1 files changed, 809 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/vtbl.c b/drivers/mtd/ubi/vtbl.c
new file mode 100644
index 000000000000..b6fd6bbd941e
--- /dev/null
+++ b/drivers/mtd/ubi/vtbl.c
@@ -0,0 +1,809 @@
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ * Copyright (c) Nokia Corporation, 2006, 2007
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ * the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ * Author: Artem Bityutskiy (Битюцкий Артём)
+ */
+
+/*
+ * This file includes volume table manipulation code. The volume table is an
+ * on-flash table containing volume meta-data like name, number of reserved
+ * physical eraseblocks, type, etc. The volume table is stored in the so-called
+ * "layout volume".
+ *
+ * The layout volume is an internal volume which is organized as follows. It
+ * consists of two logical eraseblocks - LEB 0 and LEB 1. Each logical
+ * eraseblock stores one volume table copy, i.e. LEB 0 and LEB 1 duplicate each
+ * other. This redundancy guarantees robustness to unclean reboots. The volume
+ * table is basically an array of volume table records. Each record contains
+ * full information about the volume and protected by a CRC checksum.
+ *
+ * The volume table is changed, it is first changed in RAM. Then LEB 0 is
+ * erased, and the updated volume table is written back to LEB 0. Then same for
+ * LEB 1. This scheme guarantees recoverability from unclean reboots.
+ *
+ * In this UBI implementation the on-flash volume table does not contain any
+ * information about how many data static volumes contain. This information may
+ * be found from the scanning data.
+ *
+ * But it would still be beneficial to store this information in the volume
+ * table. For example, suppose we have a static volume X, and all its physical
+ * eraseblocks became bad for some reasons. Suppose we are attaching the
+ * corresponding MTD device, the scanning has found no logical eraseblocks
+ * corresponding to the volume X. According to the volume table volume X does
+ * exist. So we don't know whether it is just empty or all its physical
+ * eraseblocks went bad. So we cannot alarm the user about this corruption.
+ *
+ * The volume table also stores so-called "update marker", which is used for
+ * volume updates. Before updating the volume, the update marker is set, and
+ * after the update operation is finished, the update marker is cleared. So if
+ * the update operation was interrupted (e.g. by an unclean reboot) - the
+ * update marker is still there and we know that the volume's contents is
+ * damaged.
+ */
+
+#include <linux/crc32.h>
+#include <linux/err.h>
+#include <asm/div64.h>
+#include "ubi.h"
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+static void paranoid_vtbl_check(const struct ubi_device *ubi);
+#else
+#define paranoid_vtbl_check(ubi)
+#endif
+
+/* Empty volume table record */
+static struct ubi_vtbl_record empty_vtbl_record;
+
+/**
+ * ubi_change_vtbl_record - change volume table record.
+ * @ubi: UBI device description object
+ * @idx: table index to change
+ * @vtbl_rec: new volume table record
+ *
+ * This function changes volume table record @idx. If @vtbl_rec is %NULL, empty
+ * volume table record is written. The caller does not have to calculate CRC of
+ * the record as it is done by this function. Returns zero in case of success
+ * and a negative error code in case of failure.
+ */
+int ubi_change_vtbl_record(struct ubi_device *ubi, int idx,
+                           struct ubi_vtbl_record *vtbl_rec)
+{
+        int i, err;
+        uint32_t crc;
+
+        ubi_assert(idx >= 0 && idx < ubi->vtbl_slots);
+
+        if (!vtbl_rec)
+                vtbl_rec = &empty_vtbl_record;
+        else {
+                crc = crc32(UBI_CRC32_INIT, vtbl_rec, UBI_VTBL_RECORD_SIZE_CRC);
+                vtbl_rec->crc = cpu_to_ubi32(crc);
+        }
+
+        dbg_msg("change record %d", idx);
+        ubi_dbg_dump_vtbl_record(vtbl_rec, idx);
+
+        mutex_lock(&ubi->vtbl_mutex);
+        memcpy(&ubi->vtbl[idx], vtbl_rec, sizeof(struct ubi_vtbl_record));
+        for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
+                err = ubi_eba_unmap_leb(ubi, UBI_LAYOUT_VOL_ID, i);
+                if (err) {
+                        mutex_unlock(&ubi->vtbl_mutex);
+                        return err;
+                }
+                err = ubi_eba_write_leb(ubi, UBI_LAYOUT_VOL_ID, i, ubi->vtbl, 0,
+                                        ubi->vtbl_size, UBI_LONGTERM);
+                if (err) {
+                        mutex_unlock(&ubi->vtbl_mutex);
+                        return err;
+                }
+        }
+
+        paranoid_vtbl_check(ubi);
+        mutex_unlock(&ubi->vtbl_mutex);
+        return ubi_wl_flush(ubi);
+}
+
+/**
+ * vol_til_check - check if volume table is not corrupted and contains sensible
+ * data.
+ *
+ * @ubi: UBI device description object
+ * @vtbl: volume table
+ *
+ * This function returns zero if @vtbl is all right, %1 if CRC is incorrect,
+ * and %-EINVAL if it contains inconsistent data.
+ */
+static int vtbl_check(const struct ubi_device *ubi,
+                      const struct ubi_vtbl_record *vtbl)
+{
+        int i, n, reserved_pebs, alignment, data_pad, vol_type, name_len;
+        int upd_marker;
+        uint32_t crc;
+        const char *name;
+
+        for (i = 0; i < ubi->vtbl_slots; i++) {
+                cond_resched();
+
+                reserved_pebs = ubi32_to_cpu(vtbl[i].reserved_pebs);
+                alignment = ubi32_to_cpu(vtbl[i].alignment);
+                data_pad = ubi32_to_cpu(vtbl[i].data_pad);
+                upd_marker = vtbl[i].upd_marker;
+                vol_type = vtbl[i].vol_type;
+                name_len = ubi16_to_cpu(vtbl[i].name_len);
+                name = &vtbl[i].name[0];
+
+                crc = crc32(UBI_CRC32_INIT, &vtbl[i], UBI_VTBL_RECORD_SIZE_CRC);
+                if (ubi32_to_cpu(vtbl[i].crc) != crc) {
+                        ubi_err("bad CRC at record %u: %#08x, not %#08x",
+                                 i, crc, ubi32_to_cpu(vtbl[i].crc));
+                        ubi_dbg_dump_vtbl_record(&vtbl[i], i);
+                        return 1;
+                }
+
+                if (reserved_pebs == 0) {
+                        if (memcmp(&vtbl[i], &empty_vtbl_record,
+                                                UBI_VTBL_RECORD_SIZE)) {
+                                dbg_err("bad empty record");
+                                goto bad;
+                        }
+                        continue;
+                }
+
+                if (reserved_pebs < 0 || alignment < 0 || data_pad < 0 ||
+                    name_len < 0) {
+                        dbg_err("negative values");
+                        goto bad;
+                }
+
+                if (alignment > ubi->leb_size || alignment == 0) {
+                        dbg_err("bad alignment");
+                        goto bad;
+                }
+
+                n = alignment % ubi->min_io_size;
+                if (alignment != 1 && n) {
+                        dbg_err("alignment is not multiple of min I/O unit");
+                        goto bad;
+                }
+
+                n = ubi->leb_size % alignment;
+                if (data_pad != n) {
+                        dbg_err("bad data_pad, has to be %d", n);
+                        goto bad;
+                }
+
+                if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
+                        dbg_err("bad vol_type");
+                        goto bad;
+                }
+
+                if (upd_marker != 0 && upd_marker != 1) {
+                        dbg_err("bad upd_marker");
+                        goto bad;
+                }
+
+                if (reserved_pebs > ubi->good_peb_count) {
+                        dbg_err("too large reserved_pebs, good PEBs %d",
+                                ubi->good_peb_count);
+                        goto bad;
+                }
+
+                if (name_len > UBI_VOL_NAME_MAX) {
+                        dbg_err("too long volume name, max %d",
+                                UBI_VOL_NAME_MAX);
+                        goto bad;
+                }
+
+                if (name[0] == '\0') {
+                        dbg_err("NULL volume name");
+                        goto bad;
+                }
+
+                if (name_len != strnlen(name, name_len + 1)) {
+                        dbg_err("bad name_len");
+                        goto bad;
+                }
+        }
+
+        /* Checks that all names are unique */
+        for (i = 0; i < ubi->vtbl_slots - 1; i++) {
+                for (n = i + 1; n < ubi->vtbl_slots; n++) {
+                        int len1 = ubi16_to_cpu(vtbl[i].name_len);
+                        int len2 = ubi16_to_cpu(vtbl[n].name_len);
+
+                        if (len1 > 0 && len1 == len2 &&
+                            !strncmp(vtbl[i].name, vtbl[n].name, len1)) {
+                                ubi_err("volumes %d and %d have the same name"
+                                        " \"%s\"", i, n, vtbl[i].name);
+                                ubi_dbg_dump_vtbl_record(&vtbl[i], i);
+                                ubi_dbg_dump_vtbl_record(&vtbl[n], n);
+                                return -EINVAL;
+                        }
+                }
+        }
+
+        return 0;
+
+bad:
+        ubi_err("volume table check failed, record %d", i);
+        ubi_dbg_dump_vtbl_record(&vtbl[i], i);
+        return -EINVAL;
+}
+
+/**
+ * create_vtbl - create a copy of volume table.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ * @copy: number of the volume table copy
+ * @vtbl: contents of the volume table
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+static int create_vtbl(const struct ubi_device *ubi, struct ubi_scan_info *si,
+                       int copy, void *vtbl)
+{
+        int err, tries = 0;
+        static struct ubi_vid_hdr *vid_hdr;
+        struct ubi_scan_volume *sv;
+        struct ubi_scan_leb *new_seb, *old_seb = NULL;
+
+        ubi_msg("create volume table (copy #%d)", copy + 1);
+
+        vid_hdr = ubi_zalloc_vid_hdr(ubi);
+        if (!vid_hdr)
+                return -ENOMEM;
+
+        /*
+         * Check if there is a logical eraseblock which would have to contain
+         * this volume table copy was found during scanning. It has to be wiped
+         * out.
+         */
+        sv = ubi_scan_find_sv(si, UBI_LAYOUT_VOL_ID);
+        if (sv)
+                old_seb = ubi_scan_find_seb(sv, copy);
+
+retry:
+        new_seb = ubi_scan_get_free_peb(ubi, si);
+        if (IS_ERR(new_seb)) {
+                err = PTR_ERR(new_seb);
+                goto out_free;
+        }
+
+        vid_hdr->vol_type = UBI_VID_DYNAMIC;
+        vid_hdr->vol_id = cpu_to_ubi32(UBI_LAYOUT_VOL_ID);
+        vid_hdr->compat = UBI_LAYOUT_VOLUME_COMPAT;
+        vid_hdr->data_size = vid_hdr->used_ebs =
+                             vid_hdr->data_pad = cpu_to_ubi32(0);
+        vid_hdr->lnum = cpu_to_ubi32(copy);
+        vid_hdr->sqnum = cpu_to_ubi64(++si->max_sqnum);
+        vid_hdr->leb_ver = cpu_to_ubi32(old_seb ? old_seb->leb_ver + 1: 0);
+
+        /* The EC header is already there, write the VID header */
+        err = ubi_io_write_vid_hdr(ubi, new_seb->pnum, vid_hdr);
+        if (err)
+                goto write_error;
+
+        /* Write the layout volume contents */
+        err = ubi_io_write_data(ubi, vtbl, new_seb->pnum, 0, ubi->vtbl_size);
+        if (err)
+                goto write_error;
+
+        /*
+         * And add it to the scanning information. Don't delete the old
+         * @old_seb as it will be deleted and freed in 'ubi_scan_add_used()'.
+         */
+        err = ubi_scan_add_used(ubi, si, new_seb->pnum, new_seb->ec,
+                                vid_hdr, 0);
+        kfree(new_seb);
+        ubi_free_vid_hdr(ubi, vid_hdr);
+        return err;
+
+write_error:
+        kfree(new_seb);
+        /* May be this physical eraseblock went bad, try to pick another one */
+        if (++tries <= 5) {
+                err = ubi_scan_add_to_list(si, new_seb->pnum, new_seb->ec,
+                                           &si->corr);
+                if (!err)
+                        goto retry;
+        }
+out_free:
+        ubi_free_vid_hdr(ubi, vid_hdr);
+        return err;
+
+}
+
+/**
+ * process_lvol - process the layout volume.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ * @sv: layout volume scanning information
+ *
+ * This function is responsible for reading the layout volume, ensuring it is
+ * not corrupted, and recovering from corruptions if needed. Returns volume
+ * table in case of success and a negative error code in case of failure.
+ */
+static struct ubi_vtbl_record *process_lvol(const struct ubi_device *ubi,
+                                            struct ubi_scan_info *si,
+                                            struct ubi_scan_volume *sv)
+{
+        int err;
+        struct rb_node *rb;
+        struct ubi_scan_leb *seb;
+        struct ubi_vtbl_record *leb[UBI_LAYOUT_VOLUME_EBS] = { NULL, NULL };
+        int leb_corrupted[UBI_LAYOUT_VOLUME_EBS] = {1, 1};
+
+        /*
+         * UBI goes through the following steps when it changes the layout
+         * volume:
+         * a. erase LEB 0;
+         * b. write new data to LEB 0;
+         * c. erase LEB 1;
+         * d. write new data to LEB 1.
+         *
+         * Before the change, both LEBs contain the same data.
+         *
+         * Due to unclean reboots, the contents of LEB 0 may be lost, but there
+         * should LEB 1. So it is OK if LEB 0 is corrupted while LEB 1 is not.
+         * Similarly, LEB 1 may be lost, but there should be LEB 0. And
+         * finally, unclean reboots may result in a situation when neither LEB
+         * 0 nor LEB 1 are corrupted, but they are different. In this case, LEB
+         * 0 contains more recent information.
+         *
+         * So the plan is to first check LEB 0. Then
+         * a. if LEB 0 is OK, it must be containing the most resent data; then
+         *    we compare it with LEB 1, and if they are different, we copy LEB
+         *    0 to LEB 1;
+         * b. if LEB 0 is corrupted, but LEB 1 has to be OK, and we copy LEB 1
+         *    to LEB 0.
+         */
+
+        dbg_msg("check layout volume");
+
+        /* Read both LEB 0 and LEB 1 into memory */
+        ubi_rb_for_each_entry(rb, seb, &sv->root, u.rb) {
+                leb[seb->lnum] = kzalloc(ubi->vtbl_size, GFP_KERNEL);
+                if (!leb[seb->lnum]) {
+                        err = -ENOMEM;
+                        goto out_free;
+                }
+
+                err = ubi_io_read_data(ubi, leb[seb->lnum], seb->pnum, 0,
+                                       ubi->vtbl_size);
+                if (err == UBI_IO_BITFLIPS || err == -EBADMSG)
+                        /* Scrub the PEB later */
+                        seb->scrub = 1;
+                else if (err)
+                        goto out_free;
+        }
+
+        err = -EINVAL;
+        if (leb[0]) {
+                leb_corrupted[0] = vtbl_check(ubi, leb[0]);
+                if (leb_corrupted[0] < 0)
+                        goto out_free;
+        }
+
+        if (!leb_corrupted[0]) {
+                /* LEB 0 is OK */
+                if (leb[1])
+                        leb_corrupted[1] = memcmp(leb[0], leb[1], ubi->vtbl_size);
+                if (leb_corrupted[1]) {
+                        ubi_warn("volume table copy #2 is corrupted");
+                        err = create_vtbl(ubi, si, 1, leb[0]);
+                        if (err)
+                                goto out_free;
+                        ubi_msg("volume table was restored");
+                }
+
+                /* Both LEB 1 and LEB 2 are OK and consistent */
+                kfree(leb[1]);
+                return leb[0];
+        } else {
+                /* LEB 0 is corrupted or does not exist */
+                if (leb[1]) {
+                        leb_corrupted[1] = vtbl_check(ubi, leb[1]);
+                        if (leb_corrupted[1] < 0)
+                                goto out_free;
+                }
+                if (leb_corrupted[1]) {
+                        /* Both LEB 0 and LEB 1 are corrupted */
+                        ubi_err("both volume tables are corrupted");
+                        goto out_free;
+                }
+
+                ubi_warn("volume table copy #1 is corrupted");
+                err = create_vtbl(ubi, si, 0, leb[1]);
+                if (err)
+                        goto out_free;
+                ubi_msg("volume table was restored");
+
+                kfree(leb[0]);
+                return leb[1];
+        }
+
+out_free:
+        kfree(leb[0]);
+        kfree(leb[1]);
+        return ERR_PTR(err);
+}
+
+/**
+ * create_empty_lvol - create empty layout volume.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ *
+ * This function returns volume table contents in case of success and a
+ * negative error code in case of failure.
+ */
+static struct ubi_vtbl_record *create_empty_lvol(const struct ubi_device *ubi,
+                                                 struct ubi_scan_info *si)
+{
+        int i;
+        struct ubi_vtbl_record *vtbl;
+
+        vtbl = kzalloc(ubi->vtbl_size, GFP_KERNEL);
+        if (!vtbl)
+                return ERR_PTR(-ENOMEM);
+
+        for (i = 0; i < ubi->vtbl_slots; i++)
+                memcpy(&vtbl[i], &empty_vtbl_record, UBI_VTBL_RECORD_SIZE);
+
+        for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
+                int err;
+
+                err = create_vtbl(ubi, si, i, vtbl);
+                if (err) {
+                        kfree(vtbl);
+                        return ERR_PTR(err);
+                }
+        }
+
+        return vtbl;
+}
+
+/**
+ * init_volumes - initialize volume information for existing volumes.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ * @vtbl: volume table
+ *
+ * This function allocates volume description objects for existing volumes.
+ * Returns zero in case of success and a negative error code in case of
+ * failure.
+ */
+static int init_volumes(struct ubi_device *ubi, const struct ubi_scan_info *si,
+                        const struct ubi_vtbl_record *vtbl)
+{
+        int i, reserved_pebs = 0;
+        struct ubi_scan_volume *sv;
+        struct ubi_volume *vol;
+
+        for (i = 0; i < ubi->vtbl_slots; i++) {
+                cond_resched();
+
+                if (ubi32_to_cpu(vtbl[i].reserved_pebs) == 0)
+                        continue; /* Empty record */
+
+                vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
+                if (!vol)
+                        return -ENOMEM;
+
+                vol->reserved_pebs = ubi32_to_cpu(vtbl[i].reserved_pebs);
+                vol->alignment = ubi32_to_cpu(vtbl[i].alignment);
+                vol->data_pad = ubi32_to_cpu(vtbl[i].data_pad);
+                vol->vol_type = vtbl[i].vol_type == UBI_VID_DYNAMIC ?
+                                        UBI_DYNAMIC_VOLUME : UBI_STATIC_VOLUME;
+                vol->name_len = ubi16_to_cpu(vtbl[i].name_len);
+                vol->usable_leb_size = ubi->leb_size - vol->data_pad;
+                memcpy(vol->name, vtbl[i].name, vol->name_len);
+                vol->name[vol->name_len] = '\0';
+                vol->vol_id = i;
+
+                ubi_assert(!ubi->volumes[i]);
+                ubi->volumes[i] = vol;
+                ubi->vol_count += 1;
+                vol->ubi = ubi;
+                reserved_pebs += vol->reserved_pebs;
+
+                /*
+                 * In case of dynamic volume UBI knows nothing about how many
+                 * data is stored there. So assume the whole volume is used.
+                 */
+                if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
+                        vol->used_ebs = vol->reserved_pebs;
+                        vol->last_eb_bytes = vol->usable_leb_size;
+                        vol->used_bytes = vol->used_ebs * vol->usable_leb_size;
+                        continue;
+                }
+
+                /* Static volumes only */
+                sv = ubi_scan_find_sv(si, i);
+                if (!sv) {
+                        /*
+                         * No eraseblocks belonging to this volume found. We
+                         * don't actually know whether this static volume is
+                         * completely corrupted or just contains no data. And
+                         * we cannot know this as long as data size is not
+                         * stored on flash. So we just assume the volume is
+                         * empty. FIXME: this should be handled.
+                         */
+                        continue;
+                }
+
+                if (sv->leb_count != sv->used_ebs) {
+                        /*
+                         * We found a static volume which misses several
+                         * eraseblocks. Treat it as corrupted.
+                         */
+                        ubi_warn("static volume %d misses %d LEBs - corrupted",
+                                 sv->vol_id, sv->used_ebs - sv->leb_count);
+                        vol->corrupted = 1;
+                        continue;
+                }
+
+                vol->used_ebs = sv->used_ebs;
+                vol->used_bytes = (vol->used_ebs - 1) * vol->usable_leb_size;
+                vol->used_bytes += sv->last_data_size;
+                vol->last_eb_bytes = sv->last_data_size;
+        }
+
+        vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
+        if (!vol)
+                return -ENOMEM;
+
+        vol->reserved_pebs = UBI_LAYOUT_VOLUME_EBS;
+        vol->alignment = 1;
+        vol->vol_type = UBI_DYNAMIC_VOLUME;
+        vol->name_len = sizeof(UBI_LAYOUT_VOLUME_NAME) - 1;
+        memcpy(vol->name, UBI_LAYOUT_VOLUME_NAME, vol->name_len + 1);
+        vol->usable_leb_size = ubi->leb_size;
+        vol->used_ebs = vol->reserved_pebs;
+        vol->last_eb_bytes = vol->reserved_pebs;
+        vol->used_bytes = vol->used_ebs * (ubi->leb_size - vol->data_pad);
+        vol->vol_id = UBI_LAYOUT_VOL_ID;
+
+        ubi_assert(!ubi->volumes[i]);
+        ubi->volumes[vol_id2idx(ubi, vol->vol_id)] = vol;
+        reserved_pebs += vol->reserved_pebs;
+        ubi->vol_count += 1;
+        vol->ubi = ubi;
+
+        if (reserved_pebs > ubi->avail_pebs)
+                ubi_err("not enough PEBs, required %d, available %d",
+                        reserved_pebs, ubi->avail_pebs);
+        ubi->rsvd_pebs += reserved_pebs;
+        ubi->avail_pebs -= reserved_pebs;
+
+        return 0;
+}
+
+/**
+ * check_sv - check volume scanning information.
+ * @vol: UBI volume description object
+ * @sv: volume scanning information
+ *
+ * This function returns zero if the volume scanning information is consistent
+ * to the data read from the volume tabla, and %-EINVAL if not.
+ */
+static int check_sv(const struct ubi_volume *vol,
+                    const struct ubi_scan_volume *sv)
+{
+        if (sv->highest_lnum >= vol->reserved_pebs) {
+                dbg_err("bad highest_lnum");
+                goto bad;
+        }
+        if (sv->leb_count > vol->reserved_pebs) {
+                dbg_err("bad leb_count");
+                goto bad;
+        }
+        if (sv->vol_type != vol->vol_type) {
+                dbg_err("bad vol_type");
+                goto bad;
+        }
+        if (sv->used_ebs > vol->reserved_pebs) {
+                dbg_err("bad used_ebs");
+                goto bad;
+        }
+        if (sv->data_pad != vol->data_pad) {
+                dbg_err("bad data_pad");
+                goto bad;
+        }
+        return 0;
+
+bad:
+        ubi_err("bad scanning information");
+        ubi_dbg_dump_sv(sv);
+        ubi_dbg_dump_vol_info(vol);
+        return -EINVAL;
+}
+
+/**
+ * check_scanning_info - check that scanning information.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ *
+ * Even though we protect on-flash data by CRC checksums, we still don't trust
+ * the media. This function ensures that scanning information is consistent to
+ * the information read from the volume table. Returns zero if the scanning
+ * information is OK and %-EINVAL if it is not.
+ */
+static int check_scanning_info(const struct ubi_device *ubi,
+                               struct ubi_scan_info *si)
+{
+        int err, i;
+        struct ubi_scan_volume *sv;
+        struct ubi_volume *vol;
+
+        if (si->vols_found > UBI_INT_VOL_COUNT + ubi->vtbl_slots) {
+                ubi_err("scanning found %d volumes, maximum is %d + %d",
+                        si->vols_found, UBI_INT_VOL_COUNT, ubi->vtbl_slots);
+                return -EINVAL;
+        }
+
+        if (si->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT&&
+            si->highest_vol_id < UBI_INTERNAL_VOL_START) {
+                ubi_err("too large volume ID %d found by scanning",
+                        si->highest_vol_id);
+                return -EINVAL;
+        }
+
+
+        for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
+                cond_resched();
+
+                sv = ubi_scan_find_sv(si, i);
+                vol = ubi->volumes[i];
+                if (!vol) {
+                        if (sv)
+                                ubi_scan_rm_volume(si, sv);
+                        continue;
+                }
+
+                if (vol->reserved_pebs == 0) {
+                        ubi_assert(i < ubi->vtbl_slots);
+
+                        if (!sv)
+                                continue;
+
+                        /*
+                         * During scanning we found a volume which does not
+                         * exist according to the information in the volume
+                         * table. This must have happened due to an unclean
+                         * reboot while the volume was being removed. Discard
+                         * these eraseblocks.
+                         */
+                        ubi_msg("finish volume %d removal", sv->vol_id);
+                        ubi_scan_rm_volume(si, sv);
+                } else if (sv) {
+                        err = check_sv(vol, sv);
+                        if (err)
+                                return err;
+                }
+        }
+
+        return 0;
+}
+
+/**
+ * ubi_read_volume_table - read volume table.
+ * information.
+ * @ubi: UBI device description object
+ * @si: scanning information
+ *
+ * This function reads volume table, checks it, recover from errors if needed,
+ * or creates it if needed. Returns zero in case of success and a negative
+ * error code in case of failure.
+ */
+int ubi_read_volume_table(struct ubi_device *ubi, struct ubi_scan_info *si)
+{
+        int i, err;
+        struct ubi_scan_volume *sv;
+
+        empty_vtbl_record.crc = cpu_to_ubi32(0xf116c36b);
+
+        /*
+         * The number of supported volumes is limited by the eraseblock size
+         * and by the UBI_MAX_VOLUMES constant.
+         */
+        ubi->vtbl_slots = ubi->leb_size / UBI_VTBL_RECORD_SIZE;
+        if (ubi->vtbl_slots > UBI_MAX_VOLUMES)
+                ubi->vtbl_slots = UBI_MAX_VOLUMES;
+
+        ubi->vtbl_size = ubi->vtbl_slots * UBI_VTBL_RECORD_SIZE;
+        ubi->vtbl_size = ALIGN(ubi->vtbl_size, ubi->min_io_size);
+
+        sv = ubi_scan_find_sv(si, UBI_LAYOUT_VOL_ID);
+        if (!sv) {
+                /*
+                 * No logical eraseblocks belonging to the layout volume were
+                 * found. This could mean that the flash is just empty. In
+                 * this case we create empty layout volume.
+                 *
+                 * But if flash is not empty this must be a corruption or the
+                 * MTD device just contains garbage.
+                 */
+                if (si->is_empty) {
+                        ubi->vtbl = create_empty_lvol(ubi, si);
+                        if (IS_ERR(ubi->vtbl))
+                                return PTR_ERR(ubi->vtbl);
+                } else {
+                        ubi_err("the layout volume was not found");
+                        return -EINVAL;
+                }
+        } else {
+                if (sv->leb_count > UBI_LAYOUT_VOLUME_EBS) {
+                        /* This must not happen with proper UBI images */
+                        dbg_err("too many LEBs (%d) in layout volume",
+                                sv->leb_count);
+                        return -EINVAL;
+                }
+
+                ubi->vtbl = process_lvol(ubi, si, sv);
+                if (IS_ERR(ubi->vtbl))
+                        return PTR_ERR(ubi->vtbl);
+        }
+
+        ubi->avail_pebs = ubi->good_peb_count;
+
+        /*
+         * The layout volume is OK, initialize the corresponding in-RAM data
+         * structures.
+         */
+        err = init_volumes(ubi, si, ubi->vtbl);
+        if (err)
+                goto out_free;
+
+        /*
+         * Get sure that the scanning information is consistent to the
+         * information stored in the volume table.
+         */
+        err = check_scanning_info(ubi, si);
+        if (err)
+                goto out_free;
+
+        return 0;
+
+out_free:
+        kfree(ubi->vtbl);
+        for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++)
+                if (ubi->volumes[i]) {
+                        kfree(ubi->volumes[i]);
+                        ubi->volumes[i] = NULL;
+                }
+        return err;
+}
+
+#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
+
+/**
+ * paranoid_vtbl_check - check volume table.
+ * @ubi: UBI device description object
+ */
+static void paranoid_vtbl_check(const struct ubi_device *ubi)
+{
+        if (vtbl_check(ubi, ubi->vtbl)) {
+                ubi_err("paranoid check failed");
+                BUG();
+        }
+}
+
+#endif /* CONFIG_MTD_UBI_DEBUG_PARANOID */