--- /dev/null
+/*
+ * linux/fs/hfs/bitmap.c
+ *
+ * Copyright (C) 1996-1997 Paul H. Hargrove
+ * (C) 2003 Ardis Technologies <roman@ardistech.com>
+ * This file may be distributed under the terms of the GNU General Public License.
+ *
+ * Based on GPLed code Copyright (C) 1995 Michael Dreher
+ *
+ * This file contains the code to modify the volume bitmap:
+ * search/set/clear bits.
+ */
+
+#include "hfs_fs.h"
+
+/*
+ * hfs_find_zero_bit()
+ *
+ * Description:
+ * Given a block of memory, its length in bits, and a starting bit number,
+ * determine the number of the first zero bits (in left-to-right ordering)
+ * in that range.
+ *
+ * Returns >= 'size' if no zero bits are found in the range.
+ *
+ * Accesses memory in 32-bit aligned chunks of 32-bits and thus
+ * may read beyond the 'size'th bit.
+ */
+static u32 hfs_find_set_zero_bits(__be32 *bitmap, u32 size, u32 offset, u32 *max)
+{
+ __be32 *curr, *end;
+ u32 mask, start, len, n;
+ __be32 val;
+ int i;
+
+ len = *max;
+ if (!len)
+ return size;
+
+ curr = bitmap + (offset / 32);
+ end = bitmap + ((size + 31) / 32);
+
+ /* scan the first partial u32 for zero bits */
+ val = *curr;
+ if (~val) {
+ n = be32_to_cpu(val);
+ i = offset % 32;
+ mask = (1U << 31) >> i;
+ for (; i < 32; mask >>= 1, i++) {
+ if (!(n & mask))
+ goto found;
+ }
+ }
+
+ /* scan complete u32s for the first zero bit */
+ while (++curr < end) {
+ val = *curr;
+ if (~val) {
+ n = be32_to_cpu(val);
+ mask = 1 << 31;
+ for (i = 0; i < 32; mask >>= 1, i++) {
+ if (!(n & mask))
+ goto found;
+ }
+ }
+ }
+ return size;
+
+found:
+ start = (curr - bitmap) * 32 + i;
+ if (start >= size)
+ return start;
+ /* do any partial u32 at the start */
+ len = min(size - start, len);
+ while (1) {
+ n |= mask;
+ if (++i >= 32)
+ break;
+ mask >>= 1;
+ if (!--len || n & mask)
+ goto done;
+ }
+ if (!--len)
+ goto done;
+ *curr++ = cpu_to_be32(n);
+ /* do full u32s */
+ while (1) {
+ n = be32_to_cpu(*curr);
+ if (len < 32)
+ break;
+ if (n) {
+ len = 32;
+ break;
+ }
+ *curr++ = cpu_to_be32(0xffffffff);
+ len -= 32;
+ }
+ /* do any partial u32 at end */
+ mask = 1U << 31;
+ for (i = 0; i < len; i++) {
+ if (n & mask)
+ break;
+ n |= mask;
+ mask >>= 1;
+ }
+done:
+ *curr = cpu_to_be32(n);
+ *max = (curr - bitmap) * 32 + i - start;
+ return start;
+}
+
+/*
+ * hfs_vbm_search_free()
+ *
+ * Description:
+ * Search for 'num_bits' consecutive cleared bits in the bitmap blocks of
+ * the hfs MDB. 'mdb' had better be locked or the returned range
+ * may be no longer free, when this functions returns!
+ * XXX Currently the search starts from bit 0, but it should start with
+ * the bit number stored in 's_alloc_ptr' of the MDB.
+ * Input Variable(s):
+ * struct hfs_mdb *mdb: Pointer to the hfs MDB
+ * u16 *num_bits: Pointer to the number of cleared bits
+ * to search for
+ * Output Variable(s):
+ * u16 *num_bits: The number of consecutive clear bits of the
+ * returned range. If the bitmap is fragmented, this will be less than
+ * requested and it will be zero, when the disk is full.
+ * Returns:
+ * The number of the first bit of the range of cleared bits which has been
+ * found. When 'num_bits' is zero, this is invalid!
+ * Preconditions:
+ * 'mdb' points to a "valid" (struct hfs_mdb).
+ * 'num_bits' points to a variable of type (u16), which contains
+ * the number of cleared bits to find.
+ * Postconditions:
+ * 'num_bits' is set to the length of the found sequence.
+ */
+u32 hfs_vbm_search_free(struct super_block *sb, u32 goal, u32 *num_bits)
+{
+ void *bitmap;
+ u32 pos;
+
+ /* make sure we have actual work to perform */
+ if (!*num_bits)
+ return 0;
+
+ mutex_lock(&HFS_SB(sb)->bitmap_lock);
+ bitmap = HFS_SB(sb)->bitmap;
+
+ pos = hfs_find_set_zero_bits(bitmap, HFS_SB(sb)->fs_ablocks, goal, num_bits);
+ if (pos >= HFS_SB(sb)->fs_ablocks) {
+ if (goal)
+ pos = hfs_find_set_zero_bits(bitmap, goal, 0, num_bits);
+ if (pos >= HFS_SB(sb)->fs_ablocks) {
+ *num_bits = pos = 0;
+ goto out;
+ }
+ }
+
+ hfs_dbg(BITMAP, "alloc_bits: %u,%u\n", pos, *num_bits);
+ HFS_SB(sb)->free_ablocks -= *num_bits;
+ hfs_bitmap_dirty(sb);
+out:
+ mutex_unlock(&HFS_SB(sb)->bitmap_lock);
+ return pos;
+}
+
+
+/*
+ * hfs_clear_vbm_bits()
+ *
+ * Description:
+ * Clear the requested bits in the volume bitmap of the hfs filesystem
+ * Input Variable(s):
+ * struct hfs_mdb *mdb: Pointer to the hfs MDB
+ * u16 start: The offset of the first bit
+ * u16 count: The number of bits
+ * Output Variable(s):
+ * None
+ * Returns:
+ * 0: no error
+ * -1: One of the bits was already clear. This is a strange
+ * error and when it happens, the filesystem must be repaired!
+ * -2: One or more of the bits are out of range of the bitmap.
+ * Preconditions:
+ * 'mdb' points to a "valid" (struct hfs_mdb).
+ * Postconditions:
+ * Starting with bit number 'start', 'count' bits in the volume bitmap
+ * are cleared. The affected bitmap blocks are marked "dirty", the free
+ * block count of the MDB is updated and the MDB is marked dirty.
+ */
+int hfs_clear_vbm_bits(struct super_block *sb, u16 start, u16 count)
+{
+ __be32 *curr;
+ u32 mask;
+ int i, len;
+
+ /* is there any actual work to be done? */
+ if (!count)
+ return 0;
+
+ hfs_dbg(BITMAP, "clear_bits: %u,%u\n", start, count);
+ /* are all of the bits in range? */
+ if ((start + count) > HFS_SB(sb)->fs_ablocks)
+ return -2;
+
+ mutex_lock(&HFS_SB(sb)->bitmap_lock);
+ /* bitmap is always on a 32-bit boundary */
+ curr = HFS_SB(sb)->bitmap + (start / 32);
+ len = count;
+
+ /* do any partial u32 at the start */
+ i = start % 32;
+ if (i) {
+ int j = 32 - i;
+ mask = 0xffffffffU << j;
+ if (j > count) {
+ mask |= 0xffffffffU >> (i + count);
+ *curr &= cpu_to_be32(mask);
+ goto out;
+ }
+ *curr++ &= cpu_to_be32(mask);
+ count -= j;
+ }
+
+ /* do full u32s */
+ while (count >= 32) {
+ *curr++ = 0;
+ count -= 32;
+ }
+ /* do any partial u32 at end */
+ if (count) {
+ mask = 0xffffffffU >> count;
+ *curr &= cpu_to_be32(mask);
+ }
+out:
+ HFS_SB(sb)->free_ablocks += len;
+ mutex_unlock(&HFS_SB(sb)->bitmap_lock);
+ hfs_bitmap_dirty(sb);
+
+ return 0;
+}
Code Review / kvmfornfv.git / blobdiff