The attached patch is for EVMS 2.2.1.  This patch rebuild a corrupt
raid5 array from the one of the most up-to-date MD superblock.  This
patch only works if all disk members are still accessible.

When you see messages regarding a RAID5 region being corrupt.
- Go to the region view/panel
- Bring up the context menu for that region, select Fix.
- The messages panel will appear again with the information about the
  "rebuilt" array.
- Important: Make sure to verify the displayed information before saving
  the changes.

To apply:
cd /usr/src/evms-2.2.1
patch -p1 < raid5_reconstruct.patch

diff -Naur evms-2.2.1a/plugins/md/md_discover.c evms-2.2.1b/plugins/md/md_discover.c
--- evms-2.2.1a/plugins/md/md_discover.c	2003-11-05 07:42:17.000000000 -0600
+++ evms-2.2.1b/plugins/md/md_discover.c	2004-01-14 19:42:46.000000000 -0600
@@ -1010,6 +1010,15 @@
 	volume->child_object[i] = NULL;
 }
 
+static void move_stale_object_to_child_list(md_volume_t *volume, int i)
+{
+	if (volume->child_object[i]) {
+		md_log_internal_bug(__FILE__, __FUNCTION__, __LINE__);
+		return;
+	}
+	volume->child_object[i] = volume->stale_object[i];
+	volume->stale_object[i] = NULL;
+}
 
 static inline void debug_print_desc(mdp_disk_t *d)
 {
@@ -1018,6 +1027,50 @@
 }
 
 /*
+ * Function: md_rebuild_array_from_master_sb
+ *
+ *     This function rebuilds the MD array from the master MD superblock
+ */
+int md_rebuild_array_from_master_sb(md_volume_t *vol)
+{
+	int i, count;
+
+	LOG_ENTRY();
+
+	if (vol->flags & MD_CORRUPT) {
+		LOG_DEFAULT("MD region %s is %s.\n", vol->name,
+			    (vol->flags & MD_CORRUPT) ? "corrupt" :
+			    (vol->flags & MD_PROBLEMATIC_SB) ? "inconsistent" : "???");
+	}
+
+	if (vol->super_block->failed_disks) {
+		LOG_ERROR("Master superblock has %d failed disks.\n",
+			  vol->super_block->failed_disks);
+		LOG_EXIT_INT(vol->flags);
+		return vol->flags;
+	}
+
+	count = md_count_children(vol) + md_count_stale_disks(vol);
+
+	if (vol->super_block->nr_disks != count) {
+		LOG_ERROR("Master superblock has %d disks, but we found only %d children.\n",
+			  vol->super_block->nr_disks, count);
+		LOG_EXIT_INT(EINVAL);
+		return EINVAL;
+	}
+
+	for (i=0; i < MAX_MD_DEVICES; i++) {
+		move_stale_object_to_child_list(vol, i);
+		md_clone_superblock(vol, i);
+	}
+
+	md_analyze_volume(vol);
+
+	LOG_EXIT_INT(vol->flags);
+	return vol->flags;
+}
+
+/*
  * Function: md_analyze_volume
  *
  *	Note:  This function can be called before the region is allocated and initilized.
diff -Naur evms-2.2.1a/plugins/md/md_discover.h evms-2.2.1b/plugins/md/md_discover.h
--- evms-2.2.1a/plugins/md/md_discover.h	2003-10-13 17:50:34.000000000 -0500
+++ evms-2.2.1b/plugins/md/md_discover.h	2004-01-14 19:38:38.000000000 -0600
@@ -37,6 +37,7 @@
 int md_register_name_space(void);
 int md_discover_final_call(dlist_t input_list, dlist_t output_list, int *count);
 int md_analyze_volume(md_volume_t *volume);
+int md_rebuild_array_from_master_sb(md_volume_t *volume);
 void md_remove_missing_disk_entries(md_volume_t * vol);
 void md_print_array_sb(char *buf, u_int32_t buf_size, mdp_super_t *sb);
 int md_free_volume(md_volume_t *volume);
diff -Naur evms-2.2.1a/plugins/md/raid5_discover.c evms-2.2.1b/plugins/md/raid5_discover.c
--- evms-2.2.1a/plugins/md/raid5_discover.c	2003-11-05 18:10:56.000000000 -0600
+++ evms-2.2.1b/plugins/md/raid5_discover.c	2004-01-14 19:38:38.000000000 -0600
@@ -573,6 +573,22 @@
 	LOG_EXIT_VOID();
 }
 
+static void raid5_rebuild_array_from_master_sb(md_volume_t *vol)
+{
+	LOG_ENTRY();
+
+	md_rebuild_array_from_master_sb(vol);
+
+	if ((vol->flags & (MD_CORRUPT | MD_PROBLEMATIC_SB)) == 0) {
+		md_print_array_sb(message_buffer, MD_MESSAGE_BUF_SIZE, vol->super_block);
+		MESSAGE("%s", message_buffer);
+		MESSAGE("Region %s has been rebuilt from one of most up-to-date MD superblocks."
+			"  Please verify the MD array information above before saving the changes.\n", vol->name);
+		vol->flags |= MD_DIRTY;
+		vol->region->flags |= (SOFLAG_DIRTY | SOFLAG_NEEDS_DEACTIVATE);
+	}
+	LOG_EXIT_VOID();
+}
 
 
 /*
@@ -653,7 +669,15 @@
 		break;
 	
 	case 2:
-		raid5_fix_master_sb(vol);
+		raid5_rebuild_array_from_master_sb(vol);
+		if (vol->flags & (MD_CORRUPT | MD_PROBLEMATIC_SB)) {
+			raid5_fix_master_sb(vol);
+		}
+		
+		if ((vol->flags & MD_CORRUPT) == 0) {
+			create_raid5_conf(vol);
+		}
+
 		break;
 	}