Added missing tegra files.HEADmaster

2 files changed, 1779 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
new file mode 100644
index 00000000000..a3a198f9b98
--- /dev/null
+++ b/drivers/mtd/ubi/scan.c
@@ -0,0 +1,1605 @@
+/*
+ * 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 scanning sub-system.
+ *
+ * This sub-system is responsible for scanning the flash media, checking UBI
+ * headers and providing complete information about the UBI flash image.
+ *
+ * The scanning information is represented by a &struct ubi_scan_info' object.
+ * Information about found volumes is represented by &struct ubi_scan_volume
+ * objects which are kept in volume RB-tree with root at the @volumes field.
+ * The RB-tree is indexed by the volume ID.
+ *
+ * Scanned logical eraseblocks are represented by &struct ubi_scan_leb objects.
+ * These objects are kept in per-volume RB-trees with the root at the
+ * corresponding &struct ubi_scan_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-eraseblock 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 case
+ * - we may lose only the data which was 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
+ * scanning, 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. 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 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 is 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 it 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"
+
+#ifdef CONFIG_MTD_UBI_DEBUG
+static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si);
+#else
+#define paranoid_check_si(ubi, si) 0
+#endif
+
+/* 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.
+ * @si: scanning information
+ * @pnum: physical eraseblock number to add
+ * @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 adds physical eraseblock @pnum to free, erase, or alien lists.
+ * 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_scan_info *si, int pnum, int ec, int to_head,
+                       struct list_head *list)
+{
+        struct ubi_scan_leb *seb;
+
+        if (list == &si->free) {
+                dbg_bld("add to free: PEB %d, EC %d", pnum, ec);
+        } else if (list == &si->erase) {
+                dbg_bld("add to erase: PEB %d, EC %d", pnum, ec);
+        } else if (list == &si->alien) {
+                dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
+                si->alien_peb_count += 1;
+        } else
+                BUG();
+
+        seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
+        if (!seb)
+                return -ENOMEM;
+
+        seb->pnum = pnum;
+        seb->ec = ec;
+        if (to_head)
+                list_add(&seb->u.list, list);
+        else
+                list_add_tail(&seb->u.list, list);
+        return 0;
+}
+
+/**
+ * add_corrupted - add a corrupted physical eraseblock.
+ * @si: scanning information
+ * @pnum: physical eraseblock number to add
+ * @ec: erase counter of the physical eraseblock
+ *
+ * This function adds corrupted physical eraseblock @pnum 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_scan_info *si, int pnum, int ec)
+{
+        struct ubi_scan_leb *seb;
+
+        dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
+
+        seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
+        if (!seb)
+                return -ENOMEM;
+
+        si->corr_peb_count += 1;
+        seb->pnum = pnum;
+        seb->ec = ec;
+        list_add(&seb->u.list, &si->corr);
+        return 0;
+}
+
+/**
+ * validate_vid_hdr - check volume identifier header.
+ * @vid_hdr: the volume identifier header to check
+ * @sv: 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_scan_volume *sv, 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 (sv->leb_count != 0) {
+                int sv_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 != sv->vol_id) {
+                        dbg_err("inconsistent vol_id");
+                        goto bad;
+                }
+
+                if (sv->vol_type == UBI_STATIC_VOLUME)
+                        sv_vol_type = UBI_VID_STATIC;
+                else
+                        sv_vol_type = UBI_VID_DYNAMIC;
+
+                if (vol_type != sv_vol_type) {
+                        dbg_err("inconsistent vol_type");
+                        goto bad;
+                }
+
+                if (used_ebs != sv->used_ebs) {
+                        dbg_err("inconsistent used_ebs");
+                        goto bad;
+                }
+
+                if (data_pad != sv->data_pad) {
+                        dbg_err("inconsistent data_pad");
+                        goto bad;
+                }
+        }
+
+        return 0;
+
+bad:
+        ubi_err("inconsistent VID header at PEB %d", pnum);
+        ubi_dbg_dump_vid_hdr(vid_hdr);
+        ubi_dbg_dump_sv(sv);
+        return -EINVAL;
+}
+
+/**
+ * add_volume - add volume to the scanning information.
+ * @si: scanning 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 scanning information, this function does nothing. Otherwise
+ * it adds corresponding volume to the scanning information. Returns a pointer
+ * to the scanning volume object in case of success and a negative error code
+ * in case of failure.
+ */
+static struct ubi_scan_volume *add_volume(struct ubi_scan_info *si, int vol_id,
+                                          int pnum,
+                                          const struct ubi_vid_hdr *vid_hdr)
+{
+        struct ubi_scan_volume *sv;
+        struct rb_node **p = &si->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;
+                sv = rb_entry(parent, struct ubi_scan_volume, rb);
+
+                if (vol_id == sv->vol_id)
+                        return sv;
+
+                if (vol_id > sv->vol_id)
+                        p = &(*p)->rb_left;
+                else
+                        p = &(*p)->rb_right;
+        }
+
+        /* The volume is absent - add it */
+        sv = kmalloc(sizeof(struct ubi_scan_volume), GFP_KERNEL);
+        if (!sv)
+                return ERR_PTR(-ENOMEM);
+
+        sv->highest_lnum = sv->leb_count = 0;
+        sv->vol_id = vol_id;
+        sv->root = RB_ROOT;
+        sv->used_ebs = be32_to_cpu(vid_hdr->used_ebs);
+        sv->data_pad = be32_to_cpu(vid_hdr->data_pad);
+        sv->compat = vid_hdr->compat;
+        sv->vol_type = vid_hdr->vol_type == UBI_VID_DYNAMIC ? UBI_DYNAMIC_VOLUME
+                                                            : UBI_STATIC_VOLUME;
+        if (vol_id > si->highest_vol_id)
+                si->highest_vol_id = vol_id;
+
+        rb_link_node(&sv->rb, parent, p);
+        rb_insert_color(&sv->rb, &si->volumes);
+        si->vols_found += 1;
+        dbg_bld("added volume %d", vol_id);
+        return sv;
+}
+
+/**
+ * compare_lebs - find out which logical eraseblock is newer.
+ * @ubi: UBI device description object
+ * @seb: 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 @seb) 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.
+ */
+static int compare_lebs(struct ubi_device *ubi, const struct ubi_scan_leb *seb,
+                        int pnum, const struct ubi_vid_hdr *vid_hdr)
+{
+        void *buf;
+        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 == seb->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\n");
+                return -EINVAL;
+        }
+
+        /* Obviously the LEB with lower sequence counter is older */
+        second_is_newer = !!(sqnum2 > seb->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 (!seb->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 = seb->pnum;
+                err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
+                if (err) {
+                        if (err == UBI_IO_BITFLIPS)
+                                bitflips = 1;
+                        else {
+                                dbg_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);
+        buf = vmalloc(len);
+        if (!buf) {
+                err = -ENOMEM;
+                goto out_free_vidh;
+        }
+
+        err = ubi_io_read_data(ubi, buf, pnum, 0, len);
+        if (err && err != UBI_IO_BITFLIPS && err != -EBADMSG)
+                goto out_free_buf;
+
+        data_crc = be32_to_cpu(vid_hdr->data_crc);
+        crc = crc32(UBI_CRC32_INIT, 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;
+        }
+
+        vfree(buf);
+        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_free_buf:
+        vfree(buf);
+out_free_vidh:
+        ubi_free_vid_hdr(ubi, vh);
+        return err;
+}
+
+/**
+ * ubi_scan_add_used - add physical eraseblock to the scanning information.
+ * @ubi: UBI device description object
+ * @si: scanning 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_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
+                      int pnum, int ec, const struct ubi_vid_hdr *vid_hdr,
+                      int bitflips)
+{
+        int err, vol_id, lnum;
+        unsigned long long sqnum;
+        struct ubi_scan_volume *sv;
+        struct ubi_scan_leb *seb;
+        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);
+
+        sv = add_volume(si, vol_id, pnum, vid_hdr);
+        if (IS_ERR(sv))
+                return PTR_ERR(sv);
+
+        if (si->max_sqnum < sqnum)
+                si->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 = &sv->root.rb_node;
+        while (*p) {
+                int cmp_res;
+
+                parent = *p;
+                seb = rb_entry(parent, struct ubi_scan_leb, u.rb);
+                if (lnum != seb->lnum) {
+                        if (lnum < seb->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", seb->pnum, seb->sqnum, seb->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
+                 * '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 (seb->sqnum == sqnum && sqnum != 0) {
+                        ubi_err("two LEBs with same sequence number %llu",
+                                sqnum);
+                        ubi_dbg_dump_seb(seb, 0);
+                        ubi_dbg_dump_vid_hdr(vid_hdr);
+                        return -EINVAL;
+                }
+
+                /*
+                 * Now we have to drop the older one and preserve the newer
+                 * one.
+                 */
+                cmp_res = compare_lebs(ubi, seb, 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, sv, pnum);
+                        if (err)
+                                return err;
+
+                        err = add_to_list(si, seb->pnum, seb->ec, cmp_res & 4,
+                                          &si->erase);
+                        if (err)
+                                return err;
+
+                        seb->ec = ec;
+                        seb->pnum = pnum;
+                        seb->scrub = ((cmp_res & 2) || bitflips);
+                        seb->copy_flag = vid_hdr->copy_flag;
+                        seb->sqnum = sqnum;
+
+                        if (sv->highest_lnum == lnum)
+                                sv->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(si, pnum, ec, cmp_res & 4,
+                                           &si->erase);
+                }
+        }
+
+        /*
+         * We've met this logical eraseblock for the first time, add it to the
+         * scanning information.
+         */
+
+        err = validate_vid_hdr(vid_hdr, sv, pnum);
+        if (err)
+                return err;
+
+        seb = kmem_cache_alloc(si->scan_leb_slab, GFP_KERNEL);
+        if (!seb)
+                return -ENOMEM;
+
+        seb->ec = ec;
+        seb->pnum = pnum;
+        seb->lnum = lnum;
+        seb->scrub = bitflips;
+        seb->copy_flag = vid_hdr->copy_flag;
+        seb->sqnum = sqnum;
+
+        if (sv->highest_lnum <= lnum) {
+                sv->highest_lnum = lnum;
+                sv->last_data_size = be32_to_cpu(vid_hdr->data_size);
+        }
+
+        sv->leb_count += 1;
+        rb_link_node(&seb->u.rb, parent, p);
+        rb_insert_color(&seb->u.rb, &sv->root);
+        return 0;
+}
+
+/**
+ * ubi_scan_find_sv - find volume in the scanning information.
+ * @si: scanning 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 scanning information.
+ */
+struct ubi_scan_volume *ubi_scan_find_sv(const struct ubi_scan_info *si,
+                                         int vol_id)
+{
+        struct ubi_scan_volume *sv;
+        struct rb_node *p = si->volumes.rb_node;
+
+        while (p) {
+                sv = rb_entry(p, struct ubi_scan_volume, rb);
+
+                if (vol_id == sv->vol_id)
+                        return sv;
+
+                if (vol_id > sv->vol_id)
+                        p = p->rb_left;
+                else
+                        p = p->rb_right;
+        }
+
+        return NULL;
+}
+
+/**
+ * ubi_scan_find_seb - find LEB in the volume scanning information.
+ * @sv: a pointer to the volume scanning information
+ * @lnum: the requested logical eraseblock
+ *
+ * This function returns a pointer to the scanning logical eraseblock or %NULL
+ * if there are no data about it in the scanning volume information.
+ */
+struct ubi_scan_leb *ubi_scan_find_seb(const struct ubi_scan_volume *sv,
+                                       int lnum)
+{
+        struct ubi_scan_leb *seb;
+        struct rb_node *p = sv->root.rb_node;
+
+        while (p) {
+                seb = rb_entry(p, struct ubi_scan_leb, u.rb);
+
+                if (lnum == seb->lnum)
+                        return seb;
+
+                if (lnum > seb->lnum)
+                        p = p->rb_left;
+                else
+                        p = p->rb_right;
+        }
+
+        return NULL;
+}
+
+/**
+ * ubi_scan_rm_volume - delete scanning information about a volume.
+ * @si: scanning information
+ * @sv: the volume scanning information to delete
+ */
+void ubi_scan_rm_volume(struct ubi_scan_info *si, struct ubi_scan_volume *sv)
+{
+        struct rb_node *rb;
+        struct ubi_scan_leb *seb;
+
+        dbg_bld("remove scanning information about volume %d", sv->vol_id);
+
+        while ((rb = rb_first(&sv->root))) {
+                seb = rb_entry(rb, struct ubi_scan_leb, u.rb);
+                rb_erase(&seb->u.rb, &sv->root);
+                list_add_tail(&seb->u.list, &si->erase);
+        }
+
+        rb_erase(&sv->rb, &si->volumes);
+        kfree(sv);
+        si->vols_found -= 1;
+}
+
+/**
+ * ubi_scan_erase_peb - erase a physical eraseblock.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ * @pnum: physical eraseblock number to erase;
+ * @ec: erase counter value to write (%UBI_SCAN_UNKNOWN_EC 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.
+ */
+int ubi_scan_erase_peb(struct ubi_device *ubi, const struct ubi_scan_info *si,
+                       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_scan_get_free_peb - get a free physical eraseblock.
+ * @ubi: UBI device description object
+ * @si: scanning 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 scanning physical eraseblock information in case of
+ * success and an error code in case of failure.
+ */
+struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
+                                           struct ubi_scan_info *si)
+{
+        int err = 0;
+        struct ubi_scan_leb *seb, *tmp_seb;
+
+        if (!list_empty(&si->free)) {
+                seb = list_entry(si->free.next, struct ubi_scan_leb, u.list);
+                list_del(&seb->u.list);
+                dbg_bld("return free PEB %d, EC %d", seb->pnum, seb->ec);
+                return seb;
+        }
+
+        /*
+         * 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(seb, tmp_seb, &si->erase, u.list) {
+                if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+                        seb->ec = si->mean_ec;
+
+                err = ubi_scan_erase_peb(ubi, si, seb->pnum, seb->ec+1);
+                if (err)
+                        continue;
+
+                seb->ec += 1;
+                list_del(&seb->u.list);
+                dbg_bld("return PEB %d, EC %d", seb->pnum, seb->ec);
+                return seb;
+        }
+
+        ubi_err("no free eraseblocks");
+        return ERR_PTR(-ENOSPC);
+}
+
+/**
+ * check_corruption - check the data area of PEB.
+ * @ubi: UBI device description object
+ * @vid_hrd: 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_buf1, 0x00, ubi->leb_size);
+
+        err = ubi_io_read(ubi, ubi->peb_buf1, pnum, ubi->leb_start,
+                          ubi->leb_size);
+        if (err == UBI_IO_BITFLIPS || err == -EBADMSG) {
+                /*
+                 * 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_buf1, 0xFF, ubi->leb_size))
+                goto out_unlock;
+
+        ubi_err("PEB %d contains corrupted VID header, and the data does not "
+                "contain all 0xFF, this may be a non-UBI PEB or a severe VID "
+                "header corruption which requires manual inspection", pnum);
+        ubi_dbg_dump_vid_hdr(vid_hdr);
+        dbg_msg("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_buf1, ubi->leb_size, 1);
+        err = 1;
+
+out_unlock:
+        mutex_unlock(&ubi->buf_mutex);
+        return err;
+}
+
+/**
+ * process_eb - read, check UBI headers, and add them to scanning information.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ * @pnum: the physical eraseblock number
+ *
+ * This function returns a zero if the physical eraseblock was successfully
+ * handled and a negative error code in case of failure.
+ */
+static int process_eb(struct ubi_device *ubi, struct ubi_scan_info *si,
+                      int pnum)
+{
+        long long uninitialized_var(ec);
+        int err, bitflips = 0, vol_id, 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) {
+                /*
+                 * FIXME: this is actually duty of the I/O sub-system to
+                 * initialize this, but MTD does not provide enough
+                 * information.
+                 */
+                si->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:
+                si->empty_peb_count += 1;
+                return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 0,
+                                   &si->erase);
+        case UBI_IO_FF_BITFLIPS:
+                si->empty_peb_count += 1;
+                return add_to_list(si, pnum, UBI_SCAN_UNKNOWN_EC, 1,
+                                   &si->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_SCAN_UNKNOWN_EC;
+                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_dbg_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 && image_seq)
+                        ubi->image_seq = image_seq;
+                if (ubi->image_seq && 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_dbg_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.
+                         */
+                        si->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(si, pnum, ec, 1, &si->erase);
+                else
+                        /* This is an unexpected corruption */
+                        err = add_corrupted(si, pnum, ec);
+                if (err)
+                        return err;
+                goto adjust_mean_ec;
+        case UBI_IO_FF_BITFLIPS:
+                err = add_to_list(si, pnum, ec, 1, &si->erase);
+                if (err)
+                        return err;
+                goto adjust_mean_ec;
+        case UBI_IO_FF:
+                if (ec_err)
+                        err = add_to_list(si, pnum, ec, 1, &si->erase);
+                else
+                        err = add_to_list(si, pnum, ec, 0, &si->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 (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:
+                        ubi_msg("\"delete\" compatible internal volume %d:%d"
+                                " found, will remove it", vol_id, lnum);
+                        err = add_to_list(si, pnum, ec, 1, &si->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(si, pnum, ec, 0, &si->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_scan_add_used(ubi, si, pnum, ec, vidh, bitflips);
+        if (err)
+                return err;
+
+adjust_mean_ec:
+        if (!ec_err) {
+                si->ec_sum += ec;
+                si->ec_count += 1;
+                if (ec > si->max_ec)
+                        si->max_ec = ec;
+                if (ec < si->min_ec)
+                        si->min_ec = ec;
+        }
+
+        return 0;
+}
+
+/**
+ * check_what_we_have - check what PEB were found by scanning.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ *
+ * This is a helper function which takes a look what PEBs were found by
+ * scanning, and decides whether the flash is empty and should be formatted and
+ * 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 check_what_we_have(struct ubi_device *ubi, struct ubi_scan_info *si)
+{
+        struct ubi_scan_leb *seb;
+        int max_corr, peb_count;
+
+        peb_count = ubi->peb_count - si->bad_peb_count - si->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 (si->corr_peb_count) {
+                ubi_err("%d PEBs are corrupted and preserved",
+                        si->corr_peb_count);
+                printk(KERN_ERR "Corrupted PEBs are:");
+                list_for_each_entry(seb, &si->corr, u.list)
+                        printk(KERN_CONT " %d", seb->pnum);
+                printk(KERN_CONT "\n");
+
+                /*
+                 * If too many PEBs are corrupted, we refuse attaching,
+                 * otherwise, only print a warning.
+                 */
+                if (si->corr_peb_count >= max_corr) {
+                        ubi_err("too many corrupted PEBs, refusing");
+                        return -EINVAL;
+                }
+        }
+
+        if (si->empty_peb_count + si->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 (si->maybe_bad_peb_count <= 2) {
+                        si->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;
+}
+
+/**
+ * ubi_scan - scan an MTD device.
+ * @ubi: UBI device description object
+ *
+ * This function does full scanning of an MTD device and returns complete
+ * information about it. In case of failure, an error code is returned.
+ */
+struct ubi_scan_info *ubi_scan(struct ubi_device *ubi)
+{
+        int err, pnum;
+        struct rb_node *rb1, *rb2;
+        struct ubi_scan_volume *sv;
+        struct ubi_scan_leb *seb;
+        struct ubi_scan_info *si;
+
+        si = kzalloc(sizeof(struct ubi_scan_info), GFP_KERNEL);
+        if (!si)
+                return ERR_PTR(-ENOMEM);
+
+        INIT_LIST_HEAD(&si->corr);
+        INIT_LIST_HEAD(&si->free);
+        INIT_LIST_HEAD(&si->erase);
+        INIT_LIST_HEAD(&si->alien);
+        si->volumes = RB_ROOT;
+
+        err = -ENOMEM;
+        si->scan_leb_slab = kmem_cache_create("ubi_scan_leb_slab",
+                                              sizeof(struct ubi_scan_leb),
+                                              0, 0, NULL);
+        if (!si->scan_leb_slab)
+                goto out_si;
+
+        ech = kzalloc(ubi->ec_hdr_alsize, GFP_KERNEL);
+        if (!ech)
+                goto out_slab;
+
+        vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
+        if (!vidh)
+                goto out_ech;
+
+        for (pnum = 0; pnum < ubi->peb_count; pnum++) {
+                cond_resched();
+
+                dbg_gen("process PEB %d", pnum);
+                err = process_eb(ubi, si, pnum);
+                if (err < 0)
+                        goto out_vidh;
+        }
+
+        dbg_msg("scanning is finished");
+
+        /* Calculate mean erase counter */
+        if (si->ec_count)
+                si->mean_ec = div_u64(si->ec_sum, si->ec_count);
+
+        err = check_what_we_have(ubi, si);
+        if (err)
+                goto out_vidh;
+
+        /*
+         * In case of unknown erase counter we use the mean erase counter
+         * value.
+         */
+        ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
+                ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb)
+                        if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+                                seb->ec = si->mean_ec;
+        }
+
+        list_for_each_entry(seb, &si->free, u.list) {
+                if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+                        seb->ec = si->mean_ec;
+        }
+
+        list_for_each_entry(seb, &si->corr, u.list)
+                if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+                        seb->ec = si->mean_ec;
+
+        list_for_each_entry(seb, &si->erase, u.list)
+                if (seb->ec == UBI_SCAN_UNKNOWN_EC)
+                        seb->ec = si->mean_ec;
+
+        err = paranoid_check_si(ubi, si);
+        if (err)
+                goto out_vidh;
+
+        ubi_free_vid_hdr(ubi, vidh);
+        kfree(ech);
+
+        return si;
+
+out_vidh:
+        ubi_free_vid_hdr(ubi, vidh);
+out_ech:
+        kfree(ech);
+out_slab:
+        kmem_cache_destroy(si->scan_leb_slab);
+out_si:
+        ubi_scan_destroy_si(si);
+        return ERR_PTR(err);
+}
+
+/**
+ * destroy_sv - free the scanning volume information
+ * @sv: scanning volume information
+ * @si: scanning information
+ *
+ * This function destroys the volume RB-tree (@sv->root) and the scanning
+ * volume information.
+ */
+static void destroy_sv(struct ubi_scan_info *si, struct ubi_scan_volume *sv)
+{
+        struct ubi_scan_leb *seb;
+        struct rb_node *this = sv->root.rb_node;
+
+        while (this) {
+                if (this->rb_left)
+                        this = this->rb_left;
+                else if (this->rb_right)
+                        this = this->rb_right;
+                else {
+                        seb = rb_entry(this, struct ubi_scan_leb, u.rb);
+                        this = rb_parent(this);
+                        if (this) {
+                                if (this->rb_left == &seb->u.rb)
+                                        this->rb_left = NULL;
+                                else
+                                        this->rb_right = NULL;
+                        }
+
+                        kmem_cache_free(si->scan_leb_slab, seb);
+                }
+        }
+        kfree(sv);
+}
+
+/**
+ * ubi_scan_destroy_si - destroy scanning information.
+ * @si: scanning information
+ */
+void ubi_scan_destroy_si(struct ubi_scan_info *si)
+{
+        struct ubi_scan_leb *seb, *seb_tmp;
+        struct ubi_scan_volume *sv;
+        struct rb_node *rb;
+
+        list_for_each_entry_safe(seb, seb_tmp, &si->alien, u.list) {
+                list_del(&seb->u.list);
+                kmem_cache_free(si->scan_leb_slab, seb);
+        }
+        list_for_each_entry_safe(seb, seb_tmp, &si->erase, u.list) {
+                list_del(&seb->u.list);
+                kmem_cache_free(si->scan_leb_slab, seb);
+        }
+        list_for_each_entry_safe(seb, seb_tmp, &si->corr, u.list) {
+                list_del(&seb->u.list);
+                kmem_cache_free(si->scan_leb_slab, seb);
+        }
+        list_for_each_entry_safe(seb, seb_tmp, &si->free, u.list) {
+                list_del(&seb->u.list);
+                kmem_cache_free(si->scan_leb_slab, seb);
+        }
+
+        /* Destroy the volume RB-tree */
+        rb = si->volumes.rb_node;
+        while (rb) {
+                if (rb->rb_left)
+                        rb = rb->rb_left;
+                else if (rb->rb_right)
+                        rb = rb->rb_right;
+                else {
+                        sv = rb_entry(rb, struct ubi_scan_volume, rb);
+
+                        rb = rb_parent(rb);
+                        if (rb) {
+                                if (rb->rb_left == &sv->rb)
+                                        rb->rb_left = NULL;
+                                else
+                                        rb->rb_right = NULL;
+                        }
+
+                        destroy_sv(si, sv);
+                }
+        }
+
+        kmem_cache_destroy(si->scan_leb_slab);
+        kfree(si);
+}
+
+#ifdef CONFIG_MTD_UBI_DEBUG
+
+/**
+ * paranoid_check_si - check the scanning information.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ *
+ * This function returns zero if the scanning information is all right, and a
+ * negative error code if not or if an error occurred.
+ */
+static int paranoid_check_si(struct ubi_device *ubi, struct ubi_scan_info *si)
+{
+        int pnum, err, vols_found = 0;
+        struct rb_node *rb1, *rb2;
+        struct ubi_scan_volume *sv;
+        struct ubi_scan_leb *seb, *last_seb;
+        uint8_t *buf;
+
+        if (!ubi->dbg->chk_gen)
+                return 0;
+
+        /*
+         * At first, check that scanning information is OK.
+         */
+        ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
+                int leb_count = 0;
+
+                cond_resched();
+
+                vols_found += 1;
+
+                if (si->is_empty) {
+                        ubi_err("bad is_empty flag");
+                        goto bad_sv;
+                }
+
+                if (sv->vol_id < 0 || sv->highest_lnum < 0 ||
+                    sv->leb_count < 0 || sv->vol_type < 0 || sv->used_ebs < 0 ||
+                    sv->data_pad < 0 || sv->last_data_size < 0) {
+                        ubi_err("negative values");
+                        goto bad_sv;
+                }
+
+                if (sv->vol_id >= UBI_MAX_VOLUMES &&
+                    sv->vol_id < UBI_INTERNAL_VOL_START) {
+                        ubi_err("bad vol_id");
+                        goto bad_sv;
+                }
+
+                if (sv->vol_id > si->highest_vol_id) {
+                        ubi_err("highest_vol_id is %d, but vol_id %d is there",
+                                si->highest_vol_id, sv->vol_id);
+                        goto out;
+                }
+
+                if (sv->vol_type != UBI_DYNAMIC_VOLUME &&
+                    sv->vol_type != UBI_STATIC_VOLUME) {
+                        ubi_err("bad vol_type");
+                        goto bad_sv;
+                }
+
+                if (sv->data_pad > ubi->leb_size / 2) {
+                        ubi_err("bad data_pad");
+                        goto bad_sv;
+                }
+
+                last_seb = NULL;
+                ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
+                        cond_resched();
+
+                        last_seb = seb;
+                        leb_count += 1;
+
+                        if (seb->pnum < 0 || seb->ec < 0) {
+                                ubi_err("negative values");
+                                goto bad_seb;
+                        }
+
+                        if (seb->ec < si->min_ec) {
+                                ubi_err("bad si->min_ec (%d), %d found",
+                                        si->min_ec, seb->ec);
+                                goto bad_seb;
+                        }
+
+                        if (seb->ec > si->max_ec) {
+                                ubi_err("bad si->max_ec (%d), %d found",
+                                        si->max_ec, seb->ec);
+                                goto bad_seb;
+                        }
+
+                        if (seb->pnum >= ubi->peb_count) {
+                                ubi_err("too high PEB number %d, total PEBs %d",
+                                        seb->pnum, ubi->peb_count);
+                                goto bad_seb;
+                        }
+
+                        if (sv->vol_type == UBI_STATIC_VOLUME) {
+                                if (seb->lnum >= sv->used_ebs) {
+                                        ubi_err("bad lnum or used_ebs");
+                                        goto bad_seb;
+                                }
+                        } else {
+                                if (sv->used_ebs != 0) {
+                                        ubi_err("non-zero used_ebs");
+                                        goto bad_seb;
+                                }
+                        }
+
+                        if (seb->lnum > sv->highest_lnum) {
+                                ubi_err("incorrect highest_lnum or lnum");
+                                goto bad_seb;
+                        }
+                }
+
+                if (sv->leb_count != leb_count) {
+                        ubi_err("bad leb_count, %d objects in the tree",
+                                leb_count);
+                        goto bad_sv;
+                }
+
+                if (!last_seb)
+                        continue;
+
+                seb = last_seb;
+
+                if (seb->lnum != sv->highest_lnum) {
+                        ubi_err("bad highest_lnum");
+                        goto bad_seb;
+                }
+        }
+
+        if (vols_found != si->vols_found) {
+                ubi_err("bad si->vols_found %d, should be %d",
+                        si->vols_found, vols_found);
+                goto out;
+        }
+
+        /* Check that scanning information is correct */
+        ubi_rb_for_each_entry(rb1, sv, &si->volumes, rb) {
+                last_seb = NULL;
+                ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb) {
+                        int vol_type;
+
+                        cond_resched();
+
+                        last_seb = seb;
+
+                        err = ubi_io_read_vid_hdr(ubi, seb->pnum, vidh, 1);
+                        if (err && err != UBI_IO_BITFLIPS) {
+                                ubi_err("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 (sv->vol_type != vol_type) {
+                                ubi_err("bad vol_type");
+                                goto bad_vid_hdr;
+                        }
+
+                        if (seb->sqnum != be64_to_cpu(vidh->sqnum)) {
+                                ubi_err("bad sqnum %llu", seb->sqnum);
+                                goto bad_vid_hdr;
+                        }
+
+                        if (sv->vol_id != be32_to_cpu(vidh->vol_id)) {
+                                ubi_err("bad vol_id %d", sv->vol_id);
+                                goto bad_vid_hdr;
+                        }
+
+                        if (sv->compat != vidh->compat) {
+                                ubi_err("bad compat %d", vidh->compat);
+                                goto bad_vid_hdr;
+                        }
+
+                        if (seb->lnum != be32_to_cpu(vidh->lnum)) {
+                                ubi_err("bad lnum %d", seb->lnum);
+                                goto bad_vid_hdr;
+                        }
+
+                        if (sv->used_ebs != be32_to_cpu(vidh->used_ebs)) {
+                                ubi_err("bad used_ebs %d", sv->used_ebs);
+                                goto bad_vid_hdr;
+                        }
+
+                        if (sv->data_pad != be32_to_cpu(vidh->data_pad)) {
+                                ubi_err("bad data_pad %d", sv->data_pad);
+                                goto bad_vid_hdr;
+                        }
+                }
+
+                if (!last_seb)
+                        continue;
+
+                if (sv->highest_lnum != be32_to_cpu(vidh->lnum)) {
+                        ubi_err("bad highest_lnum %d", sv->highest_lnum);
+                        goto bad_vid_hdr;
+                }
+
+                if (sv->last_data_size != be32_to_cpu(vidh->data_size)) {
+                        ubi_err("bad last_data_size %d", sv->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, sv, &si->volumes, rb)
+                ubi_rb_for_each_entry(rb2, seb, &sv->root, u.rb)
+                        buf[seb->pnum] = 1;
+
+        list_for_each_entry(seb, &si->free, u.list)
+                buf[seb->pnum] = 1;
+
+        list_for_each_entry(seb, &si->corr, u.list)
+                buf[seb->pnum] = 1;
+
+        list_for_each_entry(seb, &si->erase, u.list)
+                buf[seb->pnum] = 1;
+
+        list_for_each_entry(seb, &si->alien, u.list)
+                buf[seb->pnum] = 1;
+
+        err = 0;
+        for (pnum = 0; pnum < ubi->peb_count; pnum++)
+                if (!buf[pnum]) {
+                        ubi_err("PEB %d is not referred", pnum);
+                        err = 1;
+                }
+
+        kfree(buf);
+        if (err)
+                goto out;
+        return 0;
+
+bad_seb:
+        ubi_err("bad scanning information about LEB %d", seb->lnum);
+        ubi_dbg_dump_seb(seb, 0);
+        ubi_dbg_dump_sv(sv);
+        goto out;
+
+bad_sv:
+        ubi_err("bad scanning information about volume %d", sv->vol_id);
+        ubi_dbg_dump_sv(sv);
+        goto out;
+
+bad_vid_hdr:
+        ubi_err("bad scanning information about volume %d", sv->vol_id);
+        ubi_dbg_dump_sv(sv);
+        ubi_dbg_dump_vid_hdr(vidh);
+
+out:
+        ubi_dbg_dump_stack();
+        return -EINVAL;
+}
+
+#endif /* CONFIG_MTD_UBI_DEBUG */
diff --git a/drivers/mtd/ubi/scan.h b/drivers/mtd/ubi/scan.h
new file mode 100644
index 00000000000..d48aef15ab5
--- /dev/null
+++ b/drivers/mtd/ubi/scan.h
@@ -0,0 +1,174 @@
+/*
+ * 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)
+ */
+
+#ifndef __UBI_SCAN_H__
+#define __UBI_SCAN_H__
+
+/* The erase counter value for this physical eraseblock is unknown */
+#define UBI_SCAN_UNKNOWN_EC (-1)
+
+/**
+ * struct ubi_scan_leb - scanning information about a physical eraseblock.
+ * @ec: erase counter (%UBI_SCAN_UNKNOWN_EC if it is unknown)
+ * @pnum: physical eraseblock number
+ * @lnum: logical eraseblock number
+ * @scrub: if this physical eraseblock needs scrubbing
+ * @copy_flag: this LEB is a copy (@copy_flag is set in VID header of this LEB)
+ * @sqnum: sequence number
+ * @u: unions RB-tree or @list links
+ * @u.rb: link in the per-volume RB-tree of &struct ubi_scan_leb objects
+ * @u.list: link in one of the eraseblock lists
+ *
+ * One object of this type is allocated for each physical eraseblock during
+ * scanning.
+ */
+struct ubi_scan_leb {
+        int ec;
+        int pnum;
+        int lnum;
+        unsigned int scrub:1;
+        unsigned int copy_flag:1;
+        unsigned long long sqnum;
+        union {
+                struct rb_node rb;
+                struct list_head list;
+        } u;
+};
+
+/**
+ * struct ubi_scan_volume - scanning information about a volume.
+ * @vol_id: volume ID
+ * @highest_lnum: highest logical eraseblock number in this volume
+ * @leb_count: number of logical eraseblocks in this volume
+ * @vol_type: volume type
+ * @used_ebs: number of used logical eraseblocks in this volume (only for
+ *            static volumes)
+ * @last_data_size: amount of data in the last logical eraseblock of this
+ *                  volume (always equivalent to the usable logical eraseblock
+ *                  size in case of dynamic volumes)
+ * @data_pad: how many bytes at the end of logical eraseblocks of this volume
+ *            are not used (due to volume alignment)
+ * @compat: compatibility flags of this volume
+ * @rb: link in the volume RB-tree
+ * @root: root of the RB-tree containing all the eraseblock belonging to this
+ *        volume (&struct ubi_scan_leb objects)
+ *
+ * One object of this type is allocated for each volume during scanning.
+ */
+struct ubi_scan_volume {
+        int vol_id;
+        int highest_lnum;
+        int leb_count;
+        int vol_type;
+        int used_ebs;
+        int last_data_size;
+        int data_pad;
+        int compat;
+        struct rb_node rb;
+        struct rb_root root;
+};
+
+/**
+ * struct ubi_scan_info - UBI scanning information.
+ * @volumes: root of the volume RB-tree
+ * @corr: list of corrupted physical eraseblocks
+ * @free: list of free physical eraseblocks
+ * @erase: list of physical eraseblocks which have to be erased
+ * @alien: list of physical eraseblocks which should not be used by UBI (e.g.,
+ *         those belonging to "preserve"-compatible internal volumes)
+ * @corr_peb_count: count of PEBs in the @corr list
+ * @empty_peb_count: count of PEBs which are presumably empty (contain only
+ *                   0xFF bytes)
+ * @alien_peb_count: count of PEBs in the @alien list
+ * @bad_peb_count: count of bad physical eraseblocks
+ * @maybe_bad_peb_count: count of bad physical eraseblocks which are not marked
+ *                       as bad yet, but which look like bad
+ * @vols_found: number of volumes found during scanning
+ * @highest_vol_id: highest volume ID
+ * @is_empty: flag indicating whether the MTD device is empty or not
+ * @min_ec: lowest erase counter value
+ * @max_ec: highest erase counter value
+ * @max_sqnum: highest sequence number value
+ * @mean_ec: mean erase counter value
+ * @ec_sum: a temporary variable used when calculating @mean_ec
+ * @ec_count: a temporary variable used when calculating @mean_ec
+ * @scan_leb_slab: slab cache for &struct ubi_scan_leb objects
+ *
+ * This data structure contains the result of scanning and may be used by other
+ * UBI sub-systems to build final UBI data structures, further error-recovery
+ * and so on.
+ */
+struct ubi_scan_info {
+        struct rb_root volumes;
+        struct list_head corr;
+        struct list_head free;
+        struct list_head erase;
+        struct list_head alien;
+        int corr_peb_count;
+        int empty_peb_count;
+        int alien_peb_count;
+        int bad_peb_count;
+        int maybe_bad_peb_count;
+        int vols_found;
+        int highest_vol_id;
+        int is_empty;
+        int min_ec;
+        int max_ec;
+        unsigned long long max_sqnum;
+        int mean_ec;
+        uint64_t ec_sum;
+        int ec_count;
+        struct kmem_cache *scan_leb_slab;
+};
+
+struct ubi_device;
+struct ubi_vid_hdr;
+
+/*
+ * ubi_scan_move_to_list - move a PEB from the volume tree to a list.
+ *
+ * @sv: volume scanning information
+ * @seb: scanning eraseblock information
+ * @list: the list to move to
+ */
+static inline void ubi_scan_move_to_list(struct ubi_scan_volume *sv,
+                                         struct ubi_scan_leb *seb,
+                                         struct list_head *list)
+{
+                rb_erase(&seb->u.rb, &sv->root);
+                list_add_tail(&seb->u.list, list);
+}
+
+int ubi_scan_add_used(struct ubi_device *ubi, struct ubi_scan_info *si,
+                      int pnum, int ec, const struct ubi_vid_hdr *vid_hdr,
+                      int bitflips);
+struct ubi_scan_volume *ubi_scan_find_sv(const struct ubi_scan_info *si,
+                                         int vol_id);
+struct ubi_scan_leb *ubi_scan_find_seb(const struct ubi_scan_volume *sv,
+                                       int lnum);
+void ubi_scan_rm_volume(struct ubi_scan_info *si, struct ubi_scan_volume *sv);
+struct ubi_scan_leb *ubi_scan_get_free_peb(struct ubi_device *ubi,
+                                           struct ubi_scan_info *si);
+int ubi_scan_erase_peb(struct ubi_device *ubi, const struct ubi_scan_info *si,
+                       int pnum, int ec);
+struct ubi_scan_info *ubi_scan(struct ubi_device *ubi);
+void ubi_scan_destroy_si(struct ubi_scan_info *si);
+
+#endif /* !__UBI_SCAN_H__ */