source: mainline/uspace/lib/ext4/src/ialloc.c@ 6ff23ff

/*
 * Copyright (c) 2012 Frantisek Princ
 * 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 libext4
 * @{
 */
/**
 * @file  ialloc.c
 * @brief I-node (de)allocation operations.
 */

#include <errno.h>
#include <stdbool.h>
#include "ext4/bitmap.h"
#include "ext4/block_group.h"
#include "ext4/filesystem.h"
#include "ext4/ialloc.h"
#include "ext4/superblock.h"


/** Convert i-node number to relative index in block group.
 *
 * @param sb    Superblock
 * @param inode I-node number to be converted
 *
 * @return Index of the i-node in the block group
 *
 */
static uint32_t ext4_ialloc_inode2index_in_group(ext4_superblock_t *sb,
    uint32_t inode)
{
        uint32_t inodes_per_group = ext4_superblock_get_inodes_per_group(sb);
        return (inode - 1) % inodes_per_group;
}

/** Convert relative index of i-node to absolute i-node number.
 *
 * @param sb    Superblock
 * @param inode Index to be converted
 *
 * @return Absolute number of the i-node
 *
 */
static uint32_t ext4_ialloc_index_in_group2inode(ext4_superblock_t *sb,
    uint32_t index, uint32_t bgid)
{
        uint32_t inodes_per_group = ext4_superblock_get_inodes_per_group(sb);
        return bgid * inodes_per_group + (index + 1);
}

/** Compute block group number from the i-node number.
 *
 * @param sb    Superblock
 * @param inode I-node number to be found the block group for
 *
 * @return Block group number computed from i-node number
 *
 */
static uint32_t ext4_ialloc_get_bgid_of_inode(ext4_superblock_t *sb,
    uint32_t inode)
{
        uint32_t inodes_per_group = ext4_superblock_get_inodes_per_group(sb);
        return (inode - 1) / inodes_per_group;
}


/** Free i-node number and modify filesystem data structers.
 *
 * @param fs     Filesystem, where the i-node is located
 * @param index  Index of i-node to be release
 * @param is_dir Flag us for information whether i-node is directory or not
 *
 */
errno_t ext4_ialloc_free_inode(ext4_filesystem_t *fs, uint32_t index, bool is_dir)
{
        ext4_superblock_t *sb = fs->superblock;

        /* Compute index of block group and load it */
        uint32_t block_group = ext4_ialloc_get_bgid_of_inode(sb, index);

        ext4_block_group_ref_t *bg_ref;
        errno_t rc = ext4_filesystem_get_block_group_ref(fs, block_group, &bg_ref);
        if (rc != EOK)
                return rc;

        /* Load i-node bitmap */
        uint32_t bitmap_block_addr = ext4_block_group_get_inode_bitmap(
            bg_ref->block_group, sb);
        block_t *bitmap_block;
        rc = block_get(&bitmap_block, fs->device, bitmap_block_addr,
            BLOCK_FLAGS_NONE);
        if (rc != EOK)
                return rc;

        /* Free i-node in the bitmap */
        uint32_t index_in_group = ext4_ialloc_inode2index_in_group(sb, index);
        ext4_bitmap_free_bit(bitmap_block->data, index_in_group);
        bitmap_block->dirty = true;

        /* Put back the block with bitmap */
        rc = block_put(bitmap_block);
        if (rc != EOK) {
                /* Error in saving bitmap */
                ext4_filesystem_put_block_group_ref(bg_ref);
                return rc;
        }

        /* If released i-node is a directory, decrement used directories count */
        if (is_dir) {
                uint32_t bg_used_dirs = ext4_block_group_get_used_dirs_count(
                    bg_ref->block_group, sb);
                bg_used_dirs--;
                ext4_block_group_set_used_dirs_count(bg_ref->block_group, sb,
                    bg_used_dirs);
        }

        /* Update block group free inodes count */
        uint32_t free_inodes = ext4_block_group_get_free_inodes_count(
            bg_ref->block_group, sb);
        free_inodes++;
        ext4_block_group_set_free_inodes_count(bg_ref->block_group, sb,
            free_inodes);

        bg_ref->dirty = true;

        /* Put back the modified block group */
        rc = ext4_filesystem_put_block_group_ref(bg_ref);
        if (rc != EOK)
                return rc;

        /* Update superblock free inodes count */
        uint32_t sb_free_inodes =
            ext4_superblock_get_free_inodes_count(sb);
        sb_free_inodes++;
        ext4_superblock_set_free_inodes_count(sb, sb_free_inodes);

        return EOK;
}

/** I-node allocation algorithm.
 *
 * This is more simple algorithm, than Orlov allocator used
 * in the Linux kernel.
 *
 * @param fs     Filesystem to allocate i-node on
 * @param index  Output value - allocated i-node number
 * @param is_dir Flag if allocated i-node will be file or directory
 *
 * @return Error code
 *
 */
errno_t ext4_ialloc_alloc_inode(ext4_filesystem_t *fs, uint32_t *index, bool is_dir)
{
        ext4_superblock_t *sb = fs->superblock;

        uint32_t bgid = 0;
        uint32_t bg_count = ext4_superblock_get_block_group_count(sb);
        uint32_t sb_free_inodes = ext4_superblock_get_free_inodes_count(sb);
        uint32_t avg_free_inodes = sb_free_inodes / bg_count;

        /* Try to find free i-node in all block groups */
        while (bgid < bg_count) {
                /* Load block group to check */
                ext4_block_group_ref_t *bg_ref;
                errno_t rc = ext4_filesystem_get_block_group_ref(fs, bgid, &bg_ref);
                if (rc != EOK)
                        return rc;

                ext4_block_group_t *bg = bg_ref->block_group;

                /* Read necessary values for algorithm */
                uint32_t free_blocks = ext4_block_group_get_free_blocks_count(bg, sb);
                uint32_t free_inodes = ext4_block_group_get_free_inodes_count(bg, sb);
                uint32_t used_dirs = ext4_block_group_get_used_dirs_count(bg, sb);

                /*
                 * Check if this block group is a good candidate
                 * for allocation.
                 *
                 * The criterion is based on the average number
                 * of free inodes, unless we examine the last block
                 * group. In that case the last block group might
                 * have less than the average number of free inodes,
                 * but it still needs to be taken as a candidate
                 * because the previous block groups have zero free
                 * blocks.
                 */
                if (((free_inodes >= avg_free_inodes) || (bgid == bg_count - 1)) &&
                    (free_blocks > 0)) {
                        /* Load block with bitmap */
                        uint32_t bitmap_block_addr = ext4_block_group_get_inode_bitmap(
                            bg_ref->block_group, sb);

                        block_t *bitmap_block;
                        rc = block_get(&bitmap_block, fs->device, bitmap_block_addr,
                            BLOCK_FLAGS_NONE);
                        if (rc != EOK) {
                                ext4_filesystem_put_block_group_ref(bg_ref);
                                return rc;
                        }

                        /* Try to allocate i-node in the bitmap */
                        uint32_t inodes_in_group = ext4_superblock_get_inodes_in_group(sb, bgid);
                        uint32_t index_in_group;
                        rc = ext4_bitmap_find_free_bit_and_set(bitmap_block->data,
                            0, &index_in_group, inodes_in_group);

                        /* Block group has not any free i-node */
                        if (rc == ENOSPC) {
                                rc = block_put(bitmap_block);
                                if (rc != EOK) {
                                        ext4_filesystem_put_block_group_ref(bg_ref);
                                        return rc;
                                }

                                rc = ext4_filesystem_put_block_group_ref(bg_ref);
                                if (rc != EOK)
                                        return rc;

                                bgid++;
                                continue;
                        }

                        /* Free i-node found, save the bitmap */
                        bitmap_block->dirty = true;

                        rc = block_put(bitmap_block);
                        if (rc != EOK) {
                                ext4_filesystem_put_block_group_ref(bg_ref);
                                return rc;
                        }

                        /* Modify filesystem counters */
                        free_inodes--;
                        ext4_block_group_set_free_inodes_count(bg, sb, free_inodes);

                        /* Increment used directories counter */
                        if (is_dir) {
                                used_dirs++;
                                ext4_block_group_set_used_dirs_count(bg, sb, used_dirs);
                        }

                        /* Decrease unused inodes count */
                        if (ext4_block_group_has_flag(bg,
                            EXT4_BLOCK_GROUP_ITABLE_ZEROED)) {
                                uint32_t unused =
                                    ext4_block_group_get_itable_unused(bg, sb);

                                uint32_t inodes_in_group =
                                    ext4_superblock_get_inodes_in_group(sb, bgid);

                                uint32_t free = inodes_in_group - unused;

                                if (index_in_group >= free) {
                                        unused = inodes_in_group - (index_in_group + 1);
                                        ext4_block_group_set_itable_unused(bg, sb, unused);
                                }
                        }

                        /* Save modified block group */
                        bg_ref->dirty = true;

                        rc = ext4_filesystem_put_block_group_ref(bg_ref);
                        if (rc != EOK)
                                return rc;

                        /* Update superblock */
                        sb_free_inodes--;
                        ext4_superblock_set_free_inodes_count(sb, sb_free_inodes);

                        /* Compute the absolute i-nodex number */
                        *index = ext4_ialloc_index_in_group2inode(sb, index_in_group, bgid);

                        return EOK;
                }

                /* Block group not modified, put it and jump to the next block group */
                rc = ext4_filesystem_put_block_group_ref(bg_ref);
                if (rc != EOK)
                        return rc;

                ++bgid;
        }

        return ENOSPC;
}

/**
 * @}
 */