linux/fs/ntfs/bitmap.c
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   1/*
   2 * bitmap.c - NTFS kernel bitmap handling.  Part of the Linux-NTFS project.
   3 *
   4 * Copyright (c) 2004-2005 Anton Altaparmakov
   5 *
   6 * This program/include file is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License as published
   8 * by the Free Software Foundation; either version 2 of the License, or
   9 * (at your option) any later version.
  10 *
  11 * This program/include file is distributed in the hope that it will be
  12 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program (in the main directory of the Linux-NTFS
  18 * distribution in the file COPYING); if not, write to the Free Software
  19 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20 */
  21
  22#ifdef NTFS_RW
  23
  24#include <linux/pagemap.h>
  25
  26#include "bitmap.h"
  27#include "debug.h"
  28#include "aops.h"
  29#include "ntfs.h"
  30
  31/**
  32 * __ntfs_bitmap_set_bits_in_run - set a run of bits in a bitmap to a value
  33 * @vi:                 vfs inode describing the bitmap
  34 * @start_bit:          first bit to set
  35 * @count:              number of bits to set
  36 * @value:              value to set the bits to (i.e. 0 or 1)
  37 * @is_rollback:        if 'true' this is a rollback operation
  38 *
  39 * Set @count bits starting at bit @start_bit in the bitmap described by the
  40 * vfs inode @vi to @value, where @value is either 0 or 1.
  41 *
  42 * @is_rollback should always be 'false', it is for internal use to rollback
  43 * errors.  You probably want to use ntfs_bitmap_set_bits_in_run() instead.
  44 *
  45 * Return 0 on success and -errno on error.
  46 */
  47int __ntfs_bitmap_set_bits_in_run(struct inode *vi, const s64 start_bit,
  48                const s64 count, const u8 value, const bool is_rollback)
  49{
  50        s64 cnt = count;
  51        pgoff_t index, end_index;
  52        struct address_space *mapping;
  53        struct page *page;
  54        u8 *kaddr;
  55        int pos, len;
  56        u8 bit;
  57
  58        BUG_ON(!vi);
  59        ntfs_debug("Entering for i_ino 0x%lx, start_bit 0x%llx, count 0x%llx, "
  60                        "value %u.%s", vi->i_ino, (unsigned long long)start_bit,
  61                        (unsigned long long)cnt, (unsigned int)value,
  62                        is_rollback ? " (rollback)" : "");
  63        BUG_ON(start_bit < 0);
  64        BUG_ON(cnt < 0);
  65        BUG_ON(value > 1);
  66        /*
  67         * Calculate the indices for the pages containing the first and last
  68         * bits, i.e. @start_bit and @start_bit + @cnt - 1, respectively.
  69         */
  70        index = start_bit >> (3 + PAGE_CACHE_SHIFT);
  71        end_index = (start_bit + cnt - 1) >> (3 + PAGE_CACHE_SHIFT);
  72
  73        /* Get the page containing the first bit (@start_bit). */
  74        mapping = vi->i_mapping;
  75        page = ntfs_map_page(mapping, index);
  76        if (IS_ERR(page)) {
  77                if (!is_rollback)
  78                        ntfs_error(vi->i_sb, "Failed to map first page (error "
  79                                        "%li), aborting.", PTR_ERR(page));
  80                return PTR_ERR(page);
  81        }
  82        kaddr = page_address(page);
  83
  84        /* Set @pos to the position of the byte containing @start_bit. */
  85        pos = (start_bit >> 3) & ~PAGE_CACHE_MASK;
  86
  87        /* Calculate the position of @start_bit in the first byte. */
  88        bit = start_bit & 7;
  89
  90        /* If the first byte is partial, modify the appropriate bits in it. */
  91        if (bit) {
  92                u8 *byte = kaddr + pos;
  93                while ((bit & 7) && cnt) {
  94                        cnt--;
  95                        if (value)
  96                                *byte |= 1 << bit++;
  97                        else
  98                                *byte &= ~(1 << bit++);
  99                }
 100                /* If we are done, unmap the page and return success. */
 101                if (!cnt)
 102                        goto done;
 103
 104                /* Update @pos to the new position. */
 105                pos++;
 106        }
 107        /*
 108         * Depending on @value, modify all remaining whole bytes in the page up
 109         * to @cnt.
 110         */
 111        len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE - pos);
 112        memset(kaddr + pos, value ? 0xff : 0, len);
 113        cnt -= len << 3;
 114
 115        /* Update @len to point to the first not-done byte in the page. */
 116        if (cnt < 8)
 117                len += pos;
 118
 119        /* If we are not in the last page, deal with all subsequent pages. */
 120        while (index < end_index) {
 121                BUG_ON(cnt <= 0);
 122
 123                /* Update @index and get the next page. */
 124                flush_dcache_page(page);
 125                set_page_dirty(page);
 126                ntfs_unmap_page(page);
 127                page = ntfs_map_page(mapping, ++index);
 128                if (IS_ERR(page))
 129                        goto rollback;
 130                kaddr = page_address(page);
 131                /*
 132                 * Depending on @value, modify all remaining whole bytes in the
 133                 * page up to @cnt.
 134                 */
 135                len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE);
 136                memset(kaddr, value ? 0xff : 0, len);
 137                cnt -= len << 3;
 138        }
 139        /*
 140         * The currently mapped page is the last one.  If the last byte is
 141         * partial, modify the appropriate bits in it.  Note, @len is the
 142         * position of the last byte inside the page.
 143         */
 144        if (cnt) {
 145                u8 *byte;
 146
 147                BUG_ON(cnt > 7);
 148
 149                bit = cnt;
 150                byte = kaddr + len;
 151                while (bit--) {
 152                        if (value)
 153                                *byte |= 1 << bit;
 154                        else
 155                                *byte &= ~(1 << bit);
 156                }
 157        }
 158done:
 159        /* We are done.  Unmap the page and return success. */
 160        flush_dcache_page(page);
 161        set_page_dirty(page);
 162        ntfs_unmap_page(page);
 163        ntfs_debug("Done.");
 164        return 0;
 165rollback:
 166        /*
 167         * Current state:
 168         *      - no pages are mapped
 169         *      - @count - @cnt is the number of bits that have been modified
 170         */
 171        if (is_rollback)
 172                return PTR_ERR(page);
 173        if (count != cnt)
 174                pos = __ntfs_bitmap_set_bits_in_run(vi, start_bit, count - cnt,
 175                                value ? 0 : 1, true);
 176        else
 177                pos = 0;
 178        if (!pos) {
 179                /* Rollback was successful. */
 180                ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
 181                                "%li), aborting.", PTR_ERR(page));
 182        } else {
 183                /* Rollback failed. */
 184                ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
 185                                "%li) and rollback failed (error %i).  "
 186                                "Aborting and leaving inconsistent metadata.  "
 187                                "Unmount and run chkdsk.", PTR_ERR(page), pos);
 188                NVolSetErrors(NTFS_SB(vi->i_sb));
 189        }
 190        return PTR_ERR(page);
 191}
 192
 193#endif /* NTFS_RW */
 194
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