scan.c

基于linux-2.6.28的mtd驱动

/*
 * 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.
 *
 * Found 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.
 */

#include <linux/err.h>
#include <linux/crc32.h>
#include <asm/div64.h>
#include "ubi.h"

#ifdef CONFIG_MTD_UBI_DEBUG_PARANOID
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
 * @list: the list to add to
 *
 * This function adds physical eraseblock @pnum to free, erase, corrupted or
 * alien lists. 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,
		       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->corr)
		dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
	else if (list == &si->alien)
		dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
	else
		BUG();

	seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
	if (!seb)
		return -ENOMEM;

	seb->pnum = pnum;
	seb->ec = ec;
	list_add_tail(&seb->u.list, list);
	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 then 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 will work
		 * 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 {
		pnum = seb->pnum;

		vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
		if (!vh)
			return -ENOMEM;

		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", pnum);
				if (err > 0)
					err = -EIO;

				goto out_free_vidh;
			}
		}

		if (!vh->copy_flag) {
			/* It is not a copy, so it is newer */
			dbg_bld("first PEB %d is newer, copy_flag is unset",
				pnum);
			err = bitflips << 1;
			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);