/*
 * Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.   
 * Copyright (C) 2004 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 General Public License v.2.
 *
 * You should have received a copy of the GNU 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 "device.h"
#include "metadata.h"
#include "toolcontext.h"
#include "lvm-string.h"
#include "lvmcache.h"
#include "memlock.h"
#include "str_list.h"
#include "pv_alloc.h"
#include "activate.h"

static int _add_pv_to_vg(struct format_instance *fid, struct volume_group *vg,
			 const char *pv_name)
{
	struct pv_list *pvl;
	struct physical_volume *pv;
	struct dm_pool *mem = fid->fmt->cmd->mem;
	struct list mdas;

	log_verbose("Adding physical volume '%s' to volume group '%s'",
		    pv_name, vg->name);

	if (!(pvl = dm_pool_zalloc(mem, sizeof(*pvl)))) {
		log_error("pv_list allocation for '%s' failed", pv_name);
		return 0;
	}

	list_init(&mdas);
	if (!(pv = pv_read(fid->fmt->cmd, pv_name, &mdas, NULL, 1))) {
		log_error("%s not identified as an existing physical volume",
			  pv_name);
		return 0;
	}

	if (*pv->vg_name) {
		log_error("Physical volume '%s' is already in volume group "
			  "'%s'", pv_name, pv->vg_name);
		return 0;
	}

	if (pv->fmt != fid->fmt) {
		log_error("Physical volume %s is of different format type (%s)",
			  pv_name, pv->fmt->name);
		return 0;
	}

	/* Ensure PV doesn't depend on another PV already in the VG */
	if (pv_uses_vg(pv, vg)) {
		log_error("Physical volume %s might be constructed from same "
			  "volume group %s", pv_name, vg->name);
		return 0;
	}

	if (!(pv->vg_name = dm_pool_strdup(mem, vg->name))) {
		log_error("vg->name allocation failed for '%s'", pv_name);
		return 0;
	}

	memcpy(&pv->vgid, &vg->id, sizeof(vg->id));

	/* Units of 512-byte sectors */
	pv->pe_size = vg->extent_size;

	/* FIXME Do proper rounding-up alignment? */
	/* Reserved space for label; this holds 0 for PVs created by LVM1 */
	if (pv->pe_start < PE_ALIGN)
		pv->pe_start = PE_ALIGN;

	/*
	 * The next two fields should be corrected
	 * by fid->pv_setup.
	 */
	pv->pe_count = (pv->size - pv->pe_start) / vg->extent_size;

	pv->pe_alloc_count = 0;

	if (!fid->fmt->ops->pv_setup(fid->fmt, UINT64_C(0), 0,
				     vg->extent_size, 0, UINT64_C(0),
				     &fid->metadata_areas, pv, vg)) {
		log_error("Format-specific setup of physical volume '%s' "
			  "failed.", pv_name);
		return 0;
	}

	if (find_pv_in_vg(vg, pv_name)) {
		log_error("Physical volume '%s' listed more than once.",
			  pv_name);
		return 0;
	}

	if (vg->pv_count && (vg->pv_count == vg->max_pv)) {
		log_error("No space for '%s' - volume group '%s' "
			  "holds max %d physical volume(s).", pv_name,
			  vg->name, vg->max_pv);
		return 0;
	}

	if (!alloc_pv_segment_whole_pv(mem, pv)) {
		stack;
		return 0;
	}

	pvl->pv = pv;
	list_add(&vg->pvs, &pvl->list);

	vg->pv_count++;
	vg->extent_count += pv->pe_count;
	vg->free_count += pv->pe_count;

	return 1;
}

static int _copy_pv(struct physical_volume *pv_to,
		    struct physical_volume *pv_from)
{
	memcpy(pv_to, pv_from, sizeof(*pv_to));

	if (!str_list_dup(pv_to->fmt->cmd->mem, &pv_to->tags, &pv_from->tags)) {
		log_error("PV tags duplication failed");
		return 0;
	}

	if (!peg_dup(pv_to->fmt->cmd->mem, &pv_to->segments,
		     &pv_from->segments)) {
		stack;
		return 0;
	}

	return 1;
}

int get_pv_from_vg_by_id(const struct format_type *fmt, const char *vg_name,
			 const char *vgid, const char *pvid,
			 struct physical_volume *pv)
{
	struct volume_group *vg;
	struct pv_list *pvl;
	int consistent = 0;

	if (!(vg = vg_read(fmt->cmd, vg_name, vgid, &consistent))) {
		log_error("get_pv_from_vg_by_id: vg_read failed to read VG %s",
			  vg_name);
		return 0;
	}

	if (!consistent)
		log_error("Warning: Volume group %s is not consistent",
			  vg_name);

	list_iterate_items(pvl, &vg->pvs) {
		if (id_equal(&pvl->pv->id, (const struct id *) pvid)) {
			if (!_copy_pv(pv, pvl->pv)) {
				stack;
				return 0;
			}
			return 1;
		}
	}

	return 0;
}

int vg_rename(struct cmd_context *cmd, struct volume_group *vg,
	      const char *new_name)
{
	struct dm_pool *mem = cmd->mem;
	struct pv_list *pvl;

	if (!(vg->name = dm_pool_strdup(mem, new_name))) {
		log_error("vg->name allocation failed for '%s'", new_name);
		return 0;
	}

	list_iterate_items(pvl, &vg->pvs) {
		if (!(pvl->pv->vg_name = dm_pool_strdup(mem, new_name))) {
			log_error("pv->vg_name allocation failed for '%s'",
				  dev_name(pvl->pv->dev));
			return 0;
		}
	}

	return 1;
}

int vg_extend(struct format_instance *fid,
	      struct volume_group *vg, int pv_count, char **pv_names)
{
	int i;

	/* attach each pv */
	for (i = 0; i < pv_count; i++)
		if (!_add_pv_to_vg(fid, vg, pv_names[i])) {
			log_error("Unable to add physical volume '%s' to "
				  "volume group '%s'.", pv_names[i], vg->name);
			return 0;
		}

/* FIXME Decide whether to initialise and add new mdahs to format instance */

	return 1;
}

const char *strip_dir(const char *vg_name, const char *dev_dir)
{
	size_t len = strlen(dev_dir);
	if (!strncmp(vg_name, dev_dir, len))
		vg_name += len;

	return vg_name;
}

struct volume_group *vg_create(struct cmd_context *cmd, const char *vg_name,
			       uint32_t extent_size, uint32_t max_pv,
			       uint32_t max_lv, alloc_policy_t alloc,
			       int pv_count, char **pv_names)
{
	struct volume_group *vg;
	struct dm_pool *mem = cmd->mem;
	int consistent = 0;
	int old_partial;

	if (!(vg = dm_pool_zalloc(mem, sizeof(*vg)))) {
		stack;
		return NULL;
	}

	/* is this vg name already in use ? */
	old_partial = partial_mode();
	init_partial(1);
	if (vg_read(cmd, vg_name, NULL, &consistent)) {
		log_err("A volume group called '%s' already exists.", vg_name);
		goto bad;
	}
	init_partial(old_partial);

	if (!id_create(&vg->id)) {
		log_err("Couldn't create uuid for volume group '%s'.", vg_name);
		goto bad;
	}

	/* Strip dev_dir if present */
	vg_name = strip_dir(vg_name, cmd->dev_dir);

	vg->cmd = cmd;

	if (!(vg->name = dm_pool_strdup(mem, vg_name))) {
		stack;
		goto bad;
	}

	vg->seqno = 0;

	vg->status = (RESIZEABLE_VG | LVM_READ | LVM_WRITE);
	if (!(vg->system_id = dm_pool_alloc(mem, NAME_LEN))) {
		stack;
		goto bad;
	}
	*vg->system_id = '\0';

	vg->extent_size = extent_size;
	vg->extent_count = 0;
	vg->free_count = 0;

	vg->max_lv = max_lv;
	vg->max_pv = max_pv;

	vg->alloc = alloc;

	vg->pv_count = 0;
	list_init(&vg->pvs);

	vg->lv_count = 0;
	list_init(&vg->lvs);

	vg->snapshot_count = 0;

	list_init(&vg->tags);

	if (!(vg->fid = cmd->fmt->ops->create_instance(cmd->fmt, vg_name,
						       NULL, NULL))) {
		log_error("Failed to create format instance");
		goto bad;
	}

	if (vg->fid->fmt->ops->vg_setup &&
	    !vg->fid->fmt->ops->vg_setup(vg->fid, vg)) {
		log_error("Format specific setup of volume group '%s' failed.",
			  vg_name);
		goto bad;
	}

	/* attach the pv's */
	if (!vg_extend(vg->fid, vg, pv_count, pv_names))
		goto bad;

	return vg;

      bad:
	dm_pool_free(mem, vg);
	return NULL;
}

static int _recalc_extents(uint32_t *extents, const char *desc1,
			   const char *desc2, uint32_t old_size,
			   uint32_t new_size)
{
	uint64_t size = (uint64_t) old_size * (*extents);

	if (size % new_size) {
		log_error("New size %" PRIu64 " for %s%s not an exact number "
			  "of new extents.", size, desc1, desc2);
		return 0;
	}

	size /= new_size;

	if (size > UINT32_MAX) {
		log_error("New extent count %" PRIu64 " for %s%s exceeds "
			  "32 bits.", size, desc1, desc2);
		return 0;
	}

	*extents = (uint32_t) size;

	return 1;
}

int vg_change_pesize(struct cmd_context *cmd, struct volume_group *vg,
		     uint32_t new_size)
{
	uint32_t old_size = vg->extent_size;
	struct pv_list *pvl;
	struct lv_list *lvl;
	struct physical_volume *pv;
	struct logical_volume *lv;
	struct lv_segment *seg;
	struct pv_segment *pvseg;
	uint32_t s;

	vg->extent_size = new_size;

	if (vg->fid->fmt->ops->vg_setup &&
	    !vg->fid->fmt->ops->vg_setup(vg->fid, vg)) {
		stack;
		return 0;
	}

	if (!_recalc_extents(&vg->extent_count, vg->name, "", old_size,
			     new_size)) {
		stack;
		return 0;
	}

	if (!_recalc_extents(&vg->free_count, vg->name, " free space",
			     old_size, new_size)) {
		stack;
		return 0;
	}

	/* foreach PV */
	list_iterate_items(pvl, &vg->pvs) {
		pv = pvl->pv;

		pv->pe_size = new_size;
		if (!_recalc_extents(&pv->pe_count, dev_name(pv->dev), "",
				     old_size, new_size)) {
			stack;
			return 0;
		}

		if (!_recalc_extents(&pv->pe_alloc_count, dev_name(pv->dev),
				     " allocated space", old_size, new_size)) {
			stack;
			return 0;
		}

		/* foreach free PV Segment */
		list_iterate_items(pvseg, &pv->segments) {
			if (pvseg->lvseg)
				continue;

			if (!_recalc_extents(&pvseg->pe, dev_name(pv->dev),
					     " PV segment start", old_size,
					     new_size)) {
				stack;
				return 0;
			}
			if (!_recalc_extents(&pvseg->len, dev_name(pv->dev),
					     " PV segment length", old_size,
					     new_size)) {
				stack;
				return 0;
			}
		}
	}

	/* foreach LV */
	list_iterate_items(lvl, &vg->lvs) {
		lv = lvl->lv;

		if (!_recalc_extents(&lv->le_count, lv->name, "", old_size,
				     new_size)) {
			stack;
			return 0;
		}

		list_iterate_items(seg, &lv->segments) {
			if (!_recalc_extents(&seg->le, lv->name,
					     " segment start", old_size,
					     new_size)) {
				stack;
				return 0;
			}

			if (!_recalc_extents(&seg->len, lv->name,
					     " segment length", old_size,
					     new_size)) {
				stack;
				return 0;
			}

			if (!_recalc_extents(&seg->area_len, lv->name,
					     " area length", old_size,
					     new_size)) {
				stack;
				return 0;
			}

			if (!_recalc_extents(&seg->extents_copied, lv->name,
					     " extents moved", old_size,
					     new_size)) {
				stack;
				return 0;
			}

			/* foreach area */
			for (s = 0; s < seg->area_count; s++) {
				switch (seg_type(seg, s)) {
				case AREA_PV:
					if (!_recalc_extents
					    (&seg_pe(seg, s),
					     lv->name,
					     " pvseg start", old_size,
					     new_size)) {
						stack;
						return 0;
					}
					if (!_recalc_extents
					    (&seg_pvseg(seg, s)->len,
					     lv->name,
					     " pvseg length", old_size,
					     new_size)) {
						stack;
						return 0;
					}
					break;
				case AREA_LV:
					if (!_recalc_extents
					    (&seg_le(seg, s), lv->name,
					     " area start", old_size,
					     new_size)) {
						stack;
						return 0;
					}
					break;
				case AREA_UNASSIGNED:
					log_error("Unassigned area %u found in "
						  "segment", s);
					return 0;
				}
			}
		}

	}

	return 1;
}

/* Sizes in sectors */
struct physical_volume *pv_create(const struct format_type *fmt,
				  struct device *dev,
				  struct id *id, uint64_t size,
				  uint64_t pe_start,
				  uint32_t existing_extent_count,
				  uint32_t existing_extent_size,
				  int pvmetadatacopies,
				  uint64_t pvmetadatasize, struct list *mdas)
{
	struct dm_pool *mem = fmt->cmd->mem;
	struct physical_volume *pv = dm_pool_zalloc(mem, sizeof(*pv));

	if (!pv) {
		stack;
		return NULL;
	}

	if (id)
		memcpy(&pv->id, id, sizeof(*id));
	else if (!id_create(&pv->id)) {
		log_error("Failed to create random uuid for %s.",
			  dev_name(dev));
		return NULL;
	}

	pv->dev = dev;

	if (!(pv->vg_name = dm_pool_zalloc(mem, NAME_LEN))) {
		stack;
		goto bad;
	}

	pv->status = ALLOCATABLE_PV;

	if (!dev_get_size(pv->dev, &pv->size)) {
		log_error("%s: Couldn't get size.", dev_name(pv->dev));
		goto bad;
	}

	if (size) {
		if (size > pv->size)
			log_print("WARNING: %s: Overriding real size. "
				  "You could lose data.", dev_name(pv->dev));
		log_verbose("%s: Pretending size is %" PRIu64 " sectors.",
			    dev_name(pv->dev), size);
		pv->size = size;
	}

	if (pv->size < PV_MIN_SIZE) {
		log_error("%s: Size must exceed minimum of %ld sectors.",
			  dev_name(pv->dev), PV_MIN_SIZE);
		goto bad;
	}

	pv->pe_size = 0;
	pv->pe_start = 0;
	pv->pe_count = 0;
	pv->pe_alloc_count = 0;
	pv->fmt = fmt;

	list_init(&pv->tags);
	list_init(&pv->segments);

	if (!fmt->ops->pv_setup(fmt, pe_start, existing_extent_count,
				existing_extent_size,
				pvmetadatacopies, pvmetadatasize, mdas,
				pv, NULL)) {
		log_error("%s: Format-specific setup of physical volume "
			  "failed.", dev_name(pv->dev));
		goto bad;
	}
	return pv;

      bad:
	dm_pool_free(mem, pv);
	return NULL;
}

struct pv_list *find_pv_in_vg(struct volume_group *vg, const char *pv_name)
{
	struct pv_list *pvl;

	list_iterate_items(pvl, &vg->pvs)
		if (pvl->pv->dev == dev_cache_get(pv_name, vg->cmd->filter))
			return pvl;

	return NULL;
}

int pv_is_in_vg(struct volume_group *vg, struct physical_volume *pv)
{
	struct pv_list *pvl;

	list_iterate_items(pvl, &vg->pvs)
		if (pv == pvl->pv)
			 return 1;

	return 0;
}

struct physical_volume *find_pv_in_vg_by_uuid(struct volume_group *vg,
					      struct id *id)
{
	struct pv_list *pvl;

	list_iterate_items(pvl, &vg->pvs)
		if (id_equal(&pvl->pv->id, id))
			return pvl->pv;

	return NULL;
}

struct lv_list *find_lv_in_vg(struct volume_group *vg, const char *lv_name)
{
	struct lv_list *lvl;
	const char *ptr;

	/* Use last component */
	if ((ptr = strrchr(lv_name, '/')))
		ptr++;
	else
		ptr = lv_name;

	list_iterate_items(lvl, &vg->lvs)
		if (!strcmp(lvl->lv->name, ptr))
			return lvl;

	return NULL;
}

struct lv_list *find_lv_in_vg_by_lvid(struct volume_group *vg,
				      const union lvid *lvid)
{
	struct lv_list *lvl;

	list_iterate_items(lvl, &vg->lvs)
		if (!strncmp(lvl->lv->lvid.s, lvid->s, sizeof(*lvid)))
			return lvl;

	return NULL;
}

struct logical_volume *find_lv(struct volume_group *vg, const char *lv_name)
{
	struct lv_list *lvl = find_lv_in_vg(vg, lv_name);
	return lvl ? lvl->lv : NULL;
}

struct physical_volume *find_pv(struct volume_group *vg, struct device *dev)
{
	struct pv_list *pvl;

	list_iterate_items(pvl, &vg->pvs)
		if (dev == pvl->pv->dev)
			return pvl->pv;

	return NULL;
}

struct physical_volume *find_pv_by_name(struct cmd_context *cmd,
					const char *pv_name)
{
	struct physical_volume *pv;

	if (!(pv = pv_read(cmd, pv_name, NULL, NULL, 1))) {
		log_error("Physical volume %s not found", pv_name);
		return NULL;
	}

	if (!pv->vg_name[0]) {
		log_error("Physical volume %s not in a volume group", pv_name);
		return NULL;
	}

	return pv;
}

/* Find segment at a given logical extent in an LV */
struct lv_segment *find_seg_by_le(struct logical_volume *lv, uint32_t le)
{
	struct lv_segment *seg;

	list_iterate_items(seg, &lv->segments)
		if (le >= seg->le && le < seg->le + seg->len)
			return seg;

	return NULL;
}

struct lv_segment *first_seg(struct logical_volume *lv)
{
	struct lv_segment *seg = NULL;

	list_iterate_items(seg, &lv->segments)
		break;

	return seg;
}

/* Find segment at a given physical extent in a PV */
struct pv_segment *find_peg_by_pe(struct physical_volume *pv, uint32_t pe)
{
	struct pv_segment *peg;

	list_iterate_items(peg, &pv->segments)
		if (pe >= peg->pe && pe < peg->pe + peg->len)
			return peg;

	return NULL;
}

int vg_remove(struct volume_group *vg)
{
	struct metadata_area *mda;

	/* FIXME Improve recovery situation? */
	/* Remove each copy of the metadata */
	list_iterate_items(mda, &vg->fid->metadata_areas) {
		if (mda->ops->vg_remove &&
		    !mda->ops->vg_remove(vg->fid, vg, mda)) {
			stack;
			return 0;
		}
	}

	return 1;
}

int vg_validate(struct volume_group *vg)
{
	struct lv_list *lvl;

	if (!check_pv_segments(vg)) {
		log_error("Internal error: PV segments corrupted in %s.",
			  vg->name);
		return 0;
	}

	list_iterate_items(lvl, &vg->lvs) {
		if (!check_lv_segments(lvl->lv, 1)) {
			log_error("Internal error: LV segments corrupted in %s.",
				  lvl->lv->name);
			return 0;
		}
	}

	return 1;
}

/*
 * After vg_write() returns success,
 * caller MUST call either vg_commit() or vg_revert()
 */
int vg_write(struct volume_group *vg)
{
	struct list *mdah;
	struct metadata_area *mda;

	if (!vg_validate(vg)) {
		stack;
		return 0;
	}

	if (vg->status & PARTIAL_VG) {
		log_error("Cannot change metadata for partial volume group %s",
			  vg->name);
		return 0;
	}

	if (list_empty(&vg->fid->metadata_areas)) {
		log_error("Aborting vg_write: No metadata areas to write to!");
		return 0;
	}

	vg->seqno++;

	/* Write to each copy of the metadata area */
	list_iterate_items(mda, &vg->fid->metadata_areas) {
		if (!mda->ops->vg_write) {
			log_error("Format does not support writing volume"
				  "group metadata areas");
			/* Revert */
			list_uniterate(mdah, &vg->fid->metadata_areas, &mda->list) {
				mda = list_item(mdah, struct metadata_area);

				if (mda->ops->vg_revert &&
				    !mda->ops->vg_revert(vg->fid, vg, mda)) {
					stack;
				}
			}
			return 0;
		}
		if (!mda->ops->vg_write(vg->fid, vg, mda)) {
			stack;
			/* Revert */
			list_uniterate(mdah, &vg->fid->metadata_areas, &mda->list) {
				mda = list_item(mdah, struct metadata_area);

				if (mda->ops->vg_revert &&
				    !mda->ops->vg_revert(vg->fid, vg, mda)) {
					stack;
				}
			}
			return 0;
		}
	}

	/* Now pre-commit each copy of the new metadata */
	list_iterate_items(mda, &vg->fid->metadata_areas) {
		if (mda->ops->vg_precommit &&
		    !mda->ops->vg_precommit(vg->fid, vg, mda)) {
			stack;
			/* Revert */
			list_iterate_items(mda, &vg->fid->metadata_areas) {
				if (mda->ops->vg_revert &&
				    !mda->ops->vg_revert(vg->fid, vg, mda)) {
					stack;
				}
			}
			return 0;
		}
	}

	return 1;
}

/* Commit pending changes */
int vg_commit(struct volume_group *vg)
{
	struct metadata_area *mda;
	int cache_updated = 0;
	int failed = 0;

	/* Commit to each copy of the metadata area */
	list_iterate_items(mda, &vg->fid->metadata_areas) {
		failed = 0;
		if (mda->ops->vg_commit &&
		    !mda->ops->vg_commit(vg->fid, vg, mda)) {
			stack;
			failed = 1;
		}
		/* Update cache first time we succeed */
		if (!failed && !cache_updated) {
			lvmcache_update_vg(vg);
			cache_updated = 1;
		}
	}

	/* If at least one mda commit succeeded, it was committed */
	return cache_updated;
}

/* Don't commit any pending changes */
int vg_revert(struct volume_group *vg)
{
	struct metadata_area *mda;

	list_iterate_items(mda, &vg->fid->metadata_areas) {
		if (mda->ops->vg_revert &&
		    !mda->ops->vg_revert(vg->fid, vg, mda)) {
			stack;
		}
	}

	return 1;
}

/* Make orphan PVs look like a VG */
static struct volume_group *_vg_read_orphans(struct cmd_context *cmd)
{
	struct lvmcache_vginfo *vginfo;
	struct lvmcache_info *info;
	struct pv_list *pvl;
	struct volume_group *vg;
	struct physical_volume *pv;

	if (!(vginfo = vginfo_from_vgname(ORPHAN, NULL))) {
		stack;
		return NULL;
	}

	if (!(vg = dm_pool_zalloc(cmd->mem, sizeof(*vg)))) {
		log_error("vg allocation failed");
		return NULL;
	}
	list_init(&vg->pvs);
	list_init(&vg->lvs);
	list_init(&vg->tags);
	vg->cmd = cmd;
	if (!(vg->name = dm_pool_strdup(cmd->mem, ORPHAN))) {
		log_error("vg name allocation failed");
		return NULL;
	}

	list_iterate_items(info, &vginfo->infos) {
		if (!(pv = pv_read(cmd, dev_name(info->dev), NULL, NULL, 1))) {
			continue;
		}
		if (!(pvl = dm_pool_zalloc(cmd->mem, sizeof(*pvl)))) {
			log_error("pv_list allocation failed");
			return NULL;
		}
		pvl->pv = pv;
		list_add(&vg->pvs, &pvl->list);
		vg->pv_count++;
	}

	return vg;
}

/* Caller sets consistent to 1 if it's safe for vg_read to correct
 * inconsistent metadata on disk (i.e. the VG write lock is held).
 * This guarantees only consistent metadata is returned unless PARTIAL_VG.
 * If consistent is 0, caller must check whether consistent == 1 on return
 * and take appropriate action if it isn't (e.g. abort; get write lock 
 * and call vg_read again).
 *
 * If precommitted is set, use precommitted metadata if present.
 */
static struct volume_group *_vg_read(struct cmd_context *cmd,
				     const char *vgname,
				     const char *vgid,
				     int *consistent, int precommitted)
{
	struct format_instance *fid;
	const struct format_type *fmt;
	struct volume_group *vg, *correct_vg = NULL;
	struct metadata_area *mda;
	int inconsistent = 0;
	int use_precommitted = precommitted;
	struct list *pvids;
	struct pv_list *pvl;

	if (!*vgname) {
		if (use_precommitted) {
			log_error("Internal error: vg_read requires vgname "
				  "with pre-commit.");
			return NULL;
		}
		*consistent = 1;
		return _vg_read_orphans(cmd);
	}

	/* Find the vgname in the cache */
	/* If it's not there we must do full scan to be completely sure */
	if (!(fmt = fmt_from_vgname(vgname, vgid))) {
		lvmcache_label_scan(cmd, 0);
		if (!(fmt = fmt_from_vgname(vgname, vgid))) {
			if (memlock()) {
				stack;
				return NULL;
			}
			lvmcache_label_scan(cmd, 2);
			if (!(fmt = fmt_from_vgname(vgname, vgid))) {
				stack;
				return NULL;
			}
		}
	}

	if (use_precommitted && !(fmt->features & FMT_PRECOMMIT))
		use_precommitted = 0;

	/* Store pvids for later so we can check if any are missing */
	if (!(pvids = lvmcache_get_pvids(cmd, vgname, vgid))) {
		stack;
		return NULL;
	}

	/* create format instance with appropriate metadata area */
	if (!(fid = fmt->ops->create_instance(fmt, vgname, vgid, NULL))) {
		log_error("Failed to create format instance");
		return NULL;
	}

	/* Ensure contents of all metadata areas match - else do recovery */
	list_iterate_items(mda, &fid->metadata_areas) {
		if ((use_precommitted &&
		     !(vg = mda->ops->vg_read_precommit(fid, vgname, mda))) ||
		    (!use_precommitted &&
		     !(vg = mda->ops->vg_read(fid, vgname, mda)))) {
			inconsistent = 1;
			continue;
		}
		if (!correct_vg) {
			correct_vg = vg;
			continue;
		}
		/* FIXME Also ensure contents same - checksum compare? */
		if (correct_vg->seqno != vg->seqno) {
			inconsistent = 1;
			if (vg->seqno > correct_vg->seqno)
				correct_vg = vg;
		}
	}

	/* Ensure every PV in the VG was in the cache */
	if (correct_vg) {
		if (list_size(&correct_vg->pvs) != list_size(pvids)) {
			log_debug("Cached VG %s had incorrect PV list",
				  vg->name);

			if (memlock())
				inconsistent = 1;
			else
				correct_vg = NULL;
		} else list_iterate_items(pvl, &correct_vg->pvs) {
			if (!str_list_match_item(pvids, pvl->pv->dev->pvid)) {
				log_debug("Cached VG %s had incorrect PV list",
					  vg->name);
				correct_vg = NULL;
				break;
			}
		}
	}

	/* Failed to find VG where we expected it - full scan and retry */
	if (!correct_vg) {
		inconsistent = 0;

		if (memlock()) {
			stack;
			return NULL;
		}
		lvmcache_label_scan(cmd, 2);
		if (!(fmt = fmt_from_vgname(vgname, vgid))) {
			stack;
			return NULL;
		}

		if (precommitted && !(fmt->features & FMT_PRECOMMIT))
			use_precommitted = 0;

		/* create format instance with appropriate metadata area */
		if (!(fid = fmt->ops->create_instance(fmt, vgname, vgid, NULL))) {
			log_error("Failed to create format instance");
			return NULL;
		}

		/* Ensure contents of all metadata areas match - else recover */
		list_iterate_items(mda, &fid->metadata_areas) {
			if ((use_precommitted &&
			     !(vg = mda->ops->vg_read_precommit(fid, vgname,
								mda))) ||
			    (!use_precommitted &&
			     !(vg = mda->ops->vg_read(fid, vgname, mda)))) {
				inconsistent = 1;
				continue;
			}
			if (!correct_vg) {
				correct_vg = vg;
				continue;
			}
			/* FIXME Also ensure contents same - checksums same? */
			if (correct_vg->seqno != vg->seqno) {
				inconsistent = 1;
				if (vg->seqno > correct_vg->seqno)
					correct_vg = vg;
			}
		}

		/* Give up looking */
		if (!correct_vg) {
			stack;
			return NULL;
		}
	}

	lvmcache_update_vg(correct_vg);

	if (inconsistent) {
		/* FIXME Test should be if we're *using* precommitted metadata not if we were searching for it */
		if (use_precommitted) {
			log_error("Inconsistent pre-commit metadata copies "
				  "for volume group %s", vgname);
			return NULL;
		}

		if (!*consistent)
			return correct_vg;

		/* Don't touch partial volume group metadata */
		/* Should be fixed manually with vgcfgbackup/restore etc. */
		if ((correct_vg->status & PARTIAL_VG)) {
			log_error("Inconsistent metadata copies found for "
				  "partial volume group %s", vgname);
			*consistent = 0;
			return correct_vg;
		}

		log_print("Inconsistent metadata copies found - updating "
			  "to use version %u", correct_vg->seqno);
		if (!vg_write(correct_vg)) {
			log_error("Automatic metadata correction failed");
			return NULL;
		}
		if (!vg_commit(correct_vg)) {
			log_error("Automatic metadata correction commit "
				  "failed");
			return NULL;
		}
	}

	if ((correct_vg->status & PVMOVE) && !pvmove_mode()) {
		log_error("WARNING: Interrupted pvmove detected in "
			  "volume group %s", correct_vg->name);
		log_error("Please restore the metadata by running "
			  "vgcfgrestore.");
		return NULL;
	}

	*consistent = 1;
	return correct_vg;
}

struct volume_group *vg_read(struct cmd_context *cmd, const char *vgname,
			     const char *vgid, int *consistent)
{
	struct volume_group *vg;
	struct lv_list *lvl;

	if (!(vg = _vg_read(cmd, vgname, vgid, consistent, 0)))
		return NULL;

	if (!check_pv_segments(vg)) {
		log_error("Internal error: PV segments corrupted in %s.",
			  vg->name);
		return NULL;
	}

	list_iterate_items(lvl, &vg->lvs) {
		if (!check_lv_segments(lvl->lv, 1)) {
			log_error("Internal error: LV segments corrupted in %s.",
				  lvl->lv->name);
			return NULL;
		}
	}

	return vg;
}

/* This is only called by lv_from_lvid, which is only called from 
 * activate.c so we know the appropriate VG lock is already held and 
 * the vg_read is therefore safe.
 */
static struct volume_group *_vg_read_by_vgid(struct cmd_context *cmd,
					    const char *vgid,
					    int precommitted)
{
	const char *vgname;
	struct list *vgnames;
	struct volume_group *vg;
	struct lvmcache_vginfo *vginfo;
	struct str_list *strl;
	int consistent = 0;

	/* Is corresponding vgname already cached? */
	if ((vginfo = vginfo_from_vgid(vgid)) &&
	    vginfo->vgname && *vginfo->vgname) {
		if ((vg = _vg_read(cmd, vginfo->vgname, vgid,
				   &consistent, precommitted)) &&
		    !strncmp((char *)vg->id.uuid, vgid, ID_LEN)) {
			if (!consistent) {
				log_error("Volume group %s metadata is "
					  "inconsistent", vginfo->vgname);
				if (!partial_mode())
					return NULL;
			}
			return vg;
		}
	}

	/* Mustn't scan if memory locked: ensure cache gets pre-populated! */
	if (memlock())
		return NULL;

	/* FIXME Need a genuine read by ID here - don't vg_read by name! */
	/* FIXME Disabled vgrenames while active for now because we aren't
	 *       allowed to do a full scan here any more. */

	// The slow way - full scan required to cope with vgrename 
	if (!(vgnames = get_vgs(cmd, 2))) {
		log_error("vg_read_by_vgid: get_vgs failed");
		return NULL;
	}

	list_iterate_items(strl, vgnames) {
		vgname = strl->str;
		if (!vgname || !*vgname)
			continue;	// FIXME Unnecessary? 
		consistent = 0;
		if ((vg = _vg_read(cmd, vgname, vgid, &consistent,
				   precommitted)) &&
		    !strncmp((char *)vg->id.uuid, vgid, ID_LEN)) {
			if (!consistent) {
				log_error("Volume group %s metadata is "
					  "inconsistent", vgname);
				return NULL;
			}
			return vg;
		}
	}

	return NULL;
}

/* Only called by activate.c */
struct logical_volume *lv_from_lvid(struct cmd_context *cmd, const char *lvid_s,
				    int precommitted)
{
	struct lv_list *lvl;
	struct volume_group *vg;
	const union lvid *lvid;

	lvid = (const union lvid *) lvid_s;

	log_very_verbose("Finding volume group for uuid %s", lvid_s);
	if (!(vg = _vg_read_by_vgid(cmd, (char *)lvid->id[0].uuid, precommitted))) {
		log_error("Volume group for uuid not found: %s", lvid_s);
		return NULL;
	}

	log_verbose("Found volume group \"%s\"", vg->name);
	if (vg->status & EXPORTED_VG) {
		log_error("Volume group \"%s\" is exported", vg->name);
		return NULL;
	}
	if (!(lvl = find_lv_in_vg_by_lvid(vg, lvid))) {
		log_very_verbose("Can't find logical volume id %s", lvid_s);
		return NULL;
	}

	return lvl->lv;
}

/* FIXME Use label functions instead of PV functions */
struct physical_volume *pv_read(struct cmd_context *cmd, const char *pv_name,
				struct list *mdas, uint64_t *label_sector,
				int warnings)
{
	struct physical_volume *pv;
	struct label *label;
	struct lvmcache_info *info;
	struct device *dev;

	if (!(dev = dev_cache_get(pv_name, cmd->filter))) {
		stack;
		return NULL;
	}

	if (!(label_read(dev, &label))) {
		if (warnings)
			log_error("No physical volume label read from %s",
				  pv_name);
		return NULL;
	}

	info = (struct lvmcache_info *) label->info;
	if (label_sector && *label_sector)
		*label_sector = label->sector;

	if (!(pv = dm_pool_zalloc(cmd->mem, sizeof(*pv)))) {
		log_error("pv allocation for '%s' failed", pv_name);
		return NULL;
	}

	list_init(&pv->tags);
	list_init(&pv->segments);

	/* FIXME Move more common code up here */
	if (!(info->fmt->ops->pv_read(info->fmt, pv_name, pv, mdas))) {
		log_error("Failed to read existing physical volume '%s'",
			  pv_name);
		return NULL;
	}

	if (!pv->size)
		return NULL;
	
	if (!alloc_pv_segment_whole_pv(cmd->mem, pv)) {
		stack;
		return NULL;
	}

	return pv;
}

/* May return empty list */
struct list *get_vgs(struct cmd_context *cmd, int full_scan)
{
	return lvmcache_get_vgnames(cmd, full_scan);
}

struct list *get_vgids(struct cmd_context *cmd, int full_scan)
{
	return lvmcache_get_vgids(cmd, full_scan);
}

struct list *get_pvs(struct cmd_context *cmd)
{
	struct str_list *strl;
	struct list *results;
	const char *vgname, *vgid;
	struct list *pvh, *tmp;
	struct list *vgids;
	struct volume_group *vg;
	int consistent = 0;
	int old_partial;
	int old_pvmove;

	lvmcache_label_scan(cmd, 0);

	if (!(results = dm_pool_alloc(cmd->mem, sizeof(*results)))) {
		log_error("PV list allocation failed");
		return NULL;
	}

	list_init(results);

	/* Get list of VGs */
	if (!(vgids = get_vgids(cmd, 0))) {
		log_error("get_pvs: get_vgs failed");
		return NULL;
	}

	/* Read every VG to ensure cache consistency */
	/* Orphan VG is last on list */
	old_partial = partial_mode();
	old_pvmove = pvmove_mode();
	init_partial(1);
	init_pvmove(1);
	list_iterate_items(strl, vgids) {
		vgid = strl->str;
		if (!vgid)
			continue;	/* FIXME Unnecessary? */
		consistent = 0;
		if (!(vgname = vgname_from_vgid(NULL, vgid))) {
			stack;
			continue;
		}
		if (!(vg = vg_read(cmd, vgname, vgid, &consistent))) {
			stack;
			continue;
		}
		if (!consistent)
			log_print("Warning: Volume Group %s is not consistent",
				  vgname);

		/* Move PVs onto results list */
		list_iterate_safe(pvh, tmp, &vg->pvs) {
			list_add(results, pvh);
		}
	}
	init_pvmove(old_pvmove);
	init_partial(old_partial);

	return results;
}

int pv_write(struct cmd_context *cmd __attribute((unused)), struct physical_volume *pv,
	     struct list *mdas, int64_t label_sector)
{
	if (!pv->fmt->ops->pv_write) {
		log_error("Format does not support writing physical volumes");
		return 0;
	}

	if (*pv->vg_name || pv->pe_alloc_count) {
		log_error("Assertion failed: can't _pv_write non-orphan PV "
			  "(in VG %s)", pv->vg_name);
		return 0;
	}

	if (!pv->fmt->ops->pv_write(pv->fmt, pv, mdas, label_sector)) {
		stack;
		return 0;
	}

	return 1;
}