Add mem and ref_count fields to struct format_instance for own mempool use.

Format instances can be created anytime on demand and it contains
metadata area information mostly (at least for now, but in the future,
we may store more things here to update/edit in a PV/VG). In case we
have lots of metadata areas, memory consumption will rise. Using cmd
context mempool is not quite optimal here because it is destroyed too
late. So let's use a separate mempool for format instances.

Reference counting is used because fids could be shared, e.g. each PV
has either a PV-based fid or VG-based fid. If it's VG-based, each PV has
a shared fid with the VG - a reference to VG's fid.

WHATS_NEW

@@ -1,9 +1,10 @@
 Version 2.02.85 - 
 ===================================
+  Add mem and ref_count fields to struct format_instance for own mempool use.
   Use new alloc_fid fn for common format instance initialisation.
   Optimise _get_token() and _eat_space().
   Add _lv_postorder_vg() to improve efficiency for all LVs in VG.
-  Use hash tables to speedup string search in validate_vg().
+  Use hash tables to speedup string search in vg_validate().
   Refactor allocation of VG structure, add alloc_vg().
   Avoid possible endless loop in _free_vginfo when 4 or more VGs have same name.
   Use empty string instead of /dev// for LV path when there's no VG.

lib/format1/format1.c

@@ -509,8 +509,10 @@ static struct format_instance *_format1_create_instance(const struct format_type
 
 	/* Define a NULL metadata area */
 	if (!(mda = dm_pool_zalloc(fmt->cmd->mem, sizeof(*mda)))) {
+		log_error("Unable to allocate metadata area structure "
+			  "for lvm1 format");
 		dm_pool_free(fmt->cmd->mem, fid);
-		return_NULL;
+		goto bad;
 	}
 
 	mda->ops = &_metadata_format1_ops;
@@ -519,10 +521,16 @@ static struct format_instance *_format1_create_instance(const struct format_type
 	dm_list_add(&fid->metadata_areas_in_use, &mda->list);
 
 	return fid;
+
+bad:
+	dm_pool_destroy(fid->mem);
+	return NULL;
 }
 
-static void _format1_destroy_instance(struct format_instance *fid __attribute__((unused)))
+static void _format1_destroy_instance(struct format_instance *fid)
 {
+	if (--fid->ref_count <= 1)
+		dm_pool_destroy(fid->mem);
 }
 
 static void _format1_destroy(struct format_type *fmt)

lib/format_pool/format_pool.c

@@ -236,7 +236,7 @@ static struct format_instance *_pool_create_instance(const struct format_type *f
 		log_error("Unable to allocate metadata area structure "
 			  "for pool format");
 		dm_pool_free(fmt->cmd->mem, fid);
-		return NULL;
+		goto bad;
 	}
 
 	mda->ops = &_metadata_format_pool_ops;
@@ -245,10 +245,16 @@ static struct format_instance *_pool_create_instance(const struct format_type *f
 	dm_list_add(&fid->metadata_areas_in_use, &mda->list);
 
 	return fid;
+
+bad:
+	dm_pool_destroy(fid->mem);
+	return NULL;
 }
 
-static void _pool_destroy_instance(struct format_instance *fid __attribute__((unused)))
+static void _pool_destroy_instance(struct format_instance *fid)
 {
+	if (--fid->ref_count <= 1)
+		dm_pool_destroy(fid->mem);
 }
 
 static void _pool_destroy(struct format_type *fmt)

lib/format_text/format-text.c

@@ -1571,8 +1571,13 @@ static int _text_pv_initialise(const struct format_type *fmt,
 	return 1;
 }
 
-static void _text_destroy_instance(struct format_instance *fid __attribute__((unused)))
+static void _text_destroy_instance(struct format_instance *fid)
 {
+	if (--fid->ref_count <= 1) {
+		if (fid->type & FMT_INSTANCE_VG && fid->metadata_areas_index.hash)
+			dm_hash_destroy(fid->metadata_areas_index.hash);
+		dm_pool_destroy(fid->mem);
+	}
 }
 
 static void _free_dirs(struct dm_list *dir_list)
@@ -2188,28 +2193,21 @@ static int _text_pv_resize(const struct format_type *fmt,
 	return 1;
 }
 
-/* NULL vgname means use only the supplied context e.g. an archive file */
 static struct format_instance *_text_create_text_instance(const struct format_type *fmt,
 							  const struct format_instance_ctx *fic)
 {
 	struct format_instance *fid;
-	int r;
 
 	if (!(fid = alloc_fid(fmt, fic)))
 		return_NULL;
 
-	if (fid->type & FMT_INSTANCE_VG)
-		r = _create_vg_text_instance(fid, fic);
-	else
-		r = _create_pv_text_instance(fid, fic);
-
-	if (r)
+	if (fid->type & FMT_INSTANCE_VG ? _create_vg_text_instance(fid, fic) :
+					  _create_pv_text_instance(fid, fic))
 		return fid;
-	else {
-		dm_pool_free(fmt->cmd->mem, fid);
-		return NULL;
-	}
 
+	dm_pool_free(fmt->cmd->mem, fid);
+	dm_pool_destroy(fid->mem);
+	return NULL;
 }
 
 void *create_text_context(struct cmd_context *cmd, const char *path,

lib/metadata/metadata-exported.h

@@ -196,6 +196,9 @@ struct pv_segment {
 #define FMT_INSTANCE_PRIVATE_MDAS 	0x00000008U
 
 struct format_instance {
+	unsigned ref_count;
+	struct dm_pool *mem;
+
 	uint32_t type;
 	const struct format_type *fmt;
 

lib/metadata/metadata.c

@@ -3944,20 +3944,30 @@ uint32_t vg_lock_newname(struct cmd_context *cmd, const char *vgname)
 struct format_instance *alloc_fid(const struct format_type *fmt,
 				  const struct format_instance_ctx *fic)
 {
+	struct dm_pool *mem;
 	struct format_instance *fid;
 
+	if (!(mem = dm_pool_create("format_instance", 1024)))
+		return_NULL;
+
 	if (!(fid = dm_pool_zalloc(fmt->cmd->mem, sizeof(*fid)))) {
 		log_error("Couldn't allocate format_instance object.");
-		return NULL;
+		goto bad;
 	}
 
-	fid->fmt = fmt;
+	fid->ref_count = 1;
+	fid->mem = mem;
 	fid->type = fic->type;
+	fid->fmt = fmt;
 
 	dm_list_init(&fid->metadata_areas_in_use);
 	dm_list_init(&fid->metadata_areas_ignored);
 
 	return fid;
+
+bad:
+	dm_pool_destroy(mem);
+	return NULL;
 }
 
 void vg_set_fid(struct volume_group *vg,