fs/ntfs/bitmap.c

   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  */
  47 int __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_SHIFT);
  71         end_index = (start_bit + cnt - 1) >> (3 + PAGE_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_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_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_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         }
 158 done:
 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;
 165 rollback:
 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 */