Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 871 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/vtbl.c b/drivers/mtd/ubi/vtbl.c
new file mode 100644
index 000000000..f700f0e4f
--- /dev/null
+++ b/drivers/mtd/ubi/vtbl.c
@@ -0,0 +1,871 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) International Business Machines Corp., 2006
+ * Copyright (c) Nokia Corporation, 2006, 2007
+ *
+ * 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. Note,
+ * nowadays we use the atomic LEB change operation when updating the volume
+ * table, so we do not really need 2 LEBs anymore, but we preserve the older
+ * design for the backward compatibility reasons.
+ *
+ * When 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 much data static volumes contain.
+ *
+ * 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, for some reason we find 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 properly.
+ *
+ * The volume table also stores so-called "update marker", which is used for
+ * volume updates. Before updating the volume, the update marker is set, and
+ * after the update operation is finished, the update marker is cleared. So if
+ * the update operation was interrupted (e.g. by an unclean reboot) - the
+ * update marker is still there and we know that the volume's contents is
+ * damaged.
+ */
+
+#include <linux/crc32.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <asm/div64.h>
+#include "ubi.h"
+
+static void self_vtbl_check(const struct ubi_device *ubi);
+
+/* Empty volume table record */
+static struct ubi_vtbl_record empty_vtbl_record;
+
+/**
+ * ubi_update_layout_vol - helper for updatting layout volumes on flash
+ * @ubi: UBI device description object
+ */
+static int ubi_update_layout_vol(struct ubi_device *ubi)
+{
+	struct ubi_volume *layout_vol;
+	int i, err;
+
+	layout_vol = ubi->volumes[vol_id2idx(ubi, UBI_LAYOUT_VOLUME_ID)];
+	for (i = 0; i < UBI_LAYOUT_VOLUME_EBS; i++) {
+		err = ubi_eba_atomic_leb_change(ubi, layout_vol, i, ubi->vtbl,
+						ubi->vtbl_size);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+/**
+ * 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 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_be32(crc);
+	}
+
+	memcpy(&ubi->vtbl[idx], vtbl_rec, sizeof(struct ubi_vtbl_record));
+	err = ubi_update_layout_vol(ubi);
+
+	self_vtbl_check(ubi);
+	return err ? err : 0;
+}
+
+/**
+ * ubi_vtbl_rename_volumes - rename UBI volumes in the volume table.
+ * @ubi: UBI device description object
+ * @rename_list: list of &struct ubi_rename_entry objects
+ *
+ * This function re-names multiple volumes specified in @req in the volume
+ * table. Returns zero in case of success and a negative error code in case of
+ * failure.
+ */
+int ubi_vtbl_rename_volumes(struct ubi_device *ubi,
+			    struct list_head *rename_list)
+{
+	struct ubi_rename_entry *re;
+
+	list_for_each_entry(re, rename_list, list) {
+		uint32_t crc;
+		struct ubi_volume *vol = re->desc->vol;
+		struct ubi_vtbl_record *vtbl_rec = &ubi->vtbl[vol->vol_id];
+
+		if (re->remove) {
+			memcpy(vtbl_rec, &empty_vtbl_record,
+			       sizeof(struct ubi_vtbl_record));
+			continue;
+		}
+
+		vtbl_rec->name_len = cpu_to_be16(re->new_name_len);
+		memcpy(vtbl_rec->name, re->new_name, re->new_name_len);
+		memset(vtbl_rec->name + re->new_name_len, 0,
+		       UBI_VOL_NAME_MAX + 1 - re->new_name_len);
+		crc = crc32(UBI_CRC32_INIT, vtbl_rec,
+			    UBI_VTBL_RECORD_SIZE_CRC);
+		vtbl_rec->crc = cpu_to_be32(crc);
+	}
+
+	return ubi_update_layout_vol(ubi);
+}
+
+/**
+ * vtbl_check - check if volume table is not corrupted and sensible.
+ * @ubi: UBI device description object
+ * @vtbl: volume table
+ *
+ * This function returns zero if @vtbl is all right, %1 if CRC is incorrect,
+ * and %-EINVAL if it contains inconsistent data.
+ */
+static int vtbl_check(const struct ubi_device *ubi,
+		      const struct ubi_vtbl_record *vtbl)
+{
+	int i, n, reserved_pebs, alignment, data_pad, vol_type, name_len;
+	int upd_marker, err;
+	uint32_t crc;
+	const char *name;
+
+	for (i = 0; i < ubi->vtbl_slots; i++) {
+		cond_resched();
+
+		reserved_pebs = be32_to_cpu(vtbl[i].reserved_pebs);
+		alignment = be32_to_cpu(vtbl[i].alignment);
+		data_pad = be32_to_cpu(vtbl[i].data_pad);
+		upd_marker = vtbl[i].upd_marker;
+		vol_type = vtbl[i].vol_type;
+		name_len = be16_to_cpu(vtbl[i].name_len);
+		name = &vtbl[i].name[0];
+
+		crc = crc32(UBI_CRC32_INIT, &vtbl[i], UBI_VTBL_RECORD_SIZE_CRC);
+		if (be32_to_cpu(vtbl[i].crc) != crc) {
+			ubi_err(ubi, "bad CRC at record %u: %#08x, not %#08x",
+				 i, crc, be32_to_cpu(vtbl[i].crc));
+			ubi_dump_vtbl_record(&vtbl[i], i);
+			return 1;
+		}
+
+		if (reserved_pebs == 0) {
+			if (memcmp(&vtbl[i], &empty_vtbl_record,
+						UBI_VTBL_RECORD_SIZE)) {
+				err = 2;
+				goto bad;
+			}
+			continue;
+		}
+
+		if (reserved_pebs < 0 || alignment < 0 || data_pad < 0 ||
+		    name_len < 0) {
+			err = 3;
+			goto bad;
+		}
+
+		if (alignment > ubi->leb_size || alignment == 0) {
+			err = 4;
+			goto bad;
+		}
+
+		n = alignment & (ubi->min_io_size - 1);
+		if (alignment != 1 && n) {
+			err = 5;
+			goto bad;
+		}
+
+		n = ubi->leb_size % alignment;
+		if (data_pad != n) {
+			ubi_err(ubi, "bad data_pad, has to be %d", n);
+			err = 6;
+			goto bad;
+		}
+
+		if (vol_type != UBI_VID_DYNAMIC && vol_type != UBI_VID_STATIC) {
+			err = 7;
+			goto bad;
+		}
+
+		if (upd_marker != 0 && upd_marker != 1) {
+			err = 8;
+			goto bad;
+		}
+
+		if (reserved_pebs > ubi->good_peb_count) {
+			ubi_err(ubi, "too large reserved_pebs %d, good PEBs %d",
+				reserved_pebs, ubi->good_peb_count);
+			err = 9;
+			goto bad;
+		}
+
+		if (name_len > UBI_VOL_NAME_MAX) {
+			err = 10;
+			goto bad;
+		}
+
+		if (name[0] == '\0') {
+			err = 11;
+			goto bad;
+		}
+
+		if (name_len != strnlen(name, name_len + 1)) {
+			err = 12;
+			goto bad;
+		}
+	}
+
+	/* Checks that all names are unique */
+	for (i = 0; i < ubi->vtbl_slots - 1; i++) {
+		for (n = i + 1; n < ubi->vtbl_slots; n++) {
+			int len1 = be16_to_cpu(vtbl[i].name_len);
+			int len2 = be16_to_cpu(vtbl[n].name_len);
+
+			if (len1 > 0 && len1 == len2 &&
+			    !strncmp(vtbl[i].name, vtbl[n].name, len1)) {
+				ubi_err(ubi, "volumes %d and %d have the same name \"%s\"",
+					i, n, vtbl[i].name);
+				ubi_dump_vtbl_record(&vtbl[i], i);
+				ubi_dump_vtbl_record(&vtbl[n], n);
+				return -EINVAL;
+			}
+		}
+	}
+
+	return 0;
+
+bad:
+	ubi_err(ubi, "volume table check failed: record %d, error %d", i, err);
+	ubi_dump_vtbl_record(&vtbl[i], i);
+	return -EINVAL;
+}
+
+/**
+ * create_vtbl - create a copy of volume table.
+ * @ubi: UBI device description object
+ * @ai: attaching information
+ * @copy: number of the volume table copy
+ * @vtbl: contents of the volume table
+ *
+ * This function returns zero in case of success and a negative error code in
+ * case of failure.
+ */
+static int create_vtbl(struct ubi_device *ubi, struct ubi_attach_info *ai,
+		       int copy, void *vtbl)
+{
+	int err, tries = 0;
+	struct ubi_vid_io_buf *vidb;
+	struct ubi_vid_hdr *vid_hdr;
+	struct ubi_ainf_peb *new_aeb;
+
+	dbg_gen("create volume table (copy #%d)", copy + 1);
+
+	vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!vidb)
+		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
+
+retry:
+	new_aeb = ubi_early_get_peb(ubi, ai);
+	if (IS_ERR(new_aeb)) {
+		err = PTR_ERR(new_aeb);
+		goto out_free;
+	}
+
+	vid_hdr->vol_type = UBI_LAYOUT_VOLUME_TYPE;
+	vid_hdr->vol_id = cpu_to_be32(UBI_LAYOUT_VOLUME_ID);
+	vid_hdr->compat = UBI_LAYOUT_VOLUME_COMPAT;
+	vid_hdr->data_size = vid_hdr->used_ebs =
+			     vid_hdr->data_pad = cpu_to_be32(0);
+	vid_hdr->lnum = cpu_to_be32(copy);
+	vid_hdr->sqnum = cpu_to_be64(++ai->max_sqnum);
+
+	/* The EC header is already there, write the VID header */
+	err = ubi_io_write_vid_hdr(ubi, new_aeb->pnum, vidb);
+	if (err)
+		goto write_error;
+
+	/* Write the layout volume contents */
+	err = ubi_io_write_data(ubi, vtbl, new_aeb->pnum, 0, ubi->vtbl_size);
+	if (err)
+		goto write_error;
+
+	/*
+	 * And add it to the attaching information. Don't delete the old version
+	 * of this LEB as it will be deleted and freed in 'ubi_add_to_av()'.
+	 */
+	err = ubi_add_to_av(ubi, ai, new_aeb->pnum, new_aeb->ec, vid_hdr, 0);
+	ubi_free_aeb(ai, new_aeb);
+	ubi_free_vid_buf(vidb);
+	return err;
+
+write_error:
+	if (err == -EIO && ++tries <= 5) {
+		/*
+		 * Probably this physical eraseblock went bad, try to pick
+		 * another one.
+		 */
+		list_add(&new_aeb->u.list, &ai->erase);
+		goto retry;
+	}
+	ubi_free_aeb(ai, new_aeb);
+out_free:
+	ubi_free_vid_buf(vidb);
+	return err;
+
+}
+
+/**
+ * process_lvol - process the layout volume.
+ * @ubi: UBI device description object
+ * @ai: attaching information
+ * @av: layout volume attaching information
+ *
+ * This function is responsible for reading the layout volume, ensuring it is
+ * not corrupted, and recovering from corruptions if needed. Returns volume
+ * table in case of success and a negative error code in case of failure.
+ */
+static struct ubi_vtbl_record *process_lvol(struct ubi_device *ubi,
+					    struct ubi_attach_info *ai,
+					    struct ubi_ainf_volume *av)
+{
+	int err;
+	struct rb_node *rb;
+	struct ubi_ainf_peb *aeb;
+	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 recent data; then
+	 *    we compare it with LEB 1, and if they are different, we copy LEB
+	 *    0 to LEB 1;
+	 * b. if LEB 0 is corrupted, but LEB 1 has to be OK, and we copy LEB 1
+	 *    to LEB 0.
+	 */
+
+	dbg_gen("check layout volume");
+
+	/* Read both LEB 0 and LEB 1 into memory */
+	ubi_rb_for_each_entry(rb, aeb, &av->root, u.rb) {
+		leb[aeb->lnum] = vzalloc(ubi->vtbl_size);
+		if (!leb[aeb->lnum]) {
+			err = -ENOMEM;
+			goto out_free;
+		}
+
+		err = ubi_io_read_data(ubi, leb[aeb->lnum], aeb->pnum, 0,
+				       ubi->vtbl_size);
+		if (err == UBI_IO_BITFLIPS || mtd_is_eccerr(err))
+			/*
+			 * Scrub the PEB later. Note, -EBADMSG indicates an
+			 * uncorrectable ECC error, but we have our own CRC and
+			 * the data will be checked later. If the data is OK,
+			 * the PEB will be scrubbed (because we set
+			 * aeb->scrub). If the data is not OK, the contents of
+			 * the PEB will be recovered from the second copy, and
+			 * aeb->scrub will be cleared in
+			 * 'ubi_add_to_av()'.
+			 */
+			aeb->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(ubi, "volume table copy #2 is corrupted");
+			err = create_vtbl(ubi, ai, 1, leb[0]);
+			if (err)
+				goto out_free;
+			ubi_msg(ubi, "volume table was restored");
+		}
+
+		/* Both LEB 1 and LEB 2 are OK and consistent */
+		vfree(leb[1]);
+		return leb[0];
+	} else {
+		/* LEB 0 is corrupted or does not exist */
+		if (leb[1]) {
+			leb_corrupted[1] = vtbl_check(ubi, leb[1]);
+			if (leb_corrupted[1] < 0)
+				goto out_free;
+		}
+		if (leb_corrupted[1]) {
+			/* Both LEB 0 and LEB 1 are corrupted */
+			ubi_err(ubi, "both volume tables are corrupted");
+			goto out_free;
+		}
+
+		ubi_warn(ubi, "volume table copy #1 is corrupted");
+		err = create_vtbl(ubi, ai, 0, leb[1]);
+		if (err)
+			goto out_free;
+		ubi_msg(ubi, "volume table was restored");
+
+		vfree(leb[0]);
+		return leb[1];
+	}
+
+out_free:
+	vfree(leb[0]);
+	vfree(leb[1]);
+	return ERR_PTR(err);
+}
+
+/**
+ * create_empty_lvol - create empty layout volume.
+ * @ubi: UBI device description object
+ * @ai: attaching information
+ *
+ * This function returns volume table contents in case of success and a
+ * negative error code in case of failure.
+ */
+static struct ubi_vtbl_record *create_empty_lvol(struct ubi_device *ubi,
+						 struct ubi_attach_info *ai)
+{
+	int i;
+	struct ubi_vtbl_record *vtbl;
+
+	vtbl = vzalloc(ubi->vtbl_size);
+	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, ai, i, vtbl);
+		if (err) {
+			vfree(vtbl);
+			return ERR_PTR(err);
+		}
+	}
+
+	return vtbl;
+}
+
+/**
+ * init_volumes - initialize volume information for existing volumes.
+ * @ubi: UBI device description object
+ * @ai: 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_attach_info *ai,
+			const struct ubi_vtbl_record *vtbl)
+{
+	int i, err, reserved_pebs = 0;
+	struct ubi_ainf_volume *av;
+	struct ubi_volume *vol;
+
+	for (i = 0; i < ubi->vtbl_slots; i++) {
+		cond_resched();
+
+		if (be32_to_cpu(vtbl[i].reserved_pebs) == 0)
+			continue; /* Empty record */
+
+		vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
+		if (!vol)
+			return -ENOMEM;
+
+		vol->reserved_pebs = be32_to_cpu(vtbl[i].reserved_pebs);
+		vol->alignment = be32_to_cpu(vtbl[i].alignment);
+		vol->data_pad = be32_to_cpu(vtbl[i].data_pad);
+		vol->upd_marker = vtbl[i].upd_marker;
+		vol->vol_type = vtbl[i].vol_type == UBI_VID_DYNAMIC ?
+					UBI_DYNAMIC_VOLUME : UBI_STATIC_VOLUME;
+		vol->name_len = be16_to_cpu(vtbl[i].name_len);
+		vol->usable_leb_size = ubi->leb_size - vol->data_pad;
+		memcpy(vol->name, vtbl[i].name, vol->name_len);
+		vol->name[vol->name_len] = '\0';
+		vol->vol_id = i;
+
+		if (vtbl[i].flags & UBI_VTBL_SKIP_CRC_CHECK_FLG)
+			vol->skip_check = 1;
+
+		if (vtbl[i].flags & UBI_VTBL_AUTORESIZE_FLG) {
+			/* Auto re-size flag may be set only for one volume */
+			if (ubi->autoresize_vol_id != -1) {
+				ubi_err(ubi, "more than one auto-resize volume (%d and %d)",
+					ubi->autoresize_vol_id, i);
+				kfree(vol);
+				return -EINVAL;
+			}
+
+			ubi->autoresize_vol_id = i;
+		}
+
+		ubi_assert(!ubi->volumes[i]);
+		ubi->volumes[i] = vol;
+		ubi->vol_count += 1;
+		vol->ubi = ubi;
+		reserved_pebs += vol->reserved_pebs;
+
+		/*
+		 * We use ubi->peb_count and not vol->reserved_pebs because
+		 * we want to keep the code simple. Otherwise we'd have to
+		 * resize/check the bitmap upon volume resize too.
+		 * Allocating a few bytes more does not hurt.
+		 */
+		err = ubi_fastmap_init_checkmap(vol, ubi->peb_count);
+		if (err)
+			return err;
+
+		/*
+		 * In case of dynamic volume UBI knows nothing about how many
+		 * data is stored there. So assume the whole volume is used.
+		 */
+		if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
+			vol->used_ebs = vol->reserved_pebs;
+			vol->last_eb_bytes = vol->usable_leb_size;
+			vol->used_bytes =
+				(long long)vol->used_ebs * vol->usable_leb_size;
+			continue;
+		}
+
+		/* Static volumes only */
+		av = ubi_find_av(ai, i);
+		if (!av || !av->leb_count) {
+			/*
+			 * 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 (av->leb_count != av->used_ebs) {
+			/*
+			 * We found a static volume which misses several
+			 * eraseblocks. Treat it as corrupted.
+			 */
+			ubi_warn(ubi, "static volume %d misses %d LEBs - corrupted",
+				 av->vol_id, av->used_ebs - av->leb_count);
+			vol->corrupted = 1;
+			continue;
+		}
+
+		vol->used_ebs = av->used_ebs;
+		vol->used_bytes =
+			(long long)(vol->used_ebs - 1) * vol->usable_leb_size;
+		vol->used_bytes += av->last_data_size;
+		vol->last_eb_bytes = av->last_data_size;
+	}
+
+	/* And add the layout volume */
+	vol = kzalloc(sizeof(struct ubi_volume), GFP_KERNEL);
+	if (!vol)
+		return -ENOMEM;
+
+	vol->reserved_pebs = UBI_LAYOUT_VOLUME_EBS;
+	vol->alignment = UBI_LAYOUT_VOLUME_ALIGN;
+	vol->vol_type = UBI_DYNAMIC_VOLUME;
+	vol->name_len = sizeof(UBI_LAYOUT_VOLUME_NAME) - 1;
+	memcpy(vol->name, UBI_LAYOUT_VOLUME_NAME, vol->name_len + 1);
+	vol->usable_leb_size = ubi->leb_size;
+	vol->used_ebs = vol->reserved_pebs;
+	vol->last_eb_bytes = vol->reserved_pebs;
+	vol->used_bytes =
+		(long long)vol->used_ebs * (ubi->leb_size - vol->data_pad);
+	vol->vol_id = UBI_LAYOUT_VOLUME_ID;
+	vol->ref_count = 1;
+
+	ubi_assert(!ubi->volumes[i]);
+	ubi->volumes[vol_id2idx(ubi, vol->vol_id)] = vol;
+	reserved_pebs += vol->reserved_pebs;
+	ubi->vol_count += 1;
+	vol->ubi = ubi;
+	err = ubi_fastmap_init_checkmap(vol, UBI_LAYOUT_VOLUME_EBS);
+	if (err)
+		return err;
+
+	if (reserved_pebs > ubi->avail_pebs) {
+		ubi_err(ubi, "not enough PEBs, required %d, available %d",
+			reserved_pebs, ubi->avail_pebs);
+		if (ubi->corr_peb_count)
+			ubi_err(ubi, "%d PEBs are corrupted and not used",
+				ubi->corr_peb_count);
+		return -ENOSPC;
+	}
+	ubi->rsvd_pebs += reserved_pebs;
+	ubi->avail_pebs -= reserved_pebs;
+
+	return 0;
+}
+
+/**
+ * check_av - check volume attaching information.
+ * @vol: UBI volume description object
+ * @av: volume attaching information
+ *
+ * This function returns zero if the volume attaching information is consistent
+ * to the data read from the volume tabla, and %-EINVAL if not.
+ */
+static int check_av(const struct ubi_volume *vol,
+		    const struct ubi_ainf_volume *av)
+{
+	int err;
+
+	if (av->highest_lnum >= vol->reserved_pebs) {
+		err = 1;
+		goto bad;
+	}
+	if (av->leb_count > vol->reserved_pebs) {
+		err = 2;
+		goto bad;
+	}
+	if (av->vol_type != vol->vol_type) {
+		err = 3;
+		goto bad;
+	}
+	if (av->used_ebs > vol->reserved_pebs) {
+		err = 4;
+		goto bad;
+	}
+	if (av->data_pad != vol->data_pad) {
+		err = 5;
+		goto bad;
+	}
+	return 0;
+
+bad:
+	ubi_err(vol->ubi, "bad attaching information, error %d", err);
+	ubi_dump_av(av);
+	ubi_dump_vol_info(vol);
+	return -EINVAL;
+}
+
+/**
+ * check_attaching_info - check that attaching information.
+ * @ubi: UBI device description object
+ * @ai: attaching information
+ *
+ * Even though we protect on-flash data by CRC checksums, we still don't trust
+ * the media. This function ensures that attaching information is consistent to
+ * the information read from the volume table. Returns zero if the attaching
+ * information is OK and %-EINVAL if it is not.
+ */
+static int check_attaching_info(const struct ubi_device *ubi,
+			       struct ubi_attach_info *ai)
+{
+	int err, i;
+	struct ubi_ainf_volume *av;
+	struct ubi_volume *vol;
+
+	if (ai->vols_found > UBI_INT_VOL_COUNT + ubi->vtbl_slots) {
+		ubi_err(ubi, "found %d volumes while attaching, maximum is %d + %d",
+			ai->vols_found, UBI_INT_VOL_COUNT, ubi->vtbl_slots);
+		return -EINVAL;
+	}
+
+	if (ai->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT &&
+	    ai->highest_vol_id < UBI_INTERNAL_VOL_START) {
+		ubi_err(ubi, "too large volume ID %d found",
+			ai->highest_vol_id);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
+		cond_resched();
+
+		av = ubi_find_av(ai, i);
+		vol = ubi->volumes[i];
+		if (!vol) {
+			if (av)
+				ubi_remove_av(ai, av);
+			continue;
+		}
+
+		if (vol->reserved_pebs == 0) {
+			ubi_assert(i < ubi->vtbl_slots);
+
+			if (!av)
+				continue;
+
+			/*
+			 * During attaching 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(ubi, "finish volume %d removal", av->vol_id);
+			ubi_remove_av(ai, av);
+		} else if (av) {
+			err = check_av(vol, av);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * ubi_read_volume_table - read the volume table.
+ * @ubi: UBI device description object
+ * @ai: attaching 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_attach_info *ai)
+{
+	int err;
+	struct ubi_ainf_volume *av;
+
+	empty_vtbl_record.crc = cpu_to_be32(0xf116c36b);
+
+	/*
+	 * The number of supported volumes is limited by the eraseblock size
+	 * and by the UBI_MAX_VOLUMES constant.
+	 */
+	ubi->vtbl_slots = ubi->leb_size / UBI_VTBL_RECORD_SIZE;
+	if (ubi->vtbl_slots > UBI_MAX_VOLUMES)
+		ubi->vtbl_slots = UBI_MAX_VOLUMES;
+
+	ubi->vtbl_size = ubi->vtbl_slots * UBI_VTBL_RECORD_SIZE;
+	ubi->vtbl_size = ALIGN(ubi->vtbl_size, ubi->min_io_size);
+
+	av = ubi_find_av(ai, UBI_LAYOUT_VOLUME_ID);
+	if (!av) {
+		/*
+		 * 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 (ai->is_empty) {
+			ubi->vtbl = create_empty_lvol(ubi, ai);
+			if (IS_ERR(ubi->vtbl))
+				return PTR_ERR(ubi->vtbl);
+		} else {
+			ubi_err(ubi, "the layout volume was not found");
+			return -EINVAL;
+		}
+	} else {
+		if (av->leb_count > UBI_LAYOUT_VOLUME_EBS) {
+			/* This must not happen with proper UBI images */
+			ubi_err(ubi, "too many LEBs (%d) in layout volume",
+				av->leb_count);
+			return -EINVAL;
+		}
+
+		ubi->vtbl = process_lvol(ubi, ai, av);
+		if (IS_ERR(ubi->vtbl))
+			return PTR_ERR(ubi->vtbl);
+	}
+
+	ubi->avail_pebs = ubi->good_peb_count - ubi->corr_peb_count;
+
+	/*
+	 * The layout volume is OK, initialize the corresponding in-RAM data
+	 * structures.
+	 */
+	err = init_volumes(ubi, ai, ubi->vtbl);
+	if (err)
+		goto out_free;
+
+	/*
+	 * Make sure that the attaching information is consistent to the
+	 * information stored in the volume table.
+	 */
+	err = check_attaching_info(ubi, ai);
+	if (err)
+		goto out_free;
+
+	return 0;
+
+out_free:
+	vfree(ubi->vtbl);
+	ubi_free_all_volumes(ubi);
+	return err;
+}
+
+/**
+ * self_vtbl_check - check volume table.
+ * @ubi: UBI device description object
+ */
+static void self_vtbl_check(const struct ubi_device *ubi)
+{
+	if (!ubi_dbg_chk_gen(ubi))
+		return;
+
+	if (vtbl_check(ubi, ubi->vtbl)) {
+		ubi_err(ubi, "self-check failed");
+		BUG();
+	}
+}