text: /*
   * Copyright (c) International Business Machines Corp., 2006
   * Copyright (c) Nokia Corporation, 2006, 2007
   *
   * This program 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 2 of the License, or
   * (at your option) any later version.
   *
   * This program 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 this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   *
   * Author: Artem Bityutskiy (Битюцкий Артём)
   */
  
  /*
   * This file includes volume table manipulation code. The volume table is an
   * on-flash table containing volume meta-data like name, number of reserved
   * physical eraseblocks, type, etc. The volume table is stored in the so-called
   * "layout volume".
   *
   * The layout volume is an internal volume which is organized as follows. It
   * consists of two logical eraseblocks - LEB 0 and LEB 1. Each logical
   * eraseblock stores one volume table copy, i.e. LEB 0 and LEB 1 duplicate each
   * other. This redundancy guarantees robustness to unclean reboots. The volume
   * table is basically an array of volume table records. Each record contains
   * full information about the volume and protected by a CRC checksum.
   *
   * The volume table is changed, it is first changed in RAM. Then LEB 0 is
   * erased, and the updated volume table is written back to LEB 0. Then same for
   * LEB 1. This scheme guarantees recoverability from unclean reboots.
   *
   * In this UBI implementation the on-flash volume table does not contain any
   * information about how many data static volumes contain. This information may
   * be found from the scanning data.
   *
   * But it would still be beneficial to store this information in the volume
   * table. For example, suppose we have a static volume X, and all its physical
   * eraseblocks became bad for some reasons. Suppose we are attaching the
   * corresponding MTD device, the scanning has found no logical eraseblocks
   * corresponding to the volume X. According to the volume table volume X does
   * exist. So we don't know whether it is just empty or all its physical
   * eraseblocks went bad. So we cannot alarm the user about this corruption.
   *
   * The volume table also stores so-called "update marker", which is used for
   * volume updates. Before updating the volume, the update marker is set, and
   * after the update operation is finished, the update marker is cleared. So if
   * the update operation was interrupted (e.g. by an unclean reboot) - the
   * update marker is still there and we know that the volume's contents is
   * damaged.
   */
  
  #include <linux/crc32.h>
  #include <linux/err.h>
  #include <linux/slab.h>
  #include <asm/div64.h>
  #include "ubi.h"
  
  #ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
  static void paranoid_vtbl_check(const struct ubi_device *ubi);
  #else
  #define paranoid_vtbl_check(ubi)
  #endif
  
  /* Empty volume table record */
  static struct ubi_vtbl_record empty_vtbl_record;
  
  /**
   * ubi_change_vtbl_record - change volume table record.
   * @ubi: UBI device description object
   * @idx: table index to change
   * @vtbl_rec: new volume table record
   *
   * This function changes volume table record @idx. If @vtbl_rec is %NULL, empty
   * volume table record is written. The caller does not have to calculate CRC of
   * the record as it is done by this function. Returns zero in case of success
   * and a negative error code in case of failure.
   */
  int ubi_change_vtbl_record(struct ubi_device *ubi, int idx,
  			   struct ubi_vtbl_record *vtbl_rec)
  {
  	int i, err;
  	uint32_t crc;
  	struct ubi_volume *layout_vol;
  
  	ubi_assert(idx >= 0 && idx < ubi->vtbl_slots);
  	layout_vol = ubi->volumes[vol_id2idx(ubi, UBI_LAYOUT_VOLUME_ID)];
  
  	if (!vtbl_rec)
  		vtbl_rec = &empty_vtbl_record;
  	else {
  		crc = crc32(UBI_CRC32_INIT, vtbl_rec, UBI_VTBL_RECORD_SIZE_CRC);
  		vtbl_rec->crc = cpu_to_be32(crc);
  	}
  
  	memcpy(&ubi->vtbl[idx], vtbl_rec, sizeof(struct ubi_vtbl_record));
  	for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
  		err = ubi_eba_unmap_leb(ubi, layout_vol, i);
  		if (err)
  			return err;
  
  		err = ubi_eba_write_leb(ubi, layout_vol, i, ubi->vtbl, 0,
  					ubi->vtbl_size, UBI_LONGTERM);
  		if (err)
  			return err;
  	}
  
  	paranoid_vtbl_check(ubi);
  	return 0;
  }
  
  /**
   * ubi_vtbl_rename_volumes - rename UBI volumes in the volume table.
   * @ubi: UBI device description object
   * @rename_list: list of &struct ubi_rename_entry objects
   *
   * This function re-names multiple volumes specified in @req in the volume
   * table. Returns zero in case of success and a negative error code in case of
   * failure.
   */
  int ubi_vtbl_rename_volumes(struct ubi_device *ubi,
  			    struct list_head *rename_list)
  {
  	int i, err;
  	struct ubi_rename_entry *re;
  	struct ubi_volume *layout_vol;
  
  	list_for_each_entry(re, rename_list, list) {
  		uint32_t crc;
  		struct ubi_volume *vol = re->desc->vol;
  		struct ubi_vtbl_record *vtbl_rec = &ubi->vtbl[vol->vol_id];
  
  		if (re->remove) {
  			memcpy(vtbl_rec, &empty_vtbl_record,
  			       sizeof(struct ubi_vtbl_record));
  			continue;
  		}
  
  		vtbl_rec->name_len = cpu_to_be16(re->new_name_len);
  		memcpy(vtbl_rec->name, re->new_name, re->new_name_len);
  		memset(vtbl_rec->name + re->new_name_len, 0,
  		       UBI_VOL_NAME_MAX + 1 - re->new_name_len);
  		crc = crc32(UBI_CRC32_INIT, vtbl_rec,
  			    UBI_VTBL_RECORD_SIZE_CRC);
  		vtbl_rec->crc = cpu_to_be32(crc);
  	}
  
  	layout_vol = ubi->volumes[vol_id2idx(ubi, UBI_LAYOUT_VOLUME_ID)];
  	for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
  		err = ubi_eba_unmap_leb(ubi, layout_vol, i);
  		if (err)
  			return err;
  
  		err = ubi_eba_write_leb(ubi, layout_vol, i, ubi->vtbl, 0,
  					ubi->vtbl_size, UBI_LONGTERM);
  		if (err)
  			return err;
  	}
  
  	return 0;
  }
  
  /**
   * vtbl_check - check if volume table is not corrupted and sensible.
   * @ubi: UBI device description object
   * @vtbl: volume table
   *
   * This function returns zero if @vtbl is all right, %1 if CRC is incorrect,
   * and %-EINVAL if it contains inconsistent data.
   */
  static int vtbl_check(const struct ubi_device *ubi,
  		      const struct ubi_vtbl_record *vtbl)
  {
  	int i, n, reserved_pebs, alignment, data_pad, vol_type, name_len;
  	int upd_marker, err;
  	uint32_t crc;
  	const char *name;
  
  	for (i = 0; i < ubi->vtbl_slots; i++) {
  		cond_resched();
  
  		reserved_pebs = be32_to_cpu(vtbl[i].reserved_pebs);
  		alignment = be32_to_cpu(vtbl[i].alignment);
  		data_pad = be32_to_cpu(vtbl[i].data_pad);
  		upd_marker = vtbl[i].upd_marker;
  		vol_type = vtbl[i].vol_type;
  		name_len = be16_to_cpu(vtbl[i].name_len);
  		name = &vtbl[i].name[0];
  
  		crc = crc32(UBI_CRC32_INIT, &vtbl[i], UBI_VTBL_RECORD_SIZE_CRC);
  		if (be32_to_cpu(vtbl[i].crc) != crc) {
  			ubi_err("bad CRC at record %u: %#08x, not %#08x",
  				 i, crc, be32_to_cpu(vtbl[i].crc));
  			ubi_dbg_dump_vtbl_record(&vtbl[i], i);
  			return 1;
  		}
  
  		if (reserved_pebs == 0) {
  			if (memcmp(&vtbl[i], &empty_vtbl_record,
  						UBI_VTBL_RECORD_SIZE)) {
  				err = 2;
  				goto bad;
  			}
  			continue;
  		}
  
  		if (reserved_pebs < 0 || alignment < 0 || data_pad < 0 ||
  		    name_len < 0) {
  			err = 3;
  			goto bad;
  		}
  
  		if (alignment > ubi->leb_size || alignment == 0) {
  			err = 4;
  			goto bad;
  		}
  
  		n = alignment & (ubi->min_io_size - 1);
  		if (alignment != 1 && n) {
  			err = 5;
  			goto bad;
  		}
  
  		n = ubi->leb_size % alignment;
  		if (data_pad != n) {
  			dbg_err("bad data_pad, has to be %d", n);
  			err = 6;
  			goto bad;
  		}
  
  		if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
  			err = 7;
  			goto bad;
  		}
  
  		if (upd_marker != 0 && upd_marker != 1) {
  			err = 8;
  			goto bad;
  		}
  
  		if (reserved_pebs > ubi->good_peb_count) {
  			dbg_err("too large reserved_pebs %d, good PEBs %d",
  				reserved_pebs, ubi->good_peb_count);
  			err = 9;
  			goto bad;
  		}
  
  		if (name_len > UBI_VOL_NAME_MAX) {
  			err = 10;
  			goto bad;
  		}
  
  		if (name[0] == '\0') {
  			err = 11;
  			goto bad;
  		}
  
  		if (name_len != strnlen(name, name_len + 1)) {
  			err = 12;
  			goto bad;
  		}
  	}
  
  	/* Checks that all names are unique */
  	for (i = 0; i < ubi->vtbl_slots - 1; i++) {
  		for (n = i + 1; n < ubi->vtbl_slots; n++) {
  			int len1 = be16_to_cpu(vtbl[i].name_len);
  			int len2 = be16_to_cpu(vtbl[n].name_len);
  
  			if (len1 > 0 && len1 == len2 &&
  			    !strncmp(vtbl[i].name, vtbl[n].name, len1)) {
  				ubi_err("volumes %d and %d have the same name"
  					" \"%s\"", i, n, vtbl[i].name);
  				ubi_dbg_dump_vtbl_record(&vtbl[i], i);
  				ubi_dbg_dump_vtbl_record(&vtbl[n], n);
  				return -EINVAL;
  			}
  		}
  	}
  
  	return 0;
  
  bad:
  	ubi_err("volume table check failed: record %d, error %d", i, err);
  	ubi_dbg_dump_vtbl_record(&vtbl[i], i);
  	return -EINVAL;
  }
  
  /**
   * create_vtbl - create a copy of volume table.
   * @ubi: UBI device description object
   * @si: scanning information
   * @copy: number of the volume table copy
   * @vtbl: contents of the volume table
   *
   * This function returns zero in case of success and a negative error code in
   * case of failure.
   */
  static int create_vtbl(struct ubi_device *ubi, struct ubi_scan_info *si,
  		       int copy, void *vtbl)
  {
  	int err, tries = 0;
  	static struct ubi_vid_hdr *vid_hdr;
  	struct ubi_scan_volume *sv;
  	struct ubi_scan_leb *new_seb, *old_seb = NULL;
  
  	ubi_msg("create volume table (copy #%d)", copy + 1);
  
  	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
  	if (!vid_hdr)
  		return -ENOMEM;
  
  	/*
  	 * Check if there is a logical eraseblock which would have to contain
  	 * this volume table copy was found during scanning. It has to be wiped
  	 * out.
  	 */
  	sv = ubi_scan_find_sv(si, UBI_LAYOUT_VOLUME_ID);
  	if (sv)
  		old_seb = ubi_scan_find_seb(sv, copy);
  
  retry:
  	new_seb = ubi_scan_get_free_peb(ubi, si);
  	if (IS_ERR(new_seb)) {
  		err = PTR_ERR(new_seb);
  		goto out_free;
  	}
  
  	vid_hdr->vol_type = UBI_VID_DYNAMIC;
  	vid_hdr->vol_id = cpu_to_be32(UBI_LAYOUT_VOLUME_ID);
  	vid_hdr->compat = UBI_LAYOUT_VOLUME_COMPAT;
  	vid_hdr->data_size = vid_hdr->used_ebs =
  			     vid_hdr->data_pad = cpu_to_be32(0);
  	vid_hdr->lnum = cpu_to_be32(copy);
  	vid_hdr->sqnum = cpu_to_be64(++si->max_sqnum);
  
  	/* The EC header is already there, write the VID header */
  	err = ubi_io_write_vid_hdr(ubi, new_seb->pnum, vid_hdr);
  	if (err)
  		goto write_error;
  
  	/* Write the layout volume contents */
  	err = ubi_io_write_data(ubi, vtbl, new_seb->pnum, 0, ubi->vtbl_size);
  	if (err)
  		goto write_error;
  
  	/*
  	 * And add it to the scanning information. Don't delete the old
  	 * @old_seb as it will be deleted and freed in 'ubi_scan_add_used()'.
  	 */
  	err = ubi_scan_add_used(ubi, si, new_seb->pnum, new_seb->ec,
  				vid_hdr, 0);
  	kfree(new_seb);
  	ubi_free_vid_hdr(ubi, vid_hdr);
  	return err;
  
  write_error:
  	if (err == -EIO && ++tries <= 5) {
  		/*
  		 * Probably this physical eraseblock went bad, try to pick
  		 * another one.
  		 */
  		list_add_tail(&new_seb->u.list, &si->corr);
  		goto retry;
  	}
  	kfree(new_seb);
  out_free:
  	ubi_free_vid_hdr(ubi, vid_hdr);
  	return err;
  
  }
  
  /**
   * process_lvol - process the layout volume.
   * @ubi: UBI device description object
   * @si: scanning information
   * @sv: layout volume scanning information
   *
   * This function is responsible for reading the layout volume, ensuring it is
   * not corrupted, and recovering from corruptions if needed. Returns volume
   * table in case of success and a negative error code in case of failure.
   */
  static struct ubi_vtbl_record *process_lvol(struct ubi_device *ubi,
  					    struct ubi_scan_info *si,
  					    struct ubi_scan_volume *sv)
  {
  	int err;
  	struct rb_node *rb;
  	struct ubi_scan_leb *seb;
  	struct ubi_vtbl_record *leb[UBI_LAYOUT_VOLUME_EBS] = { NULL, NULL };
  	int leb_corrupted[UBI_LAYOUT_VOLUME_EBS] = {1, 1};
  
  	/*
  	 * UBI goes through the following steps when it changes the layout
  	 * volume:
  	 * a. erase LEB 0;
  	 * b. write new data to LEB 0;
  	 * c. erase LEB 1;
  	 * d. write new data to LEB 1.
  	 *
  	 * Before the change, both LEBs contain the same data.
  	 *
  	 * Due to unclean reboots, the contents of LEB 0 may be lost, but there
  	 * should LEB 1. So it is OK if LEB 0 is corrupted while LEB 1 is not.
  	 * Similarly, LEB 1 may be lost, but there should be LEB 0. And
  	 * finally, unclean reboots may result in a situation when neither LEB
  	 * 0 nor LEB 1 are corrupted, but they are different. In this case, LEB
  	 * 0 contains more recent information.
  	 *
  	 * So the plan is to first check LEB 0. Then
  	 * a. if LEB 0 is OK, it must be containing the most resent data; then
  	 *    we compare it with LEB 1, and if they are different, we copy LEB
  	 *    0 to LEB 1;
  	 * b. if LEB 0 is corrupted, but LEB 1 has to be OK, and we copy LEB 1
  	 *    to LEB 0.
  	 */
  
  	dbg_gen("check layout volume");
  
  	/* Read both LEB 0 and LEB 1 into memory */
  	ubi_rb_for_each_entry(rb, seb, &sv->root, u.rb) {
  		leb[seb->lnum] = vmalloc(ubi->vtbl_size);
  		if (!leb[seb->lnum]) {
  			err = -ENOMEM;
  			goto out_free;
  		}
  		memset(leb[seb->lnum], 0, ubi->vtbl_size);
  
  		err = ubi_io_read_data(ubi, leb[seb->lnum], seb->pnum, 0,
  				       ubi->vtbl_size);
  		if (err == UBI_IO_BITFLIPS || err == -EBADMSG)
  			/*
  			 * Scrub the PEB later. Note, -EBADMSG indicates an
  			 * uncorrectable ECC error, but we have our own CRC and
  			 * the data will be checked later. If the data is OK,
  			 * the PEB will be scrubbed (because we set
  			 * seb->scrub). If the data is not OK, the contents of
  			 * the PEB will be recovered from the second copy, and
  			 * seb->scrub will be cleared in
  			 * 'ubi_scan_add_used()'.
  			 */
  			seb->scrub = 1;
  		else if (err)
  			goto out_free;
  	}
  
  	err = -EINVAL;
  	if (leb[0]) {
  		leb_corrupted[0] = vtbl_check(ubi, leb[0]);
  		if (leb_corrupted[0] < 0)
  			goto out_free;
  	}
  
  	if (!leb_corrupted[0]) {
  		/* LEB 0 is OK */
  		if (leb[1])
  			leb_corrupted[1] = memcmp(leb[0], leb[1],
  						  ubi->vtbl_size);
  		if (leb_corrupted[1]) {
  			ubi_warn("volume table copy #2 is corrupted");
  			err = create_vtbl(ubi, si, 1, leb[0]);
  			if (err)
  				goto out_free;
  			ubi_msg("volume table was restored");
  		}
  
  		/* Both LEB 1 and LEB 2 are OK and consistent */
  		vfree(leb[1]);
  		return leb[0];
  	} else {
  		/* LEB 0 is corrupted or does not exist */
  		if (leb[1]) {
  			leb_corrupted[1] = vtbl_check(ubi, leb[1]);
  			if (leb_corrupted[1] < 0)
  				goto out_free;
  		}
  		if (leb_corrupted[1]) {
  			/* Both LEB 0 and LEB 1 are corrupted */
  			ubi_err("both volume tables are corrupted");
  			goto out_free;
  		}
  
  		ubi_warn("volume table copy #1 is corrupted");
  		err = create_vtbl(ubi, si, 0, leb[1]);
  		if (err)
  			goto out_free;
  		ubi_msg("volume table was restored");
  
  		vfree(leb[0]);
  		return leb[1];
  	}
  
  out_free:
  	vfree(leb[0]);
  	vfree(leb[1]);
  	return ERR_PTR(err);
  }
  
  /**
   * create_empty_lvol - create empty layout volume.
   * @ubi: UBI device description object
   * @si: scanning information
   *
   * This function returns volume table contents in case of success and a
   * negative error code in case of failure.
   */
  static struct ubi_vtbl_record *create_empty_lvol(struct ubi_device *ubi,
  						 struct ubi_scan_info *si)
  {
  	int i;
  	struct ubi_vtbl_record *vtbl;
  
  	vtbl = vmalloc(ubi->vtbl_size);
  	if (!vtbl)
  		return ERR_PTR(-ENOMEM);
  	memset(vtbl, 0, ubi->vtbl_size);
  
  	for (i = 0; i < ubi->vtbl_slots; i++)
  		memcpy(&vtbl[i], &empty_vtbl_record, UBI_VTBL_RECORD_SIZE);
  
  	for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
  		int err;
  
  		err = create_vtbl(ubi, si, i, vtbl);
  		if (err) {
  			vfree(vtbl);
  			return ERR_PTR(err);
  		}
  	}
  
  	return vtbl;
  }
  
  /**
   * init_volumes - initialize volume information for existing volumes.
   * @ubi: UBI device description object
   * @si: scanning information
   * @vtbl: volume table
   *
   * This function allocates volume description objects for existing volumes.
   * Returns zero in case of success and a negative error code in case of
   * failure.
   */
  static int init_volumes(struct ubi_device *ubi, const struct ubi_scan_info *si,
  			const struct ubi_vtbl_record *vtbl)
  {
  	int i, reserved_pebs = 0;
  	struct ubi_scan_volume *sv;
  	struct ubi_volume *vol;
  
  	for (i = 0; i < ubi->vtbl_slots; i++) {
  		cond_resched();
  
  		if (be32_to_cpu(vtbl[i].reserved_pebs) == 0)
  			continue; /* Empty record */
  
  		vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
  		if (!vol)
  			return -ENOMEM;
  
  		vol->reserved_pebs = be32_to_cpu(vtbl[i].reserved_pebs);
  		vol->alignment = be32_to_cpu(vtbl[i].alignment);
  		vol->data_pad = be32_to_cpu(vtbl[i].data_pad);
  		vol->upd_marker = vtbl[i].upd_marker;
  		vol->vol_type = vtbl[i].vol_type == UBI_VID_DYNAMIC ?
  					UBI_DYNAMIC_VOLUME : UBI_STATIC_VOLUME;
  		vol->name_len = be16_to_cpu(vtbl[i].name_len);
  		vol->usable_leb_size = ubi->leb_size - vol->data_pad;
  		memcpy(vol->name, vtbl[i].name, vol->name_len);
  		vol->name[vol->name_len] = '\0';
  		vol->vol_id = i;
  
  		if (vtbl[i].flags & UBI_VTBL_AUTORESIZE_FLG) {
  			/* Auto re-size flag may be set only for one volume */
  			if (ubi->autoresize_vol_id != -1) {
  				ubi_err("more than one auto-resize volume (%d "
  					"and %d)", ubi->autoresize_vol_id, i);
  				kfree(vol);
  				return -EINVAL;
  			}
  
  			ubi->autoresize_vol_id = i;
  		}
  
  		ubi_assert(!ubi->volumes[i]);
  		ubi->volumes[i] = vol;
  		ubi->vol_count += 1;
  		vol->ubi = ubi;
  		reserved_pebs += vol->reserved_pebs;
  
  		/*
  		 * In case of dynamic volume UBI knows nothing about how many
  		 * data is stored there. So assume the whole volume is used.
  		 */
  		if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
  			vol->used_ebs = vol->reserved_pebs;
  			vol->last_eb_bytes = vol->usable_leb_size;
  			vol->used_bytes =
  				(long long)vol->used_ebs * vol->usable_leb_size;
  			continue;
  		}
  
  		/* Static volumes only */
  		sv = ubi_scan_find_sv(si, i);
  		if (!sv) {
  			/*
  			 * No eraseblocks belonging to this volume found. We
  			 * don't actually know whether this static volume is
  			 * completely corrupted or just contains no data. And
  			 * we cannot know this as long as data size is not
  			 * stored on flash. So we just assume the volume is
  			 * empty. FIXME: this should be handled.
  			 */
  			continue;
  		}
  
  		if (sv->leb_count != sv->used_ebs) {
  			/*
  			 * We found a static volume which misses several
  			 * eraseblocks. Treat it as corrupted.
  			 */
  			ubi_warn("static volume %d misses %d LEBs - corrupted",
  				 sv->vol_id, sv->used_ebs - sv->leb_count);
  			vol->corrupted = 1;
  			continue;
  		}
  
  		vol->used_ebs = sv->used_ebs;
  		vol->used_bytes =
  			(long long)(vol->used_ebs - 1) * vol->usable_leb_size;
  		vol->used_bytes += sv->last_data_size;
  		vol->last_eb_bytes = sv->last_data_size;
  	}
  
  	/* And add the layout volume */
  	vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
  	if (!vol)
  		return -ENOMEM;
  
  	vol->reserved_pebs = UBI_LAYOUT_VOLUME_EBS;
  	vol->alignment = 1;
  	vol->vol_type = UBI_DYNAMIC_VOLUME;
  	vol->name_len = sizeof(UBI_LAYOUT_VOLUME_NAME) - 1;
  	memcpy(vol->name, UBI_LAYOUT_VOLUME_NAME, vol->name_len + 1);
  	vol->usable_leb_size = ubi->leb_size;
  	vol->used_ebs = vol->reserved_pebs;
  	vol->last_eb_bytes = vol->reserved_pebs;
  	vol->used_bytes =
  		(long long)vol->used_ebs * (ubi->leb_size - vol->data_pad);
  	vol->vol_id = UBI_LAYOUT_VOLUME_ID;
  	vol->ref_count = 1;
  
  	ubi_assert(!ubi->volumes[i]);
  	ubi->volumes[vol_id2idx(ubi, vol->vol_id)] = vol;
  	reserved_pebs += vol->reserved_pebs;
  	ubi->vol_count += 1;
  	vol->ubi = ubi;
  
  	if (reserved_pebs > ubi->avail_pebs)
  		ubi_err("not enough PEBs, required %d, available %d",
  			reserved_pebs, ubi->avail_pebs);
  	ubi->rsvd_pebs += reserved_pebs;
  	ubi->avail_pebs -= reserved_pebs;
  
  	return 0;
  }
  
  /**
   * check_sv - check volume scanning information.
   * @vol: UBI volume description object
   * @sv: volume scanning information
   *
   * This function returns zero if the volume scanning information is consistent
   * to the data read from the volume tabla, and %-EINVAL if not.
   */
  static int check_sv(const struct ubi_volume *vol,
  		    const struct ubi_scan_volume *sv)
  {
  	int err;
  
  	if (sv->highest_lnum >= vol->reserved_pebs) {
  		err = 1;
  		goto bad;
  	}
  	if (sv->leb_count > vol->reserved_pebs) {
  		err = 2;
  		goto bad;
  	}
  	if (sv->vol_type != vol->vol_type) {
  		err = 3;
  		goto bad;
  	}
  	if (sv->used_ebs > vol->reserved_pebs) {
  		err = 4;
  		goto bad;
  	}
  	if (sv->data_pad != vol->data_pad) {
  		err = 5;
  		goto bad;
  	}
  	return 0;
  
  bad:
  	ubi_err("bad scanning information, error %d", err);
  	ubi_dbg_dump_sv(sv);
  	ubi_dbg_dump_vol_info(vol);
  	return -EINVAL;
  }
  
  /**
   * check_scanning_info - check that scanning information.
   * @ubi: UBI device description object
   * @si: scanning information
   *
   * Even though we protect on-flash data by CRC checksums, we still don't trust
   * the media. This function ensures that scanning information is consistent to
   * the information read from the volume table. Returns zero if the scanning
   * information is OK and %-EINVAL if it is not.
   */
  static int check_scanning_info(const struct ubi_device *ubi,
  			       struct ubi_scan_info *si)
  {
  	int err, i;
  	struct ubi_scan_volume *sv;
  	struct ubi_volume *vol;
  
  	if (si->vols_found > UBI_INT_VOL_COUNT + ubi->vtbl_slots) {
  		ubi_err("scanning found %d volumes, maximum is %d + %d",
  			si->vols_found, UBI_INT_VOL_COUNT, ubi->vtbl_slots);
  		return -EINVAL;
  	}
  
  	if (si->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT &&
  	    si->highest_vol_id < UBI_INTERNAL_VOL_START) {
  		ubi_err("too large volume ID %d found by scanning",
  			si->highest_vol_id);
  		return -EINVAL;
  	}
  
  	for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
  		cond_resched();
  
  		sv = ubi_scan_find_sv(si, i);
  		vol = ubi->volumes[i];
  		if (!vol) {
  			if (sv)
  				ubi_scan_rm_volume(si, sv);
  			continue;
  		}
  
  		if (vol->reserved_pebs == 0) {
  			ubi_assert(i < ubi->vtbl_slots);
  
  			if (!sv)
  				continue;
  
  			/*
  			 * During scanning we found a volume which does not
  			 * exist according to the information in the volume
  			 * table. This must have happened due to an unclean
  			 * reboot while the volume was being removed. Discard
  			 * these eraseblocks.
  			 */
  			ubi_msg("finish volume %d removal", sv->vol_id);
  			ubi_scan_rm_volume(si, sv);
  		} else if (sv) {
  			err = check_sv(vol, sv);
  			if (err)
  				return err;
  		}
  	}
  
  	return 0;
  }
  
  /**
   * ubi_read_volume_table - read the volume table.
   * @ubi: UBI device description object
   * @si: scanning information
   *
   * This function reads volume table, checks it, recover from errors if needed,
   * or creates it if needed. Returns zero in case of success and a negative
   * error code in case of failure.
   */
  int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_scan_info *si)
  {
  	int i, err;
  	struct ubi_scan_volume *sv;
  
  	empty_vtbl_record.crc = cpu_to_be32(0xf116c36b);
  
  	/*
  	 * The number of supported volumes is limited by the eraseblock size
  	 * and by the UBI_MAX_VOLUMES constant.
  	 */
  	ubi->vtbl_slots = ubi->leb_size / UBI_VTBL_RECORD_SIZE;
  	if (ubi->vtbl_slots > UBI_MAX_VOLUMES)
  		ubi->vtbl_slots = UBI_MAX_VOLUMES;
  
  	ubi->vtbl_size = ubi->vtbl_slots * UBI_VTBL_RECORD_SIZE;
  	ubi->vtbl_size = ALIGN(ubi->vtbl_size, ubi->min_io_size);
  
  	sv = ubi_scan_find_sv(si, UBI_LAYOUT_VOLUME_ID);
  	if (!sv) {
  		/*
  		 * No logical eraseblocks belonging to the layout volume were
  		 * found. This could mean that the flash is just empty. In
  		 * this case we create empty layout volume.
  		 *
  		 * But if flash is not empty this must be a corruption or the
  		 * MTD device just contains garbage.
  		 */
  		if (si->is_empty) {
  			ubi->vtbl = create_empty_lvol(ubi, si);
  			if (IS_ERR(ubi->vtbl))
  				return PTR_ERR(ubi->vtbl);
  		} else {
  			ubi_err("the layout volume was not found");
  			return -EINVAL;
  		}
  	} else {
  		if (sv->leb_count > UBI_LAYOUT_VOLUME_EBS) {
  			/* This must not happen with proper UBI images */
  			dbg_err("too many LEBs (%d) in layout volume",
  				sv->leb_count);
  			return -EINVAL;
  		}
  
  		ubi->vtbl = process_lvol(ubi, si, sv);
  		if (IS_ERR(ubi->vtbl))
  			return PTR_ERR(ubi->vtbl);
  	}
  
  	ubi->avail_pebs = ubi->good_peb_count;
  
  	/*
  	 * The layout volume is OK, initialize the corresponding in-RAM data
  	 * structures.
  	 */
  	err = init_volumes(ubi, si, ubi->vtbl);
  	if (err)
  		goto out_free;
  
  	/*
  	 * Get sure that the scanning information is consistent to the
  	 * information stored in the volume table.
  	 */
  	err = check_scanning_info(ubi, si);
  	if (err)
  		goto out_free;
  
  	return 0;
  
  out_free:
  	vfree(ubi->vtbl);
  	for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
  		kfree(ubi->volumes[i]);
  		ubi->volumes[i] = NULL;
  	}
  	return err;
  }
  
  #ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
  
  /**
   * paranoid_vtbl_check - check volume table.
   * @ubi: UBI device description object
   */
  static void paranoid_vtbl_check(const struct ubi_device *ubi)
  {
  	if (vtbl_check(ubi, ubi->vtbl)) {
  		ubi_err("paranoid check failed");
  		BUG();
  	}
  }
  
  #endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */
  