1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * QNX4 file system, Linux implementation.
4  *
5  * Version : 0.2.1
6  *
7  * Using parts of the xiafs filesystem.
8  *
9  * History :
10  *
11  * 01-06-1998 by Richard Frowijn : first release.
12  * 21-06-1998 by Frank Denis : dcache support, fixed error codes.
13  * 04-07-1998 by Frank Denis : first step for rmdir/unlink.
14  */
15 
16 #include <linux/buffer_head.h>
17 #include "qnx4.h"
18 
19 
20 /*
21  * check if the filename is correct. For some obscure reason, qnx writes a
22  * new file twice in the directory entry, first with all possible options at 0
23  * and for a second time the way it is, they want us not to access the qnx
24  * filesystem when whe are using linux.
25  */
qnx4_match(int len,const char * name,struct buffer_head * bh,unsigned long * offset)26 static int qnx4_match(int len, const char *name,
27 		      struct buffer_head *bh, unsigned long *offset)
28 {
29 	struct qnx4_inode_entry *de;
30 	int namelen, thislen;
31 
32 	if (bh == NULL) {
33 		printk(KERN_WARNING "qnx4: matching unassigned buffer !\n");
34 		return 0;
35 	}
36 	de = (struct qnx4_inode_entry *) (bh->b_data + *offset);
37 	*offset += QNX4_DIR_ENTRY_SIZE;
38 	if ((de->di_status & QNX4_FILE_LINK) != 0) {
39 		namelen = QNX4_NAME_MAX;
40 	} else {
41 		namelen = QNX4_SHORT_NAME_MAX;
42 	}
43 	thislen = strlen( de->di_fname );
44 	if ( thislen > namelen )
45 		thislen = namelen;
46 	if (len != thislen) {
47 		return 0;
48 	}
49 	if (strncmp(name, de->di_fname, len) == 0) {
50 		if ((de->di_status & (QNX4_FILE_USED|QNX4_FILE_LINK)) != 0) {
51 			return 1;
52 		}
53 	}
54 	return 0;
55 }
56 
qnx4_find_entry(int len,struct inode * dir,const char * name,struct qnx4_inode_entry ** res_dir,int * ino)57 static struct buffer_head *qnx4_find_entry(int len, struct inode *dir,
58 	   const char *name, struct qnx4_inode_entry **res_dir, int *ino)
59 {
60 	unsigned long block, offset, blkofs;
61 	struct buffer_head *bh;
62 
63 	*res_dir = NULL;
64 	bh = NULL;
65 	block = offset = blkofs = 0;
66 	while (blkofs * QNX4_BLOCK_SIZE + offset < dir->i_size) {
67 		if (!bh) {
68 			block = qnx4_block_map(dir, blkofs);
69 			if (block)
70 				bh = sb_bread(dir->i_sb, block);
71 			if (!bh) {
72 				blkofs++;
73 				continue;
74 			}
75 		}
76 		*res_dir = (struct qnx4_inode_entry *) (bh->b_data + offset);
77 		if (qnx4_match(len, name, bh, &offset)) {
78 			*ino = block * QNX4_INODES_PER_BLOCK +
79 			    (offset / QNX4_DIR_ENTRY_SIZE) - 1;
80 			return bh;
81 		}
82 		if (offset < bh->b_size) {
83 			continue;
84 		}
85 		brelse(bh);
86 		bh = NULL;
87 		offset = 0;
88 		blkofs++;
89 	}
90 	brelse(bh);
91 	*res_dir = NULL;
92 	return NULL;
93 }
94 
qnx4_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)95 struct dentry * qnx4_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
96 {
97 	int ino;
98 	struct qnx4_inode_entry *de;
99 	struct qnx4_link_info *lnk;
100 	struct buffer_head *bh;
101 	const char *name = dentry->d_name.name;
102 	int len = dentry->d_name.len;
103 	struct inode *foundinode = NULL;
104 
105 	if (!(bh = qnx4_find_entry(len, dir, name, &de, &ino)))
106 		goto out;
107 	/* The entry is linked, let's get the real info */
108 	if ((de->di_status & QNX4_FILE_LINK) == QNX4_FILE_LINK) {
109 		lnk = (struct qnx4_link_info *) de;
110 		ino = (le32_to_cpu(lnk->dl_inode_blk) - 1) *
111                     QNX4_INODES_PER_BLOCK +
112 		    lnk->dl_inode_ndx;
113 	}
114 	brelse(bh);
115 
116 	foundinode = qnx4_iget(dir->i_sb, ino);
117 	if (IS_ERR(foundinode))
118 		QNX4DEBUG((KERN_ERR "qnx4: lookup->iget -> error %ld\n",
119 			   PTR_ERR(foundinode)));
120 out:
121 	return d_splice_alias(foundinode, dentry);
122 }
123