jbd2: 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 the code slightly.
Signed-off-by: NDuane Griffin <duaneg@dghda.com>
Signed-off-by: NMingming Cao <cmm@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

fs/jbd2/revoke.c

@@ -167,33 +167,41 @@ static struct jbd2_revoke_record_s *find_revoke_record(journal_t *journal,
 	return NULL;
 }
 
+void jbd2_journal_destroy_revoke_caches(void)
+{
+	if (jbd2_revoke_record_cache) {
+		kmem_cache_destroy(jbd2_revoke_record_cache);
+		jbd2_revoke_record_cache = NULL;
+	}
+	if (jbd2_revoke_table_cache) {
+		kmem_cache_destroy(jbd2_revoke_table_cache);
+		jbd2_revoke_table_cache = NULL;
+	}
+}
+
 int __init jbd2_journal_init_revoke_caches(void)
 {
+	J_ASSERT(!jbd2_revoke_record_cache);
+	J_ASSERT(!jbd2_revoke_table_cache);
+
 	jbd2_revoke_record_cache = kmem_cache_create("jbd2_revoke_record",
 					   sizeof(struct jbd2_revoke_record_s),
 					   0,
 					   SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY,
 					   NULL);
 	if (!jbd2_revoke_record_cache)
-		return -ENOMEM;
+		goto record_cache_failure;
 
 	jbd2_revoke_table_cache = kmem_cache_create("jbd2_revoke_table",
 					   sizeof(struct jbd2_revoke_table_s),
 					   0, SLAB_TEMPORARY, NULL);
-	if (!jbd2_revoke_table_cache) {
-		kmem_cache_destroy(jbd2_revoke_record_cache);
-		jbd2_revoke_record_cache = NULL;
-		return -ENOMEM;
-	}
+	if (!jbd2_revoke_table_cache)
+		goto table_cache_failure;
 	return 0;
-}
-
-void jbd2_journal_destroy_revoke_caches(void)
-{
-	kmem_cache_destroy(jbd2_revoke_record_cache);
-	jbd2_revoke_record_cache = NULL;
-	kmem_cache_destroy(jbd2_revoke_table_cache);
-	jbd2_revoke_table_cache = NULL;
+table_cache_failure:
+	jbd2_journal_destroy_revoke_caches();
+record_cache_failure:
+		return -ENOMEM;
 }
 
 /* Initialise the revoke table for a given journal to a given size. */