HelenOS sources

root/uspace/srv/fs/mfs/mfs_rw.c

DEFINITIONS

1. mfs_read_map
2. mfs_write_map
3. rw_map_ondisk
4. mfs_prune_ind_zones
5. reset_zone_content
6. alloc_zone_and_clear
7. read_ind_zone
8. write_ind_zone

/*
 * 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 mfs
 * @{
 */

#include <align.h>
#include "mfs.h"

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

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

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

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

static errno_t
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.
 *
 * @param b     Pointer to a 32bit number where the block number will be stored
 * @param mnode Pointer to a generic MINIX inode in memory.
 * @param pos   Position in file.
 *
 * @return      EOK on success or an error code.
 */
errno_t
mfs_read_map(uint32_t *b, const struct mfs_node *mnode, uint32_t pos)
{
        errno_t 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 (ROUND_UP(mnode->ino_i->i_size, sbi->block_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;
}

errno_t
mfs_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;

        if (pos >= sbi->max_file_size) {
                /* Can't write beyond the maximum file size */
                return EINVAL;
        }

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

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

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

        struct mfs_ino_info *ino_i = mnode->ino_i;
        struct mfs_instance *inst = mnode->instance;
        struct mfs_sb_info *sbi = inst->sbi;

        const mfs_version_t fs_version = sbi->fs_version;
        const bool deleting = write_mode && (w_block == 0);

        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;
                }
                goto out;
        }

        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 && !deleting) {
                                uint32_t zone;
                                r = alloc_zone_and_clear(inst, &zone);
                                if (r != EOK)
                                        goto out;

                                ino_i->i_izone[0] = zone;
                                ino_i->dirty = true;
                        } else {
                                /* Sparse block */
                                *b = 0;
                                goto out;
                        }
                }

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

                *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;
        }

        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 && !deleting) {
                        uint32_t zone;
                        r = alloc_zone_and_clear(inst, &zone);
                        if (r != EOK)
                                goto out;

                        ino_i->i_izone[1] = zone;
                        ino_i->dirty = true;
                } else {
                        /* Sparse block */
                        *b = 0;
                        goto out;
                }
        }

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

        /*
         * 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 && !deleting) {
                        uint32_t zone;
                        r = alloc_zone_and_clear(inst, &zone);
                        if (r != EOK)
                                goto out;

                        ind_zone[ind2_off] = zone;
                        write_ind_zone(inst, ino_i->i_izone[1], ind_zone);
                } else {
                        /* Sparse block */
                        *b = 0;
                        goto out;
                }
        }

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

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

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

/**Free unused indirect zones from a MINIX inode according to its new size.
 *
 * @param mnode         Pointer to a generic MINIX inode in memory.
 * @param new_size      The new size of the inode.
 *
 * @return              EOK on success or an error code.
 */
errno_t
mfs_prune_ind_zones(struct mfs_node *mnode, size_t new_size)
{
        struct mfs_instance *inst = mnode->instance;
        struct mfs_sb_info *sbi = inst->sbi;
        struct mfs_ino_info *ino_i = mnode->ino_i;
        int nr_direct, ptrs_per_block, rblock;
        errno_t r;
        int i;

        mfs_version_t fs_version = sbi->fs_version;

        assert(new_size <= ino_i->i_size);

        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);
        }

        rblock = new_size / sbi->block_size;

        if (rblock < nr_direct) {
                /* Free the single indirect zone */
                if (ino_i->i_izone[0]) {
                        r = mfs_free_zone(inst, ino_i->i_izone[0]);
                        if (r != EOK)
                                return r;

                        ino_i->i_izone[0] = 0;
                        ino_i->dirty = true;
                }
        }

        rblock -= nr_direct + ptrs_per_block;

        int fzone_to_free = (rblock < 0 ? 0 : rblock) / ptrs_per_block;

        if ((fzone_to_free % ptrs_per_block) != 0)
                ++fzone_to_free;

        /* Free the entire double indirect zone */
        uint32_t *dbl_zone;

        if (ino_i->i_izone[1] == 0) {
                /* Nothing to be done */
                return EOK;
        }

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

        for (i = fzone_to_free; i < ptrs_per_block; ++i) {
                if (dbl_zone[i] == 0)
                        continue;

                r = mfs_free_zone(inst, dbl_zone[i]);
                if (r != EOK)
                        goto out;
        }

        if (fzone_to_free == 0) {
                r = mfs_free_zone(inst, ino_i->i_izone[1]);
                ino_i->i_izone[1] = 0;
                ino_i->dirty = true;
        }
out:
        free(dbl_zone);
        return r;
}

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

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

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

        return block_put(b);
}

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

        r = mfs_alloc_zone(inst, zone);
        if (r != EOK)
                return r;

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

static errno_t
read_ind_zone(struct mfs_instance *inst, uint32_t zone, uint32_t **ind_zone)
{
        struct mfs_sb_info *sbi = inst->sbi;
        errno_t 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->service_id, 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]);
        }

        return block_put(b);
}

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

        r = block_get(&b, inst->service_id, zone, BLOCK_FLAGS_NOREAD);
        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;

        return block_put(b);
}

/**
 * @}
 */