LXR linux/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 */
  33int __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        }
 144done:
 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;
 151rollback:
 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 */
 180