/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * 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., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Authors: Adrian Hunter
 *          Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * This file implements the scan which is a general-purpose function for
 * determining what nodes are in an eraseblock. The scan is used to replay the
 * journal, to do garbage collection. for the TNC in-the-gaps method, and by
 * debugging functions.
 */

#include "ubifs.h"

/**
 * scan_padding_bytes - scan for padding bytes.
 * @buf: buffer to scan
 * @len: length of buffer
 *
 * This function returns the number of padding bytes on success and
 * %SCANNED_GARBAGE on failure.
 */
static int scan_padding_bytes(void *buf, int len)
{
        int pad_len = 0, max_pad_len = min_t(int, UBIFS_PAD_NODE_SZ, len);
        uint8_t *p = buf;

        dbg_scan("not a node");

        while (pad_len < max_pad_len && *p++ == UBIFS_PADDING_BYTE)
                pad_len += 1;

        if (!pad_len || (pad_len & 7))
                return SCANNED_GARBAGE;

        dbg_scan("%d padding bytes", pad_len);

        return pad_len;
}

/**
 * ubifs_scan_a_node - scan for a node or padding.
 * @c: UBIFS file-system description object
 * @buf: buffer to scan
 * @len: length of buffer
 * @lnum: logical eraseblock number
 * @offs: offset within the logical eraseblock
 * @quiet: print no messages
 *
 * This function returns a scanning code to indicate what was scanned.
 */
int ubifs_scan_a_node(const struct ubifs_info *c, void *buf, int len, int lnum,
                      int offs, int quiet)
{
        struct ubifs_ch *ch = buf;
        uint32_t magic;

        magic = le32_to_cpu(ch->magic);

        if (magic == 0xFFFFFFFF) {
                dbg_scan("hit empty space");
                return SCANNED_EMPTY_SPACE;
        }

        if (magic != UBIFS_NODE_MAGIC)
                return scan_padding_bytes(buf, len);

        if (len < UBIFS_CH_SZ)
                return SCANNED_GARBAGE;

        dbg_scan("scanning %s", dbg_ntype(ch->node_type));

        if (ubifs_check_node(c, buf, lnum, offs, quiet, 1))
                return SCANNED_A_CORRUPT_NODE;

        if (ch->node_type == UBIFS_PAD_NODE) {
                struct ubifs_pad_node *pad = buf;
                int pad_len = le32_to_cpu(pad->pad_len);
                int node_len = le32_to_cpu(ch->len);

                /* Validate the padding node */
                if (pad_len < 0 ||
                    offs + node_len + pad_len > c->leb_size) {
                        if (!quiet) {
                                ubifs_err("bad pad node at LEB %d:%d",
                                          lnum, offs);
                                dbg_dump_node(c, pad);
                        }
                        return SCANNED_A_BAD_PAD_NODE;
                }

                /* Make the node pads to 8-byte boundary */
                if ((node_len + pad_len) & 7) {
                        if (!quiet) {
                                dbg_err("bad padding length %d - %d",
                                        offs, offs + node_len + pad_len);
                        }
                        return SCANNED_A_BAD_PAD_NODE;
                }

                dbg_scan("%d bytes padded, offset now %d",
                         pad_len, ALIGN(offs + node_len + pad_len, 8));

                return node_len + pad_len;
        }

        return SCANNED_A_NODE;
}

/**
 * ubifs_start_scan - create LEB scanning information at start of scan.
 * @c: UBIFS file-system description object
 * @lnum: logical eraseblock number
 * @offs: offset to start at (usually zero)
 * @sbuf: scan buffer (must be c->leb_size)
 *
 * This function returns %0 on success and a negative error code on failure.
 */
struct ubifs_scan_leb *ubifs_start_scan(const struct ubifs_info *c, int lnum,
                                        int offs, void *sbuf)
{
        struct ubifs_scan_leb *sleb;
        int err;

        dbg_scan("scan LEB %d:%d", lnum, offs);

        sleb = kzalloc(sizeof(struct ubifs_scan_leb), GFP_NOFS);
        if (!sleb)
                return ERR_PTR(-ENOMEM);

        sleb->lnum = lnum;
        INIT_LIST_HEAD(&sleb->nodes);
        sleb->buf = sbuf;

        err = ubi_read(c->ubi, lnum, sbuf + offs, offs, c->leb_size - offs);
        if (err && err != -EBADMSG) {
                ubifs_err("cannot read %d bytes from LEB %d:%d,"
                          " error %d", c->leb_size - offs, lnum, offs, err);
                kfree(sleb);
                return ERR_PTR(err);
        }

        if (err == -EBADMSG)
                sleb->ecc = 1;

        return sleb;
}

/**
 * ubifs_end_scan - update LEB scanning information at end of scan.
 * @c: UBIFS file-system description object
 * @sleb: scanning information
 * @lnum: logical eraseblock number
 * @offs: offset to start at (usually zero)
 *
 * This function returns %0 on success and a negative error code on failure.
 */
void ubifs_end_scan(const struct ubifs_info *c, struct ubifs_scan_leb *sleb,
                    int lnum, int offs)
{
        lnum = lnum;
        dbg_scan("stop scanning LEB %d at offset %d", lnum, offs);
        ubifs_assert(offs % c->min_io_size == 0);

        sleb->endpt = ALIGN(offs, c->min_io_size);
}

/**
 * ubifs_add_snod - add a scanned node to LEB scanning information.
 * @c: UBIFS file-system description object
 * @sleb: scanning information
 * @buf: buffer containing node
 * @offs: offset of node on flash
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int ubifs_add_snod(const struct ubifs_info *c, struct ubifs_scan_leb *sleb,
                   void *buf, int offs)
{
        struct ubifs_ch *ch = buf;
        struct ubifs_ino_node *ino = buf;
        struct ubifs_scan_node *snod;

        snod = kzalloc(sizeof(struct ubifs_scan_node), GFP_NOFS);
        if (!snod)
                return -ENOMEM;

        snod->sqnum = le64_to_cpu(ch->sqnum);
        snod->type = ch->node_type;
        snod->offs = offs;
        snod->len = le32_to_cpu(ch->len);
        snod->node = buf;

        switch (ch->node_type) {
        case UBIFS_INO_NODE:
        case UBIFS_DENT_NODE:
        case UBIFS_XENT_NODE:
        case UBIFS_DATA_NODE:
        case UBIFS_TRUN_NODE:
                /*
                 * The key is in the same place in all keyed
                 * nodes.
                 */
                key_read(c, &ino->key, &snod->key);
                break;
        }
        list_add_tail(&snod->list, &sleb->nodes);
        sleb->nodes_cnt += 1;
        return 0;
}

/**
 * ubifs_scanned_corruption - print information after UBIFS scanned corruption.
 * @c: UBIFS file-system description object
 * @lnum: LEB number of corruption
 * @offs: offset of corruption
 * @buf: buffer containing corruption
 */
void ubifs_scanned_corruption(const struct ubifs_info *c, int lnum, int offs,
                              void *buf)
{
        int len;

        ubifs_err("corrupted data at LEB %d:%d", lnum, offs);
        if (dbg_failure_mode)
                return;
        len = c->leb_size - offs;
        if (len > 4096)
                len = 4096;
        dbg_err("first %d bytes from LEB %d:%d", len, lnum, offs);
        print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_OFFSET, 32, 4, buf, len, 1);
}

/**
 * ubifs_scan - scan a logical eraseblock.
 * @c: UBIFS file-system description object
 * @lnum: logical eraseblock number
 * @offs: offset to start at (usually zero)
 * @sbuf: scan buffer (must be c->leb_size)
 *
 * This function scans LEB number @lnum and returns complete information about
 * its contents. Returns an error code in case of failure.
 */
struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
                                  int offs, void *sbuf)
{
        void *buf = sbuf + offs;
        int err, len = c->leb_size - offs;
        struct ubifs_scan_leb *sleb;

        sleb = ubifs_start_scan(c, lnum, offs, sbuf);
        if (IS_ERR(sleb))
                return sleb;

        while (len >= 8) {
                struct ubifs_ch *ch = buf;
                int node_len, ret;

                dbg_scan("look at LEB %d:%d (%d bytes left)",
                         lnum, offs, len);

                cond_resched();

                ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 0);

                if (ret > 0) {
                        /* Padding bytes or a valid padding node */
                        offs += ret;
                        buf += ret;
                        len -= ret;
                        continue;
                }

                if (ret == SCANNED_EMPTY_SPACE)
                        /* Empty space is checked later */
                        break;

                switch (ret) {
                case SCANNED_GARBAGE:
                        dbg_err("garbage");
                        goto corrupted;
                case SCANNED_A_NODE:
                        break;
                case SCANNED_A_CORRUPT_NODE:
                case SCANNED_A_BAD_PAD_NODE:
                        dbg_err("bad node");
                        goto corrupted;
                default:
                        dbg_err("unknown");
                        goto corrupted;
                }

                err = ubifs_add_snod(c, sleb, buf, offs);
                if (err)
                        goto error;

                node_len = ALIGN(le32_to_cpu(ch->len), 8);
                offs += node_len;
                buf += node_len;
                len -= node_len;
        }

        if (offs % c->min_io_size)
                goto corrupted;

        ubifs_end_scan(c, sleb, lnum, offs);

        for (; len > 4; offs += 4, buf = buf + 4, len -= 4)
                if (*(uint32_t *)buf != 0xffffffff)
                        break;
        for (; len; offs++, buf++, len--)
                if (*(uint8_t *)buf != 0xff) {
                        ubifs_err("corrupt empty space at LEB %d:%d",
                                  lnum, offs);
                        goto corrupted;
                }

        return sleb;

corrupted:
        ubifs_scanned_corruption(c, lnum, offs, buf);
        err = -EUCLEAN;
error:
        ubifs_err("LEB %d scanning failed", lnum);
        ubifs_scan_destroy(sleb);
        return ERR_PTR(err);
}

/**
 * ubifs_scan_destroy - destroy LEB scanning information.
 * @sleb: scanning information to free
 */
void ubifs_scan_destroy(struct ubifs_scan_leb *sleb)
{
        struct ubifs_scan_node *node;
        struct list_head *head;

        head = &sleb->nodes;
        while (!list_empty(head)) {
                node = list_entry(head->next, struct ubifs_scan_node, list);
                list_del(&node->list);
                kfree(node);
        }
        kfree(sleb);
}