text: /*
   * logfile.c - NTFS kernel journal handling. Part of the Linux-NTFS project.
   *
   * Copyright (c) 2002-2007 Anton Altaparmakov
   *
   * This program/include file 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/include file 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 (in the main directory of the Linux-NTFS
   * distribution in the file COPYING); if not, write to the Free Software
   * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #ifdef NTFS_RW
  
  #include <linux/types.h>
  #include <linux/fs.h>
  #include <linux/highmem.h>
  #include <linux/buffer_head.h>
  #include <linux/bitops.h>
  #include <linux/log2.h>
  #include <linux/bio.h>
  
  #include "attrib.h"
  #include "aops.h"
  #include "debug.h"
  #include "logfile.h"
  #include "malloc.h"
  #include "volume.h"
  #include "ntfs.h"
  
  /**
   * ntfs_check_restart_page_header - check the page header for consistency
   * @vi:		$LogFile inode to which the restart page header belongs
   * @rp:		restart page header to check
   * @pos:	position in @vi at which the restart page header resides
   *
   * Check the restart page header @rp for consistency and return 'true' if it is
   * consistent and 'false' otherwise.
   *
   * This function only needs NTFS_BLOCK_SIZE bytes in @rp, i.e. it does not
   * require the full restart page.
   */
  static bool ntfs_check_restart_page_header(struct inode *vi,
  		RESTART_PAGE_HEADER *rp, s64 pos)
  {
  	u32 logfile_system_page_size, logfile_log_page_size;
  	u16 ra_ofs, usa_count, usa_ofs, usa_end = 0;
  	bool have_usa = true;
  
  	ntfs_debug("Entering.");
  	/*
  	 * If the system or log page sizes are smaller than the ntfs block size
  	 * or either is not a power of 2 we cannot handle this log file.
  	 */
  	logfile_system_page_size = le32_to_cpu(rp->system_page_size);
  	logfile_log_page_size = le32_to_cpu(rp->log_page_size);
  	if (logfile_system_page_size < NTFS_BLOCK_SIZE ||
  			logfile_log_page_size < NTFS_BLOCK_SIZE ||
  			logfile_system_page_size &
  			(logfile_system_page_size - 1) ||
  			!is_power_of_2(logfile_log_page_size)) {
  		ntfs_error(vi->i_sb, "$LogFile uses unsupported page size.");
  		return false;
  	}
  	/*
  	 * We must be either at !pos (1st restart page) or at pos = system page
  	 * size (2nd restart page).
  	 */
  	if (pos && pos != logfile_system_page_size) {
  		ntfs_error(vi->i_sb, "Found restart area in incorrect "
  				"position in $LogFile.");
  		return false;
  	}
  	/* We only know how to handle version 1.1. */
  	if (sle16_to_cpu(rp->major_ver) != 1 ||
  			sle16_to_cpu(rp->minor_ver) != 1) {
  		ntfs_error(vi->i_sb, "$LogFile version %i.%i is not "
  				"supported.  (This driver supports version "
  				"1.1 only.)", (int)sle16_to_cpu(rp->major_ver),
  				(int)sle16_to_cpu(rp->minor_ver));
  		return false;
  	}
  	/*
  	 * If chkdsk has been run the restart page may not be protected by an
  	 * update sequence array.
  	 */
  	if (ntfs_is_chkd_record(rp->magic) && !le16_to_cpu(rp->usa_count)) {
  		have_usa = false;
  		goto skip_usa_checks;
  	}
  	/* Verify the size of the update sequence array. */
  	usa_count = 1 + (logfile_system_page_size >> NTFS_BLOCK_SIZE_BITS);
  	if (usa_count != le16_to_cpu(rp->usa_count)) {
  		ntfs_error(vi->i_sb, "$LogFile restart page specifies "
  				"inconsistent update sequence array count.");
  		return false;
  	}
  	/* Verify the position of the update sequence array. */
  	usa_ofs = le16_to_cpu(rp->usa_ofs);
  	usa_end = usa_ofs + usa_count * sizeof(u16);
  	if (usa_ofs < sizeof(RESTART_PAGE_HEADER) ||
  			usa_end > NTFS_BLOCK_SIZE - sizeof(u16)) {
  		ntfs_error(vi->i_sb, "$LogFile restart page specifies "
  				"inconsistent update sequence array offset.");
  		return false;
  	}
  skip_usa_checks:
  	/*
  	 * Verify the position of the restart area.  It must be:
  	 *	- aligned to 8-byte boundary,
  	 *	- after the update sequence array, and
  	 *	- within the system page size.
  	 */
  	ra_ofs = le16_to_cpu(rp->restart_area_offset);
  	if (ra_ofs & 7 || (have_usa ? ra_ofs < usa_end :
  			ra_ofs < sizeof(RESTART_PAGE_HEADER)) ||
  			ra_ofs > logfile_system_page_size) {
  		ntfs_error(vi->i_sb, "$LogFile restart page specifies "
  				"inconsistent restart area offset.");
  		return false;
  	}
  	/*
  	 * Only restart pages modified by chkdsk are allowed to have chkdsk_lsn
  	 * set.
  	 */
  	if (!ntfs_is_chkd_record(rp->magic) && sle64_to_cpu(rp->chkdsk_lsn)) {
  		ntfs_error(vi->i_sb, "$LogFile restart page is not modified "
  				"by chkdsk but a chkdsk LSN is specified.");
  		return false;
  	}
  	ntfs_debug("Done.");
  	return true;
  }
  
  /**
   * ntfs_check_restart_area - check the restart area for consistency
   * @vi:		$LogFile inode to which the restart page belongs
   * @rp:		restart page whose restart area to check
   *
   * Check the restart area of the restart page @rp for consistency and return
   * 'true' if it is consistent and 'false' otherwise.
   *
   * This function assumes that the restart page header has already been
   * consistency checked.
   *
   * This function only needs NTFS_BLOCK_SIZE bytes in @rp, i.e. it does not
   * require the full restart page.
   */
  static bool ntfs_check_restart_area(struct inode *vi, RESTART_PAGE_HEADER *rp)
  {
  	u64 file_size;
  	RESTART_AREA *ra;
  	u16 ra_ofs, ra_len, ca_ofs;
  	u8 fs_bits;
  
  	ntfs_debug("Entering.");
  	ra_ofs = le16_to_cpu(rp->restart_area_offset);
  	ra = (RESTART_AREA*)((u8*)rp + ra_ofs);
  	/*
  	 * Everything before ra->file_size must be before the first word
  	 * protected by an update sequence number.  This ensures that it is
  	 * safe to access ra->client_array_offset.
  	 */
  	if (ra_ofs + offsetof(RESTART_AREA, file_size) >
  			NTFS_BLOCK_SIZE - sizeof(u16)) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"inconsistent file offset.");
  		return false;
  	}
  	/*
  	 * Now that we can access ra->client_array_offset, make sure everything
  	 * up to the log client array is before the first word protected by an
  	 * update sequence number.  This ensures we can access all of the
  	 * restart area elements safely.  Also, the client array offset must be
  	 * aligned to an 8-byte boundary.
  	 */
  	ca_ofs = le16_to_cpu(ra->client_array_offset);
  	if (((ca_ofs + 7) & ~7) != ca_ofs ||
  			ra_ofs + ca_ofs > NTFS_BLOCK_SIZE - sizeof(u16)) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"inconsistent client array offset.");
  		return false;
  	}
  	/*
  	 * The restart area must end within the system page size both when
  	 * calculated manually and as specified by ra->restart_area_length.
  	 * Also, the calculated length must not exceed the specified length.
  	 */
  	ra_len = ca_ofs + le16_to_cpu(ra->log_clients) *
  			sizeof(LOG_CLIENT_RECORD);
  	if (ra_ofs + ra_len > le32_to_cpu(rp->system_page_size) ||
  			ra_ofs + le16_to_cpu(ra->restart_area_length) >
  			le32_to_cpu(rp->system_page_size) ||
  			ra_len > le16_to_cpu(ra->restart_area_length)) {
  		ntfs_error(vi->i_sb, "$LogFile restart area is out of bounds "
  				"of the system page size specified by the "
  				"restart page header and/or the specified "
  				"restart area length is inconsistent.");
  		return false;
  	}
  	/*
  	 * The ra->client_free_list and ra->client_in_use_list must be either
  	 * LOGFILE_NO_CLIENT or less than ra->log_clients or they are
  	 * overflowing the client array.
  	 */
  	if ((ra->client_free_list != LOGFILE_NO_CLIENT &&
  			le16_to_cpu(ra->client_free_list) >=
  			le16_to_cpu(ra->log_clients)) ||
  			(ra->client_in_use_list != LOGFILE_NO_CLIENT &&
  			le16_to_cpu(ra->client_in_use_list) >=
  			le16_to_cpu(ra->log_clients))) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"overflowing client free and/or in use lists.");
  		return false;
  	}
  	/*
  	 * Check ra->seq_number_bits against ra->file_size for consistency.
  	 * We cannot just use ffs() because the file size is not a power of 2.
  	 */
  	file_size = (u64)sle64_to_cpu(ra->file_size);
  	fs_bits = 0;
  	while (file_size) {
  		file_size >>= 1;
  		fs_bits++;
  	}
  	if (le32_to_cpu(ra->seq_number_bits) != 67 - fs_bits) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"inconsistent sequence number bits.");
  		return false;
  	}
  	/* The log record header length must be a multiple of 8. */
  	if (((le16_to_cpu(ra->log_record_header_length) + 7) & ~7) !=
  			le16_to_cpu(ra->log_record_header_length)) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"inconsistent log record header length.");
  		return false;
  	}
  	/* Dito for the log page data offset. */
  	if (((le16_to_cpu(ra->log_page_data_offset) + 7) & ~7) !=
  			le16_to_cpu(ra->log_page_data_offset)) {
  		ntfs_error(vi->i_sb, "$LogFile restart area specifies "
  				"inconsistent log page data offset.");
  		return false;
  	}
  	ntfs_debug("Done.");
  	return true;
  }
  
  /**
   * ntfs_check_log_client_array - check the log client array for consistency
   * @vi:		$LogFile inode to which the restart page belongs
   * @rp:		restart page whose log client array to check
   *
   * Check the log client array of the restart page @rp for consistency and
   * return 'true' if it is consistent and 'false' otherwise.
   *
   * This function assumes that the restart page header and the restart area have
   * already been consistency checked.
   *
   * Unlike ntfs_check_restart_page_header() and ntfs_check_restart_area(), this
   * function needs @rp->system_page_size bytes in @rp, i.e. it requires the full
   * restart page and the page must be multi sector transfer deprotected.
   */
  static bool ntfs_check_log_client_array(struct inode *vi,
  		RESTART_PAGE_HEADER *rp)
  {
  	RESTART_AREA *ra;
  	LOG_CLIENT_RECORD *ca, *cr;
  	u16 nr_clients, idx;
  	bool in_free_list, idx_is_first;
  
  	ntfs_debug("Entering.");
  	ra = (RESTART_AREA*)((u8*)rp + le16_to_cpu(rp->restart_area_offset));
  	ca = (LOG_CLIENT_RECORD*)((u8*)ra +
  			le16_to_cpu(ra->client_array_offset));
  	/*
  	 * Check the ra->client_free_list first and then check the
  	 * ra->client_in_use_list.  Check each of the log client records in
  	 * each of the lists and check that the array does not overflow the
  	 * ra->log_clients value.  Also keep track of the number of records
  	 * visited as there cannot be more than ra->log_clients records and
  	 * that way we detect eventual loops in within a list.
  	 */
  	nr_clients = le16_to_cpu(ra->log_clients);
  	idx = le16_to_cpu(ra->client_free_list);
  	in_free_list = true;
  check_list:
  	for (idx_is_first = true; idx != LOGFILE_NO_CLIENT_CPU; nr_clients--,
  			idx = le16_to_cpu(cr->next_client)) {
  		if (!nr_clients || idx >= le16_to_cpu(ra->log_clients))
  			goto err_out;
  		/* Set @cr to the current log client record. */
  		cr = ca + idx;
  		/* The first log client record must not have a prev_client. */
  		if (idx_is_first) {
  			if (cr->prev_client != LOGFILE_NO_CLIENT)
  				goto err_out;
  			idx_is_first = false;
  		}
  	}
  	/* Switch to and check the in use list if we just did the free list. */
  	if (in_free_list) {
  		in_free_list = false;
  		idx = le16_to_cpu(ra->client_in_use_list);
  		goto check_list;
  	}
  	ntfs_debug("Done.");
  	return true;
  err_out:
  	ntfs_error(vi->i_sb, "$LogFile log client array is corrupt.");
  	return false;
  }
  
  /**
   * ntfs_check_and_load_restart_page - check the restart page for consistency
   * @vi:		$LogFile inode to which the restart page belongs
   * @rp:		restart page to check
   * @pos:	position in @vi at which the restart page resides
   * @wrp:	[OUT] copy of the multi sector transfer deprotected restart page
   * @lsn:	[OUT] set to the current logfile lsn on success
   *
   * Check the restart page @rp for consistency and return 0 if it is consistent
   * and -errno otherwise.  The restart page may have been modified by chkdsk in
   * which case its magic is CHKD instead of RSTR.
   *
   * This function only needs NTFS_BLOCK_SIZE bytes in @rp, i.e. it does not
   * require the full restart page.
   *
   * If @wrp is not NULL, on success, *@wrp will point to a buffer containing a
   * copy of the complete multi sector transfer deprotected page.  On failure,
   * *@wrp is undefined.
   *
   * Simillarly, if @lsn is not NULL, on success *@lsn will be set to the current
   * logfile lsn according to this restart page.  On failure, *@lsn is undefined.
   *
   * The following error codes are defined:
   *	-EINVAL	- The restart page is inconsistent.
   *	-ENOMEM	- Not enough memory to load the restart page.
   *	-EIO	- Failed to reading from $LogFile.
   */
  static int ntfs_check_and_load_restart_page(struct inode *vi,
  		RESTART_PAGE_HEADER *rp, s64 pos, RESTART_PAGE_HEADER **wrp,
  		LSN *lsn)
  {
  	RESTART_AREA *ra;
  	RESTART_PAGE_HEADER *trp;
  	int size, err;
  
  	ntfs_debug("Entering.");
  	/* Check the restart page header for consistency. */
  	if (!ntfs_check_restart_page_header(vi, rp, pos)) {
  		/* Error output already done inside the function. */
  		return -EINVAL;
  	}
  	/* Check the restart area for consistency. */
  	if (!ntfs_check_restart_area(vi, rp)) {
  		/* Error output already done inside the function. */
  		return -EINVAL;
  	}
  	ra = (RESTART_AREA*)((u8*)rp + le16_to_cpu(rp->restart_area_offset));
  	/*
  	 * Allocate a buffer to store the whole restart page so we can multi
  	 * sector transfer deprotect it.
  	 */
  	trp = ntfs_malloc_nofs(le32_to_cpu(rp->system_page_size));
  	if (!trp) {
  		ntfs_error(vi->i_sb, "Failed to allocate memory for $LogFile "
  				"restart page buffer.");
  		return -ENOMEM;
  	}
  	/*
  	 * Read the whole of the restart page into the buffer.  If it fits
  	 * completely inside @rp, just copy it from there.  Otherwise map all
  	 * the required pages and copy the data from them.
  	 */
  	size = PAGE_SIZE - (pos & ~PAGE_MASK);
  	if (size >= le32_to_cpu(rp->system_page_size)) {
  		memcpy(trp, rp, le32_to_cpu(rp->system_page_size));
  	} else {
  		pgoff_t idx;
  		struct page *page;
  		int have_read, to_read;
  
  		/* First copy what we already have in @rp. */
  		memcpy(trp, rp, size);
  		/* Copy the remaining data one page at a time. */
  		have_read = size;
  		to_read = le32_to_cpu(rp->system_page_size) - size;
  		idx = (pos + size) >> PAGE_SHIFT;
  		BUG_ON((pos + size) & ~PAGE_MASK);
  		do {
  			page = ntfs_map_page(vi->i_mapping, idx);
  			if (IS_ERR(page)) {
  				ntfs_error(vi->i_sb, "Error mapping $LogFile "
  						"page (index %lu).", idx);
  				err = PTR_ERR(page);
  				if (err != -EIO && err != -ENOMEM)
  					err = -EIO;
  				goto err_out;
  			}
  			size = min_t(int, to_read, PAGE_SIZE);
  			memcpy((u8*)trp + have_read, page_address(page), size);
  			ntfs_unmap_page(page);
  			have_read += size;
  			to_read -= size;
  			idx++;
  		} while (to_read > 0);
  	}
  	/*
  	 * Perform the multi sector transfer deprotection on the buffer if the
  	 * restart page is protected.
  	 */
  	if ((!ntfs_is_chkd_record(trp->magic) || le16_to_cpu(trp->usa_count))
  			&& post_read_mst_fixup((NTFS_RECORD*)trp,
  			le32_to_cpu(rp->system_page_size))) {
  		/*
  		 * A multi sector tranfer error was detected.  We only need to
  		 * abort if the restart page contents exceed the multi sector
  		 * transfer fixup of the first sector.
  		 */
  		if (le16_to_cpu(rp->restart_area_offset) +
  				le16_to_cpu(ra->restart_area_length) >
  				NTFS_BLOCK_SIZE - sizeof(u16)) {
  			ntfs_error(vi->i_sb, "Multi sector transfer error "
  					"detected in $LogFile restart page.");
  			err = -EINVAL;
  			goto err_out;
  		}
  	}
  	/*
  	 * If the restart page is modified by chkdsk or there are no active
  	 * logfile clients, the logfile is consistent.  Otherwise, need to
  	 * check the log client records for consistency, too.
  	 */
  	err = 0;
  	if (ntfs_is_rstr_record(rp->magic) &&
  			ra->client_in_use_list != LOGFILE_NO_CLIENT) {
  		if (!ntfs_check_log_client_array(vi, trp)) {
  			err = -EINVAL;
  			goto err_out;
  		}
  	}
  	if (lsn) {
  		if (ntfs_is_rstr_record(rp->magic))
  			*lsn = sle64_to_cpu(ra->current_lsn);
  		else /* if (ntfs_is_chkd_record(rp->magic)) */
  			*lsn = sle64_to_cpu(rp->chkdsk_lsn);
  	}
  	ntfs_debug("Done.");
  	if (wrp)
  		*wrp = trp;
  	else {
  err_out:
  		ntfs_free(trp);
  	}
  	return err;
  }
  
  /**
   * ntfs_check_logfile - check the journal for consistency
   * @log_vi:	struct inode of loaded journal $LogFile to check
   * @rp:		[OUT] on success this is a copy of the current restart page
   *
   * Check the $LogFile journal for consistency and return 'true' if it is
   * consistent and 'false' if not.  On success, the current restart page is
   * returned in *@rp.  Caller must call ntfs_free(*@rp) when finished with it.
   *
   * At present we only check the two restart pages and ignore the log record
   * pages.
   *
   * Note that the MstProtected flag is not set on the $LogFile inode and hence
   * when reading pages they are not deprotected.  This is because we do not know
   * if the $LogFile was created on a system with a different page size to ours
   * yet and mst deprotection would fail if our page size is smaller.
   */
  bool ntfs_check_logfile(struct inode *log_vi, RESTART_PAGE_HEADER **rp)
  {
  	s64 size, pos;
  	LSN rstr1_lsn, rstr2_lsn;
  	ntfs_volume *vol = NTFS_SB(log_vi->i_sb);
  	struct address_space *mapping = log_vi->i_mapping;
  	struct page *page = NULL;
  	u8 *kaddr = NULL;
  	RESTART_PAGE_HEADER *rstr1_ph = NULL;
  	RESTART_PAGE_HEADER *rstr2_ph = NULL;
  	int log_page_size, log_page_mask, err;
  	bool logfile_is_empty = true;
  	u8 log_page_bits;
  
  	ntfs_debug("Entering.");
  	/* An empty $LogFile must have been clean before it got emptied. */
  	if (NVolLogFileEmpty(vol))
  		goto is_empty;
  	size = i_size_read(log_vi);
  	/* Make sure the file doesn't exceed the maximum allowed size. */
  	if (size > MaxLogFileSize)
  		size = MaxLogFileSize;
  	/*
  	 * Truncate size to a multiple of the page cache size or the default
  	 * log page size if the page cache size is between the default log page
  	 * log page size if the page cache size is between the default log page
  	 * size and twice that.
  	 */
  	if (PAGE_SIZE >= DefaultLogPageSize && PAGE_SIZE <=
  			DefaultLogPageSize * 2)
  		log_page_size = DefaultLogPageSize;
  	else
  		log_page_size = PAGE_SIZE;
  	log_page_mask = log_page_size - 1;
  	/*
  	 * Use ntfs_ffs() instead of ffs() to enable the compiler to
  	 * optimize log_page_size and log_page_bits into constants.
  	 */
  	log_page_bits = ntfs_ffs(log_page_size) - 1;
  	size &= ~(s64)(log_page_size - 1);
  	/*
  	 * Ensure the log file is big enough to store at least the two restart
  	 * pages and the minimum number of log record pages.
  	 */
  	if (size < log_page_size * 2 || (size - log_page_size * 2) >>
  			log_page_bits < MinLogRecordPages) {
  		ntfs_error(vol->sb, "$LogFile is too small.");
  		return false;
  	}
  	/*
  	 * Read through the file looking for a restart page.  Since the restart
  	 * page header is at the beginning of a page we only need to search at
  	 * what could be the beginning of a page (for each page size) rather
  	 * than scanning the whole file byte by byte.  If all potential places
  	 * contain empty and uninitialzed records, the log file can be assumed
  	 * to be empty.
  	 */
  	for (pos = 0; pos < size; pos <<= 1) {
  		pgoff_t idx = pos >> PAGE_SHIFT;
  		if (!page || page->index != idx) {
  			if (page)
  				ntfs_unmap_page(page);
  			page = ntfs_map_page(mapping, idx);
  			if (IS_ERR(page)) {
  				ntfs_error(vol->sb, "Error mapping $LogFile "
  						"page (index %lu).", idx);
  				goto err_out;
  			}
  		}
  		kaddr = (u8*)page_address(page) + (pos & ~PAGE_MASK);
  		/*
  		 * A non-empty block means the logfile is not empty while an
  		 * empty block after a non-empty block has been encountered
  		 * means we are done.
  		 */
  		if (!ntfs_is_empty_recordp((le32*)kaddr))
  			logfile_is_empty = false;
  		else if (!logfile_is_empty)
  			break;
  		/*
  		 * A log record page means there cannot be a restart page after
  		 * this so no need to continue searching.
  		 */
  		if (ntfs_is_rcrd_recordp((le32*)kaddr))
  			break;
  		/* If not a (modified by chkdsk) restart page, continue. */
  		if (!ntfs_is_rstr_recordp((le32*)kaddr) &&
  				!ntfs_is_chkd_recordp((le32*)kaddr)) {
  			if (!pos)
  				pos = NTFS_BLOCK_SIZE >> 1;
  			continue;
  		}
  		/*
  		 * Check the (modified by chkdsk) restart page for consistency
  		 * and get a copy of the complete multi sector transfer
  		 * deprotected restart page.
  		 */
  		err = ntfs_check_and_load_restart_page(log_vi,
  				(RESTART_PAGE_HEADER*)kaddr, pos,
  				!rstr1_ph ? &rstr1_ph : &rstr2_ph,
  				!rstr1_ph ? &rstr1_lsn : &rstr2_lsn);
  		if (!err) {
  			/*
  			 * If we have now found the first (modified by chkdsk)
  			 * restart page, continue looking for the second one.
  			 */
  			if (!pos) {
  				pos = NTFS_BLOCK_SIZE >> 1;
  				continue;
  			}
  			/*
  			 * We have now found the second (modified by chkdsk)
  			 * restart page, so we can stop looking.
  			 */
  			break;
  		}
  		/*
  		 * Error output already done inside the function.  Note, we do
  		 * not abort if the restart page was invalid as we might still
  		 * find a valid one further in the file.
  		 */
  		if (err != -EINVAL) {
  			ntfs_unmap_page(page);
  			goto err_out;
  		}
  		/* Continue looking. */
  		if (!pos)
  			pos = NTFS_BLOCK_SIZE >> 1;
  	}
  	if (page)
  		ntfs_unmap_page(page);
  	if (logfile_is_empty) {
  		NVolSetLogFileEmpty(vol);
  is_empty:
  		ntfs_debug("Done.  ($LogFile is empty.)");
  		return true;
  	}
  	if (!rstr1_ph) {
  		BUG_ON(rstr2_ph);
  		ntfs_error(vol->sb, "Did not find any restart pages in "
  				"$LogFile and it was not empty.");
  		return false;
  	}
  	/* If both restart pages were found, use the more recent one. */
  	if (rstr2_ph) {
  		/*
  		 * If the second restart area is more recent, switch to it.
  		 * Otherwise just throw it away.
  		 */
  		if (rstr2_lsn > rstr1_lsn) {
  			ntfs_debug("Using second restart page as it is more "
  					"recent.");
  			ntfs_free(rstr1_ph);
  			rstr1_ph = rstr2_ph;
  			/* rstr1_lsn = rstr2_lsn; */
  		} else {
  			ntfs_debug("Using first restart page as it is more "
  					"recent.");
  			ntfs_free(rstr2_ph);
  		}
  		rstr2_ph = NULL;
  	}
  	/* All consistency checks passed. */
  	if (rp)
  		*rp = rstr1_ph;
  	else
  		ntfs_free(rstr1_ph);
  	ntfs_debug("Done.");
  	return true;
  err_out:
  	if (rstr1_ph)
  		ntfs_free(rstr1_ph);
  	return false;
  }
  
  /**
   * ntfs_is_logfile_clean - check in the journal if the volume is clean
   * @log_vi:	struct inode of loaded journal $LogFile to check
   * @rp:		copy of the current restart page
   *
   * Analyze the $LogFile journal and return 'true' if it indicates the volume was
   * shutdown cleanly and 'false' if not.
   *
   * At present we only look at the two restart pages and ignore the log record
   * pages.  This is a little bit crude in that there will be a very small number
   * of cases where we think that a volume is dirty when in fact it is clean.
   * This should only affect volumes that have not been shutdown cleanly but did
   * not have any pending, non-check-pointed i/o, i.e. they were completely idle
   * at least for the five seconds preceding the unclean shutdown.
   *
   * This function assumes that the $LogFile journal has already been consistency
   * checked by a call to ntfs_check_logfile() and in particular if the $LogFile
   * is empty this function requires that NVolLogFileEmpty() is true otherwise an
   * empty volume will be reported as dirty.
   */
  bool ntfs_is_logfile_clean(struct inode *log_vi, const RESTART_PAGE_HEADER *rp)
  {
  	ntfs_volume *vol = NTFS_SB(log_vi->i_sb);
  	RESTART_AREA *ra;
  
  	ntfs_debug("Entering.");
  	/* An empty $LogFile must have been clean before it got emptied. */
  	if (NVolLogFileEmpty(vol)) {
  		ntfs_debug("Done.  ($LogFile is empty.)");
  		return true;
  	}
  	BUG_ON(!rp);
  	if (!ntfs_is_rstr_record(rp->magic) &&
  			!ntfs_is_chkd_record(rp->magic)) {
  		ntfs_error(vol->sb, "Restart page buffer is invalid.  This is "
  				"probably a bug in that the $LogFile should "
  				"have been consistency checked before calling "
  				"this function.");
  		return false;
  	}
  	ra = (RESTART_AREA*)((u8*)rp + le16_to_cpu(rp->restart_area_offset));
  	/*
  	 * If the $LogFile has active clients, i.e. it is open, and we do not
  	 * have the RESTART_VOLUME_IS_CLEAN bit set in the restart area flags,
  	 * we assume there was an unclean shutdown.
  	 */
  	if (ra->client_in_use_list != LOGFILE_NO_CLIENT &&
  			!(ra->flags & RESTART_VOLUME_IS_CLEAN)) {
  		ntfs_debug("Done.  $LogFile indicates a dirty shutdown.");
  		return false;
  	}
  	/* $LogFile indicates a clean shutdown. */
  	ntfs_debug("Done.  $LogFile indicates a clean shutdown.");
  	return true;
  }
  
  /**
   * ntfs_empty_logfile - empty the contents of the $LogFile journal
   * @log_vi:	struct inode of loaded journal $LogFile to empty
   *
   * Empty the contents of the $LogFile journal @log_vi and return 'true' on
   * success and 'false' on error.
   *
   * This function assumes that the $LogFile journal has already been consistency
   * checked by a call to ntfs_check_logfile() and that ntfs_is_logfile_clean()
   * has been used to ensure that the $LogFile is clean.
   */
  bool ntfs_empty_logfile(struct inode *log_vi)
  {
  	VCN vcn, end_vcn;
  	ntfs_inode *log_ni = NTFS_I(log_vi);
  	ntfs_volume *vol = log_ni->vol;
  	struct super_block *sb = vol->sb;
  	runlist_element *rl;
  	unsigned long flags;
  	unsigned block_size, block_size_bits;
  	int err;
  	bool should_wait = true;
  
  	ntfs_debug("Entering.");
  	if (NVolLogFileEmpty(vol)) {
  		ntfs_debug("Done.");
  		return true;
  	}
  	/*
  	 * We cannot use ntfs_attr_set() because we may be still in the middle
  	 * of a mount operation.  Thus we do the emptying by hand by first
  	 * zapping the page cache pages for the $LogFile/$DATA attribute and
  	 * then emptying each of the buffers in each of the clusters specified
  	 * by the runlist by hand.
  	 */
  	block_size = sb->s_blocksize;
  	block_size_bits = sb->s_blocksize_bits;
  	vcn = 0;
  	read_lock_irqsave(&log_ni->size_lock, flags);
  	end_vcn = (log_ni->initialized_size + vol->cluster_size_mask) >>
  			vol->cluster_size_bits;
  	read_unlock_irqrestore(&log_ni->size_lock, flags);
  	truncate_inode_pages(log_vi->i_mapping, 0);
  	down_write(&log_ni->runlist.lock);
  	rl = log_ni->runlist.rl;
  	if (unlikely(!rl || vcn < rl->vcn || !rl->length)) {
  map_vcn:
  		err = ntfs_map_runlist_nolock(log_ni, vcn, NULL);
  		if (err) {
  			ntfs_error(sb, "Failed to map runlist fragment (error "
  					"%d).", -err);
  			goto err;
  		}
  		rl = log_ni->runlist.rl;
  		BUG_ON(!rl || vcn < rl->vcn || !rl->length);
  	}
  	/* Seek to the runlist element containing @vcn. */
  	while (rl->length && vcn >= rl[1].vcn)
  		rl++;
  	do {
  		LCN lcn;
  		sector_t block, end_block;
  		s64 len;
  
  		/*
  		 * If this run is not mapped map it now and start again as the
  		 * runlist will have been updated.
  		 */
  		lcn = rl->lcn;
  		if (unlikely(lcn == LCN_RL_NOT_MAPPED)) {
  			vcn = rl->vcn;
  			goto map_vcn;
  		}
  		/* If this run is not valid abort with an error. */
  		if (unlikely(!rl->length || lcn < LCN_HOLE))
  			goto rl_err;
  		/* Skip holes. */
  		if (lcn == LCN_HOLE)
  			continue;
  		block = lcn << vol->cluster_size_bits >> block_size_bits;
  		len = rl->length;
  		if (rl[1].vcn > end_vcn)
  			len = end_vcn - rl->vcn;
  		end_block = (lcn + len) << vol->cluster_size_bits >>
  				block_size_bits;
  		/* Iterate over the blocks in the run and empty them. */
  		do {
  			struct buffer_head *bh;
  
  			/* Obtain the buffer, possibly not uptodate. */
  			bh = sb_getblk(sb, block);
  			BUG_ON(!bh);
  			/* Setup buffer i/o submission. */
  			lock_buffer(bh);
  			bh->b_end_io = end_buffer_write_sync;
  			get_bh(bh);
  			/* Set the entire contents of the buffer to 0xff. */
  			memset(bh->b_data, -1, block_size);
  			if (!buffer_uptodate(bh))
  				set_buffer_uptodate(bh);
  			if (buffer_dirty(bh))
  				clear_buffer_dirty(bh);
  			/*
  			 * Submit the buffer and wait for i/o to complete but
  			 * only for the first buffer so we do not miss really
  			 * serious i/o errors.  Once the first buffer has
  			 * completed ignore errors afterwards as we can assume
  			 * that if one buffer worked all of them will work.
  			 */
  			submit_bh(REQ_OP_WRITE, 0, bh);
  			if (should_wait) {
  				should_wait = false;
  				wait_on_buffer(bh);
  				if (unlikely(!buffer_uptodate(bh)))
  					goto io_err;
  			}
  			brelse(bh);
  		} while (++block < end_block);
  	} while ((++rl)->vcn < end_vcn);
  	up_write(&log_ni->runlist.lock);
  	/*
  	 * Zap the pages again just in case any got instantiated whilst we were
  	 * emptying the blocks by hand.  FIXME: We may not have completed
  	 * writing to all the buffer heads yet so this may happen too early.
  	 * We really should use a kernel thread to do the emptying
  	 * asynchronously and then we can also set the volume dirty and output
  	 * an error message if emptying should fail.
  	 */
  	truncate_inode_pages(log_vi->i_mapping, 0);
  	/* Set the flag so we do not have to do it again on remount. */
  	NVolSetLogFileEmpty(vol);
  	ntfs_debug("Done.");
  	return true;
  io_err:
  	ntfs_error(sb, "Failed to write buffer.  Unmount and run chkdsk.");
  	goto dirty_err;
  rl_err:
  	ntfs_error(sb, "Runlist is corrupt.  Unmount and run chkdsk.");
  dirty_err:
  	NVolSetErrors(vol);
  	err = -EIO;
  err:
  	up_write(&log_ni->runlist.lock);
  	ntfs_error(sb, "Failed to fill $LogFile with 0xff bytes (error %d).",
  			-err);
  	return false;
  }
  
  #endif /* NTFS_RW */
  