/*
 * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
 * Copyright (C) 2004-2011 Red Hat, Inc. All rights reserved.
 *
 * This file is part of LVM2.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "lib.h"
#include "lvmcache.h"
#include "toolcontext.h"
#include "dev-cache.h"
#include "locking.h"
#include "metadata.h"
#include "memlock.h"
#include "str_list.h"
#include "format-text.h"
#include "format_pool.h"
#include "format1.h"
#include "config.h"

#include "lvmetad.h"

#define CACHE_INVALID	0x00000001
#define CACHE_LOCKED	0x00000002

/* One per device */
struct lvmcache_info {
	struct dm_list list;	/* Join VG members together */
	struct dm_list mdas;	/* list head for metadata areas */
	struct dm_list das;	/* list head for data areas */
	struct dm_list bas;	/* list head for bootloader areas */
	struct lvmcache_vginfo *vginfo;	/* NULL == unknown */
	struct label *label;
	const struct format_type *fmt;
	struct device *dev;
	uint64_t device_size;	/* Bytes */
	uint32_t status;
};

/* One per VG */
struct lvmcache_vginfo {
	struct dm_list list;	/* Join these vginfos together */
	struct dm_list infos;	/* List head for lvmcache_infos */
	const struct format_type *fmt;
	char *vgname;		/* "" == orphan */
	uint32_t status;
	char vgid[ID_LEN + 1];
	char _padding[7];
	struct lvmcache_vginfo *next; /* Another VG with same name? */
	char *creation_host;
	uint32_t mda_checksum;
	size_t mda_size;
	size_t vgmetadata_size;
	char *vgmetadata;	/* Copy of VG metadata as format_text string */
	struct dm_config_tree *cft; /* Config tree created from vgmetadata */
				    /* Lifetime is directly tied to vgmetadata */
	struct volume_group *cached_vg;
	unsigned holders;
	unsigned vg_use_count;	/* Counter of vg reusage */
	unsigned precommitted;	/* Is vgmetadata live or precommitted? */
	unsigned cached_vg_invalidated;	/* Signal to regenerate cached_vg */
	unsigned preferred_duplicates; /* preferred duplicate pvs have been set */
};

static struct dm_hash_table *_pvid_hash = NULL;
static struct dm_hash_table *_vgid_hash = NULL;
static struct dm_hash_table *_vgname_hash = NULL;
static struct dm_hash_table *_lock_hash = NULL;
static DM_LIST_INIT(_vginfos);
static int _scanning_in_progress = 0;
static int _has_scanned = 0;
static int _vgs_locked = 0;
static int _vg_global_lock_held = 0;	/* Global lock held when cache wiped? */
static int _found_duplicate_pvs = 0;	/* If we never see a duplicate PV we can skip checking for them later. */

int lvmcache_init(void)
{
	/*
	 * FIXME add a proper lvmcache_locking_reset() that
	 * resets the cache so no previous locks are locked
	 */
	_vgs_locked = 0;

	dm_list_init(&_vginfos);

	if (!(_vgname_hash = dm_hash_create(128)))
		return 0;

	if (!(_vgid_hash = dm_hash_create(128)))
		return 0;

	if (!(_pvid_hash = dm_hash_create(128)))
		return 0;

	if (!(_lock_hash = dm_hash_create(128)))
		return 0;

	/*
	 * Reinitialising the cache clears the internal record of
	 * which locks are held.  The global lock can be held during
	 * this operation so its state must be restored afterwards.
	 */
	if (_vg_global_lock_held) {
		lvmcache_lock_vgname(VG_GLOBAL, 0);
		_vg_global_lock_held = 0;
	}

	return 1;
}

/*
 * Once PV info has been populated in lvmcache and
 * lvmcache has chosen preferred duplicate devices,
 * set this flag so that lvmcache will not try to
 * compare and choose preferred duplicate devices
 * again (which may result in different preferred
 * devices.)  PV info can be populated in lvmcache
 * multiple times, each time causing lvmcache to
 * compare the duplicate devices, so we need to
 * record that the comparison/preferences have
 * already been done, so the preferrences from the
 * first time through are not changed.
 *
 * This is something of a hack to work around the
 * fact that the code isn't really designed to
 * handle duplicate PVs, and the fact that lvmetad
 * has its own way of picking a preferred duplicate
 * and lvmcache has another way based on having
 * more information than lvmetad does.
 *
 * If we come up with a better overall method to
 * handle duplicate PVs, then this can probably be
 * removed.
 *
 * FIXME: if we want to make lvmetad work with clvmd,
 * then this may need to be changed to set
 * preferred_duplicates back to 0.
 */

void lvmcache_set_preferred_duplicates(const char *vgid)
{
	struct lvmcache_vginfo *vginfo;

	if (!(vginfo = lvmcache_vginfo_from_vgid(vgid))) {
		stack;
		return;
	}

	vginfo->preferred_duplicates = 1;
}

void lvmcache_seed_infos_from_lvmetad(struct cmd_context *cmd)
{
	if (!lvmetad_active() || _has_scanned)
		return;

	if (!lvmetad_pv_list_to_lvmcache(cmd)) {
		stack;
		return;
	}

	_has_scanned = 1;
}

/* Volume Group metadata cache functions */
static void _free_cached_vgmetadata(struct lvmcache_vginfo *vginfo)
{
	if (!vginfo || !vginfo->vgmetadata)
		return;

	dm_free(vginfo->vgmetadata);

	vginfo->vgmetadata = NULL;

	/* Release also cached config tree */
	if (vginfo->cft) {
		dm_config_destroy(vginfo->cft);
		vginfo->cft = NULL;
	}

	log_debug_cache("Metadata cache: VG %s wiped.", vginfo->vgname);

	release_vg(vginfo->cached_vg);
}

/*
 * Cache VG metadata against the vginfo with matching vgid.
 */
static void _store_metadata(struct volume_group *vg, unsigned precommitted)
{
	char uuid[64] __attribute__((aligned(8)));
	struct lvmcache_vginfo *vginfo;
	char *data;
	size_t size;

	if (!(vginfo = lvmcache_vginfo_from_vgid((const char *)&vg->id))) {
		stack;
		return;
	}

	if (!(size = export_vg_to_buffer(vg, &data))) {
		stack;
		_free_cached_vgmetadata(vginfo);
		return;
	}

	/* Avoid reparsing of the same data string */
	if (vginfo->vgmetadata && vginfo->vgmetadata_size == size &&
	    strcmp(vginfo->vgmetadata, data) == 0)
		dm_free(data);
	else {
		_free_cached_vgmetadata(vginfo);
		vginfo->vgmetadata_size = size;
		vginfo->vgmetadata = data;
	}

	vginfo->precommitted = precommitted;

	if (!id_write_format((const struct id *)vginfo->vgid, uuid, sizeof(uuid))) {
		stack;
		return;
	}

	log_debug_cache("Metadata cache: VG %s (%s) stored (%" PRIsize_t " bytes%s).",
			vginfo->vgname, uuid, size,
			precommitted ? ", precommitted" : "");
}

static void _update_cache_info_lock_state(struct lvmcache_info *info,
					  int locked,
					  int *cached_vgmetadata_valid)
{
	int was_locked = (info->status & CACHE_LOCKED) ? 1 : 0;

	/*
	 * Cache becomes invalid whenever lock state changes unless
	 * exclusive VG_GLOBAL is held (i.e. while scanning).
	 */
	if (!lvmcache_vgname_is_locked(VG_GLOBAL) && (was_locked != locked)) {
		info->status |= CACHE_INVALID;
		*cached_vgmetadata_valid = 0;
	}

	if (locked)
		info->status |= CACHE_LOCKED;
	else
		info->status &= ~CACHE_LOCKED;
}

static void _update_cache_vginfo_lock_state(struct lvmcache_vginfo *vginfo,
					    int locked)
{
	struct lvmcache_info *info;
	int cached_vgmetadata_valid = 1;

	dm_list_iterate_items(info, &vginfo->infos)
		_update_cache_info_lock_state(info, locked,
					      &cached_vgmetadata_valid);

	if (!cached_vgmetadata_valid)
		_free_cached_vgmetadata(vginfo);
}

static void _update_cache_lock_state(const char *vgname, int locked)
{
	struct lvmcache_vginfo *vginfo;

	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, NULL)))
		return;

	_update_cache_vginfo_lock_state(vginfo, locked);
}

static void _drop_metadata(const char *vgname, int drop_precommitted)
{
	struct lvmcache_vginfo *vginfo;
	struct lvmcache_info *info;

	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, NULL)))
		return;

	/*
	 * Invalidate cached PV labels.
	 * If cached precommitted metadata exists that means we
	 * already invalidated the PV labels (before caching it)
	 * and we must not do it again.
	 */
	if (!drop_precommitted && vginfo->precommitted && !vginfo->vgmetadata)
		log_error(INTERNAL_ERROR "metadata commit (or revert) missing before "
			  "dropping metadata from cache.");

	if (drop_precommitted || !vginfo->precommitted)
		dm_list_iterate_items(info, &vginfo->infos)
			info->status |= CACHE_INVALID;

	_free_cached_vgmetadata(vginfo);

	/* VG revert */
	if (drop_precommitted)
		vginfo->precommitted = 0;
}

/*
 * Remote node uses this to upgrade precommitted metadata to commited state
 * when receives vg_commit notification.
 * (Note that devices can be suspended here, if so, precommitted metadata are already read.)
 */
void lvmcache_commit_metadata(const char *vgname)
{
	struct lvmcache_vginfo *vginfo;

	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, NULL)))
		return;

	if (vginfo->precommitted) {
		log_debug_cache("Precommitted metadata cache: VG %s upgraded to committed.",
				vginfo->vgname);
		vginfo->precommitted = 0;
	}
}

void lvmcache_drop_metadata(const char *vgname, int drop_precommitted)
{
	if (lvmcache_vgname_is_locked(VG_GLOBAL) && !vg_write_lock_held())
		return;

	/* For VG_ORPHANS, we need to invalidate all labels on orphan PVs. */
	if (!strcmp(vgname, VG_ORPHANS)) {
		_drop_metadata(FMT_TEXT_ORPHAN_VG_NAME, 0);
		_drop_metadata(FMT_LVM1_ORPHAN_VG_NAME, 0);
		_drop_metadata(FMT_POOL_ORPHAN_VG_NAME, 0);

		/* Indicate that PVs could now be missing from the cache */
		init_full_scan_done(0);
	} else
		_drop_metadata(vgname, drop_precommitted);
}

/*
 * Ensure vgname2 comes after vgname1 alphabetically.
 * Orphan locks come last.
 * VG_GLOBAL comes first.
 */
static int _vgname_order_correct(const char *vgname1, const char *vgname2)
{
	if (is_global_vg(vgname1))
		return 1;

	if (is_global_vg(vgname2))
		return 0;

	if (is_orphan_vg(vgname1))
		return 0;

	if (is_orphan_vg(vgname2))
		return 1;

	if (strcmp(vgname1, vgname2) < 0)
		return 1;

	return 0;
}

/*
 * Ensure VG locks are acquired in alphabetical order.
 */
int lvmcache_verify_lock_order(const char *vgname)
{
	struct dm_hash_node *n;
	const char *vgname2;

	if (!_lock_hash)
		return_0;

	dm_hash_iterate(n, _lock_hash) {
		if (!dm_hash_get_data(_lock_hash, n))
			return_0;

		if (!(vgname2 = dm_hash_get_key(_lock_hash, n))) {
			log_error(INTERNAL_ERROR "VG lock %s hits NULL.",
				 vgname);
			return 0;
		}

		if (!_vgname_order_correct(vgname2, vgname)) {
			log_errno(EDEADLK, INTERNAL_ERROR "VG lock %s must "
				  "be requested before %s, not after.",
				  vgname, vgname2);
			return 0;
		}
	}

	return 1;
}

void lvmcache_lock_vgname(const char *vgname, int read_only __attribute__((unused)))
{
	if (!_lock_hash && !lvmcache_init()) {
		log_error("Internal cache initialisation failed");
		return;
	}

	if (dm_hash_lookup(_lock_hash, vgname))
		log_error(INTERNAL_ERROR "Nested locking attempted on VG %s.",
			  vgname);

	if (!dm_hash_insert(_lock_hash, vgname, (void *) 1))
		log_error("Cache locking failure for %s", vgname);

	if (strcmp(vgname, VG_GLOBAL)) {
		_update_cache_lock_state(vgname, 1);
		_vgs_locked++;
	}
}

int lvmcache_vgname_is_locked(const char *vgname)
{
	if (!_lock_hash)
		return 0;

	return dm_hash_lookup(_lock_hash, is_orphan_vg(vgname) ? VG_ORPHANS : vgname) ? 1 : 0;
}

void lvmcache_unlock_vgname(const char *vgname)
{
	if (!dm_hash_lookup(_lock_hash, vgname))
		log_error(INTERNAL_ERROR "Attempt to unlock unlocked VG %s.",
			  vgname);

	if (strcmp(vgname, VG_GLOBAL))
		_update_cache_lock_state(vgname, 0);

	dm_hash_remove(_lock_hash, vgname);

	/* FIXME Do this per-VG */
	if (strcmp(vgname, VG_GLOBAL) && !--_vgs_locked)
		dev_close_all();
}

int lvmcache_vgs_locked(void)
{
	return _vgs_locked;
}

/*
 * When lvmcache sees a duplicate PV, this is set.
 * process_each_pv() can avoid searching for duplicates
 * by checking this and seeing that no duplicate PVs exist.
 */
int lvmcache_found_duplicate_pvs(void)
{
	return _found_duplicate_pvs;
}

static void _vginfo_attach_info(struct lvmcache_vginfo *vginfo,
				struct lvmcache_info *info)
{
	if (!vginfo)
		return;

	info->vginfo = vginfo;
	dm_list_add(&vginfo->infos, &info->list);
}

static void _vginfo_detach_info(struct lvmcache_info *info)
{
	if (!dm_list_empty(&info->list)) {
		dm_list_del(&info->list);
		dm_list_init(&info->list);
	}

	info->vginfo = NULL;
}

/* If vgid supplied, require a match. */
struct lvmcache_vginfo *lvmcache_vginfo_from_vgname(const char *vgname, const char *vgid)
{
	struct lvmcache_vginfo *vginfo;

	if (!vgname)
		return lvmcache_vginfo_from_vgid(vgid);

	if (!_vgname_hash) {
		log_debug_cache(INTERNAL_ERROR "Internal cache is no yet initialized.");
		return NULL;
	}

	if (!(vginfo = dm_hash_lookup(_vgname_hash, vgname))) {
		log_debug_cache("Metadata cache has no info for vgname: \"%s\"", vgname);
		return NULL;
	}

	if (vgid)
		do
			if (!strncmp(vgid, vginfo->vgid, ID_LEN))
				return vginfo;
		while ((vginfo = vginfo->next));

	if  (!vginfo)
		log_debug_cache("Metadata cache has not found vgname \"%s\" with vgid \"%."
				DM_TO_STRING(ID_LEN) "s\".", vgname, vgid ? : "");

	return vginfo;
}

const struct format_type *lvmcache_fmt_from_vgname(struct cmd_context *cmd,
						   const char *vgname, const char *vgid,
						   unsigned revalidate_labels)
{
	struct lvmcache_vginfo *vginfo;
	struct lvmcache_info *info;
	struct label *label;
	struct dm_list *devh, *tmp;
	struct dm_list devs;
	struct device_list *devl;
	struct volume_group *vg;
	const struct format_type *fmt;
	char vgid_found[ID_LEN + 1] __attribute__((aligned(8)));

	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, vgid))) {
		if (!lvmetad_active())
			return NULL; /* too bad */
		/* If we don't have the info but we have lvmetad, we can ask
		 * there before failing. */
		if ((vg = lvmetad_vg_lookup(cmd, vgname, vgid))) {
			fmt = vg->fid->fmt;
			release_vg(vg);
			return fmt;
		}
		return NULL;
	}

	/*
	 * If this function is called repeatedly, only the first one needs to revalidate.
	 */
	if (!revalidate_labels)
		goto out;

	/*
	 * This function is normally called before reading metadata so
 	 * we check cached labels here. Unfortunately vginfo is volatile.
 	 */
	dm_list_init(&devs);
	dm_list_iterate_items(info, &vginfo->infos) {
		if (!(devl = dm_malloc(sizeof(*devl)))) {
			log_error("device_list element allocation failed");
			return NULL;
		}
		devl->dev = info->dev;
		dm_list_add(&devs, &devl->list);
	}

	memcpy(vgid_found, vginfo->vgid, sizeof(vgid_found));

	dm_list_iterate_safe(devh, tmp, &devs) {
		devl = dm_list_item(devh, struct device_list);
		(void) label_read(devl->dev, &label, UINT64_C(0));
		dm_list_del(&devl->list);
		dm_free(devl);
	}

	/* If vginfo changed, caller needs to rescan */
	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, vgid_found)) ||
	    strncmp(vginfo->vgid, vgid_found, ID_LEN))
		return NULL;

out:
	return vginfo->fmt;
}

struct lvmcache_vginfo *lvmcache_vginfo_from_vgid(const char *vgid)
{
	struct lvmcache_vginfo *vginfo;
	char id[ID_LEN + 1] __attribute__((aligned(8)));

	if (!_vgid_hash || !vgid) {
		log_debug_cache(INTERNAL_ERROR "Internal cache cannot lookup vgid.");
		return NULL;
	}

	/* vgid not necessarily NULL-terminated */
	strncpy(&id[0], vgid, ID_LEN);
	id[ID_LEN] = '\0';

	if (!(vginfo = dm_hash_lookup(_vgid_hash, id))) {
		log_debug_cache("Metadata cache has no info for vgid \"%s\"", id);
		return NULL;
	}

	return vginfo;
}

const char *lvmcache_vgname_from_vgid(struct dm_pool *mem, const char *vgid)
{
	struct lvmcache_vginfo *vginfo;
	const char *vgname = NULL;

	if ((vginfo = lvmcache_vginfo_from_vgid(vgid)))
		vgname = vginfo->vgname;

	if (mem && vgname)
		return dm_pool_strdup(mem, vgname);

	return vgname;
}

static int _info_is_valid(struct lvmcache_info *info)
{
	if (info->status & CACHE_INVALID)
		return 0;

	/*
	 * The caller must hold the VG lock to manipulate metadata.
	 * In a cluster, remote nodes sometimes read metadata in the
	 * knowledge that the controlling node is holding the lock.
	 * So if the VG appears to be unlocked here, it should be safe
	 * to use the cached value.
	 */
	if (info->vginfo && !lvmcache_vgname_is_locked(info->vginfo->vgname))
		return 1;

	if (!(info->status & CACHE_LOCKED))
		return 0;

	return 1;
}

static int _vginfo_is_valid(struct lvmcache_vginfo *vginfo)
{
	struct lvmcache_info *info;

	/* Invalid if any info is invalid */
	dm_list_iterate_items(info, &vginfo->infos)
		if (!_info_is_valid(info))
			return 0;

	return 1;
}

/* vginfo is invalid if it does not contain at least one valid info */
static int _vginfo_is_invalid(struct lvmcache_vginfo *vginfo)
{
	struct lvmcache_info *info;

	dm_list_iterate_items(info, &vginfo->infos)
		if (_info_is_valid(info))
			return 0;

	return 1;
}

/*
 * If valid_only is set, data will only be returned if the cached data is
 * known still to be valid.
 */
struct lvmcache_info *lvmcache_info_from_pvid(const char *pvid, int valid_only)
{
	struct lvmcache_info *info;
	char id[ID_LEN + 1] __attribute__((aligned(8)));

	if (!_pvid_hash || !pvid)
		return NULL;

	strncpy(&id[0], pvid, ID_LEN);
	id[ID_LEN] = '\0';

	if (!(info = dm_hash_lookup(_pvid_hash, id)))
		return NULL;

	if (valid_only && !_info_is_valid(info))
		return NULL;

	return info;
}

const char *lvmcache_vgname_from_info(struct lvmcache_info *info)
{
	if (info->vginfo)
		return info->vginfo->vgname;
	return NULL;
}

char *lvmcache_vgname_from_pvid(struct cmd_context *cmd, const char *pvid)
{
	struct lvmcache_info *info;
	char *vgname;

	if (!lvmcache_device_from_pvid(cmd, (const struct id *)pvid, NULL, NULL)) {
		log_error("Couldn't find device with uuid %s.", pvid);
		return NULL;
	}

	info = lvmcache_info_from_pvid(pvid, 0);
	if (!info)
		return_NULL;

	if (!(vgname = dm_pool_strdup(cmd->mem, info->vginfo->vgname))) {
		log_errno(ENOMEM, "vgname allocation failed");
		return NULL;
	}
	return vgname;
}

static void _rescan_entry(struct lvmcache_info *info)
{
	struct label *label;

	if (info->status & CACHE_INVALID)
		(void) label_read(info->dev, &label, UINT64_C(0));
}

static int _scan_invalid(void)
{
	dm_hash_iter(_pvid_hash, (dm_hash_iterate_fn) _rescan_entry);

	return 1;
}

int lvmcache_label_scan(struct cmd_context *cmd, int full_scan)
{
	struct label *label;
	struct dev_iter *iter;
	struct device *dev;
	struct format_type *fmt;

	int r = 0;

	if (lvmetad_active())
		return 1;

	/* Avoid recursion when a PVID can't be found! */
	if (_scanning_in_progress)
		return 0;

	_scanning_in_progress = 1;

	if (!_vgname_hash && !lvmcache_init()) {
		log_error("Internal cache initialisation failed");
		goto out;
	}

	if (_has_scanned && !full_scan) {
		r = _scan_invalid();
		goto out;
	}

	if (full_scan == 2 && (cmd->full_filter && !cmd->full_filter->use_count) && !refresh_filters(cmd))
		goto_out;

	if (!cmd->full_filter || !(iter = dev_iter_create(cmd->full_filter, (full_scan == 2) ? 1 : 0))) {
		log_error("dev_iter creation failed");
		goto out;
	}

	while ((dev = dev_iter_get(iter)))
		(void) label_read(dev, &label, UINT64_C(0));

	dev_iter_destroy(iter);

	_has_scanned = 1;

	/* Perform any format-specific scanning e.g. text files */
	if (cmd->independent_metadata_areas)
		dm_list_iterate_items(fmt, &cmd->formats)
			if (fmt->ops->scan && !fmt->ops->scan(fmt, NULL))
				goto out;

	/*
	 * If we are a long-lived process, write out the updated persistent
	 * device cache for the benefit of short-lived processes.
	 */
	if (full_scan == 2 && cmd->is_long_lived &&
	    cmd->dump_filter && cmd->full_filter && cmd->full_filter->dump &&
	    !cmd->full_filter->dump(cmd->full_filter, 0))
		stack;

	r = 1;

      out:
	_scanning_in_progress = 0;

	return r;
}

struct volume_group *lvmcache_get_vg(struct cmd_context *cmd, const char *vgname,
				     const char *vgid, unsigned precommitted)
{
	struct lvmcache_vginfo *vginfo;
	struct volume_group *vg = NULL;
	struct format_instance *fid;
	struct format_instance_ctx fic;

	/*
	 * We currently do not store precommitted metadata in lvmetad at
	 * all. This means that any request for precommitted metadata is served
	 * using the classic scanning mechanics, and read from disk or from
	 * lvmcache.
	 */
	if (lvmetad_active() && !precommitted) {
		/* Still serve the locally cached VG if available */
		if (vgid && (vginfo = lvmcache_vginfo_from_vgid(vgid)) &&
		    vginfo->vgmetadata && (vg = vginfo->cached_vg))
			goto out;
		return lvmetad_vg_lookup(cmd, vgname, vgid);
	}

	if (!vgid || !(vginfo = lvmcache_vginfo_from_vgid(vgid)) || !vginfo->vgmetadata)
		return NULL;

	if (!_vginfo_is_valid(vginfo))
		return NULL;

	/*
	 * Don't return cached data if either:
	 * (i)  precommitted metadata is requested but we don't have it cached
	 *      - caller should read it off disk;
	 * (ii) live metadata is requested but we have precommitted metadata cached
	 *      and no devices are suspended so caller may read it off disk.
	 *
	 * If live metadata is requested but we have precommitted metadata cached
	 * and devices are suspended, we assume this precommitted metadata has
	 * already been preloaded and committed so it's OK to return it as live.
	 * Note that we do not clear the PRECOMMITTED flag.
	 */
	if ((precommitted && !vginfo->precommitted) ||
	    (!precommitted && vginfo->precommitted && !critical_section()))
		return NULL;

	/* Use already-cached VG struct when available */
	if ((vg = vginfo->cached_vg) && !vginfo->cached_vg_invalidated)
		goto out;

	release_vg(vginfo->cached_vg);

	fic.type = FMT_INSTANCE_MDAS | FMT_INSTANCE_AUX_MDAS;
	fic.context.vg_ref.vg_name = vginfo->vgname;
	fic.context.vg_ref.vg_id = vgid;
	if (!(fid = vginfo->fmt->ops->create_instance(vginfo->fmt, &fic)))
		return_NULL;

	/* Build config tree from vgmetadata, if not yet cached */
	if (!vginfo->cft &&
	    !(vginfo->cft =
	      dm_config_from_string(vginfo->vgmetadata)))
		goto_bad;

	if (!(vg = import_vg_from_config_tree(vginfo->cft, fid)))
		goto_bad;

	/* Cache VG struct for reuse */
	vginfo->cached_vg = vg;
	vginfo->holders = 1;
	vginfo->vg_use_count = 0;
	vginfo->cached_vg_invalidated = 0;
	vg->vginfo = vginfo;

	if (!dm_pool_lock(vg->vgmem, detect_internal_vg_cache_corruption()))
		goto_bad;

out:
	vginfo->holders++;
	vginfo->vg_use_count++;
	log_debug_cache("Using cached %smetadata for VG %s with %u holder(s).",
			vginfo->precommitted ? "pre-committed " : "",
			vginfo->vgname, vginfo->holders);

	return vg;

bad:
	_free_cached_vgmetadata(vginfo);
	return NULL;
}

// #if 0
int lvmcache_vginfo_holders_dec_and_test_for_zero(struct lvmcache_vginfo *vginfo)
{
	log_debug_cache("VG %s decrementing %d holder(s) at %p.",
			vginfo->cached_vg->name, vginfo->holders, vginfo->cached_vg);

	if (--vginfo->holders)
		return 0;

	if (vginfo->vg_use_count > 1)
		log_debug_cache("VG %s reused %d times.",
				vginfo->cached_vg->name, vginfo->vg_use_count);

	/* Debug perform crc check only when it's been used more then once */
	if (!dm_pool_unlock(vginfo->cached_vg->vgmem,
			    detect_internal_vg_cache_corruption() &&
			    (vginfo->vg_use_count > 1)))
		stack;

	vginfo->cached_vg->vginfo = NULL;
	vginfo->cached_vg = NULL;

	return 1;
}
// #endif

int lvmcache_get_vgnameids(struct cmd_context *cmd, int include_internal,
			   struct dm_list *vgnameids)
{
	struct vgnameid_list *vgnl;
	struct lvmcache_vginfo *vginfo;

	lvmcache_label_scan(cmd, 0);

	dm_list_iterate_items(vginfo, &_vginfos) {
		if (!include_internal && is_orphan_vg(vginfo->vgname))
			continue;

		if (!(vgnl = dm_pool_alloc(cmd->mem, sizeof(*vgnl)))) {
			log_error("vgnameid_list allocation failed.");
			return 0;
		}

		vgnl->vgid = dm_pool_strdup(cmd->mem, vginfo->vgid);
		vgnl->vg_name = dm_pool_strdup(cmd->mem, vginfo->vgname);

		if (!vgnl->vgid || !vgnl->vg_name) {
			log_error("vgnameid_list member allocation failed.");
			return 0;
		}

		dm_list_add(vgnameids, &vgnl->list);
	}

	return 1;
}

struct dm_list *lvmcache_get_vgids(struct cmd_context *cmd,
				   int include_internal)
{
	struct dm_list *vgids;
	struct lvmcache_vginfo *vginfo;

	// TODO plug into lvmetad here automagically?
	lvmcache_label_scan(cmd, 0);

	if (!(vgids = str_list_create(cmd->mem))) {
		log_error("vgids list allocation failed");
		return NULL;
	}

	dm_list_iterate_items(vginfo, &_vginfos) {
		if (!include_internal && is_orphan_vg(vginfo->vgname))
			continue;

		if (!str_list_add(cmd->mem, vgids,
				  dm_pool_strdup(cmd->mem, vginfo->vgid))) {
			log_error("strlist allocation failed");
			return NULL;
		}
	}

	return vgids;
}

struct dm_list *lvmcache_get_vgnames(struct cmd_context *cmd,
				     int include_internal)
{
	struct dm_list *vgnames;
	struct lvmcache_vginfo *vginfo;

	lvmcache_label_scan(cmd, 0);

	if (!(vgnames = str_list_create(cmd->mem))) {
		log_errno(ENOMEM, "vgnames list allocation failed");
		return NULL;
	}

	dm_list_iterate_items(vginfo, &_vginfos) {
		if (!include_internal && is_orphan_vg(vginfo->vgname))
			continue;

		if (!str_list_add(cmd->mem, vgnames,
				  dm_pool_strdup(cmd->mem, vginfo->vgname))) {
			log_errno(ENOMEM, "strlist allocation failed");
			return NULL;
		}
	}

	return vgnames;
}

struct dm_list *lvmcache_get_pvids(struct cmd_context *cmd, const char *vgname,
				const char *vgid)
{
	struct dm_list *pvids;
	struct lvmcache_vginfo *vginfo;
	struct lvmcache_info *info;

	if (!(pvids = str_list_create(cmd->mem))) {
		log_error("pvids list allocation failed");
		return NULL;
	}

	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, vgid)))
		return pvids;

	dm_list_iterate_items(info, &vginfo->infos) {
		if (!str_list_add(cmd->mem, pvids,
				  dm_pool_strdup(cmd->mem, info->dev->pvid))) {
			log_error("strlist allocation failed");
			return NULL;
		}
	}

	return pvids;
}

static struct device *_device_from_pvid(const struct id *pvid,
					uint64_t *label_sector)
{
	struct lvmcache_info *info;
	struct label *label;

	if ((info = lvmcache_info_from_pvid((const char *) pvid, 0))) {
		if (lvmetad_active()) {
			if (info->label && label_sector)
				*label_sector = info->label->sector;
			return info->dev;
		}

		if (label_read(info->dev, &label, UINT64_C(0))) {
			info = (struct lvmcache_info *) label->info;
			if (id_equal(pvid, (struct id *) &info->dev->pvid)) {
				if (label_sector)
					*label_sector = label->sector;
				return info->dev;
                        }
		}
	}
	return NULL;
}

struct device *lvmcache_device_from_pvid(struct cmd_context *cmd, const struct id *pvid,
				unsigned *scan_done_once, uint64_t *label_sector)
{
	struct device *dev;

	/* Already cached ? */
	dev = _device_from_pvid(pvid, label_sector);
	if (dev)
		return dev;

	lvmcache_label_scan(cmd, 0);

	/* Try again */
	dev = _device_from_pvid(pvid, label_sector);
	if (dev)
		return dev;

	if (critical_section() || (scan_done_once && *scan_done_once))
		return NULL;

	lvmcache_label_scan(cmd, 2);
	if (scan_done_once)
		*scan_done_once = 1;

	/* Try again */
	dev = _device_from_pvid(pvid, label_sector);
	if (dev)
		return dev;

	return NULL;
}

const char *lvmcache_pvid_from_devname(struct cmd_context *cmd,
			      const char *devname)
{
	struct device *dev;
	struct label *label;

	if (!(dev = dev_cache_get(devname, cmd->filter))) {
		log_error("%s: Couldn't find device.  Check your filters?",
			  devname);
		return NULL;
	}

	if (!(label_read(dev, &label, UINT64_C(0))))
		return NULL;

	return dev->pvid;
}


static int _free_vginfo(struct lvmcache_vginfo *vginfo)
{
	struct lvmcache_vginfo *primary_vginfo, *vginfo2;
	int r = 1;

	_free_cached_vgmetadata(vginfo);

	vginfo2 = primary_vginfo = lvmcache_vginfo_from_vgname(vginfo->vgname, NULL);

	if (vginfo == primary_vginfo) {
		dm_hash_remove(_vgname_hash, vginfo->vgname);
		if (vginfo->next && !dm_hash_insert(_vgname_hash, vginfo->vgname,
						    vginfo->next)) {
			log_error("_vgname_hash re-insertion for %s failed",
				  vginfo->vgname);
			r = 0;
		}
	} else
		while (vginfo2) {
			if (vginfo2->next == vginfo) {
				vginfo2->next = vginfo->next;
				break;
			}
			vginfo2 = vginfo2->next;
		}

	dm_free(vginfo->vgname);
	dm_free(vginfo->creation_host);

	if (*vginfo->vgid && _vgid_hash &&
	    lvmcache_vginfo_from_vgid(vginfo->vgid) == vginfo)
		dm_hash_remove(_vgid_hash, vginfo->vgid);

	dm_list_del(&vginfo->list);

	dm_free(vginfo);

	return r;
}

/*
 * vginfo must be info->vginfo unless info is NULL
 */
static int _drop_vginfo(struct lvmcache_info *info, struct lvmcache_vginfo *vginfo)
{
	if (info)
		_vginfo_detach_info(info);

	/* vginfo still referenced? */
	if (!vginfo || is_orphan_vg(vginfo->vgname) ||
	    !dm_list_empty(&vginfo->infos))
		return 1;

	if (!_free_vginfo(vginfo))
		return_0;

	return 1;
}

void lvmcache_del(struct lvmcache_info *info)
{
	if (info->dev->pvid[0] && _pvid_hash)
		dm_hash_remove(_pvid_hash, info->dev->pvid);

	_drop_vginfo(info, info->vginfo);

	info->label->labeller->ops->destroy_label(info->label->labeller,
						  info->label);
	dm_free(info);

	return;
}

static int _lvmcache_update_pvid(struct lvmcache_info *info, const char *pvid)
{
	/*
	 * Nothing to do if already stored with same pvid.
	 */

	if (((dm_hash_lookup(_pvid_hash, pvid)) == info) &&
	    !strcmp(info->dev->pvid, pvid))
		return 1;
	if (*info->dev->pvid)
		dm_hash_remove(_pvid_hash, info->dev->pvid);
	strncpy(info->dev->pvid, pvid, sizeof(info->dev->pvid));
	if (!dm_hash_insert(_pvid_hash, pvid, info)) {
		log_error("_lvmcache_update: pvid insertion failed: %s", pvid);
		return 0;
	}

	return 1;
}

/*
 * vginfo must be info->vginfo unless info is NULL (orphans)
 */
static int _lvmcache_update_vgid(struct lvmcache_info *info,
				 struct lvmcache_vginfo *vginfo,
				 const char *vgid)
{
	if (!vgid || !vginfo ||
	    !strncmp(vginfo->vgid, vgid, ID_LEN))
		return 1;

	if (vginfo && *vginfo->vgid)
		dm_hash_remove(_vgid_hash, vginfo->vgid);
	if (!vgid) {
		/* FIXME: unreachable code path */
		log_debug_cache("lvmcache: %s: clearing VGID", info ? dev_name(info->dev) : vginfo->vgname);
		return 1;
	}

	strncpy(vginfo->vgid, vgid, ID_LEN);
	vginfo->vgid[ID_LEN] = '\0';
	if (!dm_hash_insert(_vgid_hash, vginfo->vgid, vginfo)) {
		log_error("_lvmcache_update: vgid hash insertion failed: %s",
			  vginfo->vgid);
		return 0;
	}

	if (!is_orphan_vg(vginfo->vgname))
		log_debug_cache("lvmcache: %s: setting %s VGID to %s",
				(info) ? dev_name(info->dev) : "",
				vginfo->vgname, vginfo->vgid);

	return 1;
}

static int _insert_vginfo(struct lvmcache_vginfo *new_vginfo, const char *vgid,
			  uint32_t vgstatus, const char *creation_host,
			  struct lvmcache_vginfo *primary_vginfo)
{
	struct lvmcache_vginfo *last_vginfo = primary_vginfo;
	char uuid_primary[64] __attribute__((aligned(8)));
	char uuid_new[64] __attribute__((aligned(8)));
	int use_new = 0;

	/* Pre-existing VG takes precedence. Unexported VG takes precedence. */
	if (primary_vginfo) {
		if (!id_write_format((const struct id *)vgid, uuid_new, sizeof(uuid_new)))
			return_0;

		if (!id_write_format((const struct id *)&primary_vginfo->vgid, uuid_primary,
				     sizeof(uuid_primary)))
			return_0;

		/*
		 * If   Primary not exported, new exported => keep
		 * Else Primary exported, new not exported => change
		 * Else Primary has hostname for this machine => keep
		 * Else Primary has no hostname, new has one => change
		 * Else New has hostname for this machine => change
		 * Else Keep primary.
		 */
		if (!(primary_vginfo->status & EXPORTED_VG) &&
		    (vgstatus & EXPORTED_VG))
			log_warn("WARNING: Duplicate VG name %s: "
				 "Existing %s takes precedence over "
				 "exported %s", new_vginfo->vgname,
				 uuid_primary, uuid_new);
		else if ((primary_vginfo->status & EXPORTED_VG) &&
			   !(vgstatus & EXPORTED_VG)) {
			log_warn("WARNING: Duplicate VG name %s: "
				 "%s takes precedence over exported %s",
				 new_vginfo->vgname, uuid_new,
				 uuid_primary);
			use_new = 1;
		} else if (primary_vginfo->creation_host &&
			   !strcmp(primary_vginfo->creation_host,
				   primary_vginfo->fmt->cmd->hostname))
			log_warn("WARNING: Duplicate VG name %s: "
				 "Existing %s (created here) takes precedence "
				 "over %s", new_vginfo->vgname, uuid_primary,
				 uuid_new);
		else if (!primary_vginfo->creation_host && creation_host) {
			log_warn("WARNING: Duplicate VG name %s: "
				 "%s (with creation_host) takes precedence over %s",
				 new_vginfo->vgname, uuid_new,
				 uuid_primary);
			use_new = 1;
		} else if (creation_host &&
			   !strcmp(creation_host,
				   primary_vginfo->fmt->cmd->hostname)) {
			log_warn("WARNING: Duplicate VG name %s: "
				 "%s (created here) takes precedence over %s",
				 new_vginfo->vgname, uuid_new,
				 uuid_primary);
			use_new = 1;
		}

		if (!use_new) {
			while (last_vginfo->next)
				last_vginfo = last_vginfo->next;
			last_vginfo->next = new_vginfo;
			return 1;
		}

		dm_hash_remove(_vgname_hash, primary_vginfo->vgname);
	}

	if (!dm_hash_insert(_vgname_hash, new_vginfo->vgname, new_vginfo)) {
		log_error("cache_update: vg hash insertion failed: %s",
		  	new_vginfo->vgname);
		return 0;
	}

	if (primary_vginfo)
		new_vginfo->next = primary_vginfo;

	return 1;
}

static int _lvmcache_update_vgname(struct lvmcache_info *info,
				   const char *vgname, const char *vgid,
				   uint32_t vgstatus, const char *creation_host,
				   const struct format_type *fmt)
{
	struct lvmcache_vginfo *vginfo, *primary_vginfo, *orphan_vginfo;
	struct lvmcache_info *info2, *info3;
	char mdabuf[32];
	// struct lvmcache_vginfo  *old_vginfo, *next;

	if (!vgname || (info && info->vginfo && !strcmp(info->vginfo->vgname, vgname)))
		return 1;

	/* Remove existing vginfo entry */
	if (info)
		_drop_vginfo(info, info->vginfo);

	/* Get existing vginfo or create new one */
	if (!(vginfo = lvmcache_vginfo_from_vgname(vgname, vgid))) {
/*** FIXME - vginfo ends up duplicated instead of renamed.
		// Renaming?  This lookup fails.
		if ((vginfo = vginfo_from_vgid(vgid))) {
			next = vginfo->next;
			old_vginfo = vginfo_from_vgname(vginfo->vgname, NULL);
			if (old_vginfo == vginfo) {
				dm_hash_remove(_vgname_hash, old_vginfo->vgname);
				if (old_vginfo->next) {
					if (!dm_hash_insert(_vgname_hash, old_vginfo->vgname, old_vginfo->next)) {
						log_error("vg hash re-insertion failed: %s",
							  old_vginfo->vgname);
						return 0;
					}
				}
			} else do {
				if (old_vginfo->next == vginfo) {
					old_vginfo->next = vginfo->next;
					break;
				}
			} while ((old_vginfo = old_vginfo->next));
			vginfo->next = NULL;

			dm_free(vginfo->vgname);
			if (!(vginfo->vgname = dm_strdup(vgname))) {
				log_error("cache vgname alloc failed for %s", vgname);
				return 0;
			}

			// Rename so can assume new name does not already exist
			if (!dm_hash_insert(_vgname_hash, vginfo->vgname, vginfo->next)) {
				log_error("vg hash re-insertion failed: %s",
					  vginfo->vgname);
		      		return 0;
			}
		} else {
***/
		if (!(vginfo = dm_zalloc(sizeof(*vginfo)))) {
			log_error("lvmcache_update_vgname: list alloc failed");
			return 0;
		}
		if (!(vginfo->vgname = dm_strdup(vgname))) {
			dm_free(vginfo);
			log_error("cache vgname alloc failed for %s", vgname);
			return 0;
		}
		dm_list_init(&vginfo->infos);

		/*
		 * If we're scanning and there's an invalidated entry, remove it.
		 * Otherwise we risk bogus warnings of duplicate VGs.
		 */
		while ((primary_vginfo = lvmcache_vginfo_from_vgname(vgname, NULL)) &&
		       _scanning_in_progress && _vginfo_is_invalid(primary_vginfo)) {
			orphan_vginfo = lvmcache_vginfo_from_vgname(primary_vginfo->fmt->orphan_vg_name, NULL);
			if (!orphan_vginfo) {
				log_error(INTERNAL_ERROR "Orphan vginfo %s lost from cache.",
					  primary_vginfo->fmt->orphan_vg_name);
				dm_free(vginfo->vgname);
				dm_free(vginfo);
				return 0;
			}
			dm_list_iterate_items_safe(info2, info3, &primary_vginfo->infos) {
				_vginfo_detach_info(info2);
				_vginfo_attach_info(orphan_vginfo, info2);
				if (info2->mdas.n)
					sprintf(mdabuf, " with %u mdas",
						dm_list_size(&info2->mdas));
				else
					mdabuf[0] = '\0';
				log_debug_cache("lvmcache: %s: now in VG %s%s%s%s%s",
						dev_name(info2->dev),
						vgname, orphan_vginfo->vgid[0] ? " (" : "",
						orphan_vginfo->vgid[0] ? orphan_vginfo->vgid : "",
						orphan_vginfo->vgid[0] ? ")" : "", mdabuf);
			}

			if (!_drop_vginfo(NULL, primary_vginfo))
				return_0;
		}

		if (!_insert_vginfo(vginfo, vgid, vgstatus, creation_host,
				    primary_vginfo)) {
			dm_free(vginfo->vgname);
			dm_free(vginfo);
			return 0;
		}
		/* Ensure orphans appear last on list_iterate */
		if (is_orphan_vg(vgname))
			dm_list_add(&_vginfos, &vginfo->list);
		else
			dm_list_add_h(&_vginfos, &vginfo->list);
/***
		}
***/
	}

	if (info)
		_vginfo_attach_info(vginfo, info);
	else if (!_lvmcache_update_vgid(NULL, vginfo, vgid)) /* Orphans */
		return_0;

	_update_cache_vginfo_lock_state(vginfo, lvmcache_vgname_is_locked(vgname));

	/* FIXME Check consistency of list! */
	vginfo->fmt = fmt;

	if (info) {
		if (info->mdas.n)
			sprintf(mdabuf, " with %u mdas", dm_list_size(&info->mdas));
		else
			mdabuf[0] = '\0';
		log_debug_cache("lvmcache: %s: now in VG %s%s%s%s%s",
				dev_name(info->dev),
				vgname, vginfo->vgid[0] ? " (" : "",
				vginfo->vgid[0] ? vginfo->vgid : "",
				vginfo->vgid[0] ? ")" : "", mdabuf);
	} else
		log_debug_cache("lvmcache: initialised VG %s", vgname);

	return 1;
}

static int _lvmcache_update_vgstatus(struct lvmcache_info *info, uint32_t vgstatus,
				     const char *creation_host)
{
	if (!info || !info->vginfo)
		return 1;

	if ((info->vginfo->status & EXPORTED_VG) != (vgstatus & EXPORTED_VG))
		log_debug_cache("lvmcache: %s: VG %s %s exported",
				dev_name(info->dev), info->vginfo->vgname,
				vgstatus & EXPORTED_VG ? "now" : "no longer");

	info->vginfo->status = vgstatus;

	if (!creation_host)
		return 1;

	if (info->vginfo->creation_host && !strcmp(creation_host,
						   info->vginfo->creation_host))
		return 1;

	if (info->vginfo->creation_host)
		dm_free(info->vginfo->creation_host);

	if (!(info->vginfo->creation_host = dm_strdup(creation_host))) {
		log_error("cache creation host alloc failed for %s",
			  creation_host);
		return 0;
	}

	log_debug_cache("lvmcache: %s: VG %s: Set creation host to %s.",
			dev_name(info->dev), info->vginfo->vgname, creation_host);

	return 1;
}

static int _lvmcache_update_vg_mda_info(struct lvmcache_info *info, uint32_t mda_checksum,
					size_t mda_size)
{
	if (!info || !info->vginfo || !mda_size)
		return 1;

	if (info->vginfo->mda_checksum == mda_checksum || info->vginfo->mda_size == mda_size) 
		return 1;

	info->vginfo->mda_checksum = mda_checksum;
	info->vginfo->mda_size = mda_size;

	/* FIXME Add checksum index */

	log_debug_cache("lvmcache: %s: VG %s: Stored metadata checksum %" PRIu32 " with size %" PRIsize_t ".",
			dev_name(info->dev), info->vginfo->vgname, mda_checksum, mda_size);

	return 1;
}

int lvmcache_add_orphan_vginfo(const char *vgname, struct format_type *fmt)
{
	if (!_lock_hash && !lvmcache_init()) {
		log_error("Internal cache initialisation failed");
		return 0;
	}

	return _lvmcache_update_vgname(NULL, vgname, vgname, 0, "", fmt);
}

int lvmcache_update_vgname_and_id(struct lvmcache_info *info, struct lvmcache_vgsummary *vgsummary)
{
	const char *vgname = vgsummary->vgname;
	const char *vgid = (char *)&vgsummary->vgid;

	if (!vgname && !info->vginfo) {
		log_error(INTERNAL_ERROR "NULL vgname handed to cache");
		/* FIXME Remove this */
		vgname = info->fmt->orphan_vg_name;
		vgid = vgname;
	}

	/* When using lvmetad, the PV could not have become orphaned. */
	if (lvmetad_active() && is_orphan_vg(vgname) && info->vginfo)
		return 1;

	/* If PV without mdas is already in a real VG, don't make it orphan */
	if (is_orphan_vg(vgname) && info->vginfo &&
	    mdas_empty_or_ignored(&info->mdas) &&
	    !is_orphan_vg(info->vginfo->vgname) && critical_section())
		return 1;

	/* If making a PV into an orphan, any cached VG metadata may become
	 * invalid, incorrectly still referencing device structs.
	 * (Example: pvcreate -ff) */
	if (is_orphan_vg(vgname) && info->vginfo && !is_orphan_vg(info->vginfo->vgname))
		info->vginfo->cached_vg_invalidated = 1;

	/* If moving PV from orphan to real VG, always mark it valid */
	if (!is_orphan_vg(vgname))
		info->status &= ~CACHE_INVALID;

	if (!_lvmcache_update_vgname(info, vgname, vgid, vgsummary->vgstatus,
				     vgsummary->creation_host, info->fmt) ||
	    !_lvmcache_update_vgid(info, info->vginfo, vgid) ||
	    !_lvmcache_update_vgstatus(info, vgsummary->vgstatus, vgsummary->creation_host) ||
	    !_lvmcache_update_vg_mda_info(info, vgsummary->mda_checksum, vgsummary->mda_size))
		return_0;

	return 1;
}

int lvmcache_update_vg(struct volume_group *vg, unsigned precommitted)
{
	struct pv_list *pvl;
	struct lvmcache_info *info;
	char pvid_s[ID_LEN + 1] __attribute__((aligned(8)));
	struct lvmcache_vgsummary vgsummary = {
		.vgname = vg->name,
		.vgstatus = vg->status,
		.vgid = vg->id
	};

	pvid_s[sizeof(pvid_s) - 1] = '\0';

	dm_list_iterate_items(pvl, &vg->pvs) {
		strncpy(pvid_s, (char *) &pvl->pv->id, sizeof(pvid_s) - 1);
		/* FIXME Could pvl->pv->dev->pvid ever be different? */
		if ((info = lvmcache_info_from_pvid(pvid_s, 0)) &&
		    !lvmcache_update_vgname_and_id(info, &vgsummary))
			return_0;
	}

	/* store text representation of vg to cache */
	if (vg->cmd->current_settings.cache_vgmetadata)
		_store_metadata(vg, precommitted);

	return 1;
}

/*
 * Replace pv->dev with dev so that dev will appear for reporting.
 */

void lvmcache_replace_dev(struct cmd_context *cmd, struct physical_volume *pv,
			  struct device *dev)
{
	struct lvmcache_info *info;
	char pvid_s[ID_LEN + 1] __attribute__((aligned(8)));

	strncpy(pvid_s, (char *) &pv->id, sizeof(pvid_s) - 1);
	pvid_s[sizeof(pvid_s) - 1] = '\0';

	if (!(info = lvmcache_info_from_pvid(pvid_s, 0)))
		return;

	info->dev = dev;
	info->label->dev = dev;
	pv->dev = dev;
}

/*
 * We can see multiple different devices with the
 * same pvid, i.e. duplicates.
 *
 * There may be different reasons for seeing two
 * devices with the same pvid:
 * - multipath showing two paths to the same thing
 * - one device copied to another, e.g. with dd,
 *   also referred to as cloned devices.
 * - a "subsystem" taking a device and creating
 *   another device of its own that represents the
 *   underlying device it is using, e.g. using dm
 *   to create an identity mapping of a PV.
 *
 * Given duplicate devices, we have to choose one
 * of them to be the "preferred" dev, i.e. the one
 * that will be referenced in lvmcache, by pv->dev.
 * We can keep the existing dev, that's currently
 * used in lvmcache, or we can replace the existing
 * dev with the new duplicate.
 *
 * Regardless of which device is preferred, we need
 * to print messages explaining which devices were
 * found so that a user can sort out for themselves
 * what has happened if the preferred device is not
 * the one they are interested in.
 *
 * If a user wants to use the non-preferred device,
 * they will need to filter out the device that
 * lvm is preferring.
 *
 * The dev_subsystem calls check if the major number
 * of the dev is part of a subsystem like DM/MD/DRBD.
 * A dev that's part of a subsystem is preferred over a
 * duplicate of that dev that is not part of a
 * subsystem.
 *
 * The has_holders calls check if the device is being
 * used by another, and prefers one that's being used.
 *
 * FIXME: why do we prefer a device without holders
 * over a device with holders?  We should understand
 * the reason for that choice.
 *
 * FIXME: there may be other reasons to prefer one
 * device over another:
 *
 * . are there other use/open counts we could check
 *   beyond the holders?
 *
 * . check if either is bad/usable and prefer
 *   the good one?
 *
 * . prefer the one with smaller minor number?
 *   Might avoid disturbing things due to a new
 *   transient duplicate?
 */

struct lvmcache_info *lvmcache_add(struct labeller *labeller, const char *pvid,
				   struct device *dev,
				   const char *vgname, const char *vgid,
				   uint32_t vgstatus)
{
	const struct format_type *fmt = labeller->fmt;
	struct dev_types *dt = fmt->cmd->dev_types;
	struct label *label;
	struct lvmcache_info *existing, *info;
	char pvid_s[ID_LEN + 1] __attribute__((aligned(8)));
	struct lvmcache_vgsummary vgsummary = {
		.vgname = vgname,
		.vgstatus = vgstatus,
	};

	/* N.B. vgid is not NUL-terminated when called from _text_pv_write */
	if (vgid)
		strncpy((char *)&vgsummary.vgid, vgid, sizeof(vgsummary.vgid));

	if (!_vgname_hash && !lvmcache_init()) {
		log_error("Internal cache initialisation failed");
		return NULL;
	}

	strncpy(pvid_s, pvid, sizeof(pvid_s) - 1);
	pvid_s[sizeof(pvid_s) - 1] = '\0';

	if (!(existing = lvmcache_info_from_pvid(pvid_s, 0)) &&
	    !(existing = lvmcache_info_from_pvid(dev->pvid, 0))) {
		if (!(label = label_create(labeller)))
			return_NULL;
		if (!(info = dm_zalloc(sizeof(*info)))) {
			log_error("lvmcache_info allocation failed");
			label_destroy(label);
			return NULL;
		}

		label->info = info;
		info->label = label;
		dm_list_init(&info->list);
		info->dev = dev;

		lvmcache_del_mdas(info);
		lvmcache_del_das(info);
		lvmcache_del_bas(info);
	} else {
		if (existing->dev != dev) {
			int old_in_subsystem = 0;
			int new_in_subsystem = 0;
			int old_is_dm = 0;
			int new_is_dm = 0;
			int old_has_holders = 0;
			int new_has_holders = 0;

			/*
			 * Here are different devices with the same pvid:
			 * duplicates.  See comment above.
			 */

			/*
			 * This flag tells the process_each_pv code to search
			 * the devices list for duplicates, so that devices
			 * can be processed together with their duplicates
			 * (while processing the VG, rather than reporting
			 * pv->dev under the VG, and its duplicate outside
			 * the VG context.)
			 */
			_found_duplicate_pvs = 1;

			/*
			 * The new dev may not have pvid set.
			 * The process_each_pv code needs to have the pvid
			 * set in each device to detect that the devices
			 * are duplicates.
			 */
			strncpy(dev->pvid, pvid_s, sizeof(dev->pvid));

			/*
			 * Now decide if we are going to ignore the new
			 * device, or replace the existing/old device in
			 * lvmcache with the new one.
			 */
			old_in_subsystem = dev_subsystem_part_major(dt, existing->dev);
			new_in_subsystem = dev_subsystem_part_major(dt, dev);

			old_is_dm = dm_is_dm_major(MAJOR(existing->dev->dev));
			new_is_dm = dm_is_dm_major(MAJOR(dev->dev));

			old_has_holders = dm_device_has_holders(MAJOR(existing->dev->dev), MINOR(existing->dev->dev));
			new_has_holders = dm_device_has_holders(MAJOR(dev->dev), MINOR(dev->dev));

			if (old_has_holders && new_has_holders) {
				/*
				 * This is not a selection of old or new, but
				 * just a warning to be aware of.
				 */
				log_warn("WARNING: duplicate PV %s is being used from both devices %s and %s",
					 pvid_s,
					 dev_name(existing->dev),
					 dev_name(dev));
			}

			if (existing->vginfo->preferred_duplicates) {
				/*
				 * The preferred duplicate devs have already
				 * been chosen during a previous populating of
				 * lvmcache, so just use the existing preferences.
				 */
				log_verbose("Found duplicate PV %s: using existing dev %s",
					    pvid_s,
					    dev_name(existing->dev));
				return NULL;
			}

			if (old_in_subsystem && !new_in_subsystem) {
				/* Use old, ignore new. */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(existing->dev),
					 dev_name(dev));
				log_warn("Using duplicate PV %s from subsystem %s, ignoring %s",
					 dev_name(existing->dev),
					 dev_subsystem_name(dt, existing->dev),
					 dev_name(dev));
				return NULL;

			} else if (!old_in_subsystem && new_in_subsystem) {
				/* Use new, replace old. */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(dev),
					 dev_name(existing->dev));
				log_warn("Using duplicate PV %s from subsystem %s, replacing %s",
					 dev_name(dev),
					 dev_subsystem_name(dt, dev),
					 dev_name(existing->dev));

			} else if (old_has_holders && !new_has_holders) {
				/* Use new, replace old. */
				/* FIXME: why choose the one without olders? */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(dev),
					 dev_name(existing->dev));
				log_warn("Using duplicate PV %s without holders, replacing %s",
					 dev_name(dev),
					 dev_name(existing->dev));

			} else if (!old_has_holders && new_has_holders) {
				/* Use old, ignore new. */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(existing->dev),
					 dev_name(dev));
				log_warn("Using duplicate PV %s without holders, ignoring %s",
					 dev_name(existing->dev),
					 dev_name(dev));
				return NULL;

			} else if (old_is_dm && new_is_dm) {
				/* Use new, replace old. */
				/* FIXME: why choose the new instead of the old? */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(dev),
					 dev_name(existing->dev));
				log_warn("Using duplicate PV %s which is last seen, replacing %s",
					 dev_name(dev),
					 dev_name(existing->dev));

			} else if (!strcmp(pvid_s, existing->dev->pvid)) {
				/* No criteria to use for preferring old or new. */
				/* FIXME: why choose the new instead of the old? */
				/* FIXME: a transient duplicate would be a reason
				 * to select the old instead of the new. */
				log_warn("Found duplicate PV %s: using %s not %s",
					 pvid_s,
					 dev_name(dev),
					 dev_name(existing->dev));
				log_warn("Using duplicate PV %s which is last seen, replacing %s",
					 dev_name(dev),
					 dev_name(existing->dev));
			}
		} else {
			/*
			 * The new dev is the same as the existing dev.
			 *
			 * FIXME: Why can't we just return NULL here if the
			 * device already exists?  Things don't seem to work
			 * if we do that for some reason.
			 */
			log_verbose("Found same device %s with same pvid %s",
				    dev_name(existing->dev), pvid_s);
		}

		/*
		 * FIXME: when could this ever happen?
		 * If this does happen, identify when/why here, and
		 * if not, remove this code.
		 */
		if (strcmp(pvid_s, existing->dev->pvid))  {
			log_warn("Replacing dev %s pvid %s with dev %s pvid %s",
				 dev_name(existing->dev), existing->dev->pvid,
				 dev_name(dev), pvid_s);
		}

		/*
		 * Switch over to new preferred device.
		 */
		existing->dev = dev;
		info = existing;
		/* Has labeller changed? */
		if (info->label->labeller != labeller) {
			label_destroy(info->label);
			if (!(info->label = label_create(labeller)))
				/* FIXME leaves info without label! */
				return_NULL;
			info->label->info = info;
		}
		label = info->label;
	}

	info->fmt = labeller->fmt;
	info->status |= CACHE_INVALID;

	if (!_lvmcache_update_pvid(info, pvid_s)) {
		if (!existing) {
			dm_free(info);
			label_destroy(label);
		}
		return NULL;
	}

	if (!lvmcache_update_vgname_and_id(info, &vgsummary)) {
		if (!existing) {
			dm_hash_remove(_pvid_hash, pvid_s);
			strcpy(info->dev->pvid, "");
			dm_free(info);
			label_destroy(label);
		}
		return NULL;
	}

	return info;
}

static void _lvmcache_destroy_entry(struct lvmcache_info *info)
{
	_vginfo_detach_info(info);
	info->dev->pvid[0] = 0;
	label_destroy(info->label);
	dm_free(info);
}

static void _lvmcache_destroy_vgnamelist(struct lvmcache_vginfo *vginfo)
{
	struct lvmcache_vginfo *next;

	do {
		next = vginfo->next;
		if (!_free_vginfo(vginfo))
			stack;
	} while ((vginfo = next));
}

static void _lvmcache_destroy_lockname(struct dm_hash_node *n)
{
	char *vgname;

	if (!dm_hash_get_data(_lock_hash, n))
		return;

	vgname = dm_hash_get_key(_lock_hash, n);

	if (!strcmp(vgname, VG_GLOBAL))
		_vg_global_lock_held = 1;
	else
		log_error(INTERNAL_ERROR "Volume Group %s was not unlocked",
			  dm_hash_get_key(_lock_hash, n));
}

void lvmcache_destroy(struct cmd_context *cmd, int retain_orphans, int reset)
{
	struct dm_hash_node *n;
	log_verbose("Wiping internal VG cache");

	_has_scanned = 0;

	if (_vgid_hash) {
		dm_hash_destroy(_vgid_hash);
		_vgid_hash = NULL;
	}

	if (_pvid_hash) {
		dm_hash_iter(_pvid_hash, (dm_hash_iterate_fn) _lvmcache_destroy_entry);
		dm_hash_destroy(_pvid_hash);
		_pvid_hash = NULL;
	}

	if (_vgname_hash) {
		dm_hash_iter(_vgname_hash,
			  (dm_hash_iterate_fn) _lvmcache_destroy_vgnamelist);
		dm_hash_destroy(_vgname_hash);
		_vgname_hash = NULL;
	}

	if (_lock_hash) {
		if (reset)
			_vg_global_lock_held = 0;
		else
			dm_hash_iterate(n, _lock_hash)
				_lvmcache_destroy_lockname(n);
		dm_hash_destroy(_lock_hash);
		_lock_hash = NULL;
	}

	if (!dm_list_empty(&_vginfos))
		log_error(INTERNAL_ERROR "_vginfos list should be empty");
	dm_list_init(&_vginfos);

	if (retain_orphans)
		if (!init_lvmcache_orphans(cmd))
			stack;
}

int lvmcache_pvid_is_locked(const char *pvid) {
	struct lvmcache_info *info;
	info = lvmcache_info_from_pvid(pvid, 0);
	if (!info || !info->vginfo)
		return 0;

	return lvmcache_vgname_is_locked(info->vginfo->vgname);
}

int lvmcache_fid_add_mdas(struct lvmcache_info *info, struct format_instance *fid,
			  const char *id, int id_len)
{
	return fid_add_mdas(fid, &info->mdas, id, id_len);
}

int lvmcache_fid_add_mdas_pv(struct lvmcache_info *info, struct format_instance *fid)
{
	return lvmcache_fid_add_mdas(info, fid, info->dev->pvid, ID_LEN);
}

int lvmcache_fid_add_mdas_vg(struct lvmcache_vginfo *vginfo, struct format_instance *fid)
{
	struct lvmcache_info *info;
	dm_list_iterate_items(info, &vginfo->infos) {
		if (!lvmcache_fid_add_mdas_pv(info, fid))
			return_0;
	}
	return 1;
}

static int _get_pv_if_in_vg(struct lvmcache_info *info,
			    struct physical_volume *pv)
{
	char vgname[NAME_LEN + 1];
	char vgid[ID_LEN + 1];

	if (info->vginfo && info->vginfo->vgname &&
	    !is_orphan_vg(info->vginfo->vgname)) {
		/*
		 * get_pv_from_vg_by_id() may call
		 * lvmcache_label_scan() and drop cached
		 * vginfo so make a local copy of string.
		 */
		(void) dm_strncpy(vgname, info->vginfo->vgname, sizeof(vgname));
		memcpy(vgid, info->vginfo->vgid, sizeof(vgid));

		if (get_pv_from_vg_by_id(info->fmt, vgname, vgid,
					 info->dev->pvid, pv))
			return 1;
	}

	return 0;
}

int lvmcache_populate_pv_fields(struct lvmcache_info *info,
				struct physical_volume *pv,
				int scan_label_only)
{
	struct data_area_list *da;

	/* Have we already cached vgname? */
	if (!scan_label_only && _get_pv_if_in_vg(info, pv))
		return 1;

	/* Perform full scan (just the first time) and try again */
	if (!scan_label_only && !critical_section() && !full_scan_done()) {
		lvmcache_label_scan(info->fmt->cmd, 2);

		if (_get_pv_if_in_vg(info, pv))
			return 1;
	}

	/* Orphan */
	pv->dev = info->dev;
	pv->fmt = info->fmt;
	pv->size = info->device_size >> SECTOR_SHIFT;
	pv->vg_name = FMT_TEXT_ORPHAN_VG_NAME;
	memcpy(&pv->id, &info->dev->pvid, sizeof(pv->id));

	/* Currently only support exactly one data area */
	if (dm_list_size(&info->das) != 1) {
		log_error("Must be exactly one data area (found %d) on PV %s",
			  dm_list_size(&info->das), dev_name(info->dev));
		return 0;
	}

	/* Currently only support one bootloader area at most */
	if (dm_list_size(&info->bas) > 1) {
		log_error("Must be at most one bootloader area (found %d) on PV %s",
			  dm_list_size(&info->bas), dev_name(info->dev));
		return 0;
	}

	dm_list_iterate_items(da, &info->das)
		pv->pe_start = da->disk_locn.offset >> SECTOR_SHIFT;

	dm_list_iterate_items(da, &info->bas) {
		pv->ba_start = da->disk_locn.offset >> SECTOR_SHIFT;
		pv->ba_size = da->disk_locn.size >> SECTOR_SHIFT;
	}

	return 1;
}

int lvmcache_check_format(struct lvmcache_info *info, const struct format_type *fmt)
{
	if (info->fmt != fmt) {
		log_error("PV %s is a different format (seqno %s)",
			  dev_name(info->dev), info->fmt->name);
		return 0;
	}
	return 1;
}

void lvmcache_del_mdas(struct lvmcache_info *info)
{
	if (info->mdas.n)
		del_mdas(&info->mdas);
	dm_list_init(&info->mdas);
}

void lvmcache_del_das(struct lvmcache_info *info)
{
	if (info->das.n)
		del_das(&info->das);
	dm_list_init(&info->das);
}

void lvmcache_del_bas(struct lvmcache_info *info)
{
	if (info->bas.n)
		del_bas(&info->bas);
	dm_list_init(&info->bas);
}

int lvmcache_add_mda(struct lvmcache_info *info, struct device *dev,
		     uint64_t start, uint64_t size, unsigned ignored)
{
	return add_mda(info->fmt, NULL, &info->mdas, dev, start, size, ignored);
}

int lvmcache_add_da(struct lvmcache_info *info, uint64_t start, uint64_t size)
{
	return add_da(NULL, &info->das, start, size);
}

int lvmcache_add_ba(struct lvmcache_info *info, uint64_t start, uint64_t size)
{
	return add_ba(NULL, &info->bas, start, size);
}

void lvmcache_update_pv(struct lvmcache_info *info, struct physical_volume *pv,
			const struct format_type *fmt)
{
	info->device_size = pv->size << SECTOR_SHIFT;
	info->fmt = fmt;
}

int lvmcache_update_das(struct lvmcache_info *info, struct physical_volume *pv)
{
	struct data_area_list *da;
	if (info->das.n) {
		if (!pv->pe_start)
			dm_list_iterate_items(da, &info->das)
				pv->pe_start = da->disk_locn.offset >> SECTOR_SHIFT;
		del_das(&info->das);
	} else
		dm_list_init(&info->das);

	if (!add_da(NULL, &info->das, pv->pe_start << SECTOR_SHIFT, 0 /*pv->size << SECTOR_SHIFT*/))
		return_0;

	return 1;
}

int lvmcache_update_bas(struct lvmcache_info *info, struct physical_volume *pv)
{
	struct data_area_list *ba;
	if (info->bas.n) {
		if (!pv->ba_start && !pv->ba_size)
			dm_list_iterate_items(ba, &info->bas) {
				pv->ba_start = ba->disk_locn.offset >> SECTOR_SHIFT;
				pv->ba_size = ba->disk_locn.size >> SECTOR_SHIFT;
			}
		del_das(&info->bas);
	} else
		dm_list_init(&info->bas);

	if (!add_ba(NULL, &info->bas, pv->ba_start << SECTOR_SHIFT, pv->ba_size << SECTOR_SHIFT))
		return_0;

	return 1;
}

int lvmcache_foreach_pv(struct lvmcache_vginfo *vginfo,
			int (*fun)(struct lvmcache_info *, void *),
			void *baton)
{
	struct lvmcache_info *info;
	dm_list_iterate_items(info, &vginfo->infos) {
		if (!fun(info, baton))
			return_0;
	}

	return 1;
}

int lvmcache_foreach_mda(struct lvmcache_info *info,
			 int (*fun)(struct metadata_area *, void *),
			 void *baton)
{
	struct metadata_area *mda;
	dm_list_iterate_items(mda, &info->mdas) {
		if (!fun(mda, baton))
			return_0;
	}

	return 1;
}

unsigned lvmcache_mda_count(struct lvmcache_info *info)
{
	return dm_list_size(&info->mdas);
}

int lvmcache_foreach_da(struct lvmcache_info *info,
			int (*fun)(struct disk_locn *, void *),
			void *baton)
{
	struct data_area_list *da;
	dm_list_iterate_items(da, &info->das) {
		if (!fun(&da->disk_locn, baton))
			return_0;
	}

	return 1;
}

int lvmcache_foreach_ba(struct lvmcache_info *info,
			 int (*fun)(struct disk_locn *, void *),
			 void *baton)
{
	struct data_area_list *ba;
	dm_list_iterate_items(ba, &info->bas) {
		if (!fun(&ba->disk_locn, baton))
			return_0;
	}

	return 1;
}

/*
 * The lifetime of the label returned is tied to the lifetime of the
 * lvmcache_info which is the same as lvmcache itself.
 */
struct label *lvmcache_get_label(struct lvmcache_info *info) {
	return info->label;
}

void lvmcache_make_valid(struct lvmcache_info *info) {
	info->status &= ~CACHE_INVALID;
}

uint64_t lvmcache_device_size(struct lvmcache_info *info) {
	return info->device_size;
}

void lvmcache_set_device_size(struct lvmcache_info *info, uint64_t size) {
	info->device_size = size;
}

struct device *lvmcache_device(struct lvmcache_info *info) {
	return info->dev;
}

int lvmcache_is_orphan(struct lvmcache_info *info) {
	if (!info->vginfo)
		return 1; /* FIXME? */
	return is_orphan_vg(info->vginfo->vgname);
}

int lvmcache_vgid_is_cached(const char *vgid) {
	struct lvmcache_vginfo *vginfo;

	if (lvmetad_active())
		return 1;

	vginfo = lvmcache_vginfo_from_vgid(vgid);

	if (!vginfo || !vginfo->vgname)
		return 0;

	if (is_orphan_vg(vginfo->vgname))
		return 0;

	return 1;
}

/*
 * Return true iff it is impossible to find out from this info alone whether the
 * PV in question is or is not an orphan.
 */
int lvmcache_uncertain_ownership(struct lvmcache_info *info) {
	return mdas_empty_or_ignored(&info->mdas);
}

uint64_t lvmcache_smallest_mda_size(struct lvmcache_info *info)
{
	if (!info)
		return UINT64_C(0);

	return find_min_mda_size(&info->mdas);
}

const struct format_type *lvmcache_fmt(struct lvmcache_info *info) {
	return info->fmt;
}

int lvmcache_lookup_mda(struct lvmcache_vgsummary *vgsummary)
{
	struct lvmcache_vginfo *vginfo;

	if (!vgsummary->mda_size)
		return 0;

	/* FIXME Index the checksums */
	dm_list_iterate_items(vginfo, &_vginfos) {
		if (vgsummary->mda_checksum == vginfo->mda_checksum &&
		    vgsummary->mda_size == vginfo->mda_size &&
		    !is_orphan_vg(vginfo->vgname)) {
			vgsummary->vgname = vginfo->vgname;
			vgsummary->creation_host = vginfo->creation_host;
			vgsummary->vgstatus = vginfo->status;
			/* vginfo->vgid has 1 extra byte then vgsummary->vgid */
			memcpy(&vgsummary->vgid, vginfo->vgid, sizeof(vgsummary->vgid));

			return 1;
		}
	}

	return 0;
}
