thin: improve recognizing of merge in progress

Rewrite too condensed condition in more readable form,
wher decision are clearly separated and commented and
also add debug messages for them.

diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index 665919017015d1b571663223c03bc99a142b4bfe..2b108c9cfd31977b3ccf325baa18cf7d3c593966 100644 (file)
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -2764,25 +2764,52 @@ static int _add_new_lv_to_dtree(struct dev_manager *dm, struct dm_tree *dtree,
                /*
                 * Clear merge attributes if merge isn't currently possible:
                 * either origin or merging snapshot are open
-                * - but use "snapshot-merge" if it is already in use
+                * - for old snaps use "snapshot-merge" if it is already in use
                 * - open_count is always retrieved (as of dm-ioctl 4.7.0)
                 *   so just use the tree's existing nodes' info
                 */
-               /* An activating merging origin won't have a node in the tree yet */
-               if (((dinfo = _cached_dm_info(dm->mem, dtree, lv, NULL)) &&
-                    dinfo->open_count) ||
-                   ((dinfo = _cached_dm_info(dm->mem, dtree,
-                                             seg_is_thin_volume(seg) ?
-                                             seg->lv : seg->cow, NULL)) &&
-                    dinfo->open_count))
-                       snap_dev_is_open = 1;
-
-               /* Preload considers open devices. */
-               /* Resume looks at the table that will be the live one after the operation. */
-               if ((!laopts->resuming && snap_dev_is_open && (seg_is_thin_volume(seg) || !lv_has_target_type(dm->mem, lv, NULL, TARGET_NAME_SNAPSHOT_MERGE))) ||
-                   (laopts->resuming &&
-                    ((!seg_is_thin_volume(seg) && !lv_has_target_type(dm->mem, lv, NULL, TARGET_NAME_SNAPSHOT_MERGE)) ||
-                     (seg_is_thin_volume(seg) && !_thin_lv_has_device_id(dm->mem, lv, NULL, seg->device_id))))) {
+               if ((dinfo = _cached_dm_info(dm->mem, dtree,
+                                            seg_is_thin_volume(seg) ?
+                                            seg->lv : seg->cow, NULL))) {
+                       if (seg_is_thin_volume(seg)) {
+                               /* Active thin snapshot prevents merge */
+                               log_debug_activation("Merging thin snapshot %s is active.",
+                                                    display_lvname(seg->lv));
+                       } else if (dinfo->open_count) {
+                               log_debug_activation("Merging snapshot LV %s is openned.",
+                                                    display_lvname(seg->lv));
+                               snap_dev_is_open = 1;
+                       }
+               }
+
+               if ((dinfo = _cached_dm_info(dm->mem, dtree, lv, NULL))) {
+                       if (dinfo->open_count) {
+                               log_debug_activation("Merging origin volume %s is openned.", display_lvname(seg->lv));
+                               snap_dev_is_open = 1;
+                       }
+
+                       /* Check if decision needs to be preserved.
+                        * Merging origin LV needs to be present in table in this case. */
+                       if (!laopts->resuming) {
+                               if ((seg_is_thin_volume(seg) && _thin_lv_has_device_id(dm->mem, lv, NULL, seg->device_id)) ||
+                                   (!seg_is_thin_volume(seg) && lv_has_target_type(dm->mem, lv, NULL, TARGET_NAME_SNAPSHOT_MERGE))) {
+                                       log_debug_activation("Merging of snapshot volume %s is in progress.",
+                                                            display_lvname(seg->lv));
+                                       /* Merging is already running and cannot be switched */
+                                       snap_dev_is_open = 0;
+                               }
+                       } else {
+                               if ((seg_is_thin_volume(seg) && !_thin_lv_has_device_id(dm->mem, lv, NULL, seg->device_id)) ||
+                                   (!seg_is_thin_volume(seg) && !lv_has_target_type(dm->mem, lv, NULL, TARGET_NAME_SNAPSHOT_MERGE))) {
+                                       log_debug_activation("Merging of snapshot volume %s was not started before suspend.",
+                                                            display_lvname(seg->lv));
+                                       /* Merging targe table cannot be reloaded when suspend */
+                                       snap_dev_is_open = 1;
+                               }
+                       }
+               }
+
+               if (snap_dev_is_open) {
                        log_debug_activation("Postponing pending snapshot merge for origin LV %s.", display_lvname(lv));
                        laopts->no_merging = 1;
                }