         case MEM_ONLINE:
         case MEM_OFFLINE:
@@ -1499,8 +1493,8 @@ void __init kmem_cache_init(void)
         node = numa_mem_id();
 
         /* 1) create the cache_cache */
-        INIT_LIST_HEAD(&cache_chain);
-        list_add(&cache_cache.list, &cache_chain);
+        INIT_LIST_HEAD(&slab_caches);
+        list_add(&cache_cache.list, &slab_caches);
         cache_cache.colour_off = cache_line_size();
         cache_cache.array[smp_processor_id()] = &initarray_cache.cache;
         cache_cache.nodelists[node] = &initkmem_list3[CACHE_CACHE + node];
@@ -1642,11 +1636,11 @@ void __init kmem_cache_init_late(void)
         init_lock_keys();
 
         /* 6) resize the head arrays to their final sizes */
-        mutex_lock(&cache_chain_mutex);
-        list_for_each_entry(cachep, &cache_chain, list)
+        mutex_lock(&slab_mutex);
+        list_for_each_entry(cachep, &slab_caches, list)
                 if (enable_cpucache(cachep, GFP_NOWAIT))
                         BUG();
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
 
         /* Done! */
         slab_state = FULL;
@@ -2253,10 +2247,10 @@ __kmem_cache_create (const char *name, size_t size, size_t align,
          */
         if (slab_is_available()) {
                 get_online_cpus();
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
         }
 
-        list_for_each_entry(pc, &cache_chain, list) {
+        list_for_each_entry(pc, &slab_caches, list) {
                 char tmp;
                 int res;
 
@@ -2500,10 +2494,10 @@ __kmem_cache_create (const char *name, size_t size, size_t align,
         }
 
         /* cache setup completed, link it into the list */
-        list_add(&cachep->list, &cache_chain);
+        list_add(&cachep->list, &slab_caches);
 oops:
         if (slab_is_available()) {
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 put_online_cpus();
         }
         return cachep;
@@ -2622,7 +2616,7 @@ out:
         return nr_freed;
 }
 
-/* Called with cache_chain_mutex held to protect against cpu hotplug */
+/* Called with slab_mutex held to protect against cpu hotplug */
 static int __cache_shrink(struct kmem_cache *cachep)
 {
         int ret = 0, i = 0;
@@ -2657,9 +2651,9 @@ int kmem_cache_shrink(struct kmem_cache *cachep)
         BUG_ON(!cachep || in_interrupt());
 
         get_online_cpus();
-        mutex_lock(&cache_chain_mutex);
+        mutex_lock(&slab_mutex);
         ret = __cache_shrink(cachep);
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
         put_online_cpus();
         return ret;
 }
@@ -2687,15 +2681,15 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
 
         /* Find the cache in the chain of caches. */
         get_online_cpus();
-        mutex_lock(&cache_chain_mutex);
+        mutex_lock(&slab_mutex);
         /*
          * the chain is never empty, cache_cache is never destroyed
          */
         list_del(&cachep->list);
         if (__cache_shrink(cachep)) {
                 slab_error(cachep, "Can't free all objects");
-                list_add(&cachep->list, &cache_chain);
-                mutex_unlock(&cache_chain_mutex);
+                list_add(&cachep->list, &slab_caches);
+                mutex_unlock(&slab_mutex);
                 put_online_cpus();
                 return;
         }
@@ -2704,7 +2698,7 @@ void kmem_cache_destroy(struct kmem_cache *cachep)
                 rcu_barrier();
 
         __kmem_cache_destroy(cachep);
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
         put_online_cpus();
 }
 EXPORT_SYMBOL(kmem_cache_destroy);
@@ -4017,7 +4011,7 @@ static void do_ccupdate_local(void *info)
         new->new[smp_processor_id()] = old;
 }
 
-/* Always called with the cache_chain_mutex held */
+/* Always called with the slab_mutex held */
 static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
                                 int batchcount, int shared, gfp_t gfp)
 {
@@ -4061,7 +4055,7 @@ static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
         return alloc_kmemlist(cachep, gfp);
 }
 
-/* Called with cache_chain_mutex held always */
+/* Called with slab_mutex held always */
 static int enable_cpucache(struct kmem_cache *cachep, gfp_t gfp)
 {
         int err;
@@ -4163,11 +4157,11 @@ static void cache_reap(struct work_struct *w)
         int node = numa_mem_id();
         struct delayed_work *work = to_delayed_work(w);
 
-        if (!mutex_trylock(&cache_chain_mutex))
+        if (!mutex_trylock(&slab_mutex))
                 /* Give up. Setup the next iteration. */
                 goto out;
 
-        list_for_each_entry(searchp, &cache_chain, list) {
+        list_for_each_entry(searchp, &slab_caches, list) {
                 check_irq_on();
 
                 /*
@@ -4205,7 +4199,7 @@ next:
                 cond_resched();
         }
         check_irq_on();
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
         next_reap_node();
 out:
         /* Set up the next iteration */
@@ -4241,21 +4235,21 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 {
         loff_t n = *pos;
 
-        mutex_lock(&cache_chain_mutex);
+        mutex_lock(&slab_mutex);
         if (!n)
                 print_slabinfo_header(m);
 
-        return seq_list_start(&cache_chain, *pos);
+        return seq_list_start(&slab_caches, *pos);
 }
 
 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 {
-        return seq_list_next(p, &cache_chain, pos);
+        return seq_list_next(p, &slab_caches, pos);
 }
 
 static void s_stop(struct seq_file *m, void *p)
 {
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
 }
 
 static int s_show(struct seq_file *m, void *p)
@@ -4406,9 +4400,9 @@ static ssize_t slabinfo_write(struct file *file, const char __user *buffer,
                 return -EINVAL;
 
         /* Find the cache in the chain of caches. */
-        mutex_lock(&cache_chain_mutex);
+        mutex_lock(&slab_mutex);
         res = -EINVAL;
-        list_for_each_entry(cachep, &cache_chain, list) {
+        list_for_each_entry(cachep, &slab_caches, list) {
                 if (!strcmp(cachep->name, kbuf)) {
                         if (limit < 1 || batchcount < 1 ||
                                         batchcount > limit || shared < 0) {
@@ -4421,7 +4415,7 @@ static ssize_t slabinfo_write(struct file *file, const char __user *buffer,
                         break;
                 }
         }
-        mutex_unlock(&cache_chain_mutex);
+        mutex_unlock(&slab_mutex);
         if (res >= 0)
                 res = count;
         return res;
@@ -4444,8 +4438,8 @@ static const struct file_operations proc_slabinfo_operations = {
 
 static void *leaks_start(struct seq_file *m, loff_t *pos)
 {
-        mutex_lock(&cache_chain_mutex);
-        return seq_list_start(&cache_chain, *pos);
+        mutex_lock(&slab_mutex);
+        return seq_list_start(&slab_caches, *pos);
 }
 
 static inline int add_caller(unsigned long *n, unsigned long v)
@@ -4544,17 +4538,17 @@ static int leaks_show(struct seq_file *m, void *p)
         name = cachep->name;
         if (n[0] == n[1]) {
                 /* Increase the buffer size */
-                mutex_unlock(&cache_chain_mutex);
+                mutex_unlock(&slab_mutex);
                 m->private = kzalloc(n[0] * 4 * sizeof(unsigned long), GFP_KERNEL);
                 if (!m->private) {
                         /* Too bad, we are really out */
                         m->private = n;
-                        mutex_lock(&cache_chain_mutex);
+                        mutex_lock(&slab_mutex);
                         return -ENOMEM;
                 }
                 *(unsigned long *)m->private = n[0] * 2;
                 kfree(n);
-                mutex_lock(&cache_chain_mutex);
+                mutex_lock(&slab_mutex);
                 /* Now make sure this entry will be retried */
                 m->count = m->size;
                 return 0;
diff --git a/mm/slab.h b/mm/slab.h
index f9a9815cdc82..db7848caaa25 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -23,6 +23,10 @@ enum slab_state {
 
 extern enum slab_state slab_state;
 
+/* The slab cache mutex protects the management structures during changes */
+extern struct mutex slab_mutex;
+extern struct list_head slab_caches;
+
 struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
         size_t align, unsigned long flags, void (*ctor)(void *));
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index ca1aaf69a1f5..50e1ff10bff9 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -19,6 +19,8 @@
 #include "slab.h"
 
 enum slab_state slab_state;
+LIST_HEAD(slab_caches);
+DEFINE_MUTEX(slab_mutex);
 
 /*
  * kmem_cache_create - Create a cache.
diff --git a/mm/slub.c b/mm/slub.c
index 4c385164d9f7..8c4fd37541d7 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -36,13 +36,13 @@
 
 /*
  * Lock order:
- *   1. slub_lock (Global Semaphore)
+ *   1. slab_mutex (Global Mutex)
  *   2. node->list_lock
  *   3. slab_lock(page) (Only on some arches and for debugging)
  *
- *   slub_lock
+ *   slab_mutex
  *
- *   The role of the slub_lock is to protect the list of all the slabs
+ *   The role of the slab_mutex is to protect the list of all the slabs
  *   and to synchronize major metadata changes to slab cache structures.
  *
  *   The slab_lock is only used for debugging and on arches that do not
@@ -183,10 +183,6 @@ static int kmem_size = sizeof(struct kmem_cache);
 static struct notifier_block slab_notifier;
 #endif
 
-/* A list of all slab caches on the system */
-static DECLARE_RWSEM(slub_lock);
-static LIST_HEAD(slab_caches);
-
 /*
  * Tracking user of a slab.
  */
@@ -3177,11 +3173,11 @@ static inline int kmem_cache_close(struct kmem_cache *s)
  */
 void kmem_cache_destroy(struct kmem_cache *s)
 {
-        down_write(&slub_lock);
+        mutex_lock(&slab_mutex);
         s->refcount--;
         if (!s->refcount) {
                 list_del(&s->list);
-                up_write(&slub_lock);
+                mutex_unlock(&slab_mutex);
                 if (kmem_cache_close(s)) {
                         printk(KERN_ERR "SLUB %s: %s called for cache that "
                                 "still has objects.\n", s->name, __func__);
@@ -3191,7 +3187,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
                         rcu_barrier();
                 sysfs_slab_remove(s);
         } else
-                up_write(&slub_lock);
+                mutex_unlock(&slab_mutex);
 }
 EXPORT_SYMBOL(kmem_cache_destroy);
 
@@ -3253,7 +3249,7 @@ static struct kmem_cache *__init create_kmalloc_cache(const char *name,
 
         /*
          * This function is called with IRQs disabled during early-boot on
-         * single CPU so there's no need to take slub_lock here.
+         * single CPU so there's no need to take slab_mutex here.
          */
         if (!kmem_cache_open(s, name, size, ARCH_KMALLOC_MINALIGN,
                                                                 flags, NULL))
@@ -3538,10 +3534,10 @@ static int slab_mem_going_offline_callback(void *arg)
 {
         struct kmem_cache *s;
 
-        down_read(&slub_lock);
+        mutex_lock(&slab_mutex);
         list_for_each_entry(s, &slab_caches, list)
                 kmem_cache_shrink(s);
-        up_read(&slub_lock);
+        mutex_unlock(&slab_mutex);
 
         return 0;
 }
@@ -3562,7 +3558,7 @@ static void slab_mem_offline_callback(void *arg)
         if (offline_node < 0)
                 return;
 
-        down_read(&slub_lock);
+        mutex_lock(&slab_mutex);
         list_for_each_entry(s, &slab_caches, list) {
                 n = get_node(s, offline_node);
                 if (n) {
@@ -3578,7 +3574,7 @@ static void slab_mem_offline_callback(void *arg)
                         kmem_cache_free(kmem_cache_node, n);
                 }
         }
-        up_read(&slub_lock);
+        mutex_unlock(&slab_mutex);
 }
 
 static int slab_mem_going_online_callback(void *arg)
@@ -3601,7 +3597,7 @@ static int slab_mem_going_online_callback(void *arg)
          * allocate a kmem_cache_node structure in order to bring the node
          * online.
          */
-        down_read(&slub_lock);
+        mutex_lock(&slab_mutex);
         list_for_each_entry(s, &slab_caches, list) {
                 /*
                  * XXX: kmem_cache_alloc_node will fallback to other nodes
@@ -3617,7 +3613,7 @@ static int slab_mem_going_online_callback(void *arg)
                 s->node[nid] = n;
         }
 out:
-        up_read(&slub_lock);
+        mutex_unlock(&slab_mutex);
         return ret;
 }
 
@@ -3915,7 +3911,7 @@ struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
         struct kmem_cache *s;
         char *n;
 
-        down_write(&slub_lock);
+        mutex_lock(&slab_mutex);
         s = find_mergeable(size, align, flags, name, ctor);
         if (s) {
                 s->refcount++;
@@ -3930,7 +3926,7 @@ struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
                         s->refcount--;
                         goto err;
                 }
-                up_write(&slub_lock);
+                mutex_unlock(&slab_mutex);
                 return s;
         }
 
@@ -3943,9 +3939,9 @@ struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
                 if (kmem_cache_open(s, n,
                                 size, align, flags, ctor)) {
                         list_add(&s->list, &slab_caches);
-                        up_write(&slub_lock);
+                        mutex_unlock(&slab_mutex);
                         if (sysfs_slab_add(s)) {
-                                down_write(&slub_lock);
+                                mutex_lock(&slab_mutex);
                                 list_del(&s->list);
                                 kfree(n);
                                 kfree(s);
@@ -3957,7 +3953,7 @@ struct kmem_cache *__kmem_cache_create(const char *name, size_t size,
         }
         kfree(n);
 err:
-        up_write(&slub_lock);
+        mutex_unlock(&slab_mutex);
         return s;
 }
 
@@ -3978,13 +3974,13 @@ static int __cpuinit slab_cpuup_callback(struct notifier_block *nfb,
         case CPU_UP_CANCELED_FROZEN:
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
-                down_read(&slub_lock);
+                mutex_lock(&slab_mutex);
                 list_for_each_entry(s, &slab_caches, list) {
                         local_irq_save(flags);
                         __flush_cpu_slab(s, cpu);
                         local_irq_restore(flags);
                 }
-                up_read(&slub_lock);
+                mutex_unlock(&slab_mutex);
                 break;
         default:
                 break;
@@ -5360,11 +5356,11 @@ static int __init slab_sysfs_init(void)
         struct kmem_cache *s;
         int err;
 
-        down_write(&slub_lock);
+        mutex_lock(&slab_mutex);
 
         slab_kset = kset_create_and_add("slab", &slab_uevent_ops, kernel_kobj);
         if (!slab_kset) {
-                up_write(&slub_lock);
+                mutex_unlock(&slab_mutex);
                 printk(KERN_ERR "Cannot register slab subsystem.\n");
                 return -ENOSYS;
         }
@@ -5389,7 +5385,7 @@ static int __init slab_sysfs_init(void)
                 kfree(al);
         }
 
-        up_write(&slub_lock);
+        mutex_unlock(&slab_mutex);
         resiliency_test();
         return 0;
 }
@@ -5415,7 +5411,7 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 {
         loff_t n = *pos;
 
-        down_read(&slub_lock);
+        mutex_lock(&slab_mutex);
         if (!n)
                 print_slabinfo_header(m);
 
@@ -5429,7 +5425,7 @@ static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 
 static void s_stop(struct seq_file *m, void *p)
 {
-        up_read(&slub_lock);
+        mutex_unlock(&slab_mutex);
 }
 
 static int s_show(struct seq_file *m, void *p)