initial commit with v2.6.9

[linux-2.6.9-moxart.git] / fs / ntfs / logfile.c

/*
 * logfile.c - NTFS kernel journal handling. Part of the Linux-NTFS project.
 *
 * Copyright (c) 2002-2004 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 "logfile.h"
#include "volume.h"
#include "ntfs.h"
#include "debug.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 usa_count, usa_ofs, usa_end, ra_ofs;

        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) ||
                        logfile_log_page_size & (logfile_log_page_size - 1)) {
                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;
        }
        /* 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;
        }
        /*
         * 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 || ra_ofs < usa_end ||
                        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 "
                                "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:        copy of the multi sector transfer deprotected restart page
 *
 * Check the restart page @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.
 *
 * 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.
 */
static BOOL ntfs_check_and_load_restart_page(struct inode *vi,
                RESTART_PAGE_HEADER *rp, s64 pos, RESTART_PAGE_HEADER **wrp)
{
        RESTART_AREA *ra;
        RESTART_PAGE_HEADER *trp;
        int size;
        BOOL ret;

        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 FALSE;
        }
        /* Check the restart area for consistency. */
        if (!ntfs_check_restart_area(vi, rp)) {
                /* Error output already done inside the function. */
                return FALSE;
        }
        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 FALSE;
        }
        /*
         * 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_CACHE_SIZE - (pos & ~PAGE_CACHE_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_CACHE_SHIFT;
                BUG_ON((pos + size) & ~PAGE_CACHE_MASK);
                do {
                        page = ntfs_map_page(vi->i_mapping, idx);
                        if (IS_ERR(page)) {
                                ntfs_error(vi->i_sb, "Error mapping $LogFile "
                                                "page (index %lu).", idx);
                                goto err_out;
                        }
                        size = min_t(int, to_read, PAGE_CACHE_SIZE);
                        memcpy((u8*)trp + have_read, page_address(page), size);
                        ntfs_unmap_page(page);
                        have_read += size;
                        to_read -= size;
                        idx++;
                } while (to_read > 0);
        }
        /* Perform the multi sector transfer deprotection on the buffer. */
        if (post_read_mst_fixup((NTFS_RECORD*)trp,
                        le32_to_cpu(rp->system_page_size))) {
                ntfs_error(vi->i_sb, "Multi sector transfer error detected in "
                                "$LogFile restart page.");
                goto err_out;
        }
        /* Check the log client records for consistency. */
        ret = ntfs_check_log_client_array(vi, trp);
        if (ret && wrp)
                *wrp = trp;
        else
                ntfs_free(trp);
        ntfs_debug("Done.");
        return ret;
err_out:
        ntfs_free(trp);
        return FALSE;
}

/**
 * ntfs_ckeck_logfile - check in the journal if the volume is consistent
 * @log_vi:     struct inode of loaded journal $LogFile to check
 *
 * Check the $LogFile journal for consistency and return TRUE if it is
 * consistent and FALSE if not.
 *
 * 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)
{
        s64 size, pos, rstr1_pos, rstr2_pos;
        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, ofs;
        BOOL logfile_is_empty = TRUE;
        BOOL rstr1_found = FALSE;
        BOOL rstr2_found = FALSE;
        u8 log_page_bits;

        ntfs_debug("Entering.");
        /* An empty $LogFile must have been clean before it got emptied. */
        if (NVolLogFileEmpty(vol))
                goto is_empty;
        size = log_vi->i_size;
        /* Make sure the file doesn't exceed the maximum allowed size. */
        if (size > MaxLogFileSize)
                size = MaxLogFileSize;
        /*
         * Truncate size to a multiple of the page cache size or the default
         * log page size if the page cache size is between the default log page
         * log page size if the page cache size is between the default log page
         * size and twice that.
         */
        if (PAGE_CACHE_SIZE >= DefaultLogPageSize && PAGE_CACHE_SIZE <=
                        DefaultLogPageSize * 2)
                log_page_size = DefaultLogPageSize;
        else
                log_page_size = PAGE_CACHE_SIZE;
        log_page_mask = log_page_size - 1;
        /*
         * Use generic_ffs() instead of ffs() to enable the compiler to
         * optimize log_page_size and log_page_bits into constants.
         */
        log_page_bits = generic_ffs(log_page_size) - 1;
        size &= ~(log_page_size - 1);
        /*
         * Ensure the log file is big enough to store at least the two restart
         * pages and the minimum number of log record pages.
         */
        if (size < log_page_size * 2 || (size - log_page_size * 2) >>
                        log_page_bits < MinLogRecordPages) {
                ntfs_error(vol->sb, "$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_CACHE_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 $LogFile "
                                                "page (index %lu).", idx);
                                return FALSE;
                        }
                }
                kaddr = (u8*)page_address(page) + (pos & ~PAGE_CACHE_MASK);
                /*
                 * A non-empty block means the logfile is not empty while an
                 * empty block after a non-empty block has been encountered
                 * means we are done.
                 */
                if (!ntfs_is_empty_recordp((le32*)kaddr))
                        logfile_is_empty = FALSE;
                else if (!logfile_is_empty)
                        break;
                /*
                 * A log record page means there cannot be a restart page after
                 * this so no need to continue searching.
                 */
                if (ntfs_is_rcrd_recordp((le32*)kaddr))
                        break;
                /*
                 * A modified by chkdsk restart page means we cannot handle
                 * this log file.
                 */
                if (ntfs_is_chkd_recordp((le32*)kaddr)) {
                        ntfs_error(vol->sb, "$LogFile has been modified by "
                                        "chkdsk.  Mount this volume in "
                                        "Windows.");
                        goto err_out;
                }
                /* If not a restart page, continue. */
                if (!ntfs_is_rstr_recordp((le32*)kaddr)) {
                        /* Skip to the minimum page size for the next one. */
                        if (!pos)
                                pos = NTFS_BLOCK_SIZE >> 1;
                        continue;
                }
                /* We now know we have a restart page. */
                if (!pos) {
                        rstr1_found = TRUE;
                        rstr1_pos = pos;
                } else {
                        if (rstr2_found) {
                                ntfs_error(vol->sb, "Found more than two "
                                                "restart pages in $LogFile.");
                                goto err_out;
                        }
                        rstr2_found = TRUE;
                        rstr2_pos = pos;
                }
                /*
                 * Check the restart page for consistency and get a copy of the
                 * complete multi sector transfer deprotected restart page.
                 */
                if (!ntfs_check_and_load_restart_page(log_vi,
                                (RESTART_PAGE_HEADER*)kaddr, pos,
                                !pos ? &rstr1_ph : &rstr2_ph)) {
                        /* Error output already done inside the function. */
                        goto err_out;
                }
                /*
                 * We have a valid restart page.  The next one must be after
                 * a whole system page size as specified by the valid restart
                 * page.
                 */
                if (!pos)
                        pos = le32_to_cpu(rstr1_ph->system_page_size) >> 1;
        }
        if (page) {
                ntfs_unmap_page(page);
                page = NULL;
        }
        if (logfile_is_empty) {
                NVolSetLogFileEmpty(vol);
is_empty:
                ntfs_debug("Done.  ($LogFile is empty.)");
                return TRUE;
        }
        if (!rstr1_found || !rstr2_found) {
                ntfs_error(vol->sb, "Did not find two restart pages in "
                                "$LogFile.");
                goto err_out;
        }
        /*
         * The two restart areas must be identical except for the update
         * sequence number.
         */
        ofs = le16_to_cpu(rstr1_ph->usa_ofs);
        if (memcmp(rstr1_ph, rstr2_ph, ofs) || (ofs += sizeof(u16),
                        memcmp((u8*)rstr1_ph + ofs, (u8*)rstr2_ph + ofs,
                        le32_to_cpu(rstr1_ph->system_page_size) - ofs))) {
                ntfs_error(vol->sb, "The two restart pages in $LogFile do not "
                                "match.");
                goto err_out;
        }
        ntfs_free(rstr1_ph);
        ntfs_free(rstr2_ph);
        /* All consistency checks passed. */
        ntfs_debug("Done.");
        return TRUE;
err_out:
        if (page)
                ntfs_unmap_page(page);
        if (rstr1_ph)
                ntfs_free(rstr1_ph);
        if (rstr2_ph)
                ntfs_free(rstr2_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
 *
 * 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 preceeding 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)
{
        ntfs_volume *vol = NTFS_SB(log_vi->i_sb);
        struct page *page;
        RESTART_PAGE_HEADER *rp;
        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;
        }
        /*
         * Read the first restart page.  It will be possibly incomplete and
         * will not be multi sector transfer deprotected but we only need the
         * first NTFS_BLOCK_SIZE bytes so it does not matter.
         */
        page = ntfs_map_page(log_vi->i_mapping, 0);
        if (IS_ERR(page)) {
                ntfs_error(vol->sb, "Error mapping $LogFile page (index 0).");
                return FALSE;
        }
        rp = (RESTART_PAGE_HEADER*)page_address(page);
        if (!ntfs_is_rstr_record(rp->magic)) {
                ntfs_error(vol->sb, "No restart page found at offset zero in "
                                "$LogFile.  This is probably a bug in that "
                                "the $LogFile should have been consistency "
                                "checked before calling this function.");
                goto err_out;
        }
        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.");
                goto err_out;
        }
        ntfs_unmap_page(page);
        /* $LogFile indicates a clean shutdown. */
        ntfs_debug("Done.  $LogFile indicates a clean shutdown.");
        return TRUE;
err_out:
        ntfs_unmap_page(page);
        return FALSE;
}

/**
 * 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)
{
        ntfs_volume *vol = NTFS_SB(log_vi->i_sb);
        struct address_space *mapping;
        pgoff_t idx, end;

        ntfs_debug("Entering.");
        if (NVolLogFileEmpty(vol))
                goto done;
        mapping = log_vi->i_mapping;
        end = (log_vi->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
        for (idx = 0; idx < end; ++idx) {
                struct page *page;
                u8 *kaddr;

                /* Find or create the current page.  (The page is locked.) */
                page = grab_cache_page(mapping, idx);
                if (unlikely(!page)) {
                        ntfs_error(vol->sb, "Insufficient memory to grab "
                                        "$LogFile page (index %lu).", idx);
                        return FALSE;
                }
                /*
                 * Set all bytes in the page to 0xff.  It doesn't matter if we
                 * go beyond i_size, because ntfs_writepage() will take care of
                 * that for us.
                 */
                kaddr = (u8*)kmap_atomic(page, KM_USER0);
                memset(kaddr, 0xff, PAGE_CACHE_SIZE);
                flush_dcache_page(page);
                kunmap_atomic(kaddr, KM_USER0);
                /*
                 * If the page has buffers, mark them uptodate since buffer
                 * state and not page state is definitive in 2.6 kernels.
                 */
                if (page_has_buffers(page)) {
                        struct buffer_head *bh, *head;

                        bh = head = page_buffers(page);
                        do {
                                set_buffer_uptodate(bh);
                        } while ((bh = bh->b_this_page) != head);
                }
                /* Now that buffers are uptodate, set the page uptodate, too. */
                SetPageUptodate(page);
                /*
                 * Set the page and all its buffers dirty and mark the inode
                 * dirty, too. The VM will write the page later on.
                 */
                set_page_dirty(page);
                /* Finally unlock and release the page. */
                unlock_page(page);
                page_cache_release(page);
        }
        /* We set the flag so we do not clear the log file again on remount. */
        NVolSetLogFileEmpty(vol);
done:
        ntfs_debug("Done.");
        return TRUE;
}

#endif /* NTFS_RW */