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

/* vi: set sw=4 ts=4: */
/*
 * inode.c --- utility routines to read and write inodes
 *
 * Copyright (C) 1993, 1994, 1995, 1996, 1997 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 */

#include <stdio.h>
#include <string.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_ERRNO_H
#include <errno.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include "ext2_fs.h"
#include "ext2fsP.h"
#include "e2image.h"

struct ext2_struct_inode_scan {
    errcode_t       magic;
    ext2_filsys     fs;
    ext2_ino_t      current_inode;
    blk_t           current_block;
    dgrp_t          current_group;
    ext2_ino_t      inodes_left;
    blk_t           blocks_left;
    dgrp_t          groups_left;
    blk_t           inode_buffer_blocks;
    char *          inode_buffer;
    int         inode_size;
    char *          ptr;
    int         bytes_left;
    char            *temp_buffer;
    errcode_t       (*done_group)(ext2_filsys fs,
                          dgrp_t group,
                          void * priv_data);
    void *          done_group_data;
    int         bad_block_ptr;
    int         scan_flags;
    int         reserved[6];
};

/*
 * This routine flushes the icache, if it exists.
 */
errcode_t ext2fs_flush_icache(ext2_filsys fs)
{
    int i;

    if (!fs->icache)
        return 0;

    for (i=0; i < fs->icache->cache_size; i++)
        fs->icache->cache[i].ino = 0;

    fs->icache->buffer_blk = 0;
    return 0;
}

static errcode_t create_icache(ext2_filsys fs)
{
    errcode_t   retval;

    if (fs->icache)
        return 0;
    retval = ext2fs_get_mem(sizeof(struct ext2_inode_cache), &fs->icache);
    if (retval)
        return retval;

    memset(fs->icache, 0, sizeof(struct ext2_inode_cache));
    retval = ext2fs_get_mem(fs->blocksize, &fs->icache->buffer);
    if (retval) {
        ext2fs_free_mem(&fs->icache);
        return retval;
    }
    fs->icache->buffer_blk = 0;
    fs->icache->cache_last = -1;
    fs->icache->cache_size = 4;
    fs->icache->refcount = 1;
    retval = ext2fs_get_mem(sizeof(struct ext2_inode_cache_ent)
                * fs->icache->cache_size,
                &fs->icache->cache);
    if (retval) {
        ext2fs_free_mem(&fs->icache->buffer);
        ext2fs_free_mem(&fs->icache);
        return retval;
    }
    ext2fs_flush_icache(fs);
    return 0;
}

errcode_t ext2fs_open_inode_scan(ext2_filsys fs, int buffer_blocks,
                 ext2_inode_scan *ret_scan)
{
    ext2_inode_scan scan;
    errcode_t   retval;
    errcode_t (*save_get_blocks)(ext2_filsys f, ext2_ino_t ino, blk_t *blocks);

    EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

    /*
     * If fs->badblocks isn't set, then set it --- since the inode
     * scanning functions require it.
     */
    if (fs->badblocks == 0) {
        /*
         * Temporarly save fs->get_blocks and set it to zero,
         * for compatibility with old e2fsck's.
         */
        save_get_blocks = fs->get_blocks;
        fs->get_blocks = 0;
        retval = ext2fs_read_bb_inode(fs, &fs->badblocks);
        if (retval) {
            ext2fs_badblocks_list_free(fs->badblocks);
            fs->badblocks = 0;
        }
        fs->get_blocks = save_get_blocks;
    }

    retval = ext2fs_get_mem(sizeof(struct ext2_struct_inode_scan), &scan);
    if (retval)
        return retval;
    memset(scan, 0, sizeof(struct ext2_struct_inode_scan));

    scan->magic = EXT2_ET_MAGIC_INODE_SCAN;
    scan->fs = fs;
    scan->inode_size = EXT2_INODE_SIZE(fs->super);
    scan->bytes_left = 0;
    scan->current_group = 0;
    scan->groups_left = fs->group_desc_count - 1;
    scan->inode_buffer_blocks = buffer_blocks ? buffer_blocks : 8;
    scan->current_block = scan->fs->
        group_desc[scan->current_group].bg_inode_table;
    scan->inodes_left = EXT2_INODES_PER_GROUP(scan->fs->super);
    scan->blocks_left = scan->fs->inode_blocks_per_group;
    retval = ext2fs_get_mem((size_t) (scan->inode_buffer_blocks *
                      fs->blocksize),
                &scan->inode_buffer);
    scan->done_group = 0;
    scan->done_group_data = 0;
    scan->bad_block_ptr = 0;
    if (retval) {
        ext2fs_free_mem(&scan);
        return retval;
    }
    retval = ext2fs_get_mem(scan->inode_size, &scan->temp_buffer);
    if (retval) {
        ext2fs_free_mem(&scan->inode_buffer);
        ext2fs_free_mem(&scan);
        return retval;
    }
    if (scan->fs->badblocks && scan->fs->badblocks->num)
        scan->scan_flags |= EXT2_SF_CHK_BADBLOCKS;
    *ret_scan = scan;
    return 0;
}

void ext2fs_close_inode_scan(ext2_inode_scan scan)
{
    if (!scan || (scan->magic != EXT2_ET_MAGIC_INODE_SCAN))
        return;

    ext2fs_free_mem(&scan->inode_buffer);
    scan->inode_buffer = NULL;
    ext2fs_free_mem(&scan->temp_buffer);
    scan->temp_buffer = NULL;
    ext2fs_free_mem(&scan);
}

void ext2fs_set_inode_callback(ext2_inode_scan scan,
                   errcode_t (*done_group)(ext2_filsys fs,
                               dgrp_t group,
                               void * priv_data),
                   void *done_group_data)
{
    if (!scan || (scan->magic != EXT2_ET_MAGIC_INODE_SCAN))
        return;

    scan->done_group = done_group;
    scan->done_group_data = done_group_data;
}

int ext2fs_inode_scan_flags(ext2_inode_scan scan, int set_flags,
                int clear_flags)
{
    int old_flags;

    if (!scan || (scan->magic != EXT2_ET_MAGIC_INODE_SCAN))
        return 0;

    old_flags = scan->scan_flags;
    scan->scan_flags &= ~clear_flags;
    scan->scan_flags |= set_flags;
    return old_flags;
}

/*
 * This function is called by ext2fs_get_next_inode when it needs to
 * get ready to read in a new blockgroup.
 */
static errcode_t get_next_blockgroup(ext2_inode_scan scan)
{
    scan->current_group++;
    scan->groups_left--;

    scan->current_block = scan->fs->
        group_desc[scan->current_group].bg_inode_table;

    scan->current_inode = scan->current_group *
        EXT2_INODES_PER_GROUP(scan->fs->super);

    scan->bytes_left = 0;
    scan->inodes_left = EXT2_INODES_PER_GROUP(scan->fs->super);
    scan->blocks_left = scan->fs->inode_blocks_per_group;
    return 0;
}

errcode_t ext2fs_inode_scan_goto_blockgroup(ext2_inode_scan scan,
                        int group)
{
    scan->current_group = group - 1;
    scan->groups_left = scan->fs->group_desc_count - group;
    return get_next_blockgroup(scan);
}

/*
 * This function is called by get_next_blocks() to check for bad
 * blocks in the inode table.
 *
 * This function assumes that badblocks_list->list is sorted in
 * increasing order.
 */
static errcode_t check_for_inode_bad_blocks(ext2_inode_scan scan,
                        blk_t *num_blocks)
{
    blk_t   blk = scan->current_block;
    badblocks_list  bb = scan->fs->badblocks;

    /*
     * If the inode table is missing, then obviously there are no
     * bad blocks.  :-)
     */
    if (blk == 0)
        return 0;

    /*
     * If the current block is greater than the bad block listed
     * in the bad block list, then advance the pointer until this
     * is no longer the case.  If we run out of bad blocks, then
     * we don't need to do any more checking!
     */
    while (blk > bb->list[scan->bad_block_ptr]) {
        if (++scan->bad_block_ptr >= bb->num) {
            scan->scan_flags &= ~EXT2_SF_CHK_BADBLOCKS;
            return 0;
        }
    }

    /*
     * If the current block is equal to the bad block listed in
     * the bad block list, then handle that one block specially.
     * (We could try to handle runs of bad blocks, but that
     * only increases CPU efficiency by a small amount, at the
     * expense of a huge expense of code complexity, and for an
     * uncommon case at that.)
     */
    if (blk == bb->list[scan->bad_block_ptr]) {
        scan->scan_flags |= EXT2_SF_BAD_INODE_BLK;
        *num_blocks = 1;
        if (++scan->bad_block_ptr >= bb->num)
            scan->scan_flags &= ~EXT2_SF_CHK_BADBLOCKS;
        return 0;
    }

    /*
     * If there is a bad block in the range that we're about to
     * read in, adjust the number of blocks to read so that we we
     * don't read in the bad block.  (Then the next block to read
     * will be the bad block, which is handled in the above case.)
     */
    if ((blk + *num_blocks) > bb->list[scan->bad_block_ptr])
        *num_blocks = (int) (bb->list[scan->bad_block_ptr] - blk);

    return 0;
}

/*
 * This function is called by ext2fs_get_next_inode when it needs to
 * read in more blocks from the current blockgroup's inode table.
 */
static errcode_t get_next_blocks(ext2_inode_scan scan)
{
    blk_t       num_blocks;
    errcode_t   retval;

    /*
     * Figure out how many blocks to read; we read at most
     * inode_buffer_blocks, and perhaps less if there aren't that
     * many blocks left to read.
     */
    num_blocks = scan->inode_buffer_blocks;
    if (num_blocks > scan->blocks_left)
        num_blocks = scan->blocks_left;

    /*
     * If the past block "read" was a bad block, then mark the
     * left-over extra bytes as also being bad.
     */
    if (scan->scan_flags & EXT2_SF_BAD_INODE_BLK) {
        if (scan->bytes_left)
            scan->scan_flags |= EXT2_SF_BAD_EXTRA_BYTES;
        scan->scan_flags &= ~EXT2_SF_BAD_INODE_BLK;
    }

    /*
     * Do inode bad block processing, if necessary.
     */
    if (scan->scan_flags & EXT2_SF_CHK_BADBLOCKS) {
        retval = check_for_inode_bad_blocks(scan, &num_blocks);
        if (retval)
            return retval;
    }

    if ((scan->scan_flags & EXT2_SF_BAD_INODE_BLK) ||
        (scan->current_block == 0)) {
        memset(scan->inode_buffer, 0,
               (size_t) num_blocks * scan->fs->blocksize);
    } else {
        retval = io_channel_read_blk(scan->fs->io,
                         scan->current_block,
                         (int) num_blocks,
                         scan->inode_buffer);
        if (retval)
            return EXT2_ET_NEXT_INODE_READ;
    }
    scan->ptr = scan->inode_buffer;
    scan->bytes_left = num_blocks * scan->fs->blocksize;

    scan->blocks_left -= num_blocks;
    if (scan->current_block)
        scan->current_block += num_blocks;
    return 0;
}

errcode_t ext2fs_get_next_inode_full(ext2_inode_scan scan, ext2_ino_t *ino,
                     struct ext2_inode *inode, int bufsize)
{
    errcode_t   retval;
    int     extra_bytes = 0;

    EXT2_CHECK_MAGIC(scan, EXT2_ET_MAGIC_INODE_SCAN);

    /*
     * Do we need to start reading a new block group?
     */
    if (scan->inodes_left <= 0) {
    force_new_group:
        if (scan->done_group) {
            retval = (scan->done_group)
                (scan->fs, scan->current_group,
                 scan->done_group_data);
            if (retval)
                return retval;
        }
        if (scan->groups_left <= 0) {
            *ino = 0;
            return 0;
        }
        retval = get_next_blockgroup(scan);
        if (retval)
            return retval;
    }
    /*
     * This is done outside the above if statement so that the
     * check can be done for block group #0.
     */
    if (scan->current_block == 0) {
        if (scan->scan_flags & EXT2_SF_SKIP_MISSING_ITABLE) {
            goto force_new_group;
        } else
            return EXT2_ET_MISSING_INODE_TABLE;
    }


    /*
     * Have we run out of space in the inode buffer?  If so, we
     * need to read in more blocks.
     */
    if (scan->bytes_left < scan->inode_size) {
        memcpy(scan->temp_buffer, scan->ptr, scan->bytes_left);
        extra_bytes = scan->bytes_left;

        retval = get_next_blocks(scan);
        if (retval)
            return retval;
#if 0
        /*
         * XXX test  Need check for used inode somehow.
         * (Note: this is hard.)
         */
        if (is_empty_scan(scan))
            goto force_new_group;
#endif
    }

    retval = 0;
    if (extra_bytes) {
        memcpy(scan->temp_buffer+extra_bytes, scan->ptr,
               scan->inode_size - extra_bytes);
        scan->ptr += scan->inode_size - extra_bytes;
        scan->bytes_left -= scan->inode_size - extra_bytes;

#if BB_BIG_ENDIAN
        if ((scan->fs->flags & EXT2_FLAG_SWAP_BYTES) ||
            (scan->fs->flags & EXT2_FLAG_SWAP_BYTES_READ))
            ext2fs_swap_inode_full(scan->fs,
                (struct ext2_inode_large *) inode,
                (struct ext2_inode_large *) scan->temp_buffer,
                0, bufsize);
        else
#endif
            *inode = *((struct ext2_inode *) scan->temp_buffer);
        if (scan->scan_flags & EXT2_SF_BAD_EXTRA_BYTES)
            retval = EXT2_ET_BAD_BLOCK_IN_INODE_TABLE;
        scan->scan_flags &= ~EXT2_SF_BAD_EXTRA_BYTES;
    } else {
#if BB_BIG_ENDIAN
        if ((scan->fs->flags & EXT2_FLAG_SWAP_BYTES) ||
            (scan->fs->flags & EXT2_FLAG_SWAP_BYTES_READ))
            ext2fs_swap_inode_full(scan->fs,
                (struct ext2_inode_large *) inode,
                (struct ext2_inode_large *) scan->ptr,
                0, bufsize);
        else
#endif
            memcpy(inode, scan->ptr, bufsize);
        scan->ptr += scan->inode_size;
        scan->bytes_left -= scan->inode_size;
        if (scan->scan_flags & EXT2_SF_BAD_INODE_BLK)
            retval = EXT2_ET_BAD_BLOCK_IN_INODE_TABLE;
    }

    scan->inodes_left--;
    scan->current_inode++;
    *ino = scan->current_inode;
    return retval;
}

errcode_t ext2fs_get_next_inode(ext2_inode_scan scan, ext2_ino_t *ino,
                struct ext2_inode *inode)
{
    return ext2fs_get_next_inode_full(scan, ino, inode,
                        sizeof(struct ext2_inode));
}

/*
 * Functions to read and write a single inode.
 */
errcode_t ext2fs_read_inode_full(ext2_filsys fs, ext2_ino_t ino,
                 struct ext2_inode * inode, int bufsize)
{
    unsigned long   group, block, block_nr, offset;
    char        *ptr;
    errcode_t   retval;
    int     clen, i, inodes_per_block, length;
    io_channel  io;

    EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

    /* Check to see if user has an override function */
    if (fs->read_inode) {
        retval = (fs->read_inode)(fs, ino, inode);
        if (retval != EXT2_ET_CALLBACK_NOTHANDLED)
            return retval;
    }
    /* Create inode cache if not present */
    if (!fs->icache) {
        retval = create_icache(fs);
        if (retval)
            return retval;
    }
    /* Check to see if it's in the inode cache */
    if (bufsize == sizeof(struct ext2_inode)) {
        /* only old good inode can be retrieve from the cache */
        for (i=0; i < fs->icache->cache_size; i++) {
            if (fs->icache->cache[i].ino == ino) {
                *inode = fs->icache->cache[i].inode;
                return 0;
            }
        }
    }
    if ((ino == 0) || (ino > fs->super->s_inodes_count))
        return EXT2_ET_BAD_INODE_NUM;
    if (fs->flags & EXT2_FLAG_IMAGE_FILE) {
        inodes_per_block = fs->blocksize / EXT2_INODE_SIZE(fs->super);
        block_nr = fs->image_header->offset_inode / fs->blocksize;
        block_nr += (ino - 1) / inodes_per_block;
        offset = ((ino - 1) % inodes_per_block) *
            EXT2_INODE_SIZE(fs->super);
        io = fs->image_io;
    } else {
        group = (ino - 1) / EXT2_INODES_PER_GROUP(fs->super);
        offset = ((ino - 1) % EXT2_INODES_PER_GROUP(fs->super)) *
            EXT2_INODE_SIZE(fs->super);
        block = offset >> EXT2_BLOCK_SIZE_BITS(fs->super);
        if (!fs->group_desc[(unsigned)group].bg_inode_table)
            return EXT2_ET_MISSING_INODE_TABLE;
        block_nr = fs->group_desc[(unsigned)group].bg_inode_table +
            block;
        io = fs->io;
    }
    offset &= (EXT2_BLOCK_SIZE(fs->super) - 1);

    length = EXT2_INODE_SIZE(fs->super);
    if (bufsize < length)
        length = bufsize;

    ptr = (char *) inode;
    while (length) {
        clen = length;
        if ((offset + length) > fs->blocksize)
            clen = fs->blocksize - offset;

        if (block_nr != fs->icache->buffer_blk) {
            retval = io_channel_read_blk(io, block_nr, 1,
                             fs->icache->buffer);
            if (retval)
                return retval;
            fs->icache->buffer_blk = block_nr;
        }

        memcpy(ptr, ((char *) fs->icache->buffer) + (unsigned) offset,
               clen);

        offset = 0;
        length -= clen;
        ptr += clen;
        block_nr++;
    }

#if BB_BIG_ENDIAN
    if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
        (fs->flags & EXT2_FLAG_SWAP_BYTES_READ))
        ext2fs_swap_inode_full(fs, (struct ext2_inode_large *) inode,
                       (struct ext2_inode_large *) inode,
                       0, length);
#endif

    /* Update the inode cache */
    fs->icache->cache_last = (fs->icache->cache_last + 1) %
        fs->icache->cache_size;
    fs->icache->cache[fs->icache->cache_last].ino = ino;
    fs->icache->cache[fs->icache->cache_last].inode = *inode;

    return 0;
}

errcode_t ext2fs_read_inode(ext2_filsys fs, ext2_ino_t ino,
                struct ext2_inode * inode)
{
    return ext2fs_read_inode_full(fs, ino, inode,
                    sizeof(struct ext2_inode));
}

errcode_t ext2fs_write_inode_full(ext2_filsys fs, ext2_ino_t ino,
                  struct ext2_inode * inode, int bufsize)
{
    unsigned long group, block, block_nr, offset;
    errcode_t retval = 0;
    struct ext2_inode_large temp_inode, *w_inode;
    char *ptr;
    int clen, i, length;

    EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

    /* Check to see if user provided an override function */
    if (fs->write_inode) {
        retval = (fs->write_inode)(fs, ino, inode);
        if (retval != EXT2_ET_CALLBACK_NOTHANDLED)
            return retval;
    }

    /* Check to see if the inode cache needs to be updated */
    if (fs->icache) {
        for (i=0; i < fs->icache->cache_size; i++) {
            if (fs->icache->cache[i].ino == ino) {
                fs->icache->cache[i].inode = *inode;
                break;
            }
        }
    } else {
        retval = create_icache(fs);
        if (retval)
            return retval;
    }

    if (!(fs->flags & EXT2_FLAG_RW))
        return EXT2_ET_RO_FILSYS;

    if ((ino == 0) || (ino > fs->super->s_inodes_count))
        return EXT2_ET_BAD_INODE_NUM;

    length = bufsize;
    if (length < EXT2_INODE_SIZE(fs->super))
        length = EXT2_INODE_SIZE(fs->super);

    if (length > (int) sizeof(struct ext2_inode_large)) {
        w_inode = xmalloc(length);
    } else
        w_inode = &temp_inode;
    memset(w_inode, 0, length);

#if BB_BIG_ENDIAN
    if ((fs->flags & EXT2_FLAG_SWAP_BYTES) ||
        (fs->flags & EXT2_FLAG_SWAP_BYTES_WRITE))
        ext2fs_swap_inode_full(fs, w_inode,
                       (struct ext2_inode_large *) inode,
                       1, bufsize);
    else
#endif
        memcpy(w_inode, inode, bufsize);

    group = (ino - 1) / EXT2_INODES_PER_GROUP(fs->super);
    offset = ((ino - 1) % EXT2_INODES_PER_GROUP(fs->super)) *
        EXT2_INODE_SIZE(fs->super);
    block = offset >> EXT2_BLOCK_SIZE_BITS(fs->super);
    if (!fs->group_desc[(unsigned) group].bg_inode_table)
        return EXT2_ET_MISSING_INODE_TABLE;
    block_nr = fs->group_desc[(unsigned) group].bg_inode_table + block;

    offset &= (EXT2_BLOCK_SIZE(fs->super) - 1);

    length = EXT2_INODE_SIZE(fs->super);
    if (length > bufsize)
        length = bufsize;

    ptr = (char *) w_inode;

    while (length) {
        clen = length;
        if ((offset + length) > fs->blocksize)
            clen = fs->blocksize - offset;

        if (fs->icache->buffer_blk != block_nr) {
            retval = io_channel_read_blk(fs->io, block_nr, 1,
                             fs->icache->buffer);
            if (retval)
                goto errout;
            fs->icache->buffer_blk = block_nr;
        }


        memcpy((char *) fs->icache->buffer + (unsigned) offset,
               ptr, clen);

        retval = io_channel_write_blk(fs->io, block_nr, 1,
                          fs->icache->buffer);
        if (retval)
            goto errout;

        offset = 0;
        ptr += clen;
        length -= clen;
        block_nr++;
    }

    fs->flags |= EXT2_FLAG_CHANGED;
errout:
    if (w_inode && w_inode != &temp_inode)
        free(w_inode);
    return retval;
}

errcode_t ext2fs_write_inode(ext2_filsys fs, ext2_ino_t ino,
                 struct ext2_inode *inode)
{
    return ext2fs_write_inode_full(fs, ino, inode,
                       sizeof(struct ext2_inode));
}

/*
 * This function should be called when writing a new inode.  It makes
 * sure that extra part of large inodes is initialized properly.
 */
errcode_t ext2fs_write_new_inode(ext2_filsys fs, ext2_ino_t ino,
                 struct ext2_inode *inode)
{
    struct ext2_inode   *buf;
    int         size = EXT2_INODE_SIZE(fs->super);
    struct ext2_inode_large *large_inode;

    if (size == sizeof(struct ext2_inode))
        return ext2fs_write_inode_full(fs, ino, inode,
                           sizeof(struct ext2_inode));

    buf = xmalloc(size);

    memset(buf, 0, size);
    *buf = *inode;

    large_inode = (struct ext2_inode_large *) buf;
    large_inode->i_extra_isize = sizeof(struct ext2_inode_large) -
        EXT2_GOOD_OLD_INODE_SIZE;

    return ext2fs_write_inode_full(fs, ino, buf, size);
}


errcode_t ext2fs_get_blocks(ext2_filsys fs, ext2_ino_t ino, blk_t *blocks)
{
    struct ext2_inode   inode;
    int         i;
    errcode_t       retval;

    EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

    if (ino > fs->super->s_inodes_count)
        return EXT2_ET_BAD_INODE_NUM;

    if (fs->get_blocks) {
        if (!(*fs->get_blocks)(fs, ino, blocks))
            return 0;
    }
    retval = ext2fs_read_inode(fs, ino, &inode);
    if (retval)
        return retval;
    for (i=0; i < EXT2_N_BLOCKS; i++)
        blocks[i] = inode.i_block[i];
    return 0;
}

errcode_t ext2fs_check_directory(ext2_filsys fs, ext2_ino_t ino)
{
    struct  ext2_inode  inode;
    errcode_t       retval;

    EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

    if (ino > fs->super->s_inodes_count)
        return EXT2_ET_BAD_INODE_NUM;

    if (fs->check_directory) {
        retval = (fs->check_directory)(fs, ino);
        if (retval != EXT2_ET_CALLBACK_NOTHANDLED)
            return retval;
    }
    retval = ext2fs_read_inode(fs, ino, &inode);
    if (retval)
        return retval;
    if (!LINUX_S_ISDIR(inode.i_mode))
        return EXT2_ET_NO_DIRECTORY;
    return 0;
}