metadata: create former LVs when LVs are removed and interconnect with live LVs to track history

When an LV is being removed, we create an instance of
"struct former_logical_volume" wrapped up in "struct generic_logical_volume".
All instances of "struct former_logical_volume" are then recorded in "former_lvs"
list which is part of "struct volume_group".

The "former LV" is then interconnected with "live LVs" (the ones
which are not removed yet) like this:

"g" stands for "this logical_volume is wrapped with struct generic_logical_volume"
"seg" stands for "representative segment is chosen for this logical_volume"

* Simple example:

g(liveLV1) --(indirects_glvs)--> g(formerLV2) --(indirects_glvs)--> g(liveLV3)

g(liveLV1) <--(indirect_origin)-- g(formerLV2) <--(indirect_origin)-- seg(liveLV3)

* Example with more former LVs:

g(liveLV1) --(indirects_glvs)--> g(formerLV2) --(indirects_glvs)--> g(formerLV3)--(indirects_glvs)--> g(liveLV4)

g(liveLV1) <--(indirect_origin)-- g(formerLV2) <--(indirect_origin)-- g(formerLV3) <--(indirect_origin)-- seg(liveLV4)

* Or with branches:

g(liveLV1) --(indirects_glvs)--> g(formerLV2A) --(indirects_glvs)--> g(formerLV3A) --(indirects_glvs)--> g(liveLV4A)
			   \
			    -> g(formerLV2B) --(indirects_glvs)--> g(formerLV3BA) --(indirects_glvs)--> g(liveLV4BA)
							     \
							      -> g(formerLV3BB) --(indirects_glvs)--> g(liveLV4BB)

g(liveLV1) <--(indirect_origin)-- g(formerLV2A) <--(indirect_origin)-- g(formerLV3A) <--(indirect_origin)-- seg(liveLV4A)
	  \
	   -(indirect_origin)-- g(formerLV2B) <--(indirect_origin)-- g(formerLV3BA) <--(indirect_origin)-- seg(liveLV4BA)
					     \
					      -(indirect_origin)-- g(formerLV3BB) <--(indirect_origin)-- seg(liveLV4BB)

* Or simple example  when former LV is not remembered in records (compare with first "Simple example"):

g(liveLV1) --(indirects_glvs)--> g(liveLV3)

g(liveLV1) <--(indirect_origin)-- seg(liveLV3)

2 files changed, 112 insertions, 0 deletions

diff --git a/lib/metadata/metadata.c b/lib/metadata/metadata.c
index 8478abb08..89ac523bc 100644
--- a/lib/metadata/metadata.c
+++ b/lib/metadata/metadata.c
@@ -32,6 +32,7 @@
 #include "archiver.h"
 #include "defaults.h"
 #include "lvmlockd.h"
+#include "time.h"
 
 #include <math.h>
 #include <sys/param.h>
@@ -3149,7 +3150,9 @@ int vg_write(struct volume_group *vg)
         struct pv_to_write *pv_to_write, *pv_to_write_safe;
 	struct metadata_area *mda;
 	struct lv_list *lvl;
+	struct glv_list *glvl;
 	int revert = 0, wrote = 0;
+	time_t current_timestamp = 0;
 
 	dm_list_iterate_items(lvl, &vg->lvs) {
 		if (lvl->lv->lock_args && !strcmp(lvl->lv->lock_args, "pending")) {
@@ -3161,6 +3164,14 @@ int vg_write(struct volume_group *vg)
 		}
 	}
 
+	dm_list_iterate_items(glvl, &vg->former_lvs) {
+		if (!glvl->glv->former->timestamp_removed) {
+			if (!current_timestamp)
+				current_timestamp = time(NULL);
+			glvl->glv->former->timestamp_removed = (uint64_t) current_timestamp;
+		}
+	}
+
 	if (!vg_validate(vg))
 		return_0;
 
diff --git a/lib/metadata/pool_manip.c b/lib/metadata/pool_manip.c
index cb12aaacd..d2d1f8932 100644
--- a/lib/metadata/pool_manip.c
+++ b/lib/metadata/pool_manip.c
@@ -26,6 +26,7 @@
 #include "dev-type.h"
 #include "display.h"
 #include "toolcontext.h"
+#include <stddef.h>
 
 int attach_pool_metadata_lv(struct lv_segment *pool_seg,
 			    struct logical_volume *metadata_lv)
@@ -123,8 +124,81 @@ int attach_pool_lv(struct lv_segment *seg,
 	return 1;
 }
 
+static struct glv_list *_init_former_glvl(struct dm_pool *mem, struct lv_segment *seg)
+{
+	struct glv_list *glvl;
+	struct former_logical_volume *flv;
+
+	if (!(glvl = dm_pool_zalloc(mem, sizeof(struct glv_list))))
+		goto_bad;
+
+	if (!(glvl->glv = dm_pool_zalloc(mem, sizeof(struct generic_logical_volume))))
+		goto_bad;
+
+	if (!(flv = dm_pool_zalloc(mem, sizeof(struct former_logical_volume))))
+		goto_bad;
+
+	flv->lvid = seg->lv->lvid;
+	flv->name = seg->lv->name;
+	flv->vg = seg->lv->vg;
+	flv->timestamp = seg->lv->timestamp;
+	dm_list_init(&flv->indirect_glvs);
+
+	glvl->glv->is_former = 1;
+	glvl->glv->former = flv;
+
+	return glvl;
+bad:
+	log_error("Initialization of former LV representation for removed logical "
+		  "volume %s/%s failed.", seg->lv->vg->name, seg->lv->name);
+	if (glvl)
+		dm_pool_free(mem, glvl);
+	return NULL;
+}
+
+static struct generic_logical_volume *_create_former_glv(struct lv_segment *seg_to_remove)
+{
+	struct dm_pool *mem = seg_to_remove->lv->vg->vgmem;
+	struct generic_logical_volume *former_glv, *origin_glv = NULL;
+	struct glv_list *former_glvl;
+	int origin_glv_created = 0;
+
+	if (!(former_glvl = _init_former_glvl(mem, seg_to_remove)))
+		goto_bad;
+	former_glv = former_glvl->glv;
+
+	if (seg_to_remove->origin) {
+		if (!(origin_glv = get_or_create_glv(mem, seg_to_remove->origin, &origin_glv_created)))
+			goto_bad;
+
+		if (!add_glv_to_indirect_glvs(mem, origin_glv, former_glv))
+			goto_bad;
+	} else if (seg_to_remove->indirect_origin) {
+		origin_glv = seg_to_remove->indirect_origin;
+
+		if (!remove_glv_from_indirect_glvs(origin_glv, seg_to_remove->lv->this_glv))
+			goto_bad;
+
+		if (!add_glv_to_indirect_glvs(mem, origin_glv, former_glv))
+			goto_bad;
+	}
+
+	dm_list_add(&seg_to_remove->lv->vg->former_lvs, &former_glvl->list);
+	return former_glvl->glv;
+bad:
+	log_error("Failed to create former LV representation for removed logical "
+		  "volume %s/%s.", seg_to_remove->lv->vg->name, seg_to_remove->lv->name);
+	if (origin_glv_created)
+		seg_to_remove->origin->this_glv = NULL;
+	if (former_glvl)
+		dm_pool_free(mem, former_glvl);
+	return NULL;
+}
+
 int detach_pool_lv(struct lv_segment *seg)
 {
+	struct generic_logical_volume *previous_glv = NULL, *glv, *user_glv;
+	struct glv_list *user_glvl, *tglvl;
 	struct lv_thin_message *tmsg, *tmp;
 	struct seg_list *sl, *tsl;
 	int no_update = 0;
@@ -177,6 +251,9 @@ int detach_pool_lv(struct lv_segment *seg)
 		}
 	}
 
+	if (!(previous_glv = _create_former_glv(seg)))
+		return_0;
+
 	if (!detach_thin_external_origin(seg))
 		return_0;
 
@@ -202,15 +279,39 @@ int detach_pool_lv(struct lv_segment *seg)
 		    (seg->lv != sl->seg->origin))
 			continue;
 
+		if (previous_glv) {
+			if (!(user_glv = get_or_create_glv(seg->lv->vg->vgmem, sl->seg->lv, NULL)))
+				return_0;
+
+			if (!add_glv_to_indirect_glvs(seg->lv->vg->vgmem, previous_glv, user_glv))
+				return_0;
+		}
+
 		if (!remove_seg_from_segs_using_this_lv(seg->lv, sl->seg))
 			return_0;
 		/* Thin snapshot is now regular thin volume */
 		sl->seg->origin = NULL;
 	}
 
+	dm_list_iterate_items_safe(user_glvl, tglvl, &seg->lv->indirect_glvs) {
+		user_glv = user_glvl->glv;
+
+		if (!(glv = get_or_create_glv(seg->lv->vg->vgmem, seg->lv, NULL)))
+			return_0;
+
+		if (!remove_glv_from_indirect_glvs(glv, user_glv))
+			return_0;
+
+		if (previous_glv) {
+			if (!add_glv_to_indirect_glvs(seg->lv->vg->vgmem, previous_glv, user_glv))
+				return_0;
+		}
+	}
+
 	seg->lv->status &= ~THIN_VOLUME;
 	seg->pool_lv = NULL;
 	seg->origin = NULL;
+	seg->indirect_origin = NULL;
 
 	return 1;
 }