SLUB: Remove alias before installing symlink

We cannot really track the aliases that are created when aliasing
a slab. kmem_cache_destroy only decrements a refcounter. This
means that the aliases are never removed. Does not really matter
since the symlinks are there merely for decorative purposese.

However, when another slab is created with the same name then
kmem_cache_create may fail because that name is already in the
/sys/slab directory. So remove the link first.

Signed-off-by: Chriustoph Lameter <clameter@sgi.com>


Index: linux-2.6.21-rc6/mm/slub.c
===================================================================
--- linux-2.6.21-rc6.orig/mm/slub.c	2007-04-20 16:44:14.000000000 -0700
+++ linux-2.6.21-rc6/mm/slub.c	2007-04-20 17:12:18.000000000 -0700
@@ -3315,6 +3315,7 @@ static int sysfs_slab_add(struct kmem_ca
 		/* Defer until later */
 		return 0;
 
+	sysfs_remove_link(&slab_subsys.kset.kobj, s->name);
 	kobj_set_kset_s(s, slab_subsys);
 	kobject_set_name(&s->kobj, s->name);
 	kobject_init(&s->kobj);
@@ -3329,8 +3330,18 @@ static int sysfs_slab_add(struct kmem_ca
 	return 0;
 }
 
+static void sysfs_remove_aliases(struct kmem_cache *s)
+{
+	/*
+	 * Remove all symlinks pointing to the kobject of
+	 * in the kmem_cache structure
+	 */
+	sysfs_remove_links(&slab_subsys.kset, &s->kobj);
+}
+
 static void sysfs_slab_remove(struct kmem_cache *s)
 {
+	sysfs_remove_aliases(s);
 	kobject_uevent(&s->kobj, KOBJ_REMOVE);
 	kobject_del(&s->kobj);
 }
@@ -3351,9 +3362,11 @@ static int sysfs_slab_alias(struct kmem_
 {
 	struct saved_alias *al;
 
-	if (slab_state == SYSFS)
+	if (slab_state == SYSFS) {
+		sysfs_remove_link(&slab_subsys.kset.kobj, name);
 		return sysfs_create_link(&slab_subsys.kset.kobj,
 						&s->kobj, name);
+	}
 
 	al = kmalloc(sizeof(struct saved_alias), GFP_KERNEL);
 	if (!al)
Index: linux-2.6.21-rc6/fs/sysfs/symlink.c
===================================================================
--- linux-2.6.21-rc6.orig/fs/sysfs/symlink.c	2007-04-20 17:05:00.000000000 -0700
+++ linux-2.6.21-rc6/fs/sysfs/symlink.c	2007-04-20 17:18:50.000000000 -0700
@@ -117,6 +117,38 @@ void sysfs_remove_link(struct kobject * 
 	sysfs_hash_and_remove(kobj->dentry,name);
 }
 
+/*
+ * Remove all symlinks pointing to the indicated object
+ */
+void sysfs_remove_links(struct kset *kset, struct kobject *needle)
+{
+	struct list_head *entry;
+
+restart:
+	spin_lock(&kset->list_lock);
+	list_for_each(entry,&kset->list) {
+		struct kobject * k = container_of(entry, struct kobject, entry);
+		struct sysfs_symlink *sl =
+			container_of(k, struct sysfs_symlink, target_kobj);
+
+		if (sl->target_kobj == needle) {
+			/* sysfs_remove_link needs the lock. sigh */
+			spin_unlock(&kset->list_lock);
+
+			sysfs_remove_link(k, sl->link_name);
+			/*
+			 * Somehow sysfs_remove_link does
+			 * not clean up after itself
+			 */
+			kfree(sl->link_name);
+			kfree(sl);
+			kobject_put(needle);
+			goto restart;
+		}
+        }
+        spin_unlock(&kset->list_lock);
+}
+
 static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
 				 char *path)
 {
@@ -188,5 +220,6 @@ const struct inode_operations sysfs_syml
 };
 
 
-EXPORT_SYMBOL_GPL(sysfs_create_link);
 EXPORT_SYMBOL_GPL(sysfs_remove_link);
+EXPORT_SYMBOL_GPL(sysfs_remove_links);
+EXPORT_SYMBOL_GPL(sysfs_create_link);
Index: linux-2.6.21-rc6/include/linux/kobject.h
===================================================================
--- linux-2.6.21-rc6.orig/include/linux/kobject.h	2007-04-20 17:09:03.000000000 -0700
+++ linux-2.6.21-rc6/include/linux/kobject.h	2007-04-20 17:09:49.000000000 -0700
@@ -166,6 +166,9 @@ static inline struct kobj_type * get_kty
 
 extern struct kobject * kset_find_obj(struct kset *, const char *);
 
+extern void sysfs_remove_links(struct kset *kset, struct kobject *needle);
+
+
 
 /**
  * Use this when initializing an embedded kset with no other