The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/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  */
   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_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         }
  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 */

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