/*
   * Copyright (c) International Business Machines Corp., 2006
   *
   * 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)
   */
  
  /*

   * UBI attaching sub-system.

   *

   * This sub-system is responsible for attaching MTD devices and it also
   * implements flash media scanning.

   *

   * The attaching information is represented by a &struct ubi_attach_info'

   * object. Information about volumes is represented by &struct ubi_ainf_volume
   * objects which are kept in volume RB-tree with root at the @volumes field.
   * The RB-tree is indexed by the volume ID.

   *

   * Logical eraseblocks are represented by &struct ubi_ainf_peb objects. These
   * objects are kept in per-volume RB-trees with the root at the corresponding
   * &struct ubi_ainf_volume object. To put it differently, we keep an RB-tree of
   * per-volume objects and each of these objects is the root of RB-tree of
   * per-LEB objects.

   *
   * Corrupted physical eraseblocks are put to the @corr list, free physical
   * eraseblocks are put to the @free list and the physical eraseblock to be
   * erased are put to the @erase list.

   *

   * About corruptions
   * ~~~~~~~~~~~~~~~~~
   *
   * UBI protects EC and VID headers with CRC-32 checksums, so it can detect
   * whether the headers are corrupted or not. Sometimes UBI also protects the
   * data with CRC-32, e.g., when it executes the atomic LEB change operation, or
   * when it moves the contents of a PEB for wear-leveling purposes.
   *

   * UBI tries to distinguish between 2 types of corruptions.

   *
   * 1. Corruptions caused by power cuts. These are expected corruptions and UBI
   * tries to handle them gracefully, without printing too many warnings and

   * error messages. The idea is that we do not lose important data in these
   * cases - we may lose only the data which were being written to the media just
   * before the power cut happened, and the upper layers (e.g., UBIFS) are
   * supposed to handle such data losses (e.g., by using the FS journal).

   *
   * When UBI detects a corruption (CRC-32 mismatch) in a PEB, and it looks like
   * the reason is a power cut, UBI puts this PEB to the @erase list, and all
   * PEBs in the @erase list are scheduled for erasure later.

   *
   * 2. Unexpected corruptions which are not caused by power cuts. During

   * attaching, such PEBs are put to the @corr list and UBI preserves them.

   * Obviously, this lessens the amount of available PEBs, and if at some  point
   * UBI runs out of free PEBs, it switches to R/O mode. UBI also loudly informs
   * about such PEBs every time the MTD device is attached.

   *
   * However, it is difficult to reliably distinguish between these types of

   * corruptions and UBI's strategy is as follows (in case of attaching by
   * scanning). UBI assumes corruption type 2 if the VID header is corrupted and
   * the data area does not contain all 0xFFs, and there were no bit-flips or
   * integrity errors (e.g., ECC errors in case of NAND) while reading the data
   * area.  Otherwise UBI assumes corruption type 1. So the decision criteria
   * are as follows.
   *   o If the data area contains only 0xFFs, there are no data, and it is safe

   *     to just erase this PEB - this is corruption type 1.
   *   o If the data area has bit-flips or data integrity errors (ECC errors on

   *     NAND), it is probably a PEB which was being erased when power cut

   *     happened, so this is corruption type 1. However, this is just a guess,
   *     which might be wrong.

   *   o Otherwise this is corruption type 2.

   */
  
  #include <linux/err.h>

  #include <linux/slab.h>

  #include <linux/crc32.h>

  #include <linux/math64.h>

  #include <linux/random.h>

  #include "ubi.h"

  static int self_check_ai(struct ubi_device *ubi, struct ubi_attach_info *ai);

  
  /* Temporary variables used during scanning */
  static struct ubi_ec_hdr *ech;
  static struct ubi_vid_hdr *vidh;

  /**

   * add_to_list - add physical eraseblock to a list.

   * @ai: attaching information

   * @pnum: physical eraseblock number to add

   * @vol_id: the last used volume id for the PEB
   * @lnum: the last used LEB number for the PEB

   * @ec: erase counter of the physical eraseblock

   * @to_head: if not zero, add to the head of the list

   * @list: the list to add to
   *

   * This function allocates a 'struct ubi_ainf_peb' object for physical
   * eraseblock @pnum and adds it to the "free", "erase", or "alien" lists.

   * It stores the @lnum and @vol_id alongside, which can both be
   * %UBI_UNKNOWN if they are not available, not readable, or not assigned.

   * If @to_head is not zero, PEB will be added to the head of the list, which
   * basically means it will be processed first later. E.g., we add corrupted
   * PEBs (corrupted due to power cuts) to the head of the erase list to make
   * sure we erase them first and get rid of corruptions ASAP. This function
   * returns zero in case of success and a negative error code in case of

   * failure.

   */

  static int add_to_list(struct ubi_attach_info *ai, int pnum, int vol_id,
  		       int lnum, int ec, int to_head, struct list_head *list)

  {

  	struct ubi_ainf_peb *aeb;

  	if (list == &ai->free) {

  		dbg_bld("add to free: PEB %d, EC %d", pnum, ec);

  	} else if (list == &ai->erase) {

  		dbg_bld("add to erase: PEB %d, EC %d", pnum, ec);

  	} else if (list == &ai->alien) {

  		dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);

  		ai->alien_peb_count += 1;

  	} else

  		BUG();

  	aeb = kmem_cache_alloc(ai->aeb_slab_cache, GFP_KERNEL);

  	if (!aeb)

  		return -ENOMEM;

  	aeb->pnum = pnum;

  	aeb->vol_id = vol_id;
  	aeb->lnum = lnum;

  	aeb->ec = ec;

  	if (to_head)

  		list_add(&aeb->u.list, list);

  	else

  		list_add_tail(&aeb->u.list, list);

  	return 0;
  }
  
  /**

   * add_corrupted - add a corrupted physical eraseblock.

   * @ai: attaching information

   * @pnum: physical eraseblock number to add
   * @ec: erase counter of the physical eraseblock
   *

   * This function allocates a 'struct ubi_ainf_peb' object for a corrupted
   * physical eraseblock @pnum and adds it to the 'corr' list.  The corruption
   * was presumably not caused by a power cut. Returns zero in case of success
   * and a negative error code in case of failure.

   */

  static int add_corrupted(struct ubi_attach_info *ai, int pnum, int ec)

  {

  	struct ubi_ainf_peb *aeb;

  
  	dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);

  	aeb = kmem_cache_alloc(ai->aeb_slab_cache, GFP_KERNEL);

  	if (!aeb)

  		return -ENOMEM;

  	ai->corr_peb_count += 1;

  	aeb->pnum = pnum;
  	aeb->ec = ec;

  	list_add(&aeb->u.list, &ai->corr);

  	return 0;
  }
  
  /**

   * validate_vid_hdr - check volume identifier header.

   * @vid_hdr: the volume identifier header to check

   * @av: information about the volume this logical eraseblock belongs to

   * @pnum: physical eraseblock number the VID header came from
   *
   * This function checks that data stored in @vid_hdr is consistent. Returns
   * non-zero if an inconsistency was found and zero if not.
   *
   * Note, UBI does sanity check of everything it reads from the flash media.

   * Most of the checks are done in the I/O sub-system. Here we check that the

   * information in the VID header is consistent to the information in other VID
   * headers of the same volume.
   */
  static int validate_vid_hdr(const struct ubi_vid_hdr *vid_hdr,

  			    const struct ubi_ainf_volume *av, int pnum)

  {
  	int vol_type = vid_hdr->vol_type;

  	int vol_id = be32_to_cpu(vid_hdr->vol_id);
  	int used_ebs = be32_to_cpu(vid_hdr->used_ebs);
  	int data_pad = be32_to_cpu(vid_hdr->data_pad);

  	if (av->leb_count != 0) {
  		int av_vol_type;

  
  		/*
  		 * This is not the first logical eraseblock belonging to this
  		 * volume. Ensure that the data in its VID header is consistent
  		 * to the data in previous logical eraseblock headers.
  		 */

  		if (vol_id != av->vol_id) {

  			ubi_err("inconsistent vol_id");

  			goto bad;
  		}

  		if (av->vol_type == UBI_STATIC_VOLUME)
  			av_vol_type = UBI_VID_STATIC;

  		else

  			av_vol_type = UBI_VID_DYNAMIC;

  		if (vol_type != av_vol_type) {

  			ubi_err("inconsistent vol_type");

  			goto bad;
  		}

  		if (used_ebs != av->used_ebs) {

  			ubi_err("inconsistent used_ebs");

  			goto bad;
  		}

  		if (data_pad != av->data_pad) {

  			ubi_err("inconsistent data_pad");

  			goto bad;
  		}
  	}
  
  	return 0;
  
  bad:
  	ubi_err("inconsistent VID header at PEB %d", pnum);

  	ubi_dump_vid_hdr(vid_hdr);

  	ubi_dump_av(av);

  	return -EINVAL;
  }
  
  /**

   * add_volume - add volume to the attaching information.
   * @ai: attaching information

   * @vol_id: ID of the volume to add
   * @pnum: physical eraseblock number
   * @vid_hdr: volume identifier header
   *
   * If the volume corresponding to the @vid_hdr logical eraseblock is already

   * present in the attaching information, this function does nothing. Otherwise
   * it adds corresponding volume to the attaching information. Returns a pointer

   * to the allocated "av" object in case of success and a negative error code in
   * case of failure.

   */

  static struct ubi_ainf_volume *add_volume(struct ubi_attach_info *ai,

  					  int vol_id, int pnum,

  					  const struct ubi_vid_hdr *vid_hdr)
  {

  	struct ubi_ainf_volume *av;

  	struct rb_node **p = &ai->volumes.rb_node, *parent = NULL;

  	ubi_assert(vol_id == be32_to_cpu(vid_hdr->vol_id));

  
  	/* Walk the volume RB-tree to look if this volume is already present */
  	while (*p) {
  		parent = *p;

  		av = rb_entry(parent, struct ubi_ainf_volume, rb);

  		if (vol_id == av->vol_id)
  			return av;

  		if (vol_id > av->vol_id)

  			p = &(*p)->rb_left;
  		else
  			p = &(*p)->rb_right;
  	}
  
  	/* The volume is absent - add it */

  	av = kmalloc(sizeof(struct ubi_ainf_volume), GFP_KERNEL);
  	if (!av)

  		return ERR_PTR(-ENOMEM);

  	av->highest_lnum = av->leb_count = 0;
  	av->vol_id = vol_id;
  	av->root = RB_ROOT;
  	av->used_ebs = be32_to_cpu(vid_hdr->used_ebs);
  	av->data_pad = be32_to_cpu(vid_hdr->data_pad);
  	av->compat = vid_hdr->compat;
  	av->vol_type = vid_hdr->vol_type == UBI_VID_DYNAMIC ? UBI_DYNAMIC_VOLUME

  							    : UBI_STATIC_VOLUME;

  	if (vol_id > ai->highest_vol_id)
  		ai->highest_vol_id = vol_id;

  	rb_link_node(&av->rb, parent, p);
  	rb_insert_color(&av->rb, &ai->volumes);

  	ai->vols_found += 1;

  	dbg_bld("added volume %d", vol_id);

  	return av;

  }
  
  /**

   * ubi_compare_lebs - find out which logical eraseblock is newer.

   * @ubi: UBI device description object

   * @aeb: first logical eraseblock to compare

   * @pnum: physical eraseblock number of the second logical eraseblock to
   * compare
   * @vid_hdr: volume identifier header of the second logical eraseblock
   *
   * This function compares 2 copies of a LEB and informs which one is newer. In
   * case of success this function returns a positive value, in case of failure, a
   * negative error code is returned. The success return codes use the following
   * bits:

   *     o bit 0 is cleared: the first PEB (described by @aeb) is newer than the

   *       second PEB (described by @pnum and @vid_hdr);
   *     o bit 0 is set: the second PEB is newer;
   *     o bit 1 is cleared: no bit-flips were detected in the newer LEB;
   *     o bit 1 is set: bit-flips were detected in the newer LEB;
   *     o bit 2 is cleared: the older LEB is not corrupted;
   *     o bit 2 is set: the older LEB is corrupted.
   */

  int ubi_compare_lebs(struct ubi_device *ubi, const struct ubi_ainf_peb *aeb,

  			int pnum, const struct ubi_vid_hdr *vid_hdr)

  {

  	int len, err, second_is_newer, bitflips = 0, corrupted = 0;
  	uint32_t data_crc, crc;

  	struct ubi_vid_hdr *vh = NULL;

  	unsigned long long sqnum2 = be64_to_cpu(vid_hdr->sqnum);

  	if (sqnum2 == aeb->sqnum) {

  		/*

  		 * This must be a really ancient UBI image which has been
  		 * created before sequence numbers support has been added. At
  		 * that times we used 32-bit LEB versions stored in logical
  		 * eraseblocks. That was before UBI got into mainline. We do not

  		 * support these images anymore. Well, those images still work,
  		 * but only if no unclean reboots happened.

  		 */

  		ubi_err("unsupported on-flash UBI format");

  		return -EINVAL;
  	}

  	/* Obviously the LEB with lower sequence counter is older */

  	second_is_newer = (sqnum2 > aeb->sqnum);

  
  	/*
  	 * Now we know which copy is newer. If the copy flag of the PEB with
  	 * newer version is not set, then we just return, otherwise we have to
  	 * check data CRC. For the second PEB we already have the VID header,
  	 * for the first one - we'll need to re-read it from flash.
  	 *

  	 * Note: this may be optimized so that we wouldn't read twice.

  	 */
  
  	if (second_is_newer) {
  		if (!vid_hdr->copy_flag) {
  			/* It is not a copy, so it is newer */
  			dbg_bld("second PEB %d is newer, copy_flag is unset",
  				pnum);
  			return 1;
  		}
  	} else {

  		if (!aeb->copy_flag) {

  			/* It is not a copy, so it is newer */
  			dbg_bld("first PEB %d is newer, copy_flag is unset",
  				pnum);
  			return bitflips << 1;
  		}

  		vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);

  		if (!vh)

  			return -ENOMEM;

  		pnum = aeb->pnum;

  		err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);

  		if (err) {
  			if (err == UBI_IO_BITFLIPS)
  				bitflips = 1;
  			else {

  				ubi_err("VID of PEB %d header is bad, but it was OK earlier, err %d",
  					pnum, err);

  				if (err > 0)
  					err = -EIO;
  
  				goto out_free_vidh;
  			}
  		}

  		vid_hdr = vh;

  	}
  
  	/* Read the data of the copy and check the CRC */

  	len = be32_to_cpu(vid_hdr->data_size);

  	mutex_lock(&ubi->buf_mutex);
  	err = ubi_io_read_data(ubi, ubi->peb_buf, pnum, 0, len);

  	if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))

  		goto out_unlock;

  	data_crc = be32_to_cpu(vid_hdr->data_crc);

  	crc = crc32(UBI_CRC32_INIT, ubi->peb_buf, len);

  	if (crc != data_crc) {
  		dbg_bld("PEB %d CRC error: calculated %#08x, must be %#08x",
  			pnum, crc, data_crc);
  		corrupted = 1;
  		bitflips = 0;
  		second_is_newer = !second_is_newer;
  	} else {
  		dbg_bld("PEB %d CRC is OK", pnum);
  		bitflips = !!err;
  	}

  	mutex_unlock(&ubi->buf_mutex);

  	ubi_free_vid_hdr(ubi, vh);

  
  	if (second_is_newer)
  		dbg_bld("second PEB %d is newer, copy_flag is set", pnum);
  	else
  		dbg_bld("first PEB %d is newer, copy_flag is set", pnum);
  
  	return second_is_newer | (bitflips << 1) | (corrupted << 2);

  out_unlock:
  	mutex_unlock(&ubi->buf_mutex);

  out_free_vidh:

  	ubi_free_vid_hdr(ubi, vh);

  	return err;
  }
  
  /**

   * ubi_add_to_av - add used physical eraseblock to the attaching information.

   * @ubi: UBI device description object

   * @ai: attaching information

   * @pnum: the physical eraseblock number
   * @ec: erase counter
   * @vid_hdr: the volume identifier header
   * @bitflips: if bit-flips were detected when this physical eraseblock was read
   *

   * This function adds information about a used physical eraseblock to the
   * 'used' tree of the corresponding volume. The function is rather complex
   * because it has to handle cases when this is not the first physical
   * eraseblock belonging to the same logical eraseblock, and the newer one has
   * to be picked, while the older one has to be dropped. This function returns
   * zero in case of success and a negative error code in case of failure.

   */

  int ubi_add_to_av(struct ubi_device *ubi, struct ubi_attach_info *ai, int pnum,
  		  int ec, const struct ubi_vid_hdr *vid_hdr, int bitflips)

  {
  	int err, vol_id, lnum;

  	unsigned long long sqnum;

  	struct ubi_ainf_volume *av;

  	struct ubi_ainf_peb *aeb;

  	struct rb_node **p, *parent = NULL;

  	vol_id = be32_to_cpu(vid_hdr->vol_id);
  	lnum = be32_to_cpu(vid_hdr->lnum);
  	sqnum = be64_to_cpu(vid_hdr->sqnum);

  	dbg_bld("PEB %d, LEB %d:%d, EC %d, sqnum %llu, bitflips %d",
  		pnum, vol_id, lnum, ec, sqnum, bitflips);

  	av = add_volume(ai, vol_id, pnum, vid_hdr);
  	if (IS_ERR(av))
  		return PTR_ERR(av);

  	if (ai->max_sqnum < sqnum)
  		ai->max_sqnum = sqnum;

  	/*
  	 * Walk the RB-tree of logical eraseblocks of volume @vol_id to look
  	 * if this is the first instance of this logical eraseblock or not.
  	 */

  	p = &av->root.rb_node;

  	while (*p) {
  		int cmp_res;
  
  		parent = *p;

  		aeb = rb_entry(parent, struct ubi_ainf_peb, u.rb);
  		if (lnum != aeb->lnum) {
  			if (lnum < aeb->lnum)

  				p = &(*p)->rb_left;
  			else
  				p = &(*p)->rb_right;
  			continue;
  		}
  
  		/*
  		 * There is already a physical eraseblock describing the same
  		 * logical eraseblock present.
  		 */

  		dbg_bld("this LEB already exists: PEB %d, sqnum %llu, EC %d",
  			aeb->pnum, aeb->sqnum, aeb->ec);

  
  		/*
  		 * Make sure that the logical eraseblocks have different
  		 * sequence numbers. Otherwise the image is bad.
  		 *

  		 * However, if the sequence number is zero, we assume it must
  		 * be an ancient UBI image from the era when UBI did not have
  		 * sequence numbers. We still can attach these images, unless
  		 * there is a need to distinguish between old and new
  		 * eraseblocks, in which case we'll refuse the image in

  		 * 'ubi_compare_lebs()'. In other words, we attach old clean

  		 * images, but refuse attaching old images with duplicated
  		 * logical eraseblocks because there was an unclean reboot.

  		 */

  		if (aeb->sqnum == sqnum && sqnum != 0) {

  			ubi_err("two LEBs with same sequence number %llu",
  				sqnum);

  			ubi_dump_aeb(aeb, 0);

  			ubi_dump_vid_hdr(vid_hdr);

  			return -EINVAL;
  		}
  
  		/*
  		 * Now we have to drop the older one and preserve the newer
  		 * one.
  		 */

  		cmp_res = ubi_compare_lebs(ubi, aeb, pnum, vid_hdr);

  		if (cmp_res < 0)
  			return cmp_res;
  
  		if (cmp_res & 1) {
  			/*

  			 * This logical eraseblock is newer than the one

  			 * found earlier.
  			 */

  			err = validate_vid_hdr(vid_hdr, av, pnum);

  			if (err)
  				return err;

  			err = add_to_list(ai, aeb->pnum, aeb->vol_id,
  					  aeb->lnum, aeb->ec, cmp_res & 4,

  					  &ai->erase);

  			if (err)
  				return err;

  			aeb->ec = ec;
  			aeb->pnum = pnum;

  			aeb->vol_id = vol_id;
  			aeb->lnum = lnum;

  			aeb->scrub = ((cmp_res & 2) || bitflips);
  			aeb->copy_flag = vid_hdr->copy_flag;
  			aeb->sqnum = sqnum;

  			if (av->highest_lnum == lnum)
  				av->last_data_size =

  					be32_to_cpu(vid_hdr->data_size);

  
  			return 0;
  		} else {
  			/*

  			 * This logical eraseblock is older than the one found

  			 * previously.
  			 */

  			return add_to_list(ai, pnum, vol_id, lnum, ec,
  					   cmp_res & 4, &ai->erase);

  		}
  	}
  
  	/*
  	 * We've met this logical eraseblock for the first time, add it to the

  	 * attaching information.

  	 */

  	err = validate_vid_hdr(vid_hdr, av, pnum);

  	if (err)
  		return err;

  	aeb = kmem_cache_alloc(ai->aeb_slab_cache, GFP_KERNEL);

  	if (!aeb)

  		return -ENOMEM;

  	aeb->ec = ec;
  	aeb->pnum = pnum;

  	aeb->vol_id = vol_id;

  	aeb->lnum = lnum;
  	aeb->scrub = bitflips;
  	aeb->copy_flag = vid_hdr->copy_flag;
  	aeb->sqnum = sqnum;

  	if (av->highest_lnum <= lnum) {
  		av->highest_lnum = lnum;
  		av->last_data_size = be32_to_cpu(vid_hdr->data_size);

  	}

  	av->leb_count += 1;

  	rb_link_node(&aeb->u.rb, parent, p);

  	rb_insert_color(&aeb->u.rb, &av->root);

  	return 0;
  }
  
  /**

   * ubi_find_av - find volume in the attaching information.

   * @ai: attaching information

   * @vol_id: the requested volume ID
   *
   * This function returns a pointer to the volume description or %NULL if there

   * are no data about this volume in the attaching information.

   */

  struct ubi_ainf_volume *ubi_find_av(const struct ubi_attach_info *ai,
  				    int vol_id)

  {

  	struct ubi_ainf_volume *av;

  	struct rb_node *p = ai->volumes.rb_node;

  
  	while (p) {

  		av = rb_entry(p, struct ubi_ainf_volume, rb);

  		if (vol_id == av->vol_id)
  			return av;

  		if (vol_id > av->vol_id)

  			p = p->rb_left;
  		else
  			p = p->rb_right;
  	}
  
  	return NULL;
  }
  
  /**

   * ubi_remove_av - delete attaching information about a volume.

   * @ai: attaching information

   * @av: the volume attaching information to delete

   */

  void ubi_remove_av(struct ubi_attach_info *ai, struct ubi_ainf_volume *av)

  {
  	struct rb_node *rb;

  	struct ubi_ainf_peb *aeb;

  	dbg_bld("remove attaching information about volume %d", av->vol_id);

  	while ((rb = rb_first(&av->root))) {

  		aeb = rb_entry(rb, struct ubi_ainf_peb, u.rb);

  		rb_erase(&aeb->u.rb, &av->root);

  		list_add_tail(&aeb->u.list, &ai->erase);

  	}

  	rb_erase(&av->rb, &ai->volumes);
  	kfree(av);

  	ai->vols_found -= 1;

  }
  
  /**

   * early_erase_peb - erase a physical eraseblock.

   * @ubi: UBI device description object

   * @ai: attaching information

   * @pnum: physical eraseblock number to erase;

   * @ec: erase counter value to write (%UBI_UNKNOWN if it is unknown)

   *
   * This function erases physical eraseblock 'pnum', and writes the erase
   * counter header to it. This function should only be used on UBI device

   * initialization stages, when the EBA sub-system had not been yet initialized.
   * This function returns zero in case of success and a negative error code in
   * case of failure.

   */

  static int early_erase_peb(struct ubi_device *ubi,
  			   const struct ubi_attach_info *ai, int pnum, int ec)

  {
  	int err;
  	struct ubi_ec_hdr *ec_hdr;

  	if ((long long)ec >= UBI_MAX_ERASECOUNTER) {
  		/*
  		 * Erase counter overflow. Upgrade UBI and use 64-bit
  		 * erase counters internally.
  		 */
  		ubi_err("erase counter overflow at PEB %d, EC %d", pnum, ec);
  		return -EINVAL;
  	}

  	ec_hdr = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
  	if (!ec_hdr)
  		return -ENOMEM;

  	ec_hdr->ec = cpu_to_be64(ec);

  
  	err = ubi_io_sync_erase(ubi, pnum, 0);
  	if (err < 0)
  		goto out_free;
  
  	err = ubi_io_write_ec_hdr(ubi, pnum, ec_hdr);
  
  out_free:
  	kfree(ec_hdr);
  	return err;
  }
  
  /**

   * ubi_early_get_peb - get a free physical eraseblock.

   * @ubi: UBI device description object

   * @ai: attaching information

   *
   * This function returns a free physical eraseblock. It is supposed to be

   * called on the UBI initialization stages when the wear-leveling sub-system is
   * not initialized yet. This function picks a physical eraseblocks from one of
   * the lists, writes the EC header if it is needed, and removes it from the
   * list.

   *

   * This function returns a pointer to the "aeb" of the found free PEB in case
   * of success and an error code in case of failure.

   */

  struct ubi_ainf_peb *ubi_early_get_peb(struct ubi_device *ubi,
  				       struct ubi_attach_info *ai)

  {

  	int err = 0;

  	struct ubi_ainf_peb *aeb, *tmp_aeb;

  	if (!list_empty(&ai->free)) {
  		aeb = list_entry(ai->free.next, struct ubi_ainf_peb, u.list);

  		list_del(&aeb->u.list);
  		dbg_bld("return free PEB %d, EC %d", aeb->pnum, aeb->ec);
  		return aeb;

  	}

  	/*
  	 * We try to erase the first physical eraseblock from the erase list
  	 * and pick it if we succeed, or try to erase the next one if not. And
  	 * so forth. We don't want to take care about bad eraseblocks here -
  	 * they'll be handled later.
  	 */

  	list_for_each_entry_safe(aeb, tmp_aeb, &ai->erase, u.list) {

  		if (aeb->ec == UBI_UNKNOWN)

  			aeb->ec = ai->mean_ec;

  		err = early_erase_peb(ubi, ai, aeb->pnum, aeb->ec+1);

  		if (err)
  			continue;

  		aeb->ec += 1;
  		list_del(&aeb->u.list);
  		dbg_bld("return PEB %d, EC %d", aeb->pnum, aeb->ec);
  		return aeb;

  	}

  	ubi_err("no free eraseblocks");

  	return ERR_PTR(-ENOSPC);
  }
  
  /**

   * check_corruption - check the data area of PEB.

   * @ubi: UBI device description object

   * @vid_hdr: the (corrupted) VID header of this PEB

   * @pnum: the physical eraseblock number to check
   *
   * This is a helper function which is used to distinguish between VID header
   * corruptions caused by power cuts and other reasons. If the PEB contains only

   * 0xFF bytes in the data area, the VID header is most probably corrupted

   * because of a power cut (%0 is returned in this case). Otherwise, it was

   * probably corrupted for some other reasons (%1 is returned in this case). A
   * negative error code is returned if a read error occurred.

   *
   * If the corruption reason was a power cut, UBI can safely erase this PEB.
   * Otherwise, it should preserve it to avoid possibly destroying important
   * information.
   */

  static int check_corruption(struct ubi_device *ubi, struct ubi_vid_hdr *vid_hdr,
  			    int pnum)

  {
  	int err;
  
  	mutex_lock(&ubi->buf_mutex);

  	memset(ubi->peb_buf, 0x00, ubi->leb_size);

  	err = ubi_io_read(ubi, ubi->peb_buf, pnum, ubi->leb_start,

  			  ubi->leb_size);

  	if (err == UBI_IO_BITFLIPS || mtd_is_eccerr(err)) {

  		/*
  		 * Bit-flips or integrity errors while reading the data area.
  		 * It is difficult to say for sure what type of corruption is
  		 * this, but presumably a power cut happened while this PEB was
  		 * erased, so it became unstable and corrupted, and should be
  		 * erased.
  		 */

  		err = 0;
  		goto out_unlock;

  	}
  
  	if (err)

  		goto out_unlock;

  	if (ubi_check_pattern(ubi->peb_buf, 0xFF, ubi->leb_size))

  		goto out_unlock;

  	ubi_err("PEB %d contains corrupted VID header, and the data does not contain all 0xFF",
  		pnum);
  	ubi_err("this may be a non-UBI PEB or a severe VID header corruption which requires manual inspection");

  	ubi_dump_vid_hdr(vid_hdr);

  	pr_err("hexdump of PEB %d offset %d, length %d",
  	       pnum, ubi->leb_start, ubi->leb_size);

  	ubi_dbg_print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 1,

  			       ubi->peb_buf, ubi->leb_size, 1);

  	err = 1;
  
  out_unlock:

  	mutex_unlock(&ubi->buf_mutex);

  	return err;

  }
  
  /**

   * scan_peb - scan and process UBI headers of a PEB.

   * @ubi: UBI device description object

   * @ai: attaching information

   * @pnum: the physical eraseblock number

   * @vid: The volume ID of the found volume will be stored in this pointer
   * @sqnum: The sqnum of the found volume will be stored in this pointer

   *

   * This function reads UBI headers of PEB @pnum, checks them, and adds
   * information about this PEB to the corresponding list or RB-tree in the
   * "attaching info" structure. Returns zero if the physical eraseblock was
   * successfully handled and a negative error code in case of failure.

   */

  static int scan_peb(struct ubi_device *ubi, struct ubi_attach_info *ai,

  		    int pnum, int *vid, unsigned long long *sqnum)

  {

  	long long uninitialized_var(ec);

  	int err, bitflips = 0, vol_id = -1, ec_err = 0;

  
  	dbg_bld("scan PEB %d", pnum);
  
  	/* Skip bad physical eraseblocks */
  	err = ubi_io_is_bad(ubi, pnum);
  	if (err < 0)
  		return err;
  	else if (err) {

  		ai->bad_peb_count += 1;

  		return 0;
  	}
  
  	err = ubi_io_read_ec_hdr(ubi, pnum, ech, 0);
  	if (err < 0)
  		return err;

  	switch (err) {
  	case 0:
  		break;
  	case UBI_IO_BITFLIPS:

  		bitflips = 1;

  		break;
  	case UBI_IO_FF:

  		ai->empty_peb_count += 1;

  		return add_to_list(ai, pnum, UBI_UNKNOWN, UBI_UNKNOWN,
  				   UBI_UNKNOWN, 0, &ai->erase);

  	case UBI_IO_FF_BITFLIPS:

  		ai->empty_peb_count += 1;

  		return add_to_list(ai, pnum, UBI_UNKNOWN, UBI_UNKNOWN,
  				   UBI_UNKNOWN, 1, &ai->erase);

  	case UBI_IO_BAD_HDR_EBADMSG:

  	case UBI_IO_BAD_HDR:

  		/*
  		 * We have to also look at the VID header, possibly it is not
  		 * corrupted. Set %bitflips flag in order to make this PEB be
  		 * moved and EC be re-created.
  		 */

  		ec_err = err;

  		ec = UBI_UNKNOWN;

  		bitflips = 1;

  		break;
  	default:
  		ubi_err("'ubi_io_read_ec_hdr()' returned unknown code %d", err);
  		return -EINVAL;

  	}

  	if (!ec_err) {

  		int image_seq;

  		/* Make sure UBI version is OK */
  		if (ech->version != UBI_VERSION) {
  			ubi_err("this UBI version is %d, image version is %d",
  				UBI_VERSION, (int)ech->version);
  			return -EINVAL;
  		}

  		ec = be64_to_cpu(ech->ec);

  		if (ec > UBI_MAX_ERASECOUNTER) {
  			/*
  			 * Erase counter overflow. The EC headers have 64 bits
  			 * reserved, but we anyway make use of only 31 bit
  			 * values, as this seems to be enough for any existing
  			 * flash. Upgrade UBI and use 64-bit erase counters
  			 * internally.
  			 */
  			ubi_err("erase counter overflow, max is %d",
  				UBI_MAX_ERASECOUNTER);

  			ubi_dump_ec_hdr(ech);

  			return -EINVAL;
  		}

  		/*
  		 * Make sure that all PEBs have the same image sequence number.
  		 * This allows us to detect situations when users flash UBI
  		 * images incorrectly, so that the flash has the new UBI image
  		 * and leftovers from the old one. This feature was added
  		 * relatively recently, and the sequence number was always
  		 * zero, because old UBI implementations always set it to zero.
  		 * For this reasons, we do not panic if some PEBs have zero
  		 * sequence number, while other PEBs have non-zero sequence
  		 * number.
  		 */

  		image_seq = be32_to_cpu(ech->image_seq);

  		if (!ubi->image_seq)

  			ubi->image_seq = image_seq;

  		if (image_seq && ubi->image_seq != image_seq) {

  			ubi_err("bad image sequence number %d in PEB %d, expected %d",
  				image_seq, pnum, ubi->image_seq);

  			ubi_dump_ec_hdr(ech);

  			return -EINVAL;
  		}

  	}
  
  	/* OK, we've done with the EC header, let's look at the VID header */
  
  	err = ubi_io_read_vid_hdr(ubi, pnum, vidh, 0);
  	if (err < 0)
  		return err;

  	switch (err) {
  	case 0:
  		break;
  	case UBI_IO_BITFLIPS:

  		bitflips = 1;

  		break;
  	case UBI_IO_BAD_HDR_EBADMSG:

  		if (ec_err == UBI_IO_BAD_HDR_EBADMSG)
  			/*
  			 * Both EC and VID headers are corrupted and were read
  			 * with data integrity error, probably this is a bad
  			 * PEB, bit it is not marked as bad yet. This may also
  			 * be a result of power cut during erasure.
  			 */

  			ai->maybe_bad_peb_count += 1;

  	case UBI_IO_BAD_HDR:

  		if (ec_err)
  			/*
  			 * Both headers are corrupted. There is a possibility
  			 * that this a valid UBI PEB which has corresponding
  			 * LEB, but the headers are corrupted. However, it is
  			 * impossible to distinguish it from a PEB which just

  			 * contains garbage because of a power cut during erase

  			 * operation. So we just schedule this PEB for erasure.

  			 *

  			 * Besides, in case of NOR flash, we deliberately

  			 * corrupt both headers because NOR flash erasure is
  			 * slow and can start from the end.

  			 */
  			err = 0;
  		else
  			/*
  			 * The EC was OK, but the VID header is corrupted. We
  			 * have to check what is in the data area.
  			 */

  			err = check_corruption(ubi, vidh, pnum);

  
  		if (err < 0)
  			return err;
  		else if (!err)

  			/* This corruption is caused by a power cut */

  			err = add_to_list(ai, pnum, UBI_UNKNOWN,
  					  UBI_UNKNOWN, ec, 1, &ai->erase);

  		else
  			/* This is an unexpected corruption */

  			err = add_corrupted(ai, pnum, ec);

  		if (err)
  			return err;
  		goto adjust_mean_ec;

  	case UBI_IO_FF_BITFLIPS:

  		err = add_to_list(ai, pnum, UBI_UNKNOWN, UBI_UNKNOWN,
  				  ec, 1, &ai->erase);

  		if (err)
  			return err;
  		goto adjust_mean_ec;

  	case UBI_IO_FF:

  		if (ec_err || bitflips)

  			err = add_to_list(ai, pnum, UBI_UNKNOWN,
  					  UBI_UNKNOWN, ec, 1, &ai->erase);

  		else

  			err = add_to_list(ai, pnum, UBI_UNKNOWN,
  					  UBI_UNKNOWN, ec, 0, &ai->free);

  		if (err)
  			return err;
  		goto adjust_mean_ec;

  	default:
  		ubi_err("'ubi_io_read_vid_hdr()' returned unknown code %d",
  			err);
  		return -EINVAL;

  	}

  	vol_id = be32_to_cpu(vidh->vol_id);

  	if (vid)
  		*vid = vol_id;
  	if (sqnum)
  		*sqnum = be64_to_cpu(vidh->sqnum);

  	if (vol_id > UBI_MAX_VOLUMES && vol_id != UBI_LAYOUT_VOLUME_ID) {

  		int lnum = be32_to_cpu(vidh->lnum);

  
  		/* Unsupported internal volume */
  		switch (vidh->compat) {
  		case UBI_COMPAT_DELETE:

  			if (vol_id != UBI_FM_SB_VOLUME_ID
  			    && vol_id != UBI_FM_DATA_VOLUME_ID) {
  				ubi_msg("\"delete\" compatible internal volume %d:%d found, will remove it",
  					vol_id, lnum);
  			}

  			err = add_to_list(ai, pnum, vol_id, lnum,
  					  ec, 1, &ai->erase);

  			if (err)
  				return err;

  			return 0;

  
  		case UBI_COMPAT_RO:

  			ubi_msg("read-only compatible internal volume %d:%d found, switch to read-only mode",

  				vol_id, lnum);
  			ubi->ro_mode = 1;
  			break;
  
  		case UBI_COMPAT_PRESERVE:

  			ubi_msg("\"preserve\" compatible internal volume %d:%d found",
  				vol_id, lnum);

  			err = add_to_list(ai, pnum, vol_id, lnum,
  					  ec, 0, &ai->alien);

  			if (err)
  				return err;

  			return 0;
  
  		case UBI_COMPAT_REJECT:
  			ubi_err("incompatible internal volume %d:%d found",
  				vol_id, lnum);
  			return -EINVAL;
  		}
  	}

  	if (ec_err)

  		ubi_warn("valid VID header but corrupted EC header at PEB %d",
  			 pnum);

  	err = ubi_add_to_av(ubi, ai, pnum, ec, vidh, bitflips);

  	if (err)
  		return err;
  
  adjust_mean_ec:

  	if (!ec_err) {

  		ai->ec_sum += ec;
  		ai->ec_count += 1;
  		if (ec > ai->max_ec)
  			ai->max_ec = ec;
  		if (ec < ai->min_ec)
  			ai->min_ec = ec;

  	}
  
  	return 0;
  }
  
  /**

   * late_analysis - analyze the overall situation with PEB.

   * @ubi: UBI device description object

   * @ai: attaching information

   *

   * This is a helper function which takes a look what PEBs we have after we
   * gather information about all of them ("ai" is compete). It decides whether
   * the flash is empty and should be formatted of whether there are too many
   * corrupted PEBs and we should not attach this MTD device. Returns zero if we
   * should proceed with attaching the MTD device, and %-EINVAL if we should not.

   */

  static int late_analysis(struct ubi_device *ubi, struct ubi_attach_info *ai)

  {

  	struct ubi_ainf_peb *aeb;

  	int max_corr, peb_count;

  	peb_count = ubi->peb_count - ai->bad_peb_count - ai->alien_peb_count;

  	max_corr = peb_count / 20 ?: 8;

  
  	/*

  	 * Few corrupted PEBs is not a problem and may be just a result of

  	 * unclean reboots. However, many of them may indicate some problems
  	 * with the flash HW or driver.
  	 */

  	if (ai->corr_peb_count) {

  		ubi_err("%d PEBs are corrupted and preserved",

  			ai->corr_peb_count);

  		pr_err("Corrupted PEBs are:");

  		list_for_each_entry(aeb, &ai->corr, u.list)

  			pr_cont(" %d", aeb->pnum);
  		pr_cont("
  ");

  
  		/*
  		 * If too many PEBs are corrupted, we refuse attaching,
  		 * otherwise, only print a warning.
  		 */

  		if (ai->corr_peb_count >= max_corr) {

  			ubi_err("too many corrupted PEBs, refusing");

  			return -EINVAL;
  		}
  	}

  	if (ai->empty_peb_count + ai->maybe_bad_peb_count == peb_count) {

  		/*
  		 * All PEBs are empty, or almost all - a couple PEBs look like
  		 * they may be bad PEBs which were not marked as bad yet.
  		 *
  		 * This piece of code basically tries to distinguish between
  		 * the following situations:
  		 *
  		 * 1. Flash is empty, but there are few bad PEBs, which are not
  		 *    marked as bad so far, and which were read with error. We
  		 *    want to go ahead and format this flash. While formatting,
  		 *    the faulty PEBs will probably be marked as bad.
  		 *
  		 * 2. Flash contains non-UBI data and we do not want to format
  		 *    it and destroy possibly important information.
  		 */

  		if (ai->maybe_bad_peb_count <= 2) {
  			ai->is_empty = 1;

  			ubi_msg("empty MTD device detected");

  			get_random_bytes(&ubi->image_seq,
  					 sizeof(ubi->image_seq));

  		} else {

  			ubi_err("MTD device is not UBI-formatted and possibly contains non-UBI data - refusing it");

  			return -EINVAL;
  		}

  	}

  	return 0;
  }
  
  /**

   * destroy_av - free volume attaching information.
   * @av: volume attaching information
   * @ai: attaching information
   *
   * This function destroys the volume attaching information.
   */
  static void destroy_av(struct ubi_attach_info *ai, struct ubi_ainf_volume *av)
  {
  	struct ubi_ainf_peb *aeb;
  	struct rb_node *this = av->root.rb_node;
  
  	while (this) {
  		if (this->rb_left)
  			this = this->rb_left;
  		else if (this->rb_right)
  			this = this->rb_right;
  		else {
  			aeb = rb_entry(this, struct ubi_ainf_peb, u.rb);
  			this = rb_parent(this);
  			if (this) {
  				if (this->rb_left == &aeb->u.rb)
  					this->rb_left = NULL;
  				else
  					this->rb_right = NULL;
  			}
  
  			kmem_cache_free(ai->aeb_slab_cache, aeb);
  		}
  	}
  	kfree(av);
  }
  
  /**
   * destroy_ai - destroy attaching information.
   * @ai: attaching information
   */
  static void destroy_ai(struct ubi_attach_info *ai)
  {
  	struct ubi_ainf_peb *aeb, *aeb_tmp;
  	struct ubi_ainf_volume *av;
  	struct rb_node *rb;
  
  	list_for_each_entry_safe(aeb, aeb_tmp, &ai->alien, u.list) {
  		list_del(&aeb->u.list);
  		kmem_cache_free(ai->aeb_slab_cache, aeb);
  	}
  	list_for_each_entry_safe(aeb, aeb_tmp, &ai->erase, u.list) {
  		list_del(&aeb->u.list);
  		kmem_cache_free(ai->aeb_slab_cache, aeb);
  	}
  	list_for_each_entry_safe(aeb, aeb_tmp, &ai->corr, u.list) {
  		list_del(&aeb->u.list);
  		kmem_cache_free(ai->aeb_slab_cache, aeb);
  	}
  	list_for_each_entry_safe(aeb, aeb_tmp, &ai->free, u.list) {
  		list_del(&aeb->u.list);
  		kmem_cache_free(ai->aeb_slab_cache, aeb);
  	}
  
  	/* Destroy the volume RB-tree */
  	rb = ai->volumes.rb_node;
  	while (rb) {
  		if (rb->rb_left)
  			rb = rb->rb_left;
  		else if (rb->rb_right)
  			rb = rb->rb_right;
  		else {
  			av = rb_entry(rb, struct ubi_ainf_volume, rb);
  
  			rb = rb_parent(rb);
  			if (rb) {
  				if (rb->rb_left == &av->rb)
  					rb->rb_left = NULL;
  				else
  					rb->rb_right = NULL;
  			}
  
  			destroy_av(ai, av);
  		}
  	}
  
  	if (ai->aeb_slab_cache)
  		kmem_cache_destroy(ai->aeb_slab_cache);
  
  	kfree(ai);
  }
  
  /**

   * scan_all - scan entire MTD device.

   * @ubi: UBI device description object

   * @ai: attach info object
   * @start: start scanning at this PEB

   *
   * This function does full scanning of an MTD device and returns complete

   * information about it in form of a "struct ubi_attach_info" object. In case
   * of failure, an error code is returned.

   */

  static int scan_all(struct ubi_device *ubi, struct ubi_attach_info *ai,
  		    int start)

  {
  	int err, pnum;
  	struct rb_node *rb1, *rb2;

  	struct ubi_ainf_volume *av;

  	struct ubi_ainf_peb *aeb;

  
  	err = -ENOMEM;

  	ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
  	if (!ech)

  		return err;

  	vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);

  	if (!vidh)
  		goto out_ech;

  	for (pnum = start; pnum < ubi->peb_count; pnum++) {

  		cond_resched();

  		dbg_gen("process PEB %d", pnum);

  		err = scan_peb(ubi, ai, pnum, NULL, NULL);

  		if (err < 0)
  			goto out_vidh;
  	}

  	ubi_msg("scanning is finished");

  	/* Calculate mean erase counter */

  	if (ai->ec_count)
  		ai->mean_ec = div_u64(ai->ec_sum, ai->ec_count);

  	err = late_analysis(ubi, ai);

  	if (err)
  		goto out_vidh;

  
  	/*

  	 * In case of unknown erase counter we use the mean erase counter
  	 * value.
  	 */

  	ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
  		ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb)

  			if (aeb->ec == UBI_UNKNOWN)

  				aeb->ec = ai->mean_ec;

  	}

  	list_for_each_entry(aeb, &ai->free, u.list) {

  		if (aeb->ec == UBI_UNKNOWN)

  			aeb->ec = ai->mean_ec;

  	}

  	list_for_each_entry(aeb, &ai->corr, u.list)

  		if (aeb->ec == UBI_UNKNOWN)

  			aeb->ec = ai->mean_ec;

  	list_for_each_entry(aeb, &ai->erase, u.list)

  		if (aeb->ec == UBI_UNKNOWN)

  			aeb->ec = ai->mean_ec;

  	err = self_check_ai(ubi, ai);

  	if (err)

  		goto out_vidh;

  
  	ubi_free_vid_hdr(ubi, vidh);
  	kfree(ech);

  	return 0;

  
  out_vidh:
  	ubi_free_vid_hdr(ubi, vidh);
  out_ech:
  	kfree(ech);

  	return err;
  }
  
  #ifdef CONFIG_MTD_UBI_FASTMAP
  
  /**
   * scan_fastmap - try to find a fastmap and attach from it.
   * @ubi: UBI device description object
   * @ai: attach info object
   *
   * Returns 0 on success, negative return values indicate an internal
   * error.
   * UBI_NO_FASTMAP denotes that no fastmap was found.
   * UBI_BAD_FASTMAP denotes that the found fastmap was invalid.
   */
  static int scan_fast(struct ubi_device *ubi, struct ubi_attach_info *ai)
  {
  	int err, pnum, fm_anchor = -1;
  	unsigned long long max_sqnum = 0;
  
  	err = -ENOMEM;
  
  	ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
  	if (!ech)
  		goto out;
  
  	vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
  	if (!vidh)
  		goto out_ech;
  
  	for (pnum = 0; pnum < UBI_FM_MAX_START; pnum++) {
  		int vol_id = -1;
  		unsigned long long sqnum = -1;
  		cond_resched();
  
  		dbg_gen("process PEB %d", pnum);
  		err = scan_peb(ubi, ai, pnum, &vol_id, &sqnum);
  		if (err < 0)
  			goto out_vidh;
  
  		if (vol_id == UBI_FM_SB_VOLUME_ID && sqnum > max_sqnum) {
  			max_sqnum = sqnum;
  			fm_anchor = pnum;
  		}
  	}
  
  	ubi_free_vid_hdr(ubi, vidh);
  	kfree(ech);
  
  	if (fm_anchor < 0)
  		return UBI_NO_FASTMAP;
  
  	return ubi_scan_fastmap(ubi, ai, fm_anchor);
  
  out_vidh:
  	ubi_free_vid_hdr(ubi, vidh);
  out_ech:
  	kfree(ech);
  out:
  	return err;
  }
  
  #endif
  
  static struct ubi_attach_info *alloc_ai(const char *slab_name)
  {
  	struct ubi_attach_info *ai;
  
  	ai = kzalloc(sizeof(struct ubi_attach_info), GFP_KERNEL);
  	if (!ai)
  		return ai;
  
  	INIT_LIST_HEAD(&ai->corr);
  	INIT_LIST_HEAD(&ai->free);
  	INIT_LIST_HEAD(&ai->erase);
  	INIT_LIST_HEAD(&ai->alien);
  	ai->volumes = RB_ROOT;
  	ai->aeb_slab_cache = kmem_cache_create(slab_name,
  					       sizeof(struct ubi_ainf_peb),
  					       0, 0, NULL);
  	if (!ai->aeb_slab_cache) {
  		kfree(ai);
  		ai = NULL;
  	}
  
  	return ai;

  }
  
  /**

   * ubi_attach - attach an MTD device.
   * @ubi: UBI device descriptor

   * @force_scan: if set to non-zero attach by scanning

   *
   * This function returns zero in case of success and a negative error code in
   * case of failure.
   */

  int ubi_attach(struct ubi_device *ubi, int force_scan)

  {
  	int err;
  	struct ubi_attach_info *ai;

  	ai = alloc_ai("ubi_aeb_slab_cache");
  	if (!ai)
  		return -ENOMEM;
  
  #ifdef CONFIG_MTD_UBI_FASTMAP
  	/* On small flash devices we disable fastmap in any case. */
  	if ((int)mtd_div_by_eb(ubi->mtd->size, ubi->mtd) <= UBI_FM_MAX_START) {
  		ubi->fm_disabled = 1;
  		force_scan = 1;
  	}
  
  	if (force_scan)
  		err = scan_all(ubi, ai, 0);
  	else {
  		err = scan_fast(ubi, ai);
  		if (err > 0) {
  			if (err != UBI_NO_FASTMAP) {
  				destroy_ai(ai);
  				ai = alloc_ai("ubi_aeb_slab_cache2");
  				if (!ai)
  					return -ENOMEM;

  				err = scan_all(ubi, ai, 0);
  			} else {
  				err = scan_all(ubi, ai, UBI_FM_MAX_START);
  			}

  		}
  	}
  #else
  	err = scan_all(ubi, ai, 0);
  #endif
  	if (err)
  		goto out_ai;

  
  	ubi->bad_peb_count = ai->bad_peb_count;
  	ubi->good_peb_count = ubi->peb_count - ubi->bad_peb_count;
  	ubi->corr_peb_count = ai->corr_peb_count;
  	ubi->max_ec = ai->max_ec;
  	ubi->mean_ec = ai->mean_ec;

  	dbg_gen("max. sequence number:       %llu", ai->max_sqnum);

  
  	err = ubi_read_volume_table(ubi, ai);
  	if (err)
  		goto out_ai;
  
  	err = ubi_wl_init(ubi, ai);
  	if (err)
  		goto out_vtbl;
  
  	err = ubi_eba_init(ubi, ai);
  	if (err)
  		goto out_wl;

  #ifdef CONFIG_MTD_UBI_FASTMAP

  	if (ubi->fm && ubi_dbg_chk_gen(ubi)) {

  		struct ubi_attach_info *scan_ai;
  
  		scan_ai = alloc_ai("ubi_ckh_aeb_slab_cache");

  		if (!scan_ai) {
  			err = -ENOMEM;

  			goto out_wl;

  		}

  
  		err = scan_all(ubi, scan_ai, 0);
  		if (err) {
  			destroy_ai(scan_ai);
  			goto out_wl;
  		}
  
  		err = self_check_eba(ubi, ai, scan_ai);
  		destroy_ai(scan_ai);
  
  		if (err)
  			goto out_wl;
  	}
  #endif
  
  	destroy_ai(ai);

  	return 0;
  
  out_wl:
  	ubi_wl_close(ubi);
  out_vtbl:
  	ubi_free_internal_volumes(ubi);
  	vfree(ubi->vtbl);
  out_ai:

  	destroy_ai(ai);

  	return err;
  }
  
  /**

   * self_check_ai - check the attaching information.

   * @ubi: UBI device description object

   * @ai: attaching information

   *

   * This function returns zero if the attaching information is all right, and a

   * negative error code if not or if an error occurred.

   */

  static int self_check_ai(struct ubi_device *ubi, struct ubi_attach_info *ai)

  {
  	int pnum, err, vols_found = 0;
  	struct rb_node *rb1, *rb2;

  	struct ubi_ainf_volume *av;

  	struct ubi_ainf_peb *aeb, *last_aeb;

  	uint8_t *buf;

  	if (!ubi_dbg_chk_gen(ubi))

  		return 0;

  	/*

  	 * At first, check that attaching information is OK.

  	 */

  	ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {

  		int leb_count = 0;
  
  		cond_resched();
  
  		vols_found += 1;

  		if (ai->is_empty) {

  			ubi_err("bad is_empty flag");

  			goto bad_av;

  		}

  		if (av->vol_id < 0 || av->highest_lnum < 0 ||
  		    av->leb_count < 0 || av->vol_type < 0 || av->used_ebs < 0 ||
  		    av->data_pad < 0 || av->last_data_size < 0) {

  			ubi_err("negative values");

  			goto bad_av;

  		}

  		if (av->vol_id >= UBI_MAX_VOLUMES &&
  		    av->vol_id < UBI_INTERNAL_VOL_START) {

  			ubi_err("bad vol_id");

  			goto bad_av;

  		}

  		if (av->vol_id > ai->highest_vol_id) {

  			ubi_err("highest_vol_id is %d, but vol_id %d is there",

  				ai->highest_vol_id, av->vol_id);

  			goto out;
  		}

  		if (av->vol_type != UBI_DYNAMIC_VOLUME &&
  		    av->vol_type != UBI_STATIC_VOLUME) {

  			ubi_err("bad vol_type");

  			goto bad_av;

  		}

  		if (av->data_pad > ubi->leb_size / 2) {

  			ubi_err("bad data_pad");

  			goto bad_av;

  		}

  		last_aeb = NULL;

  		ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {

  			cond_resched();

  			last_aeb = aeb;

  			leb_count += 1;

  			if (aeb->pnum < 0 || aeb->ec < 0) {

  				ubi_err("negative values");

  				goto bad_aeb;

  			}

  			if (aeb->ec < ai->min_ec) {
  				ubi_err("bad ai->min_ec (%d), %d found",
  					ai->min_ec, aeb->ec);

  				goto bad_aeb;

  			}

  			if (aeb->ec > ai->max_ec) {
  				ubi_err("bad ai->max_ec (%d), %d found",
  					ai->max_ec, aeb->ec);

  				goto bad_aeb;

  			}

  			if (aeb->pnum >= ubi->peb_count) {

  				ubi_err("too high PEB number %d, total PEBs %d",

  					aeb->pnum, ubi->peb_count);
  				goto bad_aeb;