/* 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;
}