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-rw-r--r--fs/gfs2/bits.c178
1 files changed, 178 insertions, 0 deletions
diff --git a/fs/gfs2/bits.c b/fs/gfs2/bits.c
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+/*
+ * Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
+ * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
+ *
+ * This copyrighted material is made available to anyone wishing to use,
+ * modify, copy, or redistribute it subject to the terms and conditions
+ * of the GNU General Public License v.2.
+ */
+
+/*
+ * These routines are used by the resource group routines (rgrp.c)
+ * to keep track of block allocation. Each block is represented by two
+ * bits. One bit indicates whether or not the block is used. (1=used,
+ * 0=free) The other bit indicates whether or not the block contains a
+ * dinode or not. (1=dinode, 0=not-dinode) So, each byte represents
+ * GFS2_NBBY (i.e. 4) blocks.
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <asm/semaphore.h>
+
+#include "gfs2.h"
+#include "bits.h"
+
+static const char valid_change[16] = {
+ /* current */
+ /* n */ 0, 1, 0, 1,
+ /* e */ 1, 0, 0, 0,
+ /* w */ 0, 0, 0, 0,
+ 1, 0, 0, 0
+};
+
+/**
+ * gfs2_setbit - Set a bit in the bitmaps
+ * @buffer: the buffer that holds the bitmaps
+ * @buflen: the length (in bytes) of the buffer
+ * @block: the block to set
+ * @new_state: the new state of the block
+ *
+ */
+
+void gfs2_setbit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
+ unsigned int buflen, uint32_t block, unsigned char new_state)
+{
+ unsigned char *byte, *end, cur_state;
+ unsigned int bit;
+
+ byte = buffer + (block / GFS2_NBBY);
+ bit = (block % GFS2_NBBY) * GFS2_BIT_SIZE;
+ end = buffer + buflen;
+
+ gfs2_assert(rgd->rd_sbd, byte < end);
+
+ cur_state = (*byte >> bit) & GFS2_BIT_MASK;
+
+ if (valid_change[new_state * 4 + cur_state]) {
+ *byte ^= cur_state << bit;
+ *byte |= new_state << bit;
+ } else
+ gfs2_consist_rgrpd(rgd);
+}
+
+/**
+ * gfs2_testbit - test a bit in the bitmaps
+ * @buffer: the buffer that holds the bitmaps
+ * @buflen: the length (in bytes) of the buffer
+ * @block: the block to read
+ *
+ */
+
+unsigned char gfs2_testbit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
+ unsigned int buflen, uint32_t block)
+{
+ unsigned char *byte, *end, cur_state;
+ unsigned int bit;
+
+ byte = buffer + (block / GFS2_NBBY);
+ bit = (block % GFS2_NBBY) * GFS2_BIT_SIZE;
+ end = buffer + buflen;
+
+ gfs2_assert(rgd->rd_sbd, byte < end);
+
+ cur_state = (*byte >> bit) & GFS2_BIT_MASK;
+
+ return cur_state;
+}
+
+/**
+ * gfs2_bitfit - Search an rgrp's bitmap buffer to find a bit-pair representing
+ * a block in a given allocation state.
+ * @buffer: the buffer that holds the bitmaps
+ * @buflen: the length (in bytes) of the buffer
+ * @goal: start search at this block's bit-pair (within @buffer)
+ * @old_state: GFS2_BLKST_XXX the state of the block we're looking for;
+ * bit 0 = alloc(1)/free(0), bit 1 = meta(1)/data(0)
+ *
+ * Scope of @goal and returned block number is only within this bitmap buffer,
+ * not entire rgrp or filesystem. @buffer will be offset from the actual
+ * beginning of a bitmap block buffer, skipping any header structures.
+ *
+ * Return: the block number (bitmap buffer scope) that was found
+ */
+
+uint32_t gfs2_bitfit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
+ unsigned int buflen, uint32_t goal,
+ unsigned char old_state)
+{
+ unsigned char *byte, *end, alloc;
+ uint32_t blk = goal;
+ unsigned int bit;
+
+ byte = buffer + (goal / GFS2_NBBY);
+ bit = (goal % GFS2_NBBY) * GFS2_BIT_SIZE;
+ end = buffer + buflen;
+ alloc = (old_state & 1) ? 0 : 0x55;
+
+ while (byte < end) {
+ if ((*byte & 0x55) == alloc) {
+ blk += (8 - bit) >> 1;
+
+ bit = 0;
+ byte++;
+
+ continue;
+ }
+
+ if (((*byte >> bit) & GFS2_BIT_MASK) == old_state)
+ return blk;
+
+ bit += GFS2_BIT_SIZE;
+ if (bit >= 8) {
+ bit = 0;
+ byte++;
+ }
+
+ blk++;
+ }
+
+ return BFITNOENT;
+}
+
+/**
+ * gfs2_bitcount - count the number of bits in a certain state
+ * @buffer: the buffer that holds the bitmaps
+ * @buflen: the length (in bytes) of the buffer
+ * @state: the state of the block we're looking for
+ *
+ * Returns: The number of bits
+ */
+
+uint32_t gfs2_bitcount(struct gfs2_rgrpd *rgd, unsigned char *buffer,
+ unsigned int buflen, unsigned char state)
+{
+ unsigned char *byte = buffer;
+ unsigned char *end = buffer + buflen;
+ unsigned char state1 = state << 2;
+ unsigned char state2 = state << 4;
+ unsigned char state3 = state << 6;
+ uint32_t count = 0;
+
+ for (; byte < end; byte++) {
+ if (((*byte) & 0x03) == state)
+ count++;
+ if (((*byte) & 0x0C) == state1)
+ count++;
+ if (((*byte) & 0x30) == state2)
+ count++;
+ if (((*byte) & 0xC0) == state3)
+ count++;
+ }
+
+ return count;
+}
+