/*
   * 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 at LEB %d:%d", lnum, offs);
  		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 at LEB %d:%d",
  		 dbg_ntype(ch->node_type), lnum, offs);
  
  	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);
  				ubifs_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)
  				ubifs_err("bad padding length %d - %d",
  					  offs, offs + node_len + pad_len);
  			return SCANNED_A_BAD_PAD_NODE;
  		}
  
  		dbg_scan("%d bytes padded at LEB %d:%d, offset now %d", pad_len,
  			 lnum, offs, 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 = ubifs_leb_read(c, lnum, sbuf + offs, offs, c->leb_size - offs, 0);
  	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 = kmalloc(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:
  		/*
  		 * The key is in the same place in all keyed
  		 * nodes.
  		 */
  		key_read(c, &ino->key, &snod->key);
  		break;
  	default:
  		invalid_key_init(c, &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("corruption at LEB %d:%d", lnum, offs);
  	len = c->leb_size - offs;
  	if (len > 8192)
  		len = 8192;
  	ubifs_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 of @c->leb_size bytes in size)
   * @quiet: print no messages
   *
   * This function scans LEB number @lnum and returns complete information about
   * its contents. Returns the scaned information in case of success and,
   * %-EUCLEAN if the LEB neads recovery, and other negative error codes in case
   * of failure.
   *
   * If @quiet is non-zero, this function does not print large and scary
   * error messages and flash dumps in case of errors.
   */
  struct ubifs_scan_leb *ubifs_scan(const struct ubifs_info *c, int lnum,
  				  int offs, void *sbuf, int quiet)
  {
  	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, quiet);
  		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:
  			ubifs_err("garbage");
  			goto corrupted;
  		case SCANNED_A_NODE:
  			break;
  		case SCANNED_A_CORRUPT_NODE:
  		case SCANNED_A_BAD_PAD_NODE:
  			ubifs_err("bad node");
  			goto corrupted;
  		default:
  			ubifs_err("unknown");
  			err = -EINVAL;
  			goto error;
  		}
  
  		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) {
  		if (!quiet)
  			ubifs_err("empty space starts at non-aligned offset %d",
  				  offs);
  		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) {
  			if (!quiet)
  				ubifs_err("corrupt empty space at LEB %d:%d",
  					  lnum, offs);
  			goto corrupted;
  		}
  
  	return sleb;
  
  corrupted:
  	if (!quiet) {
  		ubifs_scanned_corruption(c, lnum, offs, buf);
  		ubifs_err("LEB %d scanning failed", lnum);
  	}
  	err = -EUCLEAN;
  	ubifs_scan_destroy(sleb);
  	return ERR_PTR(err);
  
  error:
  	ubifs_err("LEB %d scanning failed, error %d", lnum, err);
  	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);
  }