/* lvm.c - module to read Logical Volumes.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2006,2007,2008,2009  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/dl.h>
#include <grub/disk.h>
#include <grub/mm.h>
#include <grub/err.h>
#include <grub/misc.h>
#include <grub/lvm.h>

#ifdef GRUB_UTIL
#include <grub/emu/misc.h>
#include <grub/emu/hostdisk.h>
#endif

GRUB_MOD_LICENSE ("GPLv3+");

static struct grub_lvm_vg *vg_list;
static int lv_count;
static int scan_depth = 0;

static int is_lv_readable (struct grub_lvm_lv *lv);


/* Go the string STR and return the number after STR.  *P will point
   at the number.  In case STR is not found, *P will be NULL and the
   return value will be 0.  */
static int
grub_lvm_getvalue (char **p, char *str)
{
  *p = grub_strstr (*p, str);
  if (! *p)
    return 0;
  *p += grub_strlen (str);
  return grub_strtoul (*p, NULL, 10);
}

#if 0
static int
grub_lvm_checkvalue (char **p, char *str, char *tmpl)
{
  int tmpllen = grub_strlen (tmpl);
  *p = grub_strstr (*p, str);
  if (! *p)
    return 0;
  *p += grub_strlen (str);
  if (**p != '"')
    return 0;
  return (grub_memcmp (*p + 1, tmpl, tmpllen) == 0 && (*p)[tmpllen + 1] == '"');
}
#endif

static int
grub_lvm_check_flag (char *p, char *str, char *flag)
{
  int len_str = grub_strlen (str), len_flag = grub_strlen (flag);
  while (1)
    {
      char *q;
      p = grub_strstr (p, str);
      if (! p)
	return 0;
      p += len_str;
      if (grub_memcmp (p, " = [", sizeof (" = [") - 1) != 0)
	continue;
      q = p + sizeof (" = [") - 1;
      while (1)
	{
	  while (grub_isspace (*q))
	    q++;
	  if (*q != '"')
	    return 0;
	  q++;
	  if (grub_memcmp (q, flag, len_flag) == 0 && q[len_flag] == '"')
	    return 1;
	  while (*q != '"')
	    q++;
	  q++;
	  if (*q == ']')
	    return 0;
	  q++;
	}
    }
}

static struct grub_lvm_lv *
find_lv (const char *name)
{
  struct grub_lvm_vg *vg;
  struct grub_lvm_lv *lv = NULL;
  for (vg = vg_list; vg; vg = vg->next)
    {
      if (vg->lvs)
	for (lv = vg->lvs; lv; lv = lv->next)
	  if ((grub_strcmp (lv->fullname, name) == 0
	       || grub_strcmp (lv->compatname, name) == 0)
	      && is_lv_readable (lv))
	    return lv;
    }
  return NULL;
}

static void
do_lvm_scan (const char *scan_for)
{
  auto int grub_lvm_scan_device (const char *name);
  int grub_lvm_scan_device (const char *name)
  {
    grub_err_t err;
    grub_disk_t disk;
    grub_uint64_t mda_offset, mda_size;
    char buf[GRUB_LVM_LABEL_SIZE];
    char vg_id[GRUB_LVM_ID_STRLEN+1];
    char pv_id[GRUB_LVM_ID_STRLEN+1];
    char *metadatabuf, *p, *q, *vgname;
    struct grub_lvm_label_header *lh = (struct grub_lvm_label_header *) buf;
    struct grub_lvm_pv_header *pvh;
    struct grub_lvm_disk_locn *dlocn;
    struct grub_lvm_mda_header *mdah;
    struct grub_lvm_raw_locn *rlocn;
    unsigned int i, j, vgname_len;
    struct grub_lvm_vg *vg;
    struct grub_lvm_pv *pv;

#ifdef GRUB_UTIL
    grub_util_info ("scanning %s for LVM", name);
#endif

    disk = grub_disk_open (name);
    if (!disk)
      {
	if (grub_errno == GRUB_ERR_OUT_OF_RANGE)
	  grub_errno = GRUB_ERR_NONE;
	return 0;
      }

    for (vg = vg_list; vg; vg = vg->next)
      for (pv = vg->pvs; pv; pv = pv->next)
	if (pv->disk && pv->disk->id == disk->id
	    && pv->disk->dev->id == disk->dev->id)
	  {
	    grub_disk_close (disk);
	    return 0;
	  }

    /* Search for label. */
    for (i = 0; i < GRUB_LVM_LABEL_SCAN_SECTORS; i++)
      {
	err = grub_disk_read (disk, i, 0, sizeof(buf), buf);
	if (err)
	  goto fail;

	if ((! grub_strncmp ((char *)lh->id, GRUB_LVM_LABEL_ID,
			     sizeof (lh->id)))
	    && (! grub_strncmp ((char *)lh->type, GRUB_LVM_LVM2_LABEL,
				sizeof (lh->type))))
	  break;
      }

    /* Return if we didn't find a label. */
    if (i == GRUB_LVM_LABEL_SCAN_SECTORS)
      {
#ifdef GRUB_UTIL
	grub_util_info ("no LVM signature found");
#endif
	goto fail;
      }

    pvh = (struct grub_lvm_pv_header *) (buf + grub_le_to_cpu32(lh->offset_xl));

    for (i = 0, j = 0; i < GRUB_LVM_ID_LEN; i++)
      {
	pv_id[j++] = pvh->pv_uuid[i];
	if ((i != 1) && (i != 29) && (i % 4 == 1))
	  pv_id[j++] = '-';
      }
    pv_id[j] = '\0';

    dlocn = pvh->disk_areas_xl;

    dlocn++;
    /* Is it possible to have multiple data/metadata areas? I haven't
       seen devices that have it. */
    if (dlocn->offset)
      {
	grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
		    "we don't support multiple LVM data areas");

#ifdef GRUB_UTIL
	grub_util_info ("we don't support multiple LVM data areas\n");
#endif
	goto fail;
      }

    dlocn++;
    mda_offset = grub_le_to_cpu64 (dlocn->offset);
    mda_size = grub_le_to_cpu64 (dlocn->size);

    /* It's possible to have multiple copies of metadata areas, we just use the
       first one.  */

    /* Allocate buffer space for the circular worst-case scenario. */
    metadatabuf = grub_malloc (2 * mda_size);
    if (! metadatabuf)
      goto fail;

    err = grub_disk_read (disk, 0, mda_offset, mda_size, metadatabuf);
    if (err)
      goto fail2;

    mdah = (struct grub_lvm_mda_header *) metadatabuf;
    if ((grub_strncmp ((char *)mdah->magic, GRUB_LVM_FMTT_MAGIC,
		       sizeof (mdah->magic)))
	|| (grub_le_to_cpu32 (mdah->version) != GRUB_LVM_FMTT_VERSION))
      {
	grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
		    "unknown LVM metadata header");
#ifdef GRUB_UTIL
	grub_util_info ("unknown LVM metadata header\n");
#endif
	goto fail2;
      }

    rlocn = mdah->raw_locns;
    if (grub_le_to_cpu64 (rlocn->offset) + grub_le_to_cpu64 (rlocn->size) >
	grub_le_to_cpu64 (mdah->size))
      {
	/* Metadata is circular. Copy the wrap in place. */
	grub_memcpy (metadatabuf + mda_size,
		     metadatabuf + GRUB_LVM_MDA_HEADER_SIZE,
		     grub_le_to_cpu64 (rlocn->offset) +
		     grub_le_to_cpu64 (rlocn->size) -
		     grub_le_to_cpu64 (mdah->size));
      }
    p = q = metadatabuf + grub_le_to_cpu64 (rlocn->offset);

    while (*q != ' ' && q < metadatabuf + mda_size)
      q++;

    if (q == metadatabuf + mda_size)
      {
#ifdef GRUB_UTIL
	grub_util_info ("error parsing metadata\n");
#endif
	goto fail2;
      }

    vgname_len = q - p;
    vgname = grub_malloc (vgname_len + 1);
    if (!vgname)
      goto fail2;

    grub_memcpy (vgname, p, vgname_len);
    vgname[vgname_len] = '\0';

    p = grub_strstr (q, "id = \"");
    if (p == NULL)
      {
#ifdef GRUB_UTIL
	grub_util_info ("couldn't find ID\n");
#endif
	goto fail3;
      }
    p += sizeof ("id = \"") - 1;
    grub_memcpy (vg_id, p, GRUB_LVM_ID_STRLEN);
    vg_id[GRUB_LVM_ID_STRLEN] = '\0';

    for (vg = vg_list; vg; vg = vg->next)
      {
	if (! grub_memcmp(vg_id, vg->id, GRUB_LVM_ID_STRLEN))
	  break;
      }

    if (! vg)
      {
	/* First time we see this volume group. We've to create the
	   whole volume group structure. */
	vg = grub_malloc (sizeof (*vg));
	if (! vg)
	  goto fail3;
	vg->name = vgname;
	grub_memcpy (vg->id, vg_id, GRUB_LVM_ID_STRLEN+1);

	vg->extent_size = grub_lvm_getvalue (&p, "extent_size = ");
	if (p == NULL)
	  {
#ifdef GRUB_UTIL
	    grub_util_info ("unknown extent size\n");
#endif
	    goto fail4;
	  }

	vg->lvs = NULL;
	vg->pvs = NULL;

	p = grub_strstr (p, "physical_volumes {");
	if (p)
	  {
	    p += sizeof ("physical_volumes {") - 1;

	    /* Add all the pvs to the volume group. */
	    while (1)
	      {
		int s;
		while (grub_isspace (*p))
		  p++;

		if (*p == '}')
		  break;

		pv = grub_malloc (sizeof (*pv));
		q = p;
		while (*q != ' ')
		  q++;

		s = q - p;
		pv->name = grub_malloc (s + 1);
		grub_memcpy (pv->name, p, s);
		pv->name[s] = '\0';

		p = grub_strstr (p, "id = \"");
		if (p == NULL)
		  goto pvs_fail;
		p += sizeof("id = \"") - 1;

		grub_memcpy (pv->id, p, GRUB_LVM_ID_STRLEN);
		pv->id[GRUB_LVM_ID_STRLEN] = '\0';

		pv->start = grub_lvm_getvalue (&p, "pe_start = ");
		if (p == NULL)
		  {
#ifdef GRUB_UTIL
		    grub_util_info ("unknown pe_start\n");
#endif
		    goto pvs_fail;
		  }

		p = grub_strchr (p, '}');
		if (p == NULL)
		  {
#ifdef GRUB_UTIL
		    grub_util_info ("error parsing pe_start\n");
#endif
		    goto pvs_fail;
		  }
		p++;

		pv->disk = NULL;
		pv->next = vg->pvs;
		vg->pvs = pv;

		continue;
	      pvs_fail:
		grub_free (pv->name);
		grub_free (pv);
		goto fail4;
	      }
	  }

	p = grub_strstr (p, "logical_volumes");
	if (p)
	  {
	    p += 18;

	    /* And add all the lvs to the volume group. */
	    while (1)
	      {
		int s;
		int skip_lv = 0;
		struct grub_lvm_lv *lv;
		struct grub_lvm_segment *seg;
		int is_pvmove;

		while (grub_isspace (*p))
		  p++;

		if (*p == '}')
		  break;

		lv = grub_malloc (sizeof (*lv));

		q = p;
		while (*q != ' ')
		  q++;

		s = q - p;
		lv->name = grub_strndup (p, s);
		if (!lv->name)
		  goto lvs_fail;
		lv->compatname = grub_malloc (vgname_len + 1 + s + 1);
		if (!lv->compatname)
		  goto lvs_fail;
		grub_memcpy (lv->compatname, vgname, vgname_len);
		lv->compatname[vgname_len] = '-';
		grub_memcpy (lv->compatname + vgname_len + 1, p, s);
		lv->compatname[vgname_len + 1 + s] = '\0';

		{
		  const char *iptr;
		  char *optr;
		  lv->fullname = grub_malloc (sizeof("lvm/") + 2 * vgname_len
					      + 1 + 2 * s + 1);
		  if (!lv->fullname)
		    goto lvs_fail;

		  optr = lv->fullname;
		  grub_memcpy (optr, "lvm/", sizeof ("lvm/") - 1);
		  optr += sizeof ("lvm/") - 1;
		  for (iptr = vgname; iptr < vgname + vgname_len; iptr++)
		    {
		      *optr++ = *iptr;
		      if (*iptr == '-')
			*optr++ = '-';
		    }
		  *optr++ = '-';
		  for (iptr = p; iptr < p + s; iptr++)
		    {
		      *optr++ = *iptr;
		      if (*iptr == '-')
			*optr++ = '-';
		    }
		  *optr++ = 0;
		}

		lv->size = 0;

		lv->visible = grub_lvm_check_flag (p, "status", "VISIBLE");
		is_pvmove = grub_lvm_check_flag (p, "status", "PVMOVE");

		lv->segment_count = grub_lvm_getvalue (&p, "segment_count = ");
		if (p == NULL)
		  {
#ifdef GRUB_UTIL
		    grub_util_info ("unknown segment_count\n");
#endif
		    goto lvs_fail;
		  }
		lv->segments = grub_malloc (sizeof (*seg) * lv->segment_count);
		seg = lv->segments;

		for (i = 0; i < lv->segment_count; i++)
		  {

		    p = grub_strstr (p, "segment");
		    if (p == NULL)
		      {
#ifdef GRUB_UTIL
			grub_util_info ("unknown segment\n");
#endif
			goto lvs_segment_fail;
		      }

		    seg->start_extent = grub_lvm_getvalue (&p, "start_extent = ");
		    if (p == NULL)
		      {
#ifdef GRUB_UTIL
			grub_util_info ("unknown start_extent\n");
#endif
			goto lvs_segment_fail;
		      }
		    seg->extent_count = grub_lvm_getvalue (&p, "extent_count = ");
		    if (p == NULL)
		      {
#ifdef GRUB_UTIL
			grub_util_info ("unknown extent_count\n");
#endif
			goto lvs_segment_fail;
		      }

		    p = grub_strstr (p, "type = \"");
		    if (p == NULL)
		      goto lvs_segment_fail;
		    p += sizeof("type = \"") - 1;

		    lv->size += seg->extent_count * vg->extent_size;

		    if (grub_memcmp (p, "striped\"",
				     sizeof ("striped\"") - 1) == 0)
		      {
			struct grub_lvm_node *stripe;

			seg->type = GRUB_LVM_STRIPED;
			seg->node_count = grub_lvm_getvalue (&p, "stripe_count = ");
			if (p == NULL)
			  {
#ifdef GRUB_UTIL
			    grub_util_info ("unknown stripe_count\n");
#endif
			    goto lvs_segment_fail;
			  }

			if (seg->node_count != 1)
			  seg->stripe_size = grub_lvm_getvalue (&p, "stripe_size = ");

			seg->nodes = grub_zalloc (sizeof (*stripe)
						  * seg->node_count);
			stripe = seg->nodes;

			p = grub_strstr (p, "stripes = [");
			if (p == NULL)
			  {
#ifdef GRUB_UTIL
			    grub_util_info ("unknown stripes\n");
#endif
			    goto lvs_segment_fail2;
			  }
			p += sizeof("stripes = [") - 1;

			for (j = 0; j < seg->node_count; j++)
			  {
			    p = grub_strchr (p, '"');
			    if (p == NULL)
			      continue;
			    q = ++p;
			    while (*q != '"')
			      q++;

			    s = q - p;

			    stripe->name = grub_malloc (s + 1);
			    if (stripe->name == NULL)
			      goto lvs_segment_fail2;

			    grub_memcpy (stripe->name, p, s);
			    stripe->name[s] = '\0';

			    stripe->start = grub_lvm_getvalue (&p, ",");
			    if (p == NULL)
			      continue;

			    stripe++;
			  }
		      }
		    else if (grub_memcmp (p, "mirror\"", sizeof ("mirror\"") - 1)
			     == 0)
		      {
			seg->type = GRUB_LVM_MIRROR;
			seg->node_count = grub_lvm_getvalue (&p, "mirror_count = ");
			if (p == NULL)
			  {
#ifdef GRUB_UTIL
			    grub_util_info ("unknown mirror_count\n");
#endif
			    goto lvs_segment_fail;
			  }

			seg->nodes = grub_zalloc (sizeof (seg->nodes[0])
						  * seg->node_count);

			p = grub_strstr (p, "mirrors = [");
			if (p == NULL)
			  {
#ifdef GRUB_UTIL
			    grub_util_info ("unknown mirrors\n");
#endif
			    goto lvs_segment_fail2;
			  }
			p += sizeof("mirrors = [") - 1;

			for (j = 0; j < seg->node_count; j++)
			  {
			    char *lvname;

			    p = grub_strchr (p, '"');
			    if (p == NULL)
			      continue;
			    q = ++p;
			    while (*q != '"')
			      q++;

			    s = q - p;

			    lvname = grub_malloc (s + 1);
			    if (lvname == NULL)
			      goto lvs_segment_fail2;

			    grub_memcpy (lvname, p, s);
			    lvname[s] = '\0';
			    seg->nodes[j].name = lvname;
			    p = q + 1;
			  }
			/* Only first (original) is ok with in progress pvmove.  */
			if (is_pvmove)
			  seg->node_count = 1;
		      }
		    else
		      {
#ifdef GRUB_UTIL
			char *p2;
			p2 = grub_strchr (p, '"');
			if (p2)
			  *p2 = 0;
			grub_util_info ("unknown LVM type %s\n", p);
			if (p2)
			  *p2 ='"';
#endif
			/* Found a non-supported type, give up and move on. */
			skip_lv = 1;
			break;
		      }

		    seg++;

		    continue;
		  lvs_segment_fail2:
		    grub_free (seg->nodes);
		  lvs_segment_fail:
		    goto fail4;
		  }

		if (p != NULL)
		  p = grub_strchr (p, '}');
		if (p == NULL)
		  goto lvs_fail;
		p += 3;

		if (skip_lv)
		  {
		    grub_free (lv->name);
		    grub_free (lv);
		    continue;
		  }

		lv->number = lv_count++;
		lv->vg = vg;
		lv->next = vg->lvs;
		vg->lvs = lv;

		continue;
	      lvs_fail:
		grub_free (lv->name);
		grub_free (lv);
		goto fail4;
	      }
	  }

	/* Match lvs.  */
	{
	  struct grub_lvm_lv *lv1;
	  struct grub_lvm_lv *lv2;
	  for (lv1 = vg->lvs; lv1; lv1 = lv1->next)
	    for (i = 0; i < lv1->segment_count; i++)
	      for (j = 0; j < lv1->segments[i].node_count; j++)
		{
		  if (vg->pvs)
		    for (pv = vg->pvs; pv; pv = pv->next)
		      {
			if (! grub_strcmp (pv->name,
					   lv1->segments[i].nodes[j].name))
			  {
			    lv1->segments[i].nodes[j].pv = pv;
			    break;
			  }
		      }
		  if (lv1->segments[i].nodes[j].pv == NULL)
		    for (lv2 = vg->lvs; lv2; lv2 = lv2->next)
		      if (grub_strcmp (lv2->name + grub_strlen (vg->name) + 1,
				       lv1->segments[i].nodes[j].name) == 0)
			lv1->segments[i].nodes[j].lv = lv2;
		}
	
	}

	vg->next = vg_list;
	vg_list = vg;
      }
    else
      {
	grub_free (vgname);
      }

    /* Match the device we are currently reading from with the right
       PV. */
    if (vg->pvs)
      for (pv = vg->pvs; pv; pv = pv->next)
	{
	  if (! grub_memcmp (pv->id, pv_id, GRUB_LVM_ID_STRLEN))
	    {
	      /* This could happen to LVM on RAID, pv->disk points to the
		 raid device, we shouldn't change it.  */
	      if (! pv->disk)
		pv->disk = grub_disk_open (name);
	      break;
	    }
	}

    goto fail2;

    /* Failure path.  */
  fail4:
    grub_free (vg);
  fail3:
    grub_free (vgname);

    /* Normal exit path.  */
  fail2:
    grub_free (metadatabuf);
  fail:
    grub_disk_close (disk);
    if (grub_errno == GRUB_ERR_OUT_OF_RANGE)
      grub_errno = GRUB_ERR_NONE;
    grub_print_error ();
    if (scan_for && find_lv (scan_for))
      return 1;
    return 0;
  }

  scan_depth++;
  grub_device_iterate (&grub_lvm_scan_device);
  scan_depth--;
}

static int
grub_lvm_iterate (int (*hook) (const char *name),
		  grub_disk_pull_t pull)
{
  struct grub_lvm_vg *vg;
  unsigned old_count = 0;
  if (pull == GRUB_DISK_PULL_RESCAN && scan_depth)
    return 0;

  if (pull == GRUB_DISK_PULL_RESCAN)
    {
      old_count = lv_count;
      if (!scan_depth)
	do_lvm_scan (NULL);
    }
  if (pull != GRUB_DISK_PULL_RESCAN && pull != GRUB_DISK_PULL_NONE)
    return GRUB_ERR_NONE;
  for (vg = vg_list; vg; vg = vg->next)
    {
      struct grub_lvm_lv *lv;
      if (vg->lvs)
	for (lv = vg->lvs; lv; lv = lv->next)
	  if (lv->visible && lv->number >= old_count)
	    {
	      if (hook (lv->fullname))
		return 1;
	    }
    }

  return 0;
}

#ifdef GRUB_UTIL
static grub_disk_memberlist_t
grub_lvm_memberlist (grub_disk_t disk)
{
  struct grub_lvm_lv *lv = disk->data;
  grub_disk_memberlist_t list = NULL, tmp;
  struct grub_lvm_pv *pv;

  if (lv->vg->pvs)
    for (pv = lv->vg->pvs; pv; pv = pv->next)
      {
	if (!pv->disk)
	  grub_util_error ("Couldn't find PV %s. Check your device.map",
			   pv->name);
	tmp = grub_malloc (sizeof (*tmp));
	tmp->disk = pv->disk;
	tmp->next = list;
	list = tmp;
      }

  return list;
}
#endif

static grub_err_t
grub_lvm_open (const char *name, grub_disk_t disk)
{
  struct grub_lvm_lv *lv = NULL;
  int explicit = 0;

  if (grub_memcmp (name, "lvm/", sizeof ("lvm/") - 1) == 0)
    explicit = 1;

  lv = find_lv (name);

  if (! lv && !scan_depth && explicit)
    {
      do_lvm_scan (name);
      if (grub_errno)
	{
	  grub_print_error ();
	  grub_errno = GRUB_ERR_NONE;
	}
      lv = find_lv (name);
    }

  if (! lv)
    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "unknown LVM device %s", name);

  disk->id = lv->number;
  disk->data = lv;
  disk->total_sectors = lv->size;

  return 0;
}

static void
grub_lvm_close (grub_disk_t disk __attribute ((unused)))
{
  return;
}

static grub_err_t
read_lv (struct grub_lvm_lv *lv, grub_disk_addr_t sector,
	 grub_size_t size, char *buf);

static grub_err_t
read_node (const struct grub_lvm_node *node, grub_disk_addr_t sector,
	   grub_size_t size, char *buf)
{
  /* Check whether we actually know the physical volume we want to
     read from.  */
  if (node->pv)
    {
      if (node->pv->disk)
	return grub_disk_read (node->pv->disk, sector + node->pv->start, 0,
			       size << GRUB_DISK_SECTOR_BITS, buf);
      else
	return grub_error (GRUB_ERR_UNKNOWN_DEVICE,
			   "physical volume %s not found", node->pv->name);

    }
  if (node->lv)
    return read_lv (node->lv, sector, size, buf);
  return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "unknown node '%s'", node->name);
}

static grub_err_t
read_lv (struct grub_lvm_lv *lv, grub_disk_addr_t sector,
	 grub_size_t size, char *buf)
{
  grub_err_t err = 0;
  struct grub_lvm_vg *vg = lv->vg;
  struct grub_lvm_segment *seg = lv->segments;
  struct grub_lvm_node *node;
  grub_uint64_t offset;
  grub_uint64_t extent;
  unsigned int i;

  if (!lv)
    return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "unknown volume");

  extent = grub_divmod64 (sector, vg->extent_size, NULL);

  /* Find the right segment.  */
  for (i = 0; i < lv->segment_count; i++)
    {
      if ((seg->start_extent <= extent)
	  && ((seg->start_extent + seg->extent_count) > extent))
	{
	  break;
	}

      seg++;
    }

  if (i == lv->segment_count)
    return grub_error (GRUB_ERR_READ_ERROR, "incorrect segment");

  switch (seg->type)
    {
    case GRUB_LVM_STRIPED:
      if (seg->node_count == 1)
	{
	  /* This segment is linear, so that's easy.  We just need to find
	     out the offset in the physical volume and read SIZE bytes
	     from that.  */
	  struct grub_lvm_node *stripe = seg->nodes;
	  grub_uint64_t seg_offset; /* Offset of the segment in PV device.  */

	  node = stripe;
	  seg_offset = ((grub_uint64_t) stripe->start
			* (grub_uint64_t) vg->extent_size);

	  offset = sector - ((grub_uint64_t) seg->start_extent
			     * (grub_uint64_t) vg->extent_size) + seg_offset;
	}
      else
	{
	  /* This is a striped segment. We have to find the right PV
	     similar to RAID0. */
	  struct grub_lvm_node *stripe = seg->nodes;
	  grub_uint64_t a, b;
	  grub_uint64_t seg_offset; /* Offset of the segment in PV device.  */
	  grub_uint64_t stripenr;

	  offset = sector - ((grub_uint64_t) seg->start_extent
			     * (grub_uint64_t) vg->extent_size);

	  a = grub_divmod64 (offset, seg->stripe_size, NULL);
	  grub_divmod64 (a, seg->node_count, &stripenr);

	  a = grub_divmod64 (offset, seg->stripe_size * seg->node_count, NULL);
	  grub_divmod64 (offset, seg->stripe_size, &b);
	  offset = a * seg->stripe_size + b;

	  stripe += stripenr;
	  node = stripe;

	  seg_offset = ((grub_uint64_t) stripe->start
			* (grub_uint64_t) vg->extent_size);

	  offset += seg_offset;
	}
      return read_node (node, offset, size, buf);
    case GRUB_LVM_MIRROR:
      i = 0;
      while (1)
	{
	  err = read_node (&seg->nodes[i], sector, size, buf);
	  if (!err)
	    return err;
	  if (++i >= seg->node_count)
	    return err;
	  grub_errno = GRUB_ERR_NONE;
	}
    }
  return grub_error (GRUB_ERR_IO, "unknown LVM segment");
}

static grub_err_t
is_node_readable (const struct grub_lvm_node *node)
{
  /* Check whether we actually know the physical volume we want to
     read from.  */
  if (node->pv)
    return !!(node->pv->disk);
  if (node->lv)
    return is_lv_readable (node->lv);
  return 0;
}

static int
is_lv_readable (struct grub_lvm_lv *lv)
{
  unsigned int i, j;

  if (!lv)
    return 0;

  /* Find the right segment.  */
  for (i = 0; i < lv->segment_count; i++)
    switch (lv->segments[i].type)
      {
      case GRUB_LVM_STRIPED:
	for (j = 0; j < lv->segments[i].node_count; j++)
	  if (!is_node_readable (lv->segments[i].nodes + j))
	    return 0;
	break;
      case GRUB_LVM_MIRROR:
	for (j = 0; j < lv->segments[i].node_count; j++)
	  if (is_node_readable (lv->segments[i].nodes + j))
	    break;
	if (j == lv->segments[i].node_count)
	  return 0;
      default:
	return 0;
      }

  return 1;
}


static grub_err_t
grub_lvm_read (grub_disk_t disk, grub_disk_addr_t sector,
		grub_size_t size, char *buf)
{
  return read_lv (disk->data, sector, size, buf);
}

static grub_err_t
grub_lvm_write (grub_disk_t disk __attribute ((unused)),
		 grub_disk_addr_t sector __attribute ((unused)),
		 grub_size_t size __attribute ((unused)),
		 const char *buf __attribute ((unused)))
{
  return GRUB_ERR_NOT_IMPLEMENTED_YET;
}

static struct grub_disk_dev grub_lvm_dev =
  {
    .name = "lvm",
    .id = GRUB_DISK_DEVICE_LVM_ID,
    .iterate = grub_lvm_iterate,
    .open = grub_lvm_open,
    .close = grub_lvm_close,
    .read = grub_lvm_read,
    .write = grub_lvm_write,
#ifdef GRUB_UTIL
    .memberlist = grub_lvm_memberlist,
#endif
    .next = 0
  };


GRUB_MOD_INIT(lvm)
{
  grub_disk_dev_register (&grub_lvm_dev);
}

GRUB_MOD_FINI(lvm)
{
  grub_disk_dev_unregister (&grub_lvm_dev);
  vg_list = NULL;
  /* FIXME: free the lvm list. */
}