linux/fs/hfsplus/bitmap.c
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   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_CACHE_SIZE * 8)
  17
  18int 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        dprint(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        dprint(DBG_BITMAP, "bitmap full\n");
  93        start = size;
  94        goto out;
  95
  96found:
  97        start = offset + (curr - pptr) * 32 + i;
  98        if (start >= size) {
  99                dprint(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        }
 141last:
 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        }
 150done:
 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        dprint(DBG_BITMAP, "-> %u,%u\n", start, *max);
 158out:
 159        mutex_unlock(&sbi->alloc_mutex);
 160        return start;
 161}
 162
 163int 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        dprint(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 -2;
 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        pptr = kmap(page);
 186        curr = pptr + (offset & (PAGE_CACHE_BITS - 1)) / 32;
 187        end = pptr + PAGE_CACHE_BITS / 32;
 188        len = count;
 189
 190        /* do any partial u32 at the start */
 191        i = offset % 32;
 192        if (i) {
 193                int j = 32 - i;
 194                mask = 0xffffffffU << j;
 195                if (j > count) {
 196                        mask |= 0xffffffffU >> (i + count);
 197                        *curr++ &= cpu_to_be32(mask);
 198                        goto out;
 199                }
 200                *curr++ &= cpu_to_be32(mask);
 201                count -= j;
 202        }
 203
 204        /* do full u32s */
 205        while (1) {
 206                while (curr < end) {
 207                        if (count < 32)
 208                                goto done;
 209                        *curr++ = 0;
 210                        count -= 32;
 211                }
 212                if (!count)
 213                        break;
 214                set_page_dirty(page);
 215                kunmap(page);
 216                page = read_mapping_page(mapping, ++pnr, NULL);
 217                pptr = kmap(page);
 218                curr = pptr;
 219                end = pptr + PAGE_CACHE_BITS / 32;
 220        }
 221done:
 222        /* do any partial u32 at end */
 223        if (count) {
 224                mask = 0xffffffffU >> count;
 225                *curr &= cpu_to_be32(mask);
 226        }
 227out:
 228        set_page_dirty(page);
 229        kunmap(page);
 230        sbi->free_blocks += len;
 231        hfsplus_mark_mdb_dirty(sb);
 232        mutex_unlock(&sbi->alloc_mutex);
 233
 234        return 0;
 235}
 236
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