fs/hfsplus/bitmap.c

   1 /*
   2  *  linux/fs/hfsplus/bitmap.c
   3  *
   4  * Copyright (C) 2001
   5  * Brad Boyer (flar@allandria.com)
   6  * (C) 2003 Ardis Technologies <roman@ardistech.com>
   7  *
   8  * Handling of allocation file
   9  */
  10
  11 #include <linux/pagemap.h>
  12
  13 #include "hfsplus_fs.h"
  14 #include "hfsplus_raw.h"
  15
  16 #define PAGE_CACHE_BITS (PAGE_SIZE * 8)
  17
  18 int hfsplus_block_allocate(struct super_block *sb, u32 size,
  19                 u32 offset, u32 *max)
  20 {
  21         struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
  22         struct page *page;
  23         struct address_space *mapping;
  24         __be32 *pptr, *curr, *end;
  25         u32 mask, start, len, n;
  26         __be32 val;
  27         int i;
  28
  29         len = *max;
  30         if (!len)
  31                 return size;
  32
  33         hfs_dbg(BITMAP, "block_allocate: %u,%u,%u\n", size, offset, len);
  34         mutex_lock(&sbi->alloc_mutex);
  35         mapping = sbi->alloc_file->i_mapping;
  36         page = read_mapping_page(mapping, offset / PAGE_CACHE_BITS, NULL);
  37         if (IS_ERR(page)) {
  38                 start = size;
  39                 goto out;
  40         }
  41         pptr = kmap(page);
  42         curr = pptr + (offset & (PAGE_CACHE_BITS - 1)) / 32;
  43         i = offset % 32;
  44         offset &= ~(PAGE_CACHE_BITS - 1);
  45         if ((size ^ offset) / PAGE_CACHE_BITS)
  46                 end = pptr + PAGE_CACHE_BITS / 32;
  47         else
  48                 end = pptr + ((size + 31) & (PAGE_CACHE_BITS - 1)) / 32;
  49
  50         /* scan the first partial u32 for zero bits */
  51         val = *curr;
  52         if (~val) {
  53                 n = be32_to_cpu(val);
  54                 mask = (1U << 31) >> i;
  55                 for (; i < 32; mask >>= 1, i++) {
  56                         if (!(n & mask))
  57                                 goto found;
  58                 }
  59         }
  60         curr++;
  61
  62         /* scan complete u32s for the first zero bit */
  63         while (1) {
  64                 while (curr < end) {
  65                         val = *curr;
  66                         if (~val) {
  67                                 n = be32_to_cpu(val);
  68                                 mask = 1 << 31;
  69                                 for (i = 0; i < 32; mask >>= 1, i++) {
  70                                         if (!(n & mask))
  71                                                 goto found;
  72                                 }
  73                         }
  74                         curr++;
  75                 }
  76                 kunmap(page);
  77                 offset += PAGE_CACHE_BITS;
  78                 if (offset >= size)
  79                         break;
  80                 page = read_mapping_page(mapping, offset / PAGE_CACHE_BITS,
  81                                          NULL);
  82                 if (IS_ERR(page)) {
  83                         start = size;
  84                         goto out;
  85                 }
  86                 curr = pptr = kmap(page);
  87                 if ((size ^ offset) / PAGE_CACHE_BITS)
  88                         end = pptr + PAGE_CACHE_BITS / 32;
  89                 else
  90                         end = pptr + ((size + 31) & (PAGE_CACHE_BITS - 1)) / 32;
  91         }
  92         hfs_dbg(BITMAP, "bitmap full\n");
  93         start = size;
  94         goto out;
  95
  96 found:
  97         start = offset + (curr - pptr) * 32 + i;
  98         if (start >= size) {
  99                 hfs_dbg(BITMAP, "bitmap full\n");
 100                 goto out;
 101         }
 102         /* do any partial u32 at the start */
 103         len = min(size - start, len);
 104         while (1) {
 105                 n |= mask;
 106                 if (++i >= 32)
 107                         break;
 108                 mask >>= 1;
 109                 if (!--len || n & mask)
 110                         goto done;
 111         }
 112         if (!--len)
 113                 goto done;
 114         *curr++ = cpu_to_be32(n);
 115         /* do full u32s */
 116         while (1) {
 117                 while (curr < end) {
 118                         n = be32_to_cpu(*curr);
 119                         if (len < 32)
 120                                 goto last;
 121                         if (n) {
 122                                 len = 32;
 123                                 goto last;
 124                         }
 125                         *curr++ = cpu_to_be32(0xffffffff);
 126                         len -= 32;
 127                 }
 128                 set_page_dirty(page);
 129                 kunmap(page);
 130                 offset += PAGE_CACHE_BITS;
 131                 page = read_mapping_page(mapping, offset / PAGE_CACHE_BITS,
 132                                          NULL);
 133                 if (IS_ERR(page)) {
 134                         start = size;
 135                         goto out;
 136                 }
 137                 pptr = kmap(page);
 138                 curr = pptr;
 139                 end = pptr + PAGE_CACHE_BITS / 32;
 140         }
 141 last:
 142         /* do any partial u32 at end */
 143         mask = 1U << 31;
 144         for (i = 0; i < len; i++) {
 145                 if (n & mask)
 146                         break;
 147                 n |= mask;
 148                 mask >>= 1;
 149         }
 150 done:
 151         *curr = cpu_to_be32(n);
 152         set_page_dirty(page);
 153         kunmap(page);
 154         *max = offset + (curr - pptr) * 32 + i - start;
 155         sbi->free_blocks -= *max;
 156         hfsplus_mark_mdb_dirty(sb);
 157         hfs_dbg(BITMAP, "-> %u,%u\n", start, *max);
 158 out:
 159         mutex_unlock(&sbi->alloc_mutex);
 160         return start;
 161 }
 162
 163 int hfsplus_block_free(struct super_block *sb, u32 offset, u32 count)
 164 {
 165         struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
 166         struct page *page;
 167         struct address_space *mapping;
 168         __be32 *pptr, *curr, *end;
 169         u32 mask, len, pnr;
 170         int i;
 171
 172         /* is there any actual work to be done? */
 173         if (!count)
 174                 return 0;
 175
 176         hfs_dbg(BITMAP, "block_free: %u,%u\n", offset, count);
 177         /* are all of the bits in range? */
 178         if ((offset + count) > sbi->total_blocks)
 179                 return -ENOENT;
 180
 181         mutex_lock(&sbi->alloc_mutex);
 182         mapping = sbi->alloc_file->i_mapping;
 183         pnr = offset / PAGE_CACHE_BITS;
 184         page = read_mapping_page(mapping, pnr, NULL);
 185         if (IS_ERR(page))
 186                 goto kaboom;
 187         pptr = kmap(page);
 188         curr = pptr + (offset & (PAGE_CACHE_BITS - 1)) / 32;
 189         end = pptr + PAGE_CACHE_BITS / 32;
 190         len = count;
 191
 192         /* do any partial u32 at the start */
 193         i = offset % 32;
 194         if (i) {
 195                 int j = 32 - i;
 196                 mask = 0xffffffffU << j;
 197                 if (j > count) {
 198                         mask |= 0xffffffffU >> (i + count);
 199                         *curr++ &= cpu_to_be32(mask);
 200                         goto out;
 201                 }
 202                 *curr++ &= cpu_to_be32(mask);
 203                 count -= j;
 204         }
 205
 206         /* do full u32s */
 207         while (1) {
 208                 while (curr < end) {
 209                         if (count < 32)
 210                                 goto done;
 211                         *curr++ = 0;
 212                         count -= 32;
 213                 }
 214                 if (!count)
 215                         break;
 216                 set_page_dirty(page);
 217                 kunmap(page);
 218                 page = read_mapping_page(mapping, ++pnr, NULL);
 219                 if (IS_ERR(page))
 220                         goto kaboom;
 221                 pptr = kmap(page);
 222                 curr = pptr;
 223                 end = pptr + PAGE_CACHE_BITS / 32;
 224         }
 225 done:
 226         /* do any partial u32 at end */
 227         if (count) {
 228                 mask = 0xffffffffU >> count;
 229                 *curr &= cpu_to_be32(mask);
 230         }
 231 out:
 232         set_page_dirty(page);
 233         kunmap(page);
 234         sbi->free_blocks += len;
 235         hfsplus_mark_mdb_dirty(sb);
 236         mutex_unlock(&sbi->alloc_mutex);
 237
 238         return 0;
 239
 240 kaboom:
 241         pr_crit("unable to mark blocks free: error %ld\n", PTR_ERR(page));
 242         mutex_unlock(&sbi->alloc_mutex);
 243
 244         return -EIO;
 245 }