handle LV with unrecognized metadata

If LV metadata (typically a flag) is unrecognized by lvm,
then lvm should refuse to allow that LV to be used, but
can continue to allow the VG, and other recognized LVs
to be used.

This can happen if a version of lvm containing a new
feature writes metadata for an LV containing a new flag,
then an old version of lvm is used to access the VG.
The old lvm does not recognize the new flag.  Previously,
the old lvm would refuse to recognize or access the entire
VG, when it should have just disallowed access to the
unrecognized LV.

This initial implementation for handling an unrecognized
LV involves setting an internal LV_UNUSABLE flag and
clearing the VISIBLE_LV flag, making the problematic LV
not visible (without -a).  Existing code paths generally
disallow accessing an LV that's not visible.  Further
changes should be made to make that code distinguish LVs
that are UNUSABLE as opposed to just not VISIBLE.

lib/format_text/flags.c

@@ -105,6 +105,7 @@ static const struct flag _lv_flags[] = {
 	{WRITECACHE, NULL, 0},
 	{LV_PENDING_DELETE, NULL, 0}, /* FIXME Display like COMPATIBLE_FLAG */
 	{LV_REMOVED, NULL, 0},
+	{LV_UNUSABLE, NULL, 0},
 	{0, NULL, 0}
 };
 

lib/format_text/import_vsn1.c

@@ -140,13 +140,13 @@ static int _read_flag_config(const struct dm_config_node *n, uint64_t *status, i
 
 	/* For backward compatible metadata accept both type of flags */
 	if (!(read_flags(status, type, STATUS_FLAG | SEGTYPE_FLAG, cv))) {
-		log_error("Could not read status flags.");
+		log_debug("Could not read status flags %llx.", (unsigned long long)*status);
 		return 0;
 	}
 
 	if (dm_config_get_list(n, "flags", &cv)) {
 		if (!(read_flags(status, type, COMPATIBLE_FLAG, cv))) {
-			log_error("Could not read flags.");
+			log_debug("Could not read flags %llx.", (unsigned long long)*status);
 			return 0;
 		}
 	}
@@ -610,15 +610,17 @@ static int _read_lvnames(struct cmd_context *cmd,
 	log_debug_metadata("Importing logical volume %s.", display_lvname(lv));
 
 	if (!(lvn = lvn->child)) {
-		log_error("Empty logical volume section for %s.",
-			  display_lvname(lv));
-		return 0;
+		log_warn("Empty logical volume section for %s.",
+			 display_lvname(lv));
+		lvstatus |= LV_UNUSABLE;
+		lvstatus &= ~VISIBLE_LV;
 	}
 
 	if (!_read_flag_config(lvn, &lvstatus, LV_FLAGS)) {
-		log_error("Couldn't read status flags for logical volume %s.",
-			  display_lvname(lv));
-		return 0;
+		log_warn("Couldn't read status flags for logical volume %s.",
+			 display_lvname(lv));
+		lvstatus |= LV_UNUSABLE;
+		lvstatus &= ~VISIBLE_LV;
 	}
 
 	if (lvstatus & LVM_WRITE_LOCKED) {
@@ -629,19 +631,22 @@ static int _read_lvnames(struct cmd_context *cmd,
 
 	if (dm_config_has_node(lvn, "creation_time")) {
 		if (!_read_uint64(lvn, "creation_time", &timestamp)) {
-			log_error("Invalid creation_time for logical volume %s.",
-				  display_lvname(lv));
-			return 0;
+			log_warn("Invalid creation_time for logical volume %s.",
+				 display_lvname(lv));
+			lvstatus |= LV_UNUSABLE;
+			lvstatus &= ~VISIBLE_LV;
 		}
 		if (!dm_config_get_str(lvn, "creation_host", &hostname)) {
-			log_error("Couldn't read creation_host for logical volume %s.",
-				  display_lvname(lv));
-			return 0;
+			log_warn("Couldn't read creation_host for logical volume %s.",
+				 display_lvname(lv));
+			lvstatus |= LV_UNUSABLE;
+			lvstatus &= ~VISIBLE_LV;
 		}
 	} else if (dm_config_has_node(lvn, "creation_host")) {
-		log_error("Missing creation_time for logical volume %s.",
-			  display_lvname(lv));
-		return 0;
+		log_warn("Missing creation_time for logical volume %s.",
+			 display_lvname(lv));
+		lvstatus |= LV_UNUSABLE;
+		lvstatus &= ~VISIBLE_LV;
 	}
 
 	/*
@@ -664,8 +669,12 @@ static int _read_lvnames(struct cmd_context *cmd,
 	 * the lock_args before using it to access the lock manager.
 	 */
 	if (dm_config_get_str(lvn, "lock_args", &str)) {
-		if (!(lv->lock_args = dm_pool_strdup(mem, str)))
-			return_0;
+		if (!(lv->lock_args = dm_pool_strdup(mem, str))) {
+			log_warn("No memory for lock_args for logical volume %s.",
+				 display_lvname(lv));
+			lvstatus |= LV_UNUSABLE;
+			lvstatus &= ~VISIBLE_LV;
+		}
 	}
 
 	if (dm_config_get_str(lvn, "allocation_policy", &str)) {
@@ -682,9 +691,10 @@ static int _read_lvnames(struct cmd_context *cmd,
 		log_debug_metadata("Adding profile configuration %s for LV %s.",
 				   str, display_lvname(lv));
 		if (!(lv->profile = add_profile(cmd, str, CONFIG_PROFILE_METADATA))) {
-			log_error("Failed to add configuration profile %s for LV %s.",
-				  str, display_lvname(lv));
-			return 0;
+			log_warn("Failed to add configuration profile %s for LV %s.",
+				 str, display_lvname(lv));
+			lvstatus |= LV_UNUSABLE;
+			lvstatus &= ~VISIBLE_LV;
 		}
 	}
 
@@ -707,27 +717,34 @@ static int _read_lvnames(struct cmd_context *cmd,
 	/* Optional tags */
 	if (dm_config_get_list(lvn, "tags", &cv) &&
 	    !(_read_str_list(mem, &lv->tags, cv))) {
-		log_error("Couldn't read tags for logical volume %s.",
-			  display_lvname(lv));
-		return 0;
+		log_warn("Couldn't read tags for logical volume %s.",
+			 display_lvname(lv));
+		lvstatus |= LV_UNUSABLE;
+		lvstatus &= ~VISIBLE_LV;
 	}
 
 	if (!dm_hash_insert(lv_hash, lv->name, lv))
 		return_0;
 
-	if (timestamp && !lv_set_creation(lv, hostname, timestamp))
-		return_0;
+	if (timestamp && !lv_set_creation(lv, hostname, timestamp)) {
+		log_warn("Failed to set creation timestamp for logical volume %s.",
+			 display_lvname(lv));
+		lvstatus |= LV_UNUSABLE;
+		lvstatus &= ~VISIBLE_LV;
+	}
 
 	if (!lv_is_visible(lv) && strstr(lv->name, "_pmspare")) {
 		if (vg->pool_metadata_spare_lv) {
-			log_error("Couldn't use another pool metadata spare "
-				  "logical volume %s.", display_lvname(lv));
-			return 0;
+			log_warn("Couldn't use another pool metadata spare "
+				 "logical volume %s.", display_lvname(lv));
+			lvstatus |= LV_UNUSABLE;
+			lvstatus &= ~VISIBLE_LV;
+		} else {
+			log_debug_metadata("Logical volume %s is pool metadata spare.",
+					   display_lvname(lv));
+			lv->status |= POOL_METADATA_SPARE;
+			vg->pool_metadata_spare_lv = lv;
 		}
-		log_debug_metadata("Logical volume %s is pool metadata spare.",
-				   display_lvname(lv));
-		lv->status |= POOL_METADATA_SPARE;
-		vg->pool_metadata_spare_lv = lv;
 	}
 
 	if (!lv_is_visible(lv) && !strcmp(lv->name, LOCKD_SANLOCK_LV_NAME)) {

lib/metadata/metadata-exported.h

@@ -81,6 +81,7 @@
 #define LV_NOTSYNCED		UINT64_C(0x0000000000080000)	/* LV */
 #define LV_REBUILD		UINT64_C(0x0000000000100000)	/* LV */
 //#define PRECOMMITTED		UINT64_C(0x0000000000200000)	/* VG - internal use only */
+#define LV_UNUSABLE		UINT64_C(0x0000000000200000)	/* LV */
 #define CONVERTING		UINT64_C(0x0000000000400000)	/* LV */
 
 #define MISSING_PV		UINT64_C(0x0000000000800000)	/* PV */