fs/ntfs/bitmap.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * bitmap.c - NTFS kernel bitmap handling.  Part of the Linux-NTFS project.
   4  *
   5  * Copyright (c) 2004-2005 Anton Altaparmakov
   6  */
   7
   8 #ifdef NTFS_RW
   9
  10 #include <linux/pagemap.h>
  11
  12 #include "bitmap.h"
  13 #include "debug.h"
  14 #include "aops.h"
  15 #include "ntfs.h"
  16
  17 /**
  18  * __ntfs_bitmap_set_bits_in_run - set a run of bits in a bitmap to a value
  19  * @vi:                 vfs inode describing the bitmap
  20  * @start_bit:          first bit to set
  21  * @count:              number of bits to set
  22  * @value:              value to set the bits to (i.e. 0 or 1)
  23  * @is_rollback:        if 'true' this is a rollback operation
  24  *
  25  * Set @count bits starting at bit @start_bit in the bitmap described by the
  26  * vfs inode @vi to @value, where @value is either 0 or 1.
  27  *
  28  * @is_rollback should always be 'false', it is for internal use to rollback
  29  * errors.  You probably want to use ntfs_bitmap_set_bits_in_run() instead.
  30  *
  31  * Return 0 on success and -errno on error.
  32  */
  33 int __ntfs_bitmap_set_bits_in_run(struct inode *vi, const s64 start_bit,
  34                 const s64 count, const u8 value, const bool is_rollback)
  35 {
  36         s64 cnt = count;
  37         pgoff_t index, end_index;
  38         struct address_space *mapping;
  39         struct page *page;
  40         u8 *kaddr;
  41         int pos, len;
  42         u8 bit;
  43
  44         BUG_ON(!vi);
  45         ntfs_debug("Entering for i_ino 0x%lx, start_bit 0x%llx, count 0x%llx, "
  46                         "value %u.%s", vi->i_ino, (unsigned long long)start_bit,
  47                         (unsigned long long)cnt, (unsigned int)value,
  48                         is_rollback ? " (rollback)" : "");
  49         BUG_ON(start_bit < 0);
  50         BUG_ON(cnt < 0);
  51         BUG_ON(value > 1);
  52         /*
  53          * Calculate the indices for the pages containing the first and last
  54          * bits, i.e. @start_bit and @start_bit + @cnt - 1, respectively.
  55          */
  56         index = start_bit >> (3 + PAGE_SHIFT);
  57         end_index = (start_bit + cnt - 1) >> (3 + PAGE_SHIFT);
  58
  59         /* Get the page containing the first bit (@start_bit). */
  60         mapping = vi->i_mapping;
  61         page = ntfs_map_page(mapping, index);
  62         if (IS_ERR(page)) {
  63                 if (!is_rollback)
  64                         ntfs_error(vi->i_sb, "Failed to map first page (error "
  65                                         "%li), aborting.", PTR_ERR(page));
  66                 return PTR_ERR(page);
  67         }
  68         kaddr = page_address(page);
  69
  70         /* Set @pos to the position of the byte containing @start_bit. */
  71         pos = (start_bit >> 3) & ~PAGE_MASK;
  72
  73         /* Calculate the position of @start_bit in the first byte. */
  74         bit = start_bit & 7;
  75
  76         /* If the first byte is partial, modify the appropriate bits in it. */
  77         if (bit) {
  78                 u8 *byte = kaddr + pos;
  79                 while ((bit & 7) && cnt) {
  80                         cnt--;
  81                         if (value)
  82                                 *byte |= 1 << bit++;
  83                         else
  84                                 *byte &= ~(1 << bit++);
  85                 }
  86                 /* If we are done, unmap the page and return success. */
  87                 if (!cnt)
  88                         goto done;
  89
  90                 /* Update @pos to the new position. */
  91                 pos++;
  92         }
  93         /*
  94          * Depending on @value, modify all remaining whole bytes in the page up
  95          * to @cnt.
  96          */
  97         len = min_t(s64, cnt >> 3, PAGE_SIZE - pos);
  98         memset(kaddr + pos, value ? 0xff : 0, len);
  99         cnt -= len << 3;
 100
 101         /* Update @len to point to the first not-done byte in the page. */
 102         if (cnt < 8)
 103                 len += pos;
 104
 105         /* If we are not in the last page, deal with all subsequent pages. */
 106         while (index < end_index) {
 107                 BUG_ON(cnt <= 0);
 108
 109                 /* Update @index and get the next page. */
 110                 flush_dcache_page(page);
 111                 set_page_dirty(page);
 112                 ntfs_unmap_page(page);
 113                 page = ntfs_map_page(mapping, ++index);
 114                 if (IS_ERR(page))
 115                         goto rollback;
 116                 kaddr = page_address(page);
 117                 /*
 118                  * Depending on @value, modify all remaining whole bytes in the
 119                  * page up to @cnt.
 120                  */
 121                 len = min_t(s64, cnt >> 3, PAGE_SIZE);
 122                 memset(kaddr, value ? 0xff : 0, len);
 123                 cnt -= len << 3;
 124         }
 125         /*
 126          * The currently mapped page is the last one.  If the last byte is
 127          * partial, modify the appropriate bits in it.  Note, @len is the
 128          * position of the last byte inside the page.
 129          */
 130         if (cnt) {
 131                 u8 *byte;
 132
 133                 BUG_ON(cnt > 7);
 134
 135                 bit = cnt;
 136                 byte = kaddr + len;
 137                 while (bit--) {
 138                         if (value)
 139                                 *byte |= 1 << bit;
 140                         else
 141                                 *byte &= ~(1 << bit);
 142                 }
 143         }
 144 done:
 145         /* We are done.  Unmap the page and return success. */
 146         flush_dcache_page(page);
 147         set_page_dirty(page);
 148         ntfs_unmap_page(page);
 149         ntfs_debug("Done.");
 150         return 0;
 151 rollback:
 152         /*
 153          * Current state:
 154          *      - no pages are mapped
 155          *      - @count - @cnt is the number of bits that have been modified
 156          */
 157         if (is_rollback)
 158                 return PTR_ERR(page);
 159         if (count != cnt)
 160                 pos = __ntfs_bitmap_set_bits_in_run(vi, start_bit, count - cnt,
 161                                 value ? 0 : 1, true);
 162         else
 163                 pos = 0;
 164         if (!pos) {
 165                 /* Rollback was successful. */
 166                 ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
 167                                 "%li), aborting.", PTR_ERR(page));
 168         } else {
 169                 /* Rollback failed. */
 170                 ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
 171                                 "%li) and rollback failed (error %i).  "
 172                                 "Aborting and leaving inconsistent metadata.  "
 173                                 "Unmount and run chkdsk.", PTR_ERR(page), pos);
 174                 NVolSetErrors(NTFS_SB(vi->i_sb));
 175         }
 176         return PTR_ERR(page);
 177 }
 178
 179 #endif /* NTFS_RW */