// SPDX-License-Identifier: GPL-2.0
/* 
 * 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)
{
        union qnx4_directory_entry *de;
        const char *fname;
        int fnamelen;

        if (bh == NULL) {
                printk(KERN_WARNING "qnx4: matching unassigned buffer !\n");
                return 0;
        }
        de = (union qnx4_directory_entry *) (bh->b_data + *offset);
        *offset += QNX4_DIR_ENTRY_SIZE;

        fname = get_entry_fname(de, &fnamelen);
        if (!fname || len != fnamelen)
                return 0;

        if (strncmp(name, fname, len) == 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;
        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)));
out:
        return d_splice_alias(foundinode, dentry);
}