// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * 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);

#define AV_FIND         BIT(0)
#define AV_ADD          BIT(1)
#define AV_FIND_OR_ADD  (AV_FIND | AV_ADD)

/**
 * find_or_add_av - internal function to find a volume, add a volume or do
 *                  both (find and add if missing).
 * @ai: attaching information
 * @vol_id: the requested volume ID
 * @flags: a combination of the %AV_FIND and %AV_ADD flags describing the
 *         expected operation. If only %AV_ADD is set, -EEXIST is returned
 *         if the volume already exists. If only %AV_FIND is set, NULL is
 *         returned if the volume does not exist. And if both flags are
 *         set, the helper first tries to find an existing volume, and if
 *         it does not exist it creates a new one.
 * @created: in value used to inform the caller whether it"s a newly created
 *           volume or not.
 *
 * This function returns a pointer to a volume description or an ERR_PTR if
 * the operation failed. It can also return NULL if only %AV_FIND is set and
 * the volume does not exist.
 */
static struct ubi_ainf_volume *find_or_add_av(struct ubi_attach_info *ai,
                                              int vol_id, unsigned int flags,
                                              bool *created)
{
        struct ubi_ainf_volume *av;
        struct rb_node **p = &ai->volumes.rb_node, *parent = NULL;

        /* 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) {
                        *created = false;

                        if (!(flags & AV_FIND))
                                return ERR_PTR(-EEXIST);

                        return av;
                }

                if (vol_id > av->vol_id)
                        p = &(*p)->rb_left;
                else
                        p = &(*p)->rb_right;
        }

        if (!(flags & AV_ADD))
                return NULL;

        /* The volume is absent - add it */
        av = kzalloc_obj(*av);
        if (!av)
                return ERR_PTR(-ENOMEM);

        av->vol_id = vol_id;

        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;
        *created = true;
        dbg_bld("added volume %d", vol_id);
        return av;
}

/**
 * ubi_find_or_add_av - search for a volume in the attaching information and
 *                      add one if it does not exist.
 * @ai: attaching information
 * @vol_id: the requested volume ID
 * @created: whether the volume has been created or not
 *
 * This function returns a pointer to the new volume description or an
 * ERR_PTR if the operation failed.
 */
static struct ubi_ainf_volume *ubi_find_or_add_av(struct ubi_attach_info *ai,
                                                  int vol_id, bool *created)
{
        return find_or_add_av(ai, vol_id, AV_FIND_OR_ADD, created);
}

/**
 * ubi_alloc_aeb - allocate an aeb element
 * @ai: attaching information
 * @pnum: physical eraseblock number
 * @ec: erase counter of the physical eraseblock
 *
 * Allocate an aeb object and initialize the pnum and ec information.
 * vol_id and lnum are set to UBI_UNKNOWN, and the other fields are
 * initialized to zero.
 * Note that the element is not added in any list or RB tree.
 */
struct ubi_ainf_peb *ubi_alloc_aeb(struct ubi_attach_info *ai, int pnum,
                                   int ec)
{
        struct ubi_ainf_peb *aeb;

        aeb = kmem_cache_zalloc(ai->aeb_slab_cache, GFP_KERNEL);
        if (!aeb)
                return NULL;

        aeb->pnum = pnum;
        aeb->ec = ec;
        aeb->vol_id = UBI_UNKNOWN;
        aeb->lnum = UBI_UNKNOWN;

        return aeb;
}

/**
 * ubi_free_aeb - free an aeb element
 * @ai: attaching information
 * @aeb: the element to free
 *
 * Free an aeb object. The caller must have removed the element from any list
 * or RB tree.
 */
void ubi_free_aeb(struct ubi_attach_info *ai, struct ubi_ainf_peb *aeb)
{
        kmem_cache_free(ai->aeb_slab_cache, aeb);
}

/**
 * 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 = ubi_alloc_aeb(ai, pnum, ec);
        if (!aeb)
                return -ENOMEM;

        aeb->vol_id = vol_id;
        aeb->lnum = lnum;
        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 = ubi_alloc_aeb(ai, pnum, ec);
        if (!aeb)
                return -ENOMEM;

        ai->corr_peb_count += 1;
        list_add(&aeb->u.list, &ai->corr);
        return 0;
}

/**
 * add_fastmap - add a Fastmap related physical eraseblock.
 * @ai: attaching information
 * @pnum: physical eraseblock number the VID header came from
 * @vid_hdr: the volume identifier header
 * @ec: erase counter of the physical eraseblock
 *
 * This function allocates a 'struct ubi_ainf_peb' object for a Fastamp
 * physical eraseblock @pnum and adds it to the 'fastmap' list.
 * Such blocks can be Fastmap super and data blocks from both the most
 * recent Fastmap we're attaching from or from old Fastmaps which will
 * be erased.
 */
static int add_fastmap(struct ubi_attach_info *ai, int pnum,
                       struct ubi_vid_hdr *vid_hdr, int ec)
{
        struct ubi_ainf_peb *aeb;

        aeb = ubi_alloc_aeb(ai, pnum, ec);
        if (!aeb)
                return -ENOMEM;

        aeb->vol_id = be32_to_cpu(vid_hdr->vol_id);
        aeb->sqnum = be64_to_cpu(vid_hdr->sqnum);
        list_add(&aeb->u.list, &ai->fastmap);

        dbg_bld("add to fastmap list: PEB %d, vol_id %d, sqnum: %llu", pnum,
                aeb->vol_id, aeb->sqnum);

        return 0;
}

/**
 * validate_vid_hdr - check volume identifier header.
 * @ubi: UBI device description object
 * @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_device *ubi,
                            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(ubi, "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(ubi, "inconsistent vol_type");
                        goto bad;
                }

                if (used_ebs != av->used_ebs) {
                        ubi_err(ubi, "inconsistent used_ebs");
                        goto bad;
                }

                if (data_pad != av->data_pad) {
                        ubi_err(ubi, "inconsistent data_pad");
                        goto bad;
                }
        }

        return 0;

bad:
        ubi_err(ubi, "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;
        bool created;

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

        av = ubi_find_or_add_av(ai, vol_id, &created);
        if (IS_ERR(av) || !created)
                return av;

        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;

        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_io_buf *vidb = 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(ubi, "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;
                }

                vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
                if (!vidb)
                        return -ENOMEM;

                pnum = aeb->pnum;
                err = ubi_io_read_vid_hdr(ubi, pnum, vidb, 0);
                if (err) {
                        if (err == UBI_IO_BITFLIPS)
                                bitflips = 1;
                        else {
                                ubi_err(ubi, "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 = ubi_get_vid_hdr(vidb);
        }

        /* 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_buf(vidb);

        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_buf(vidb);
        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(ubi, "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(ubi, 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(ubi, vid_hdr, av, pnum);
        if (err)
                return err;

        aeb = ubi_alloc_aeb(ai, pnum, ec);
        if (!aeb)
                return -ENOMEM;

        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_add_av - add volume to the attaching information.
 * @ai: attaching information
 * @vol_id: the requested volume ID
 *
 * This function returns a pointer to the new volume description or an
 * ERR_PTR if the operation failed.
 */
struct ubi_ainf_volume *ubi_add_av(struct ubi_attach_info *ai, int vol_id)
{
        bool created;

        return find_or_add_av(ai, vol_id, AV_ADD, &created);
}

/**
 * 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)
{
        bool created;

        return find_or_add_av((struct ubi_attach_info *)ai, vol_id, AV_FIND,
                              &created);
}

static void destroy_av(struct ubi_attach_info *ai, struct ubi_ainf_volume *av,
                       struct list_head *list);

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

        rb_erase(&av->rb, &ai->volumes);
        destroy_av(ai, av, &ai->erase);
        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(ubi, "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(ubi, "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(ubi, "PEB %d contains corrupted VID header, and the data does not contain all 0xFF",
                pnum);
        ubi_err(ubi, "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;
}

static bool vol_ignored(int vol_id)
{
        switch (vol_id) {
                case UBI_LAYOUT_VOLUME_ID:
                return true;
        }

#ifdef CONFIG_MTD_UBI_FASTMAP
        return ubi_is_fm_vol(vol_id);
#else
        return false;
#endif
}

/**
 * scan_peb - scan and process UBI headers of a PEB.
 * @ubi: UBI device description object
 * @ai: attaching information
 * @pnum: the physical eraseblock number
 * @fast: true if we're scanning for a Fastmap
 *
 * 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, bool fast)
{
        struct ubi_ec_hdr *ech = ai->ech;
        struct ubi_vid_io_buf *vidb = ai->vidb;
        struct ubi_vid_hdr *vidh = ubi_get_vid_hdr(vidb);
        long long 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, "'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(ubi, "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(ubi, "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(ubi, "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, vidb, 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;
                fallthrough;
        case UBI_IO_BAD_HDR:
                        /*
                         * If we're facing a bad VID header we have to drop *all*
                         * Fastmap data structures we find. The most recent Fastmap
                         * could be bad and therefore there is a chance that we attach
                         * from an old one. On a fine MTD stack a PEB must not render
                         * bad all of a sudden, but the reality is different.
                         * So, let's be paranoid and help finding the root cause by
                         * falling back to scanning mode instead of attaching with a
                         * bad EBA table and cause data corruption which is hard to
                         * analyze.
                         */
                        if (fast)
                                ai->force_full_scan = 1;

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

        vol_id = be32_to_cpu(vidh->vol_id);
        if (vol_id > UBI_MAX_VOLUMES && !vol_ignored(vol_id)) {
                int lnum = be32_to_cpu(vidh->lnum);

                /* Unsupported internal volume */
                switch (vidh->compat) {
                case UBI_COMPAT_DELETE:
                        ubi_msg(ubi, "\"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(ubi, "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(ubi, "\"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(ubi, "incompatible internal volume %d:%d found",
                                vol_id, lnum);
                        return -EINVAL;
                }
        }

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

        if (ubi_is_fm_vol(vol_id))
                err = add_fastmap(ai, pnum, vidh, ec);
        else
                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(ubi, "%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("\n");

                /*
                 * If too many PEBs are corrupted, we refuse attaching,
                 * otherwise, only print a warning.
                 */
                if (ai->corr_peb_count >= max_corr) {
                        ubi_err(ubi, "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(ubi, "empty MTD device detected");
                        get_random_bytes(&ubi->image_seq,
                                         sizeof(ubi->image_seq));
                } else {
                        ubi_err(ubi, "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
 * @list: put the aeb elements in there if !NULL, otherwise free them
 *
 * This function destroys the volume attaching information.
 */
static void destroy_av(struct ubi_attach_info *ai, struct ubi_ainf_volume *av,
                       struct list_head *list)
{
        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;
                        }

                        if (list)
                                list_add_tail(&aeb->u.list, list);
                        else
                                ubi_free_aeb(ai, 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);
                ubi_free_aeb(ai, aeb);
        }
        list_for_each_entry_safe(aeb, aeb_tmp, &ai->erase, u.list) {
                list_del(&aeb->u.list);
                ubi_free_aeb(ai, aeb);
        }
        list_for_each_entry_safe(aeb, aeb_tmp, &ai->corr, u.list) {
                list_del(&aeb->u.list);
                ubi_free_aeb(ai, aeb);
        }
        list_for_each_entry_safe(aeb, aeb_tmp, &ai->free, u.list) {
                list_del(&aeb->u.list);
                ubi_free_aeb(ai, aeb);
        }
        list_for_each_entry_safe(aeb, aeb_tmp, &ai->fastmap, u.list) {
                list_del(&aeb->u.list);
                ubi_free_aeb(ai, 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, NULL);
                }
        }

        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;

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

        ai->vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
        if (!ai->vidb)
                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, false);
                if (err < 0)
                        goto out_vidh;
        }

        ubi_msg(ubi, "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_buf(ai->vidb);
        kfree(ai->ech);

        return 0;

out_vidh:
        ubi_free_vid_buf(ai->vidb);
out_ech:
        kfree(ai->ech);
        return err;
}

static struct ubi_attach_info *alloc_ai(const char *slab_name)
{
        struct ubi_attach_info *ai;

        ai = kzalloc_obj(struct ubi_attach_info);
        if (!ai)
                return ai;

        INIT_LIST_HEAD(&ai->corr);
        INIT_LIST_HEAD(&ai->free);
        INIT_LIST_HEAD(&ai->erase);
        INIT_LIST_HEAD(&ai->alien);
        INIT_LIST_HEAD(&ai->fastmap);
        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;
}

#ifdef CONFIG_MTD_UBI_FASTMAP

/**
 * scan_fast - 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;
        struct ubi_attach_info *scan_ai;

        err = -ENOMEM;

        scan_ai = alloc_ai("ubi_aeb_slab_cache_fastmap");
        if (!scan_ai)
                goto out;

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

        scan_ai->vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
        if (!scan_ai->vidb)
                goto out_ech;

        for (pnum = 0; pnum < UBI_FM_MAX_START; pnum++) {
                cond_resched();

                dbg_gen("process PEB %d", pnum);
                err = scan_peb(ubi, scan_ai, pnum, true);
                if (err < 0)
                        goto out_vidh;
        }

        ubi_free_vid_buf(scan_ai->vidb);
        kfree(scan_ai->ech);

        if (scan_ai->force_full_scan)
                err = UBI_NO_FASTMAP;
        else
                err = ubi_scan_fastmap(ubi, *ai, scan_ai);

        if (err) {
                /*
                 * Didn't attach via fastmap, do a full scan but reuse what
                 * we've aready scanned.
                 */
                destroy_ai(*ai);
                *ai = scan_ai;
        } else
                destroy_ai(scan_ai);

        return err;

out_vidh:
        ubi_free_vid_buf(scan_ai->vidb);
out_ech:
        kfree(scan_ai->ech);
out_ai:
        destroy_ai(scan_ai);
out:
        return err;
}

#endif

/**
 * 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 || mtd_is_eccerr(err)) {
                        if (err != UBI_NO_FASTMAP) {
                                destroy_ai(ai);
                                ai = alloc_ai("ubi_aeb_slab_cache");
                                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_fm;

        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_fastmap(ubi)) {
                struct ubi_attach_info *scan_ai;

                scan_ai = alloc_ai("ubi_aeb_slab_cache_dbg_chk_fastmap");
                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_all_volumes(ubi);
        vfree(ubi->vtbl);
out_fm:
        ubi_free_fastmap(ubi);
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)
{
        struct ubi_vid_io_buf *vidb = ai->vidb;
        struct ubi_vid_hdr *vidh = ubi_get_vid_hdr(vidb);
        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(ubi, "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(ubi, "negative values");
                        goto bad_av;
                }

                if (av->vol_id >= UBI_MAX_VOLUMES &&
                    av->vol_id < UBI_INTERNAL_VOL_START) {
                        ubi_err(ubi, "bad vol_id");
                        goto bad_av;
                }

                if (av->vol_id > ai->highest_vol_id) {
                        ubi_err(ubi, "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(ubi, "bad vol_type");
                        goto bad_av;
                }

                if (av->data_pad > ubi->leb_size / 2) {
                        ubi_err(ubi, "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(ubi, "negative values");
                                goto bad_aeb;
                        }

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

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

                        if (aeb->pnum >= ubi->peb_count) {
                                ubi_err(ubi, "too high PEB number %d, total PEBs %d",
                                        aeb->pnum, ubi->peb_count);
                                goto bad_aeb;
                        }

                        if (av->vol_type == UBI_STATIC_VOLUME) {
                                if (aeb->lnum >= av->used_ebs) {
                                        ubi_err(ubi, "bad lnum or used_ebs");
                                        goto bad_aeb;
                                }
                        } else {
                                if (av->used_ebs != 0) {
                                        ubi_err(ubi, "non-zero used_ebs");
                                        goto bad_aeb;
                                }
                        }

                        if (aeb->lnum > av->highest_lnum) {
                                ubi_err(ubi, "incorrect highest_lnum or lnum");
                                goto bad_aeb;
                        }
                }

                if (av->leb_count != leb_count) {
                        ubi_err(ubi, "bad leb_count, %d objects in the tree",
                                leb_count);
                        goto bad_av;
                }

                if (!last_aeb)
                        continue;

                aeb = last_aeb;

                if (aeb->lnum != av->highest_lnum) {
                        ubi_err(ubi, "bad highest_lnum");
                        goto bad_aeb;
                }
        }

        if (vols_found != ai->vols_found) {
                ubi_err(ubi, "bad ai->vols_found %d, should be %d",
                        ai->vols_found, vols_found);
                goto out;
        }

        /* Check that attaching information is correct */
        ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb) {
                last_aeb = NULL;
                ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb) {
                        int vol_type;

                        cond_resched();

                        last_aeb = aeb;

                        err = ubi_io_read_vid_hdr(ubi, aeb->pnum, vidb, 1);
                        if (err && err != UBI_IO_BITFLIPS) {
                                ubi_err(ubi, "VID header is not OK (%d)",
                                        err);
                                if (err > 0)
                                        err = -EIO;
                                return err;
                        }

                        vol_type = vidh->vol_type == UBI_VID_DYNAMIC ?
                                   UBI_DYNAMIC_VOLUME : UBI_STATIC_VOLUME;
                        if (av->vol_type != vol_type) {
                                ubi_err(ubi, "bad vol_type");
                                goto bad_vid_hdr;
                        }

                        if (aeb->sqnum != be64_to_cpu(vidh->sqnum)) {
                                ubi_err(ubi, "bad sqnum %llu", aeb->sqnum);
                                goto bad_vid_hdr;
                        }

                        if (av->vol_id != be32_to_cpu(vidh->vol_id)) {
                                ubi_err(ubi, "bad vol_id %d", av->vol_id);
                                goto bad_vid_hdr;
                        }

                        if (av->compat != vidh->compat) {
                                ubi_err(ubi, "bad compat %d", vidh->compat);
                                goto bad_vid_hdr;
                        }

                        if (aeb->lnum != be32_to_cpu(vidh->lnum)) {
                                ubi_err(ubi, "bad lnum %d", aeb->lnum);
                                goto bad_vid_hdr;
                        }

                        if (av->used_ebs != be32_to_cpu(vidh->used_ebs)) {
                                ubi_err(ubi, "bad used_ebs %d", av->used_ebs);
                                goto bad_vid_hdr;
                        }

                        if (av->data_pad != be32_to_cpu(vidh->data_pad)) {
                                ubi_err(ubi, "bad data_pad %d", av->data_pad);
                                goto bad_vid_hdr;
                        }
                }

                if (!last_aeb)
                        continue;

                if (av->highest_lnum != be32_to_cpu(vidh->lnum)) {
                        ubi_err(ubi, "bad highest_lnum %d", av->highest_lnum);
                        goto bad_vid_hdr;
                }

                if (av->last_data_size != be32_to_cpu(vidh->data_size)) {
                        ubi_err(ubi, "bad last_data_size %d",
                                av->last_data_size);
                        goto bad_vid_hdr;
                }
        }

        /*
         * Make sure that all the physical eraseblocks are in one of the lists
         * or trees.
         */
        buf = kzalloc(ubi->peb_count, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        for (pnum = 0; pnum < ubi->peb_count; pnum++) {
                err = ubi_io_is_bad(ubi, pnum);
                if (err < 0) {
                        kfree(buf);
                        return err;
                } else if (err)
                        buf[pnum] = 1;
        }

        ubi_rb_for_each_entry(rb1, av, &ai->volumes, rb)
                ubi_rb_for_each_entry(rb2, aeb, &av->root, u.rb)
                        buf[aeb->pnum] = 1;

        list_for_each_entry(aeb, &ai->free, u.list)
                buf[aeb->pnum] = 1;

        list_for_each_entry(aeb, &ai->corr, u.list)
                buf[aeb->pnum] = 1;

        list_for_each_entry(aeb, &ai->erase, u.list)
                buf[aeb->pnum] = 1;

        list_for_each_entry(aeb, &ai->alien, u.list)
                buf[aeb->pnum] = 1;

        err = 0;
        for (pnum = 0; pnum < ubi->peb_count; pnum++)
                if (!buf[pnum]) {
                        ubi_err(ubi, "PEB %d is not referred", pnum);
                        err = 1;
                }

        kfree(buf);
        if (err)
                goto out;
        return 0;

bad_aeb:
        ubi_err(ubi, "bad attaching information about LEB %d", aeb->lnum);
        ubi_dump_aeb(aeb, 0);
        ubi_dump_av(av);
        goto out;

bad_av:
        ubi_err(ubi, "bad attaching information about volume %d", av->vol_id);
        ubi_dump_av(av);
        goto out;

bad_vid_hdr:
        ubi_err(ubi, "bad attaching information about volume %d", av->vol_id);
        ubi_dump_av(av);
        ubi_dump_vid_hdr(vidh);

out:
        dump_stack();
        return -EINVAL;
}