xref: /kernel/linux/linux-5.10/fs/qnx4/dir.c (revision 8c2ecf20) 
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 * 28-05-1998 by Richard Frowijn : first release.
12 * 20-06-1998 by Frank Denis : Linux 2.1.99+ & dcache support.
13 */
14
15#include <linux/buffer_head.h>
16#include "qnx4.h"
17
18/*
19 * A qnx4 directory entry is an inode entry or link info
20 * depending on the status field in the last byte. The
21 * first byte is where the name start either way, and a
22 * zero means it's empty.
23 *
24 * Also, due to a bug in gcc, we don't want to use the
25 * real (differently sized) name arrays in the inode and
26 * link entries, but always the 'de_name[]' one in the
27 * fake struct entry.
28 *
29 * See
30 *
31 *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
32 *
33 * for details, but basically gcc will take the size of the
34 * 'name' array from one of the used union entries randomly.
35 *
36 * This use of 'de_name[]' (48 bytes) avoids the false positive
37 * warnings that would happen if gcc decides to use 'inode.di_name'
38 * (16 bytes) even when the pointer and size were to come from
39 * 'link.dl_name' (48 bytes).
40 *
41 * In all cases the actual name pointer itself is the same, it's
42 * only the gcc internal 'what is the size of this field' logic
43 * that can get confused.
44 */
45union qnx4_directory_entry {
46	struct {
47		const char de_name[48];
48		u8 de_pad[15];
49		u8 de_status;
50	};
51	struct qnx4_inode_entry inode;
52	struct qnx4_link_info link;
53};
54
55static int qnx4_readdir(struct file *file, struct dir_context *ctx)
56{
57	struct inode *inode = file_inode(file);
58	unsigned int offset;
59	struct buffer_head *bh;
60	unsigned long blknum;
61	int ix, ino;
62	int size;
63
64	QNX4DEBUG((KERN_INFO "qnx4_readdir:i_size = %ld\n", (long) inode->i_size));
65	QNX4DEBUG((KERN_INFO "pos                 = %ld\n", (long) ctx->pos));
66
67	while (ctx->pos < inode->i_size) {
68		blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
69		bh = sb_bread(inode->i_sb, blknum);
70		if (bh == NULL) {
71			printk(KERN_ERR "qnx4_readdir: bread failed (%ld)\n", blknum);
72			return 0;
73		}
74		ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
75		for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
76			union qnx4_directory_entry *de;
77
78			offset = ix * QNX4_DIR_ENTRY_SIZE;
79			de = (union qnx4_directory_entry *) (bh->b_data + offset);
80
81			if (!de->de_name[0])
82				continue;
83			if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
84				continue;
85			if (!(de->de_status & QNX4_FILE_LINK)) {
86				size = sizeof(de->inode.di_fname);
87				ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
88			} else {
89				size = sizeof(de->link.dl_fname);
90				ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
91					QNX4_INODES_PER_BLOCK +
92					de->link.dl_inode_ndx;
93			}
94			size = strnlen(de->de_name, size);
95			QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
96			if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
97				brelse(bh);
98				return 0;
99			}
100		}
101		brelse(bh);
102	}
103	return 0;
104}
105
106const struct file_operations qnx4_dir_operations =
107{
108	.llseek		= generic_file_llseek,
109	.read		= generic_read_dir,
110	.iterate_shared	= qnx4_readdir,
111	.fsync		= generic_file_fsync,
112};
113
114const struct inode_operations qnx4_dir_inode_operations =
115{
116	.lookup		= qnx4_lookup,
117};
118