usbloadergx/source/libntfs/logfile.c

/**
 * logfile.c - NTFS journal handling. Originated from the Linux-NTFS project.
 *
 * Copyright (c) 2002-2005 Anton Altaparmakov
 * Copyright (c) 2005 Yura Pakhuchiy
 * Copyright (c) 2005-2009 Szabolcs Szakacsits
 *
 * 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 NTFS-3G
 * 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 HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif

#include "attrib.h"
#include "debug.h"
#include "logfile.h"
#include "volume.h"
#include "mst.h"
#include "logging.h"
#include "misc.h"

/**
 * ntfs_check_restart_page_header - check the page header for consistency
 * @rp:		restart page header to check
 * @pos:	position in logfile 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(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_log_trace("Entering.\n");
    /*
     * 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_log_error("$LogFile uses unsupported page size.\n");
        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_log_error("Found restart area in incorrect "
                "position in $LogFile.\n");
        return FALSE;
    }
    /* We only know how to handle version 1.1. */
    if (sle16_to_cpu(rp->major_ver) != 1 || sle16_to_cpu(rp->minor_ver) != 1)
    {
        ntfs_log_error("$LogFile version %i.%i is not "
                "supported.  (This driver supports version "
                "1.1 only.)\n", (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_log_error("$LogFile restart page specifies "
                "inconsistent update sequence array count.\n");
        return FALSE;
    }
    /* Verify the position of the update sequence array. */
    usa_ofs = le16_to_cpu(rp->usa_ofs);
    usa_end = usa_ofs + usa_count * sizeof(u16);
    if (usa_ofs < sizeof(RESTART_PAGE_HEADER) || usa_end > NTFS_BLOCK_SIZE - sizeof(u16))
    {
        ntfs_log_error("$LogFile restart page specifies "
                "inconsistent update sequence array offset.\n");
        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_log_error("$LogFile restart page specifies "
                "inconsistent restart area offset.\n");
        return FALSE;
    }
    /*
     * Only restart pages modified by chkdsk are allowed to have chkdsk_lsn
     * set.
     */
    if (!ntfs_is_chkd_record(rp->magic) && sle64_to_cpu(rp->chkdsk_lsn))
    {
        ntfs_log_error("$LogFile restart page is not modified "
                "by chkdsk but a chkdsk LSN is specified.\n");
        return FALSE;
    }
    ntfs_log_trace("Done.\n");
    return TRUE;
}

/**
 * ntfs_check_restart_area - check the restart area for consistency
 * @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(RESTART_PAGE_HEADER *rp)
{
    u64 file_size;
    RESTART_AREA *ra;
    u16 ra_ofs, ra_len, ca_ofs;
    u8 fs_bits;

    ntfs_log_trace("Entering.\n");
    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_log_error("$LogFile restart area specifies "
                "inconsistent file offset.\n");
        return FALSE;
    }
    /*
     * Now that we can access ra->client_array_offset, make sure everything
     * up to the log client array is before the first word protected by an
     * update sequence number.  This ensures we can access all of the
     * restart area elements safely.  Also, the client array offset must be
     * aligned to an 8-byte boundary.
     */
    ca_ofs = le16_to_cpu(ra->client_array_offset);
    if (((ca_ofs + 7) & ~7) != ca_ofs || ra_ofs + ca_ofs > (u16) (NTFS_BLOCK_SIZE - sizeof(u16)))
    {
        ntfs_log_error("$LogFile restart area specifies "
                "inconsistent client array offset.\n");
        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 ((u32) (ra_ofs + ra_len) > le32_to_cpu(rp->system_page_size) || (u32) (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_log_error("$LogFile restart area is out of bounds "
                "of the system page size specified by the "
                "restart page header and/or the specified "
                "restart area length is inconsistent.\n");
        return FALSE;
    }
    /*
     * The ra->client_free_list and ra->client_in_use_list must be either
     * LOGFILE_NO_CLIENT or less than ra->log_clients or they are
     * overflowing the client array.
     */
    if ((ra->client_free_list != LOGFILE_NO_CLIENT && le16_to_cpu(ra->client_free_list) >= le16_to_cpu(ra->log_clients))
            || (ra->client_in_use_list != LOGFILE_NO_CLIENT && le16_to_cpu(ra->client_in_use_list)
                    >= le16_to_cpu(ra->log_clients)))
    {
        ntfs_log_error("$LogFile restart area specifies "
                "overflowing client free and/or in use lists.\n");
        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) != (u32) (67 - fs_bits))
    {
        ntfs_log_error("$LogFile restart area specifies "
                "inconsistent sequence number bits.\n");
        return FALSE;
    }
    /* The log record header length must be a multiple of 8. */
    if (((le16_to_cpu(ra->log_record_header_length) + 7) & ~7) != le16_to_cpu(ra->log_record_header_length))
    {
        ntfs_log_error("$LogFile restart area specifies "
                "inconsistent log record header length.\n");
        return FALSE;
    }
    /* Ditto 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_log_error("$LogFile restart area specifies "
                "inconsistent log page data offset.\n");
        return FALSE;
    }
    ntfs_log_trace("Done.\n");
    return TRUE;
}

/**
 * ntfs_check_log_client_array - check the log client array for consistency
 * @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(RESTART_PAGE_HEADER *rp)
{
    RESTART_AREA *ra;
    LOG_CLIENT_RECORD *ca, *cr;
    u16 nr_clients, idx;
    BOOL in_free_list, idx_is_first;

    ntfs_log_trace("Entering.\n");
    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_log_trace("Done.\n");
    return TRUE;
    err_out: ntfs_log_error("$LogFile log client array is corrupt.\n");
    return FALSE;
}

/**
 * ntfs_check_and_load_restart_page - check the restart page for consistency
 * @log_na:	opened ntfs attribute for journal $LogFile
 * @rp:		restart page to check
 * @pos:	position in @log_na 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.
 *
 * Similarly, 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(ntfs_attr *log_na, RESTART_PAGE_HEADER *rp, s64 pos,
        RESTART_PAGE_HEADER **wrp, LSN *lsn)
{
    RESTART_AREA *ra;
    RESTART_PAGE_HEADER *trp;
    int err;

    ntfs_log_trace("Entering.\n");
    /* Check the restart page header for consistency. */
    if (!ntfs_check_restart_page_header(rp, pos))
    {
        /* Error output already done inside the function. */
        return EINVAL;
    }
    /* Check the restart area for consistency. */
    if (!ntfs_check_restart_area(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(le32_to_cpu(rp->system_page_size));
    if (!trp) return errno;
    /*
     * Read the whole of the restart page into the buffer.  If it fits
     * completely inside @rp, just copy it from there.  Otherwise read it
     * from disk.
     */
    if (le32_to_cpu(rp->system_page_size) <= NTFS_BLOCK_SIZE)
        memcpy(trp, rp, le32_to_cpu(rp->system_page_size));
    else if (ntfs_attr_pread(log_na, pos, le32_to_cpu(rp->system_page_size), trp) != le32_to_cpu(rp->system_page_size))
    {
        err = errno;
        ntfs_log_error("Failed to read whole restart page into the "
                "buffer.\n");
        if (err != ENOMEM) err = EIO;
        goto err_out;
    }
    /*
     * 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)) && ntfs_mst_post_read_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
                - (int) sizeof(u16))
        {
            ntfs_log_error("Multi sector transfer error "
                    "detected in $LogFile restart page.\n");
            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(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_log_trace("Done.\n");
    if (wrp)
        *wrp = trp;
    else
    {
        err_out: free(trp);
    }
    return err;
}

/**
 * ntfs_check_logfile - check in the journal if the volume is consistent
 * @log_na:	ntfs attribute 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(ntfs_attr *log_na, RESTART_PAGE_HEADER **rp)
{
    s64 size, pos;
    LSN rstr1_lsn, rstr2_lsn;
    ntfs_volume *vol = log_na->ni->vol;
    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_log_trace("Entering.\n");
    /* An empty $LogFile must have been clean before it got emptied. */
    if (NVolLogFileEmpty(vol)) goto is_empty;
    size = log_na->data_size;
    /* Make sure the file doesn't exceed the maximum allowed size. */
    if (size > (s64) MaxLogFileSize) size = MaxLogFileSize;
    log_page_size = DefaultLogPageSize;
    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 = 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_log_error("$LogFile is too small.\n");
        return FALSE;
    }
    /* Allocate memory for restart page. */
    kaddr = ntfs_malloc(NTFS_BLOCK_SIZE);
    if (!kaddr) 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 uninitialized records, the log file can be assumed
     * to be empty.
     */
    for (pos = 0; pos < size; pos <<= 1)
    {
        /*
         * Read first NTFS_BLOCK_SIZE bytes of potential restart page.
         */
        if (ntfs_attr_pread(log_na, pos, NTFS_BLOCK_SIZE, kaddr) != NTFS_BLOCK_SIZE)
        {
            ntfs_log_error("Failed to read first NTFS_BLOCK_SIZE "
                    "bytes of potential restart page.\n");
            goto err_out;
        }

        /*
         * 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_na, (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) goto err_out;
        /* Continue looking. */
        if (!pos) pos = NTFS_BLOCK_SIZE >> 1;
    }
    if (kaddr)
    {
        free(kaddr);
        kaddr = NULL;
    }
    if (logfile_is_empty)
    {
        NVolSetLogFileEmpty(vol);
        is_empty:
        ntfs_log_trace("Done.  ($LogFile is empty.)\n");
        return TRUE;
    }
    if (!rstr1_ph)
    {
        if (rstr2_ph) ntfs_log_error("BUG: rstr2_ph isn't NULL!\n");
        ntfs_log_error("Did not find any restart pages in "
                "$LogFile and it was not empty.\n");
        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_log_debug("Using second restart page as it is more "
                    "recent.\n");
            free(rstr1_ph);
            rstr1_ph = rstr2_ph;
            /* rstr1_lsn = rstr2_lsn; */
        }
        else
        {
            ntfs_log_debug("Using first restart page as it is more "
                    "recent.\n");
            free(rstr2_ph);
        }
        rstr2_ph = NULL;
    }
    /* All consistency checks passed. */
    if (rp)
        *rp = rstr1_ph;
    else free(rstr1_ph);
    ntfs_log_trace("Done.\n");
    return TRUE;
    err_out: free(kaddr);
    free(rstr1_ph);
    free(rstr2_ph);
    return FALSE;
}

/**
 * ntfs_is_logfile_clean - check in the journal if the volume is clean
 * @log_na:	ntfs attribute 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(ntfs_attr *log_na, RESTART_PAGE_HEADER *rp)
{
    RESTART_AREA *ra;

    ntfs_log_trace("Entering.\n");
    /* An empty $LogFile must have been clean before it got emptied. */
    if (NVolLogFileEmpty(log_na->ni->vol))
    {
        ntfs_log_trace("$LogFile is empty\n");
        return TRUE;
    }
    if (!rp)
    {
        ntfs_log_error("Restart page header is NULL\n");
        return FALSE;
    }
    if (!ntfs_is_rstr_record(rp->magic) && !ntfs_is_chkd_record(rp->magic))
    {
        ntfs_log_error("Restart page buffer is invalid\n");
        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_log_error("The disk contains an unclean file system (%d, "
                "%d).\n", le16_to_cpu(ra->client_in_use_list),
                le16_to_cpu(ra->flags));
        return FALSE;
    }
    /* $LogFile indicates a clean shutdown. */
    ntfs_log_trace("$LogFile indicates a clean shutdown\n");
    return TRUE;
}

/**
 * ntfs_empty_logfile - empty the contents of the $LogFile journal
 * @na:		ntfs attribute of journal $LogFile to empty
 *
 * Empty the contents of the $LogFile journal @na and return 0 on success and
 * -1 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.
 */
int ntfs_empty_logfile(ntfs_attr *na)
{
    s64 pos, count;
    char buf[NTFS_BUF_SIZE];

    ntfs_log_trace("Entering.\n");

    if (NVolLogFileEmpty(na->ni->vol)) return 0;

    if (!NAttrNonResident(na))
    {
        errno = EIO;
        ntfs_log_perror("Resident $LogFile $DATA attribute");
        return -1;
    }

    memset(buf, -1, NTFS_BUF_SIZE);

    pos = 0;
    while ((count = na->data_size - pos) > 0)
    {

        if (count > NTFS_BUF_SIZE) count = NTFS_BUF_SIZE;

        count = ntfs_attr_pwrite(na, pos, count, buf);
        if (count <= 0)
        {
            ntfs_log_perror("Failed to reset $LogFile");
            if (count != -1) errno = EIO;
            return -1;
        }
        pos += count;
    }

    NVolSetLogFileEmpty(na->ni->vol);

    return 0;
}