Il CD di internet/CD.iso/SOURCE/KERNEL-S/V1.0/LINUX-1.0/LINUX-1/linux/fs/ext2/dir.c

C/C++ Source or Header | 1994-01-09 | 4.4 KB | 171 lines

/*
 *  linux/fs/ext2/dir.c
 *
 *  Copyright (C) 1992, 1993, 1994  Remy Card ([e-mail])
 *                                  Laboratoire MASI - Institut Blaise Pascal
 *                                  Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/dir.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  ext2 directory handling functions
 */

#include <asm/segment.h>

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/ext2_fs.h>
#include <linux/sched.h>
#include <linux/stat.h>

static int ext2_dir_read (struct inode * inode, struct file * filp,
                char * buf, int count)
{
    return -EISDIR;
}

static int ext2_readdir (struct inode *, struct file *, struct dirent *, int);

static struct file_operations ext2_dir_operations = {
    NULL,            /* lseek - default */
    ext2_dir_read,        /* read */
    NULL,            /* write - bad */
    ext2_readdir,        /* readdir */
    NULL,            /* select - default */
    ext2_ioctl,        /* ioctl */
    NULL,            /* mmap */
    NULL,            /* no special open code */
    NULL,            /* no special release code */
    file_fsync        /* fsync */
};

/*
 * directories can handle most operations...
 */
struct inode_operations ext2_dir_inode_operations = {
    &ext2_dir_operations,    /* default directory file-ops */
    ext2_create,        /* create */
    ext2_lookup,        /* lookup */
    ext2_link,        /* link */
    ext2_unlink,        /* unlink */
    ext2_symlink,        /* symlink */
    ext2_mkdir,        /* mkdir */
    ext2_rmdir,        /* rmdir */
    ext2_mknod,        /* mknod */
    ext2_rename,        /* rename */
    NULL,            /* readlink */
    NULL,            /* follow_link */
    NULL,            /* bmap */
    ext2_truncate,        /* truncate */
    ext2_permission        /* permission */
};

int ext2_check_dir_entry (char * function, struct inode * dir,
              struct ext2_dir_entry * de, struct buffer_head * bh,
              unsigned long offset)
{
    char * error_msg = NULL;

    if (de->rec_len < EXT2_DIR_REC_LEN(1))
        error_msg = "rec_len is smaller than minimal";
    else if (de->rec_len % 4 != 0)
        error_msg = "rec_len % 4 != 0";
    else if (de->rec_len < EXT2_DIR_REC_LEN(de->name_len))
        error_msg = "rec_len is too small for name_len";
    else if (dir && ((char *) de - bh->b_data) + de->rec_len >
         dir->i_sb->s_blocksize)
        error_msg = "directory entry across blocks";

    if (error_msg != NULL)
        ext2_error (dir->i_sb, function, "bad directory entry: %s\n"
                "offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
                error_msg, offset, de->inode, de->rec_len,
                de->name_len);
    return error_msg == NULL ? 1 : 0;
}

static int ext2_readdir (struct inode * inode, struct file * filp,
             struct dirent * dirent, int count)
{
    unsigned long offset, blk;
    int i, num;
    struct buffer_head * bh, * tmp, * bha[16];
    struct ext2_dir_entry * de;
    struct super_block * sb;
    int err;

    if (!inode || !S_ISDIR(inode->i_mode))
        return -EBADF;
    sb = inode->i_sb;
    while (filp->f_pos < inode->i_size) {
        offset = filp->f_pos & (sb->s_blocksize - 1);
        blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
        bh = ext2_bread (inode, blk, 0, &err);
        if (!bh) {
            filp->f_pos += sb->s_blocksize - offset;
            continue;
        }

        /*
         * Do the readahead
         */
        if (!offset) {
            for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
                 i > 0; i--) {
                tmp = ext2_getblk (inode, ++blk, 0, &err);
                if (tmp && !tmp->b_uptodate && !tmp->b_lock)
                    bha[num++] = tmp;
                else
                    brelse (tmp);
            }
            if (num) {
                ll_rw_block (READA, num, bha);
                for (i = 0; i < num; i++)
                    brelse (bha[i]);
            }
        }

        de = (struct ext2_dir_entry *) (offset + bh->b_data);
        while (offset < sb->s_blocksize && filp->f_pos < inode->i_size) {
            if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
                           bh, offset)) {
                brelse (bh);
                return 0;
            }
            offset += de->rec_len;
            filp->f_pos += de->rec_len;
            if (de->inode) {
                memcpy_tofs (dirent->d_name, de->name,
                         de->name_len);
                put_fs_long (de->inode, &dirent->d_ino);
                put_fs_byte (0, de->name_len + dirent->d_name);
                put_fs_word (de->name_len, &dirent->d_reclen);
#ifndef DONT_USE_DCACHE
                ext2_dcache_add (inode->i_dev, inode->i_ino,
                         de->name, de->name_len,
                         de->inode);
#endif
                i = de->name_len;
                brelse (bh);
                if (!IS_RDONLY(inode)) {
                    inode->i_atime = CURRENT_TIME;
                    inode->i_dirt = 1;
                }
                return i;
            }
            de = (struct ext2_dir_entry *) ((char *) de +
                            de->rec_len);
        }
        brelse (bh);
    }
    if (!IS_RDONLY(inode)) {
        inode->i_atime = CURRENT_TIME;
        inode->i_dirt = 1;
    }
    return 0;
}