source: MondoRescue/branches/2.2.5/mindi-busybox/e2fsprogs/old_e2fsprogs/ext2fs/icount.c@ 1765

/* vi: set sw=4 ts=4: */
/*
 * icount.c --- an efficient inode count abstraction
 *
 * Copyright (C) 1997 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <stdio.h>

#include "ext2_fs.h"
#include "ext2fs.h"

/*
 * The data storage strategy used by icount relies on the observation
 * that most inode counts are either zero (for non-allocated inodes),
 * one (for most files), and only a few that are two or more
 * (directories and files that are linked to more than one directory).
 *
 * Also, e2fsck tends to load the icount data sequentially.
 *
 * So, we use an inode bitmap to indicate which inodes have a count of
 * one, and then use a sorted list to store the counts for inodes
 * which are greater than one.
 *
 * We also use an optional bitmap to indicate which inodes are already
 * in the sorted list, to speed up the use of this abstraction by
 * e2fsck's pass 2.  Pass 2 increments inode counts as it finds them,
 * so this extra bitmap avoids searching the sorted list to see if a
 * particular inode is on the sorted list already.
 */

struct ext2_icount_el {
    ext2_ino_t  ino;
    __u16   count;
};

struct ext2_icount {
    errcode_t       magic;
    ext2fs_inode_bitmap single;
    ext2fs_inode_bitmap multiple;
    ext2_ino_t      count;
    ext2_ino_t      size;
    ext2_ino_t      num_inodes;
    ext2_ino_t      cursor;
    struct ext2_icount_el   *list;
};

void ext2fs_free_icount(ext2_icount_t icount)
{
    if (!icount)
        return;

    icount->magic = 0;
    ext2fs_free_mem(&icount->list);
    ext2fs_free_inode_bitmap(icount->single);
    ext2fs_free_inode_bitmap(icount->multiple);
    ext2fs_free_mem(&icount);
}

errcode_t ext2fs_create_icount2(ext2_filsys fs, int flags, unsigned int size,
                ext2_icount_t hint, ext2_icount_t *ret)
{
    ext2_icount_t   icount;
    errcode_t   retval;
    size_t      bytes;
    ext2_ino_t  i;

    if (hint) {
        EXT2_CHECK_MAGIC(hint, EXT2_ET_MAGIC_ICOUNT);
        if (hint->size > size)
            size = (size_t) hint->size;
    }

    retval = ext2fs_get_mem(sizeof(struct ext2_icount), &icount);
    if (retval)
        return retval;
    memset(icount, 0, sizeof(struct ext2_icount));

    retval = ext2fs_allocate_inode_bitmap(fs, 0,
                          &icount->single);
    if (retval)
        goto errout;

    if (flags & EXT2_ICOUNT_OPT_INCREMENT) {
        retval = ext2fs_allocate_inode_bitmap(fs, 0,
                              &icount->multiple);
        if (retval)
            goto errout;
    } else
        icount->multiple = 0;

    if (size) {
        icount->size = size;
    } else {
        /*
         * Figure out how many special case inode counts we will
         * have.  We know we will need one for each directory;
         * we also need to reserve some extra room for file links
         */
        retval = ext2fs_get_num_dirs(fs, &icount->size);
        if (retval)
            goto errout;
        icount->size += fs->super->s_inodes_count / 50;
    }

    bytes = (size_t) (icount->size * sizeof(struct ext2_icount_el));
    retval = ext2fs_get_mem(bytes, &icount->list);
    if (retval)
        goto errout;
    memset(icount->list, 0, bytes);

    icount->magic = EXT2_ET_MAGIC_ICOUNT;
    icount->count = 0;
    icount->cursor = 0;
    icount->num_inodes = fs->super->s_inodes_count;

    /*
     * Populate the sorted list with those entries which were
     * found in the hint icount (since those are ones which will
     * likely need to be in the sorted list this time around).
     */
    if (hint) {
        for (i=0; i < hint->count; i++)
            icount->list[i].ino = hint->list[i].ino;
        icount->count = hint->count;
    }

    *ret = icount;
    return 0;

errout:
    ext2fs_free_icount(icount);
    return retval;
}

errcode_t ext2fs_create_icount(ext2_filsys fs, int flags,
                   unsigned int size,
                   ext2_icount_t *ret)
{
    return ext2fs_create_icount2(fs, flags, size, 0, ret);
}

/*
 * insert_icount_el() --- Insert a new entry into the sorted list at a
 *  specified position.
 */
static struct ext2_icount_el *insert_icount_el(ext2_icount_t icount,
                        ext2_ino_t ino, int pos)
{
    struct ext2_icount_el   *el;
    errcode_t       retval;
    ext2_ino_t          new_size = 0;
    int         num;

    if (icount->count >= icount->size) {
        if (icount->count) {
            new_size = icount->list[(unsigned)icount->count-1].ino;
            new_size = (ext2_ino_t) (icount->count *
                ((float) icount->num_inodes / new_size));
        }
        if (new_size < (icount->size + 100))
            new_size = icount->size + 100;
        retval = ext2fs_resize_mem((size_t) icount->size *
                       sizeof(struct ext2_icount_el),
                       (size_t) new_size *
                       sizeof(struct ext2_icount_el),
                       &icount->list);
        if (retval)
            return 0;
        icount->size = new_size;
    }
    num = (int) icount->count - pos;
    if (num < 0)
        return 0;   /* should never happen */
    if (num) {
        memmove(&icount->list[pos+1], &icount->list[pos],
            sizeof(struct ext2_icount_el) * num);
    }
    icount->count++;
    el = &icount->list[pos];
    el->count = 0;
    el->ino = ino;
    return el;
}

/*
 * get_icount_el() --- given an inode number, try to find icount
 *  information in the sorted list.  If the create flag is set,
 *  and we can't find an entry, create one in the sorted list.
 */
static struct ext2_icount_el *get_icount_el(ext2_icount_t icount,
                        ext2_ino_t ino, int create)
{
    float   range;
    int low, high, mid;
    ext2_ino_t  lowval, highval;

    if (!icount || !icount->list)
        return 0;

    if (create && ((icount->count == 0) ||
               (ino > icount->list[(unsigned)icount->count-1].ino))) {
        return insert_icount_el(icount, ino, (unsigned) icount->count);
    }
    if (icount->count == 0)
        return 0;

    if (icount->cursor >= icount->count)
        icount->cursor = 0;
    if (ino == icount->list[icount->cursor].ino)
        return &icount->list[icount->cursor++];
    low = 0;
    high = (int) icount->count-1;
    while (low <= high) {
        if (low == high)
            mid = low;
        else {
            /* Interpolate for efficiency */
            lowval = icount->list[low].ino;
            highval = icount->list[high].ino;

            if (ino < lowval)
                range = 0;
            else if (ino > highval)
                range = 1;
            else
                range = ((float) (ino - lowval)) /
                    (highval - lowval);
            mid = low + ((int) (range * (high-low)));
        }
        if (ino == icount->list[mid].ino) {
            icount->cursor = mid+1;
            return &icount->list[mid];
        }
        if (ino < icount->list[mid].ino)
            high = mid-1;
        else
            low = mid+1;
    }
    /*
     * If we need to create a new entry, it should be right at
     * low (where high will be left at low-1).
     */
    if (create)
        return insert_icount_el(icount, ino, low);
    return 0;
}

errcode_t ext2fs_icount_validate(ext2_icount_t icount, FILE *out)
{
    errcode_t   ret = 0;
    unsigned int    i;
    const char *bad = "bad icount";

    EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

    if (icount->count > icount->size) {
        fprintf(out, "%s: count > size\n", bad);
        return EXT2_ET_INVALID_ARGUMENT;
    }
    for (i=1; i < icount->count; i++) {
        if (icount->list[i-1].ino >= icount->list[i].ino) {
            fprintf(out, "%s: list[%d].ino=%u, list[%d].ino=%u\n",
                bad, i-1, icount->list[i-1].ino,
                i, icount->list[i].ino);
            ret = EXT2_ET_INVALID_ARGUMENT;
        }
    }
    return ret;
}

errcode_t ext2fs_icount_fetch(ext2_icount_t icount, ext2_ino_t ino, __u16 *ret)
{
    struct ext2_icount_el   *el;

    EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

    if (!ino || (ino > icount->num_inodes))
        return EXT2_ET_INVALID_ARGUMENT;

    if (ext2fs_test_inode_bitmap(icount->single, ino)) {
        *ret = 1;
        return 0;
    }
    if (icount->multiple &&
        !ext2fs_test_inode_bitmap(icount->multiple, ino)) {
        *ret = 0;
        return 0;
    }
    el = get_icount_el(icount, ino, 0);
    if (!el) {
        *ret = 0;
        return 0;
    }
    *ret = el->count;
    return 0;
}

errcode_t ext2fs_icount_increment(ext2_icount_t icount, ext2_ino_t ino,
                  __u16 *ret)
{
    struct ext2_icount_el   *el;

    EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

    if (!ino || (ino > icount->num_inodes))
        return EXT2_ET_INVALID_ARGUMENT;

    if (ext2fs_test_inode_bitmap(icount->single, ino)) {
        /*
         * If the existing count is 1, then we know there is
         * no entry in the list.
         */
        el = get_icount_el(icount, ino, 1);
        if (!el)
            return EXT2_ET_NO_MEMORY;
        ext2fs_unmark_inode_bitmap(icount->single, ino);
        el->count = 2;
    } else if (icount->multiple) {
        /*
         * The count is either zero or greater than 1; if the
         * inode is set in icount->multiple, then there should
         * be an entry in the list, so find it using
         * get_icount_el().
         */
        if (ext2fs_test_inode_bitmap(icount->multiple, ino)) {
            el = get_icount_el(icount, ino, 1);
            if (!el)
                return EXT2_ET_NO_MEMORY;
            el->count++;
        } else {
            /*
             * The count was zero; mark the single bitmap
             * and return.
             */
        zero_count:
            ext2fs_mark_inode_bitmap(icount->single, ino);
            if (ret)
                *ret = 1;
            return 0;
        }
    } else {
        /*
         * The count is either zero or greater than 1; try to
         * find an entry in the list to determine which.
         */
        el = get_icount_el(icount, ino, 0);
        if (!el) {
            /* No entry means the count was zero */
            goto zero_count;
        }
        el = get_icount_el(icount, ino, 1);
        if (!el)
            return EXT2_ET_NO_MEMORY;
        el->count++;
    }
    if (icount->multiple)
        ext2fs_mark_inode_bitmap(icount->multiple, ino);
    if (ret)
        *ret = el->count;
    return 0;
}

errcode_t ext2fs_icount_decrement(ext2_icount_t icount, ext2_ino_t ino,
                  __u16 *ret)
{
    struct ext2_icount_el   *el;

    if (!ino || (ino > icount->num_inodes))
        return EXT2_ET_INVALID_ARGUMENT;

    EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

    if (ext2fs_test_inode_bitmap(icount->single, ino)) {
        ext2fs_unmark_inode_bitmap(icount->single, ino);
        if (icount->multiple)
            ext2fs_unmark_inode_bitmap(icount->multiple, ino);
        else {
            el = get_icount_el(icount, ino, 0);
            if (el)
                el->count = 0;
        }
        if (ret)
            *ret = 0;
        return 0;
    }

    if (icount->multiple &&
        !ext2fs_test_inode_bitmap(icount->multiple, ino))
        return EXT2_ET_INVALID_ARGUMENT;

    el = get_icount_el(icount, ino, 0);
    if (!el || el->count == 0)
        return EXT2_ET_INVALID_ARGUMENT;

    el->count--;
    if (el->count == 1)
        ext2fs_mark_inode_bitmap(icount->single, ino);
    if ((el->count == 0) && icount->multiple)
        ext2fs_unmark_inode_bitmap(icount->multiple, ino);

    if (ret)
        *ret = el->count;
    return 0;
}

errcode_t ext2fs_icount_store(ext2_icount_t icount, ext2_ino_t ino,
                  __u16 count)
{
    struct ext2_icount_el   *el;

    if (!ino || (ino > icount->num_inodes))
        return EXT2_ET_INVALID_ARGUMENT;

    EXT2_CHECK_MAGIC(icount, EXT2_ET_MAGIC_ICOUNT);

    if (count == 1) {
        ext2fs_mark_inode_bitmap(icount->single, ino);
        if (icount->multiple)
            ext2fs_unmark_inode_bitmap(icount->multiple, ino);
        return 0;
    }
    if (count == 0) {
        ext2fs_unmark_inode_bitmap(icount->single, ino);
        if (icount->multiple) {
            /*
             * If the icount->multiple bitmap is enabled,
             * we can just clear both bitmaps and we're done
             */
            ext2fs_unmark_inode_bitmap(icount->multiple, ino);
        } else {
            el = get_icount_el(icount, ino, 0);
            if (el)
                el->count = 0;
        }
        return 0;
    }

    /*
     * Get the icount element
     */
    el = get_icount_el(icount, ino, 1);
    if (!el)
        return EXT2_ET_NO_MEMORY;
    el->count = count;
    ext2fs_unmark_inode_bitmap(icount->single, ino);
    if (icount->multiple)
        ext2fs_mark_inode_bitmap(icount->multiple, ino);
    return 0;
}

ext2_ino_t ext2fs_get_icount_size(ext2_icount_t icount)
{
    if (!icount || icount->magic != EXT2_ET_MAGIC_ICOUNT)
        return 0;

    return icount->size;
}