linux-kernel - Re: [PATCH powerpc 2/2] kfree the cache name of pgtable cache if SLUB is used

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Date:	Tue, 3 Jul 2012 15:36:54 -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>
Subject: Re: [PATCH powerpc 2/2] kfree the cache name  of pgtable cache if
 SLUB is used

Looking through the emails it seems that there is an issue with alias
strings. That can be solved by duping the name of the slab earlier in kmem_cache_create().
Does this patch fix the issue?

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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