source: mainline/uspace/srv/fs/minixfs/mfs_rw.c@ 6b40ea7

/*
 * 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 <assert.h>
#include <errno.h>
#include "mfs.h"
#include "mfs_utils.h"

static int
rw_map_ondisk(uint32_t *b, const struct mfs_node *mnode, int rblock,
                                bool write_mode, uint32_t w_block);

static int
reset_zone_content(struct mfs_instance *inst, uint32_t zone);

static int
alloc_zone_and_clear(struct mfs_instance *inst, uint32_t *zone);

static int
read_ind_zone(struct mfs_instance *inst, uint32_t zone, uint32_t **ind_zone);

static int
write_ind_zone(struct mfs_instance *inst, uint32_t zone, uint32_t *ind_zone);


/**Given the position in the file expressed in
 *bytes, this function returns the on-disk block
 *relative to that position.
 *Returns zero if the block does not exist.
 */
int
read_map(uint32_t *b, const struct mfs_node *mnode, uint32_t pos)
{
        int r;
        const struct mfs_sb_info *sbi = mnode->instance->sbi;
        const int block_size = sbi->block_size;

        /*Compute relative block number in file*/
        int rblock = pos / block_size;

        if (mnode->ino_i->i_size < pos) {
                /*Trying to read beyond the end of file*/
                r = EOK;
                *b = 0;
                goto out;
        }

        r = rw_map_ondisk(b, mnode, rblock, false, 0);
out:
        return r;
}

int
write_map(struct mfs_node *mnode, const uint32_t pos, uint32_t new_zone, 
                                uint32_t *old_zone)
{
        const struct mfs_sb_info *sbi = mnode->instance->sbi;
        const int block_size = sbi->block_size;

        /*Compute the relative block number in file*/
        int rblock = pos / block_size;

        return rw_map_ondisk(old_zone, mnode, rblock, true, new_zone);
}

int
free_zone(struct mfs_node *mnode, const uint32_t zone)
{
        int r;
        uint32_t old_zone;

        r = rw_map_ondisk(&old_zone, mnode, zone, true, 0);
        if (r != EOK)
                return r;

        if (old_zone > 0)
                r = mfs_free_bit(mnode->instance, old_zone, BMAP_ZONE);

        return r;
}

static int
rw_map_ondisk(uint32_t *b, const struct mfs_node *mnode, int rblock,
                                bool write_mode, uint32_t w_block)
{
        int r, nr_direct;
        int ptrs_per_block;
        uint32_t *ind_zone, *ind2_zone;

        assert(mnode);
        struct mfs_ino_info *ino_i = mnode->ino_i;

        assert(ino_i);
        assert(mnode->instance);

        struct mfs_instance *inst = mnode->instance;
        struct mfs_sb_info *sbi = inst->sbi;
        assert(sbi);

        const mfs_version_t fs_version = sbi->fs_version;

        if (fs_version == MFS_VERSION_V1) {
                nr_direct = V1_NR_DIRECT_ZONES;
                ptrs_per_block = MFS_BLOCKSIZE / sizeof(uint16_t);
        } else {
                nr_direct = V2_NR_DIRECT_ZONES;
                ptrs_per_block = sbi->block_size / sizeof(uint32_t);
        }

        /*Check if the wanted block is in the direct zones*/
        if (rblock < nr_direct) {
                *b = ino_i->i_dzone[rblock];
                if (write_mode) {
                        ino_i->i_dzone[rblock] = w_block;
                        ino_i->dirty = true;
                }
                return EOK;
        }

        rblock -= nr_direct;

        if (rblock < ptrs_per_block) {
                /*The wanted block is in the single indirect zone chain*/
                if (ino_i->i_izone[0] == 0) {
                        if (write_mode) {
                                uint32_t zone;
                                r = alloc_zone_and_clear(inst, &zone);
                                if (r != EOK)
                                        return r;

                                ino_i->i_izone[0] = zone;
                                ino_i->dirty = true;
                        } else {
                                return -1;
                        }
                }

                r = read_ind_zone(inst, ino_i->i_izone[0], &ind_zone);
                if (r != EOK)
                        return r;

                *b = ind_zone[rblock];
                if (write_mode) {
                        ind_zone[rblock] = w_block;
                        write_ind_zone(inst, ino_i->i_izone[0], ind_zone);
                }

                goto out_free_ind1;
        }

        rblock -= ptrs_per_block;

        /*The wanted block is in the double indirect zone chain*/

        /*read the first indirect zone of the chain*/
        if (ino_i->i_izone[1] == 0) {
                if (write_mode) {
                        uint32_t zone;
                        r = alloc_zone_and_clear(inst, &zone);
                        if (r != EOK)
                                return r;

                        ino_i->i_izone[1] = zone;
                        ino_i->dirty = true;
                } else
                        return -1;
        }

        r = read_ind_zone(inst, ino_i->i_izone[1], &ind_zone);
        if (r != EOK)
                return r;

        /*
         *Compute the position of the second indirect
         *zone pointer in the chain.
         */
        uint32_t ind2_off = rblock / ptrs_per_block;

        /*read the second indirect zone of the chain*/
        if (ind_zone[ind2_off] == 0) {
                if (write_mode) {
                        uint32_t zone;
                        r = alloc_zone_and_clear(inst, &zone);
                        if(r != EOK)
                                goto out_free_ind1;
                        ind_zone[ind2_off] = zone;
                        write_ind_zone(inst, ino_i->i_izone[1], ind_zone);
                } else {
                        r = -1;
                        goto out_free_ind1;
                }
        }

        r = read_ind_zone(inst, ind_zone[ind2_off], &ind2_zone);
        if (r != EOK)
                goto out_free_ind1;

        *b = ind2_zone[ind2_off % ptrs_per_block];
        if (write_mode) {
                ind2_zone[ind2_off % ptrs_per_block] = w_block;
                write_ind_zone(inst, ind_zone[ind2_off], ind2_zone);
        }

        r = EOK;

        free(ind2_zone);
out_free_ind1:
        free(ind_zone);
        return r;
}


static int
reset_zone_content(struct mfs_instance *inst, uint32_t zone)
{
        block_t *b;
        int r;

        r = block_get(&b, inst->handle, zone, BLOCK_FLAGS_NOREAD);
        if (r != EOK)
                return r;

        memset(b->data, 0, b->size);
        b->dirty = true;
        block_put(b);

        return EOK;
}

static int
alloc_zone_and_clear(struct mfs_instance *inst, uint32_t *zone)
{
        int r;

        r = mfs_alloc_bit(inst, zone, BMAP_ZONE);
        if (r != EOK)
                goto out;

        r = reset_zone_content(inst, *zone);
out:
        return r;
}

static int
read_ind_zone(struct mfs_instance *inst, uint32_t zone, uint32_t **ind_zone)
{
        struct mfs_sb_info *sbi = inst->sbi;
        int r;
        unsigned i;
        block_t *b;
        const int max_ind_zone_ptrs = (MFS_MAX_BLOCKSIZE / sizeof(uint16_t)) *
                                sizeof(uint32_t);

        *ind_zone = malloc(max_ind_zone_ptrs);
        if (*ind_zone == NULL)
                return ENOMEM;

        r = block_get(&b, inst->handle, zone, BLOCK_FLAGS_NONE);
        if (r != EOK) {
                free(*ind_zone);
                return r;
        }

        if (sbi->fs_version == MFS_VERSION_V1) {
                uint16_t *src_ptr = b->data;

                for (i = 0; i < sbi->block_size / sizeof(uint16_t); ++i)
                        (*ind_zone)[i] = conv16(sbi->native, src_ptr[i]);
        } else {
                uint32_t *src_ptr = b->data;

                for (i = 0; i < sbi->block_size / sizeof(uint32_t); ++i)
                        (*ind_zone)[i] = conv32(sbi->native, src_ptr[i]);
        }

        block_put(b);
        
        return EOK;
}

static int
write_ind_zone(struct mfs_instance *inst, uint32_t zone, uint32_t *ind_zone)
{
        struct mfs_sb_info *sbi = inst->sbi;
        int r;
        unsigned i;
        block_t *b;

        r = block_get(&b, inst->handle, zone, BLOCK_FLAGS_NONE);
        if (r != EOK)
                return r;

        if (sbi->fs_version == MFS_VERSION_V1) {
                uint16_t *dest_ptr = b->data;

                for (i = 0; i < sbi->block_size / sizeof(uint16_t); ++i)
                        dest_ptr[i] = conv16(sbi->native, ind_zone[i]);
        } else {
                uint32_t *dest_ptr = b->data;

                for (i = 0; i < sbi->block_size / sizeof(uint32_t); ++i)
                        dest_ptr[i] = conv32(sbi->native, ind_zone[i]);

        }
        b->dirty = true;
        block_put(b);
        return EOK;
}


/**
 * @}
 */