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Subject[S+Q3 10/23] slub: Allow removal of slab caches during boot V2
Serialize kmem_cache_create and kmem_cache_destroy using the slub_lock. Only
possible after the use of the slub_lock during dynamic dma creation has been
removed.

Then make sure that the setup of the slab sysfs entries does not race
with kmem_cache_create and kmem_cache destroy.

If a slab cache is removed before we have setup sysfs then simply skip over
the sysfs handling.

V1->V2:
- Do proper synchronization to address race conditions

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Roland Dreier <rdreier@cisco.com>
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>

---
mm/slub.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c 2010-07-27 22:51:41.000000000 -0500
+++ linux-2.6/mm/slub.c 2010-07-27 22:51:43.000000000 -0500
@@ -2482,7 +2482,6 @@ void kmem_cache_destroy(struct kmem_cach
s->refcount--;
if (!s->refcount) {
list_del(&s->list);
- up_write(&slub_lock);
if (kmem_cache_close(s)) {
printk(KERN_ERR "SLUB %s: %s called for cache that "
"still has objects.\n", s->name, __func__);
@@ -2491,8 +2490,8 @@ void kmem_cache_destroy(struct kmem_cach
if (s->flags & SLAB_DESTROY_BY_RCU)
rcu_barrier();
sysfs_slab_remove(s);
- } else
- up_write(&slub_lock);
+ }
+ up_write(&slub_lock);
}
EXPORT_SYMBOL(kmem_cache_destroy);

@@ -3147,14 +3146,12 @@ struct kmem_cache *kmem_cache_create(con
*/
s->objsize = max(s->objsize, (int)size);
s->inuse = max_t(int, s->inuse, ALIGN(size, sizeof(void *)));
- up_write(&slub_lock);

if (sysfs_slab_alias(s, name)) {
- down_write(&slub_lock);
s->refcount--;
- up_write(&slub_lock);
goto err;
}
+ up_write(&slub_lock);
return s;
}

@@ -3163,14 +3160,12 @@ struct kmem_cache *kmem_cache_create(con
if (kmem_cache_open(s, name,
size, align, flags, ctor)) {
list_add(&s->list, &slab_caches);
- up_write(&slub_lock);
if (sysfs_slab_add(s)) {
- down_write(&slub_lock);
list_del(&s->list);
- up_write(&slub_lock);
kfree(s);
goto err;
}
+ up_write(&slub_lock);
return s;
}
kfree(s);
@@ -4418,6 +4413,13 @@ static int sysfs_slab_add(struct kmem_ca

static void sysfs_slab_remove(struct kmem_cache *s)
{
+ if (slab_state < SYSFS)
+ /*
+ * Sysfs has not been setup yet so no need to remove the
+ * cache from sysfs.
+ */
+ return;
+
kobject_uevent(&s->kobj, KOBJ_REMOVE);
kobject_del(&s->kobj);
kobject_put(&s->kobj);
@@ -4463,8 +4465,11 @@ static int __init slab_sysfs_init(void)
struct kmem_cache *s;
int err;

+ down_write(&slub_lock);
+
slab_kset = kset_create_and_add("slab", &slab_uevent_ops, kernel_kobj);
if (!slab_kset) {
+ up_write(&slub_lock);
printk(KERN_ERR "Cannot register slab subsystem.\n");
return -ENOSYS;
}
@@ -4489,6 +4494,7 @@ static int __init slab_sysfs_init(void)
kfree(al);
}

+ up_write(&slub_lock);
resiliency_test();
return 0;
}


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