linux-kernel - Re: [PATCH SLAB 1/2 v3] duplicate the cache name in SLUB's saved

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Date:	Fri, 6 Jul 2012 08:56:04 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Li Zhong <zhong@...ux.vnet.ibm.com>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	linux-mm <linux-mm@...ck.org>,
	PowerPC email list <linuxppc-dev@...ts.ozlabs.org>,
	Wanlong Gao <gaowanlong@...fujitsu.com>,
	Glauber Costa <glommer@...allels.com>
Subject: Re: [PATCH SLAB 1/2 v3] duplicate the cache name in SLUB's saved_alias
 list, SLAB, and SLOB

I thought I posted this a couple of days ago. Would this not fix things
without having to change all the allocators?


Subject: slub: Dup name earlier in kmem_cache_create

Dup the name earlier in kmem_cache_create so that alias
processing is done using the copy of the string and not
the string itself.

Signed-off-by: Christoph Lameter <cl@...ux.com>

---
 mm/slub.c |   29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

Index: linux-2.6/mm/slub.c
===================================================================
--- linux-2.6.orig/mm/slub.c	2012-06-11 08:49:56.000000000 -0500
+++ linux-2.6/mm/slub.c	2012-07-03 15:17:37.000000000 -0500
@@ -3933,8 +3933,12 @@ struct kmem_cache *kmem_cache_create(con
 	if (WARN_ON(!name))
 		return NULL;

+	n = kstrdup(name, GFP_KERNEL);
+	if (!n)
+		goto out;
+
 	down_write(&slub_lock);
-	s = find_mergeable(size, align, flags, name, ctor);
+	s = find_mergeable(size, align, flags, n, ctor);
 	if (s) {
 		s->refcount++;
 		/*
@@ -3944,7 +3948,7 @@ 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 *)));

-		if (sysfs_slab_alias(s, name)) {
+		if (sysfs_slab_alias(s, n)) {
 			s->refcount--;
 			goto err;
 		}
@@ -3952,31 +3956,26 @@ struct kmem_cache *kmem_cache_create(con
 		return s;
 	}

-	n = kstrdup(name, GFP_KERNEL);
-	if (!n)
-		goto err;
-
 	s = kmalloc(kmem_size, GFP_KERNEL);
 	if (s) {
 		if (kmem_cache_open(s, n,
 				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);
-				kfree(n);
-				kfree(s);
-				goto err;
-			}
-			return s;
+			if (!sysfs_slab_add(s))
+				return s;
+
+			down_write(&slub_lock);
+			list_del(&s->list);
 		}
 		kfree(s);
 	}
-	kfree(n);
+
 err:
+	kfree(n);
 	up_write(&slub_lock);

+out:
 	if (flags & SLAB_PANIC)
 		panic("Cannot create slabcache %s\n", name);
 	else
--
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