config: add metadata/removed_ancestor_lv_names_to_trackdev-prajnoha-report-select-extensions

Limit the number of removed ancestor LV names to track - the number
of removed LVs from the ancestor chain can go into infinity otherwise
by adding new items and then removing to/from the ancestry chain.

Add metadata/removed_ancestor_lv_names_to_track to limit the number
of removed LVs to track in the ancestry chain or even disable it
completely (metadata/removed_ancestor_lv_names=0).

7 files changed, 54 insertions, 9 deletions

diff --git a/conf/example.conf.in b/conf/example.conf.in
index 3900ad41b..48a298b34 100644
--- a/conf/example.conf.in
+++ b/conf/example.conf.in
@@ -1366,6 +1366,20 @@ activation {
 	# This configuration option is advanced.
 	# stripesize = 64
 
+	# Configuration option metadata/removed_ancestor_lv_names_to_track.
+	# Number of removed ancestor LV names to track.
+	# Thin snapshots can be chained so that one thin snapshot can
+	# be an origin for another thin snapshot (snapshot of a snapshot),
+	# hence creating an ancestry chain. The length of the chain is
+	# limited only by available metadata and memory size. When an LV
+	# is removed from the chain, LVM is able to remember its name.
+	# Then, LVM is able to display even removed LVs when ancestors and
+	# descendants are reported (lv_full_ancestors and lv_full_descendants
+	# reporting fields).
+	# This setting limits the number of removed LVs to track.
+	# Set to 0 to disable this feature.
+	# removed_ancestor_lv_names_to_track = 10
+
 	# Configuration option metadata/dirs.
 	# Directories holding live copies of text format metadata.
 	# These directories must not be on logical volumes!
diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c
index 002627bd3..3a74350e6 100644
--- a/lib/commands/toolcontext.c
+++ b/lib/commands/toolcontext.c
@@ -477,6 +477,7 @@ int process_profilable_config(struct cmd_context *cmd)
 	cmd->report_binary_values_as_numeric = find_config_tree_bool(cmd, report_binary_values_as_numeric_CFG, NULL);
 	cmd->default_settings.suffix = find_config_tree_bool(cmd, global_suffix_CFG, NULL);
 	cmd->report_list_item_separator = find_config_tree_str(cmd, report_list_item_separator_CFG, NULL);
+	cmd->removed_ancestor_lv_names_to_track = find_config_tree_int(cmd, metadata_removed_ancestor_lv_names_to_track_CFG, NULL);
 	if (!(cmd->time_format = _set_time_format(cmd)))
 		return 0;
 
diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index 283783f5d..eddc5abca 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -95,6 +95,7 @@ struct cmd_context {
 	unsigned ignore_clustered_vgs:1;
 	unsigned threaded:1;		/* Set if running within a thread e.g. clvmd */
 
+	unsigned removed_ancestor_lv_names_to_track;
 	const char *time_format;
 
 	unsigned independent_metadata_areas:1;	/* Active formats have MDAs outside PVs */
diff --git a/lib/config/config_settings.h b/lib/config/config_settings.h
index ce03b36be..1fb4f3fea 100644
--- a/lib/config/config_settings.h
+++ b/lib/config/config_settings.h
@@ -1318,6 +1318,19 @@ cfg(metadata_pvmetadataignore_CFG, "pvmetadataignore", metadata_CFG_SECTION, CFG
 
 cfg(metadata_stripesize_CFG, "stripesize", metadata_CFG_SECTION, CFG_ADVANCED | CFG_DEFAULT_COMMENTED, CFG_TYPE_INT, DEFAULT_STRIPESIZE, vsn(1, 0, 0), NULL, 0, NULL, NULL)
 
+cfg(metadata_removed_ancestor_lv_names_to_track_CFG, "removed_ancestor_lv_names_to_track", metadata_CFG_SECTION, CFG_PROFILABLE | CFG_DEFAULT_COMMENTED, CFG_TYPE_INT, DEFAULT_REMOVED_ANCESTOR_LV_NAMES_TO_TRACK, vsn(2, 2, 126), NULL, 0, NULL,
+	"Number of removed ancestor LV names to track.\n"
+	"Thin snapshots can be chained so that one thin snapshot can\n"
+	"be an origin for another thin snapshot (snapshot of a snapshot),\n"
+	"hence creating an ancestry chain. The length of the chain is\n"
+	"limited only by available metadata and memory size. When an LV\n"
+	"is removed from the chain, LVM is able to remember its name.\n"
+	"Then, LVM is able to display even removed LVs when ancestors and\n"
+	"descendants are reported (lv_full_ancestors and lv_full_descendants\n"
+	"reporting fields).\n"
+	"This setting limits the number of removed LVs to track.\n"
+	"Set to 0 to disable this feature.\n")
+
 cfg_array(metadata_dirs_CFG, "dirs", metadata_CFG_SECTION, CFG_ADVANCED | CFG_DEFAULT_UNDEFINED, CFG_TYPE_STRING, NULL, vsn(1, 0, 0), NULL, 0, NULL,
 	"Directories holding live copies of text format metadata.\n"
 	"These directories must not be on logical volumes!\n"
diff --git a/lib/config/defaults.h b/lib/config/defaults.h
index 5ee9b1c4e..578a8e897 100644
--- a/lib/config/defaults.h
+++ b/lib/config/defaults.h
@@ -129,6 +129,7 @@
 #define DEFAULT_PVMETADATASIZE 255
 #define DEFAULT_PVMETADATACOPIES 1
 #define DEFAULT_VGMETADATACOPIES 0
+#define DEFAULT_REMOVED_ANCESTOR_LV_NAMES_TO_TRACK 10
 #define DEFAULT_LABELSECTOR UINT64_C(1)
 #define DEFAULT_READ_AHEAD "auto"
 #define DEFAULT_UDEV_RULES 1
diff --git a/lib/format_text/import_vsn1.c b/lib/format_text/import_vsn1.c
index 12564714d..3304ae131 100644
--- a/lib/format_text/import_vsn1.c
+++ b/lib/format_text/import_vsn1.c
@@ -155,12 +155,18 @@ static int _read_flag_config(const struct dm_config_node *n, uint64_t *status, i
 	return 1;
 }
 
-static int _read_str_list(struct dm_pool *mem, struct dm_list *list, const struct dm_config_value *cv)
+static int _read_str_list(struct dm_pool *mem, struct dm_list *list,
+			  const struct dm_config_value *cv,
+			  int is_limited, unsigned limit)
 {
+	unsigned i = 0;
+
 	if (cv->type == DM_CFG_EMPTY_ARRAY)
 		return 1;
 
 	while (cv) {
+		if (is_limited && (i >= limit))
+			break;
 		if (cv->type != DM_CFG_STRING) {
 			log_error("Found an item that is not a string");
 			return 0;
@@ -170,6 +176,7 @@ static int _read_str_list(struct dm_pool *mem, struct dm_list *list, const struc
 			return_0;
 
 		cv = cv->next;
+		i++;
 	}
 
 	return 1;
@@ -291,7 +298,7 @@ static int _read_pv(struct format_instance *fid,
 
 	/* Optional tags */
 	if (dm_config_get_list(pvn, "tags", &cv) &&
-	    !(_read_str_list(mem, &pv->tags, cv))) {
+	    !(_read_str_list(mem, &pv->tags, cv, 0, 0))) {
 		log_error("Couldn't read tags for physical volume %s in %s.",
 			  pv_dev_name(pv), vg->name);
 		return 0;
@@ -402,7 +409,7 @@ static int _read_segment(struct logical_volume *lv, const struct dm_config_node
 
 	/* Optional tags */
 	if (dm_config_get_list(sn_child, "tags", &cv) &&
-	    !(_read_str_list(mem, &seg->tags, cv))) {
+	    !(_read_str_list(mem, &seg->tags, cv, 0, 0))) {
 		log_error("Couldn't read tags for a segment of %s/%s.",
 			  lv->vg->name, lv->name);
 		return 0;
@@ -662,14 +669,15 @@ static int _read_lvnames(struct format_instance *fid __attribute__((unused)),
 
 	/* Optional tags */
 	if (dm_config_get_list(lvn, "tags", &cv) &&
-	    !(_read_str_list(mem, &lv->tags, cv))) {
+	    !(_read_str_list(mem, &lv->tags, cv, 0, 0))) {
 		log_error("Couldn't read tags for logical volume %s/%s.",
 			  vg->name, lv->name);
 		return 0;
 	}
 
 	if (dm_config_get_list(lvn, "removed_ancestor_lv_names", &cv) &&
-	    !(_read_str_list(mem, &lv->removed_ancestor_lv_names, cv))) {
+	    !(_read_str_list(mem, &lv->removed_ancestor_lv_names, cv, 1,
+			     vg->cmd->removed_ancestor_lv_names_to_track))) {
 		log_error("Couldn't read removed ancestor names for logical "
 			  "volume %s/%s.", vg->name, lv->name);
 		return 0;
@@ -976,7 +984,7 @@ static struct volume_group *_read_vg(struct format_instance *fid,
 
 	/* Optional tags */
 	if (dm_config_get_list(vgn, "tags", &cv) &&
-	    !(_read_str_list(vg->vgmem, &vg->tags, cv))) {
+	    !(_read_str_list(vg->vgmem, &vg->tags, cv, 0, 0))) {
 		log_error("Couldn't read tags for volume group %s.", vg->name);
 		goto bad;
 	}
diff --git a/lib/metadata/pool_manip.c b/lib/metadata/pool_manip.c
index 5ed7ad638..a71d79587 100644
--- a/lib/metadata/pool_manip.c
+++ b/lib/metadata/pool_manip.c
@@ -125,18 +125,23 @@ int attach_pool_lv(struct lv_segment *seg,
 }
 
 static int _copy_removed_ancestor_lv_names(struct logical_volume *lv_from,
-					   struct logical_volume *lv_to)
+					   struct logical_volume *lv_to,
+					   unsigned limit)
 {
 	struct dm_str_list *sl_from, *sl_to;
 	const char *lv_name;
+	unsigned i = 0;
 
 	dm_list_iterate_items(sl_from, &lv_from->removed_ancestor_lv_names) {
+		if (i >= limit)
+			break;
 		if (!(sl_to = dm_pool_alloc(lv_to->vg->vgmem, sizeof(*sl_to))) ||
 		    !(lv_name = dm_pool_strdup(lv_to->vg->vgmem, sl_from->str)))
 			return_0;
 
 		sl_to->str = lv_name;
 		dm_list_add(&lv_to->removed_ancestor_lv_names, &sl_to->list);
+		i++;
 	}
 
 	return 1;
@@ -236,7 +241,8 @@ int detach_pool_lv(struct lv_segment *seg)
 		    !attach_thin_indirect_origin(sl->seg, origin))
 			return_0;
 
-		if (!_copy_removed_ancestor_lv_names(seg->lv, sl->seg->lv))
+		if (!_copy_removed_ancestor_lv_names(seg->lv, sl->seg->lv,
+				sl->seg->lv->vg->cmd->removed_ancestor_lv_names_to_track - 1))
 			return_0;
 
 		if (!str_list_add_h_no_dup_check(sl->seg->lv->vg->vgmem,
@@ -263,7 +269,8 @@ int detach_pool_lv(struct lv_segment *seg)
 		    !attach_thin_indirect_origin(sl->seg, origin))
 			return_0;
 
-		if (!_copy_removed_ancestor_lv_names(seg->lv, sl->seg->lv))
+		if (!_copy_removed_ancestor_lv_names(seg->lv, sl->seg->lv,
+				sl->seg->lv->vg->cmd->removed_ancestor_lv_names_to_track - 1))
 			return_0;
 
 		if (!str_list_add_h_no_dup_check(seg->lv->vg->vgmem,