Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
This commit is contained in:
Linus Torvalds
243
fs/hfs/bitmap.c
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243
fs/hfs/bitmap.c
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/*
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* linux/fs/hfs/bitmap.c
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*
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* Copyright (C) 1996-1997 Paul H. Hargrove
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* (C) 2003 Ardis Technologies <roman@ardistech.com>
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* This file may be distributed under the terms of the GNU General Public License.
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*
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* Based on GPLed code Copyright (C) 1995 Michael Dreher
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*
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* This file contains the code to modify the volume bitmap:
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* search/set/clear bits.
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*/
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#include "hfs_fs.h"
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/*
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* hfs_find_zero_bit()
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*
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* Description:
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* Given a block of memory, its length in bits, and a starting bit number,
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* determine the number of the first zero bits (in left-to-right ordering)
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* in that range.
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*
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* Returns >= 'size' if no zero bits are found in the range.
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*
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* Accesses memory in 32-bit aligned chunks of 32-bits and thus
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* may read beyond the 'size'th bit.
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*/
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static u32 hfs_find_set_zero_bits(__be32 *bitmap, u32 size, u32 offset, u32 *max)
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{
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__be32 *curr, *end;
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u32 mask, start, len, n;
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__be32 val;
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int i;
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len = *max;
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if (!len)
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return size;
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curr = bitmap + (offset / 32);
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end = bitmap + ((size + 31) / 32);
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/* scan the first partial u32 for zero bits */
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val = *curr;
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if (~val) {
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n = be32_to_cpu(val);
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i = offset % 32;
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mask = (1U << 31) >> i;
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for (; i < 32; mask >>= 1, i++) {
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if (!(n & mask))
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goto found;
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}
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}
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/* scan complete u32s for the first zero bit */
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while (++curr < end) {
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val = *curr;
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if (~val) {
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n = be32_to_cpu(val);
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mask = 1 << 31;
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for (i = 0; i < 32; mask >>= 1, i++) {
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if (!(n & mask))
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goto found;
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}
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}
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}
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return size;
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found:
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start = (curr - bitmap) * 32 + i;
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if (start >= size)
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return start;
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/* do any partial u32 at the start */
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len = min(size - start, len);
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while (1) {
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n |= mask;
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if (++i >= 32)
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break;
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mask >>= 1;
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if (!--len || n & mask)
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goto done;
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}
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if (!--len)
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goto done;
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*curr++ = cpu_to_be32(n);
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/* do full u32s */
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while (1) {
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n = be32_to_cpu(*curr);
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if (len < 32)
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break;
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if (n) {
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len = 32;
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break;
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}
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*curr++ = cpu_to_be32(0xffffffff);
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len -= 32;
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}
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/* do any partial u32 at end */
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mask = 1U << 31;
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for (i = 0; i < len; i++) {
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if (n & mask)
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break;
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n |= mask;
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mask >>= 1;
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}
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done:
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*curr = cpu_to_be32(n);
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*max = (curr - bitmap) * 32 + i - start;
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return start;
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}
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/*
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* hfs_vbm_search_free()
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*
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* Description:
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* Search for 'num_bits' consecutive cleared bits in the bitmap blocks of
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* the hfs MDB. 'mdb' had better be locked or the returned range
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* may be no longer free, when this functions returns!
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* XXX Currently the search starts from bit 0, but it should start with
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* the bit number stored in 's_alloc_ptr' of the MDB.
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* Input Variable(s):
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* struct hfs_mdb *mdb: Pointer to the hfs MDB
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* u16 *num_bits: Pointer to the number of cleared bits
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* to search for
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* Output Variable(s):
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* u16 *num_bits: The number of consecutive clear bits of the
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* returned range. If the bitmap is fragmented, this will be less than
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* requested and it will be zero, when the disk is full.
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* Returns:
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* The number of the first bit of the range of cleared bits which has been
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* found. When 'num_bits' is zero, this is invalid!
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* Preconditions:
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* 'mdb' points to a "valid" (struct hfs_mdb).
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* 'num_bits' points to a variable of type (u16), which contains
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* the number of cleared bits to find.
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* Postconditions:
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* 'num_bits' is set to the length of the found sequence.
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*/
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u32 hfs_vbm_search_free(struct super_block *sb, u32 goal, u32 *num_bits)
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{
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void *bitmap;
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u32 pos;
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/* make sure we have actual work to perform */
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if (!*num_bits)
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return 0;
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down(&HFS_SB(sb)->bitmap_lock);
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bitmap = HFS_SB(sb)->bitmap;
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pos = hfs_find_set_zero_bits(bitmap, HFS_SB(sb)->fs_ablocks, goal, num_bits);
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if (pos >= HFS_SB(sb)->fs_ablocks) {
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if (goal)
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pos = hfs_find_set_zero_bits(bitmap, goal, 0, num_bits);
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if (pos >= HFS_SB(sb)->fs_ablocks) {
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*num_bits = pos = 0;
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goto out;
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}
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}
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dprint(DBG_BITMAP, "alloc_bits: %u,%u\n", pos, *num_bits);
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HFS_SB(sb)->free_ablocks -= *num_bits;
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hfs_bitmap_dirty(sb);
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out:
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up(&HFS_SB(sb)->bitmap_lock);
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return pos;
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}
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/*
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* hfs_clear_vbm_bits()
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*
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* Description:
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* Clear the requested bits in the volume bitmap of the hfs filesystem
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* Input Variable(s):
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* struct hfs_mdb *mdb: Pointer to the hfs MDB
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* u16 start: The offset of the first bit
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* u16 count: The number of bits
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* Output Variable(s):
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* None
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* Returns:
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* 0: no error
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* -1: One of the bits was already clear. This is a strange
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* error and when it happens, the filesystem must be repaired!
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* -2: One or more of the bits are out of range of the bitmap.
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* Preconditions:
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* 'mdb' points to a "valid" (struct hfs_mdb).
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* Postconditions:
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* Starting with bit number 'start', 'count' bits in the volume bitmap
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* are cleared. The affected bitmap blocks are marked "dirty", the free
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* block count of the MDB is updated and the MDB is marked dirty.
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*/
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int hfs_clear_vbm_bits(struct super_block *sb, u16 start, u16 count)
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{
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__be32 *curr;
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u32 mask;
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int i, len;
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/* is there any actual work to be done? */
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if (!count)
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return 0;
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dprint(DBG_BITMAP, "clear_bits: %u,%u\n", start, count);
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/* are all of the bits in range? */
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if ((start + count) > HFS_SB(sb)->fs_ablocks)
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return -2;
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down(&HFS_SB(sb)->bitmap_lock);
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/* bitmap is always on a 32-bit boundary */
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curr = HFS_SB(sb)->bitmap + (start / 32);
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len = count;
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/* do any partial u32 at the start */
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i = start % 32;
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if (i) {
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int j = 32 - i;
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mask = 0xffffffffU << j;
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if (j > count) {
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mask |= 0xffffffffU >> (i + count);
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*curr &= cpu_to_be32(mask);
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goto out;
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}
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*curr++ &= cpu_to_be32(mask);
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count -= j;
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}
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/* do full u32s */
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while (count >= 32) {
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*curr++ = 0;
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count -= 32;
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}
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/* do any partial u32 at end */
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if (count) {
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mask = 0xffffffffU >> count;
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*curr &= cpu_to_be32(mask);
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}
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out:
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HFS_SB(sb)->free_ablocks += len;
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up(&HFS_SB(sb)->bitmap_lock);
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hfs_bitmap_dirty(sb);
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return 0;
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}
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