1 files changed, 243 insertions, 0 deletions
diff --git a/fs/hfs/bitmap.c b/fs/hfs/bitmap.c
new file mode 100644
index 000000000000..24e75798ddf0
--- /dev/null
+++ b/fs/hfs/bitmap.c
@@ -0,0 +1,243 @@
+/*
+ *  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;
+
+	down(&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;
+		}
+	}
+
+	dprint(DBG_BITMAP, "alloc_bits: %u,%u\n", pos, *num_bits);
+	HFS_SB(sb)->free_ablocks -= *num_bits;
+	hfs_bitmap_dirty(sb);
+out:
+	up(&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;
+
+	dprint(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;
+
+	down(&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;
+	up(&HFS_SB(sb)->bitmap_lock);
+	hfs_bitmap_dirty(sb);
+
+	return 0;
+}