jbd: tidy up revoke cache initialisation and destruction

Make revocation cache destruction safe to call if initialisation fails
partially or entirely.  This allows it to be used to cleanup in the case
of initialisation failure, simplifying that code slightly.
Signed-off-by: NDuane Griffin <duaneg@dghda.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/jbd/revoke.c

@@ -166,33 +166,43 @@ static struct jbd_revoke_record_s *find_revoke_record(journal_t *journal,
 	return NULL;
 }
 
+void journal_destroy_revoke_caches(void)
+{
+	if (revoke_record_cache) {
+		kmem_cache_destroy(revoke_record_cache);
+		revoke_record_cache = NULL;
+	}
+	if (revoke_table_cache) {
+		kmem_cache_destroy(revoke_table_cache);
+		revoke_table_cache = NULL;
+	}
+}
+
 int __init journal_init_revoke_caches(void)
 {
+	J_ASSERT(!revoke_record_cache);
+	J_ASSERT(!revoke_table_cache);
+
 	revoke_record_cache = kmem_cache_create("revoke_record",
 					   sizeof(struct jbd_revoke_record_s),
 					   0,
 					   SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
 					   NULL);
 	if (!revoke_record_cache)
-		return -ENOMEM;
+		goto record_cache_failure;
 
 	revoke_table_cache = kmem_cache_create("revoke_table",
 					   sizeof(struct jbd_revoke_table_s),
 					   0, SLAB_TEMPORARY, NULL);
-	if (!revoke_table_cache) {
-		kmem_cache_destroy(revoke_record_cache);
-		revoke_record_cache = NULL;
-		return -ENOMEM;
-	}
+	if (!revoke_table_cache)
+		goto table_cache_failure;
+
 	return 0;
-}
 
-void journal_destroy_revoke_caches(void)
-{
-	kmem_cache_destroy(revoke_record_cache);
-	revoke_record_cache = NULL;
-	kmem_cache_destroy(revoke_table_cache);
-	revoke_table_cache = NULL;
+table_cache_failure:
+	journal_destroy_revoke_caches();
+record_cache_failure:
+	return -ENOMEM;
 }
 
 static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)