Index: modules/block/block.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.module,v
retrieving revision 1.421
diff -u -p -r1.421 block.module
--- modules/block/block.module	13 May 2010 07:53:02 -0000	1.421
+++ modules/block/block.module	22 May 2010 02:01:30 -0000
@@ -356,6 +356,11 @@ function _block_rehash($theme = NULL) {
   foreach ($database_blocks as $block) {
     // Preserve info which is not in the database.
     $block->info = $current_blocks[$block->module][$block->delta]['info'];
+    // The cache mode is only settable from hook_block_info(), so that has
+    // precedence over the database's value.
+    if (isset($current_blocks[$block->module][$block->delta]['cache'])) {
+      $block->cache = $current_blocks[$block->module][$block->delta]['cache'];
+    }
     // Blocks stored in the database override the blocks defined in code.
     $current_blocks[$block->module][$block->delta] = get_object_vars($block);
     // Preserve this block.
Index: modules/block/block.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.test,v
retrieving revision 1.52
diff -u -p -r1.52 block.test
--- modules/block/block.test	26 Apr 2010 14:10:40 -0000	1.52
+++ modules/block/block.test	22 May 2010 02:01:30 -0000
@@ -261,6 +261,27 @@ class BlockTestCase extends DrupalWebTes
     ));
     $this->assertFieldByXPath($xpath, FALSE, t('Custom block found in %region_name region.', array('%region_name' => $region['name'])));
   }
+
+  /**
+   * Test _block_rehash().
+   */
+  function testBlockRehash() {
+    module_enable(array('block_test'));
+    $this->assertTrue(module_exists('block_test'), t('Test block module enabled.'));
+    _block_rehash();
+
+    // Our test block's caching should default to DRUPAL_CACHE_PER_ROLE.
+    $current_caching = db_query("SELECT cache FROM {block} WHERE module = 'block_test' AND delta = 'test_cache'")->fetchField();
+    $this->assertEqual($current_caching, DRUPAL_CACHE_PER_ROLE, t('Test block cache mode defaults to DRUPAL_CACHE_PER_ROLE.'));
+
+    // Disable caching for this block.
+    variable_set('block_test_caching', DRUPAL_NO_CACHE);
+    _block_rehash();
+
+    // Verify that changing the caching mode affected the database.
+    $current_caching = db_query("SELECT cache FROM {block} WHERE module = 'block_test' AND delta = 'test_cache'")->fetchField();
+    $this->assertEqual($current_caching, DRUPAL_NO_CACHE, t("Test block's database entry updated to DRUPAL_NO_CACHE."));
+  }
 }
 
 class NonDefaultBlockAdmin extends DrupalWebTestCase {
Index: modules/block/tests/block_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/tests/block_test.module,v
retrieving revision 1.2
diff -u -p -r1.2 block_test.module
--- modules/block/tests/block_test.module	26 Apr 2010 14:10:40 -0000	1.2
+++ modules/block/tests/block_test.module	22 May 2010 02:01:30 -0000
@@ -12,6 +12,7 @@
 function block_test_block_info() {
   $blocks['test_cache'] = array(
     'info' => t('Test block caching'),
+    'cache' => variable_get('block_test_caching', DRUPAL_CACHE_PER_ROLE),
   );
 
   $blocks['test_html_id'] = array(