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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 <linux/gfs2_ondisk.h>
- #include <asm/semaphore.h>
- #include "gfs2.h"
- #include "lm_interface.h"
- #include "incore.h"
- #include "bits.h"
- #include "util.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;
- }
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