namei.c

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/* 
 * QNX4 file system, Linux implementation.
 * 
 * Version : 0.2.1
 * 
 * Using parts of the xiafs filesystem.
 * 
 * History :
 * 
 * 01-06-1998 by Richard Frowijn : first release.
 * 21-06-1998 by Frank Denis : dcache support, fixed error codes.
 * 04-07-1998 by Frank Denis : first step for rmdir/unlink.
 */

#include <linux/buffer_head.h>
#include "qnx4.h"


/*
 * check if the filename is correct. For some obscure reason, qnx writes a
 * new file twice in the directory entry, first with all possible options at 0
 * and for a second time the way it is, they want us not to access the qnx
 * filesystem when whe are using linux.
 */
static int qnx4_match(int len, const char *name,
              struct buffer_head *bh, unsigned long *offset)
{
    struct qnx4_inode_entry *de;
    int namelen, thislen;

    if (bh == NULL) {
        printk(KERN_WARNING "qnx4: matching unassigned buffer !\n");
        return 0;
    }
    de = (struct qnx4_inode_entry *) (bh->b_data + *offset);
    *offset += QNX4_DIR_ENTRY_SIZE;
    if ((de->di_status & QNX4_FILE_LINK) != 0) {
        namelen = QNX4_NAME_MAX;
    } else {
        namelen = QNX4_SHORT_NAME_MAX;
    }
    thislen = strlen( de->di_fname );
    if ( thislen > namelen )
        thislen = namelen;
    if (len != thislen) {
        return 0;
    }
    if (strncmp(name, de->di_fname, len) == 0) {
        if ((de->di_status & (QNX4_FILE_USED|QNX4_FILE_LINK)) != 0) {
            return 1;
        }
    }
    return 0;
}

static struct buffer_head *qnx4_find_entry(int len, struct inode *dir,
       const char *name, struct qnx4_inode_entry **res_dir, int *ino)
{
    unsigned long block, offset, blkofs;
    struct buffer_head *bh;

    *res_dir = NULL;
    if (!dir->i_sb) {
        printk(KERN_WARNING "qnx4: no superblock on dir.\n");
        return NULL;
    }
    bh = NULL;
    block = offset = blkofs = 0;
    while (blkofs * QNX4_BLOCK_SIZE + offset < dir->i_size) {
        if (!bh) {
            block = qnx4_block_map(dir, blkofs);
            if (block)
                bh = sb_bread(dir->i_sb, block);
            if (!bh) {
                blkofs++;
                continue;
            }
        }
        *res_dir = (struct qnx4_inode_entry *) (bh->b_data + offset);
        if (qnx4_match(len, name, bh, &offset)) {
            *ino = block * QNX4_INODES_PER_BLOCK +
                (offset / QNX4_DIR_ENTRY_SIZE) - 1;
            return bh;
        }
        if (offset < bh->b_size) {
            continue;
        }
        brelse(bh);
        bh = NULL;
        offset = 0;
        blkofs++;
    }
    brelse(bh);
    *res_dir = NULL;
    return NULL;
}

struct dentry * qnx4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
    int ino;
    struct qnx4_inode_entry *de;
    struct qnx4_link_info *lnk;
    struct buffer_head *bh;
    const char *name = dentry->d_name.name;
    int len = dentry->d_name.len;
    struct inode *foundinode = NULL;

    if (!(bh = qnx4_find_entry(len, dir, name, &de, &ino)))
        goto out;
    /* The entry is linked, let's get the real info */
    if ((de->di_status & QNX4_FILE_LINK) == QNX4_FILE_LINK) {
        lnk = (struct qnx4_link_info *) de;
        ino = (le32_to_cpu(lnk->dl_inode_blk) - 1) *
                    QNX4_INODES_PER_BLOCK +
            lnk->dl_inode_ndx;
    }
    brelse(bh);

    foundinode = qnx4_iget(dir->i_sb, ino);
    if (IS_ERR(foundinode)) {
        QNX4DEBUG((KERN_ERR "qnx4: lookup->iget -> error %ld\n",
               PTR_ERR(foundinode)));
        return ERR_CAST(foundinode);
    }
out:
    d_add(dentry, foundinode);

    return NULL;
}