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Diffstat (limited to 'fs/gfs2/bits.c')
| -rw-r--r-- | fs/gfs2/bits.c | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/fs/gfs2/bits.c b/fs/gfs2/bits.c new file mode 100644 index 00000000000..57d420a86ad --- /dev/null +++ b/fs/gfs2/bits.c @@ -0,0 +1,178 @@ +/* + * 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; +} + |