source: mainline/uspace/srv/fs/minixfs/mfs_balloc.c@ efa5fa1

/*
 * Copyright (c) 2011 Maurizio Lombardi
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup fs
 * @{
 */

#include <stdlib.h>
#include "mfs.h"
#include "mfs_utils.h"

static int
find_free_bit_and_set(bitchunk_t *b, const int bsize,
                      const bool native, unsigned start_bit);

int
mfs_free_bit(struct mfs_instance *inst, uint32_t idx, bmap_id_t bid)
{
        struct mfs_sb_info *sbi;
        int r;
        unsigned start_block;
        block_t *b;

        assert(inst != NULL);
        sbi = inst->sbi;
        assert(sbi != NULL);

        if (bid == BMAP_ZONE) {
                idx -= sbi->firstdatazone;
                start_block = 2 + sbi->ibmap_blocks;
                if (idx > sbi->nzones) {
                        printf(NAME ": Error! Trying to free beyond the" \
                               "bitmap max size\n");
                        return -1;
                }
        } else {
                /*bid == BMAP_INODE*/
                start_block = 2;
                if (idx > sbi->ninodes) {
                        printf(NAME ": Error! Trying to free beyond the" \
                               "bitmap max size\n");
                        return -1;
                }
        }

        /*Compute the bitmap block*/
        uint32_t block = idx / (sbi->block_size * 8) + start_block;

        r = block_get(&b, inst->handle, block, BLOCK_FLAGS_NONE);
        on_error(r, goto out_err);

        /*Compute the bit index in the block*/
        idx %= (sbi->block_size * 8);
        bitchunk_t *ptr = b->data;
        bitchunk_t chunk;
        const size_t chunk_bits = sizeof(bitchunk_t) * 8;

        chunk = conv32(sbi->native, ptr[idx / chunk_bits]);
        chunk &= ~(1 << (idx % chunk_bits));
        ptr[idx / chunk_bits] = conv32(sbi->native, chunk);
        b->dirty = true;
        r = block_put(b);
        mfsdebug("free index %u\n", idx);

out_err:
        return r;
}

int
mfs_alloc_bit(struct mfs_instance *inst, uint32_t *idx, bmap_id_t bid)
{
        struct mfs_sb_info *sbi;
        uint32_t limit;
        unsigned long nblocks;
        unsigned *search, i, start_block;
        unsigned bits_per_block;
        int r, freebit;

        assert(inst != NULL);
        sbi = inst->sbi;
        assert(sbi != NULL);

        if (bid == BMAP_ZONE) {
                search = &sbi->zsearch;
                start_block = 2 + sbi->ibmap_blocks;
                nblocks = sbi->zbmap_blocks;
                limit = sbi->nzones;
        } else {
                /*bid == BMAP_INODE*/
                search = &sbi->isearch;
                start_block = 2;
                nblocks = sbi->ibmap_blocks;
                limit = sbi->ninodes;
        }
        bits_per_block = sbi->block_size * 8;

        block_t *b;

retry:

        for (i = *search / bits_per_block; i < nblocks; ++i) {
                r = block_get(&b, inst->handle, i + start_block,
                              BLOCK_FLAGS_NONE);

                on_error(r, goto out);

                unsigned tmp = *search % bits_per_block;

                freebit = find_free_bit_and_set(b->data, sbi->block_size,
                                                sbi->native, tmp);
                if (freebit == -1) {
                        /*No free bit in this block*/
                        block_put(b);
                        continue;
                }

                /*Free bit found in this block, compute the real index*/
                *idx = freebit + bits_per_block * i;
                *idx += (bid == BMAP_INODE) ? 1 : 0;
                mfsdebug("alloc index %d %d\n", (int) *idx, i);
                if (*idx > limit) {
                        /*Index is beyond the limit, it is invalid*/
                        r = block_put(b);
                        on_error(r, goto out);
                        break;
                }

                *search = *idx;

                if (bid == BMAP_ZONE)
                        *idx += sbi->firstdatazone;

                b->dirty = true;
                r = block_put(b);
                goto out;
        }

        if (*search > 0) {
                /*Repeat the search from the first bitmap block*/
                *search = 0;
                goto retry;
        }

        /*Free bit not found, return error*/
        return ENOSPC;

out:
        return r;
}

static int
find_free_bit_and_set(bitchunk_t *b, const int bsize,
                      const bool native, unsigned start_bit)
{
        int r = -1;
        unsigned i, j;
        bitchunk_t chunk;
        const size_t chunk_bits = sizeof(bitchunk_t) * 8;

        for (i = start_bit / chunk_bits;
             i < bsize / sizeof(bitchunk_t); ++i) {
                if (!(~b[i])) {
                        /*No free bit in this chunk*/
                        continue;
                }

                chunk = conv32(native, b[i]);

                for (j = 0; j < chunk_bits; ++j) {
                        if (!(chunk & (1 << j))) {
                                r = i * chunk_bits + j;
                                chunk |= 1 << j;
                                b[i] = conv32(native, chunk);
                                goto found;
                        }
                }
        }
found:
        return r;
}

/**
 * @}
 */