xref: /kernel/linux/linux-5.10/fs/omfs/dir.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * OMFS (as used by RIO Karma) directory operations.
4 * Copyright (C) 2005 Bob Copeland <me@bobcopeland.com>
5 */
6
7#include <linux/fs.h>
8#include <linux/ctype.h>
9#include <linux/buffer_head.h>
10#include "omfs.h"
11
12static int omfs_hash(const char *name, int namelen, int mod)
13{
14	int i, hash = 0;
15	for (i = 0; i < namelen; i++)
16		hash ^= tolower(name[i]) << (i % 24);
17	return hash % mod;
18}
19
20/*
21 * Finds the bucket for a given name and reads the containing block;
22 * *ofs is set to the offset of the first list entry.
23 */
24static struct buffer_head *omfs_get_bucket(struct inode *dir,
25		const char *name, int namelen, int *ofs)
26{
27	int nbuckets = (dir->i_size - OMFS_DIR_START)/8;
28	int bucket = omfs_hash(name, namelen, nbuckets);
29
30	*ofs = OMFS_DIR_START + bucket * 8;
31	return omfs_bread(dir->i_sb, dir->i_ino);
32}
33
34static struct buffer_head *omfs_scan_list(struct inode *dir, u64 block,
35				const char *name, int namelen,
36				u64 *prev_block)
37{
38	struct buffer_head *bh;
39	struct omfs_inode *oi;
40	int err = -ENOENT;
41	*prev_block = ~0;
42
43	while (block != ~0) {
44		bh = omfs_bread(dir->i_sb, block);
45		if (!bh) {
46			err = -EIO;
47			goto err;
48		}
49
50		oi = (struct omfs_inode *) bh->b_data;
51		if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, block)) {
52			brelse(bh);
53			goto err;
54		}
55
56		if (strncmp(oi->i_name, name, namelen) == 0)
57			return bh;
58
59		*prev_block = block;
60		block = be64_to_cpu(oi->i_sibling);
61		brelse(bh);
62	}
63err:
64	return ERR_PTR(err);
65}
66
67static struct buffer_head *omfs_find_entry(struct inode *dir,
68					   const char *name, int namelen)
69{
70	struct buffer_head *bh;
71	int ofs;
72	u64 block, dummy;
73
74	bh = omfs_get_bucket(dir, name, namelen, &ofs);
75	if (!bh)
76		return ERR_PTR(-EIO);
77
78	block = be64_to_cpu(*((__be64 *) &bh->b_data[ofs]));
79	brelse(bh);
80
81	return omfs_scan_list(dir, block, name, namelen, &dummy);
82}
83
84int omfs_make_empty(struct inode *inode, struct super_block *sb)
85{
86	struct omfs_sb_info *sbi = OMFS_SB(sb);
87	struct buffer_head *bh;
88	struct omfs_inode *oi;
89
90	bh = omfs_bread(sb, inode->i_ino);
91	if (!bh)
92		return -ENOMEM;
93
94	memset(bh->b_data, 0, sizeof(struct omfs_inode));
95
96	if (S_ISDIR(inode->i_mode)) {
97		memset(&bh->b_data[OMFS_DIR_START], 0xff,
98			sbi->s_sys_blocksize - OMFS_DIR_START);
99	} else
100		omfs_make_empty_table(bh, OMFS_EXTENT_START);
101
102	oi = (struct omfs_inode *) bh->b_data;
103	oi->i_head.h_self = cpu_to_be64(inode->i_ino);
104	oi->i_sibling = ~cpu_to_be64(0ULL);
105
106	mark_buffer_dirty(bh);
107	brelse(bh);
108	return 0;
109}
110
111static int omfs_add_link(struct dentry *dentry, struct inode *inode)
112{
113	struct inode *dir = d_inode(dentry->d_parent);
114	const char *name = dentry->d_name.name;
115	int namelen = dentry->d_name.len;
116	struct omfs_inode *oi;
117	struct buffer_head *bh;
118	u64 block;
119	__be64 *entry;
120	int ofs;
121
122	/* just prepend to head of queue in proper bucket */
123	bh = omfs_get_bucket(dir, name, namelen, &ofs);
124	if (!bh)
125		goto out;
126
127	entry = (__be64 *) &bh->b_data[ofs];
128	block = be64_to_cpu(*entry);
129	*entry = cpu_to_be64(inode->i_ino);
130	mark_buffer_dirty(bh);
131	brelse(bh);
132
133	/* now set the sibling and parent pointers on the new inode */
134	bh = omfs_bread(dir->i_sb, inode->i_ino);
135	if (!bh)
136		goto out;
137
138	oi = (struct omfs_inode *) bh->b_data;
139	memcpy(oi->i_name, name, namelen);
140	memset(oi->i_name + namelen, 0, OMFS_NAMELEN - namelen);
141	oi->i_sibling = cpu_to_be64(block);
142	oi->i_parent = cpu_to_be64(dir->i_ino);
143	mark_buffer_dirty(bh);
144	brelse(bh);
145
146	dir->i_ctime = current_time(dir);
147
148	/* mark affected inodes dirty to rebuild checksums */
149	mark_inode_dirty(dir);
150	mark_inode_dirty(inode);
151	return 0;
152out:
153	return -ENOMEM;
154}
155
156static int omfs_delete_entry(struct dentry *dentry)
157{
158	struct inode *dir = d_inode(dentry->d_parent);
159	struct inode *dirty;
160	const char *name = dentry->d_name.name;
161	int namelen = dentry->d_name.len;
162	struct omfs_inode *oi;
163	struct buffer_head *bh, *bh2;
164	__be64 *entry, next;
165	u64 block, prev;
166	int ofs;
167	int err = -ENOMEM;
168
169	/* delete the proper node in the bucket's linked list */
170	bh = omfs_get_bucket(dir, name, namelen, &ofs);
171	if (!bh)
172		goto out;
173
174	entry = (__be64 *) &bh->b_data[ofs];
175	block = be64_to_cpu(*entry);
176
177	bh2 = omfs_scan_list(dir, block, name, namelen, &prev);
178	if (IS_ERR(bh2)) {
179		err = PTR_ERR(bh2);
180		goto out_free_bh;
181	}
182
183	oi = (struct omfs_inode *) bh2->b_data;
184	next = oi->i_sibling;
185	brelse(bh2);
186
187	if (prev != ~0) {
188		/* found in middle of list, get list ptr */
189		brelse(bh);
190		bh = omfs_bread(dir->i_sb, prev);
191		if (!bh)
192			goto out;
193
194		oi = (struct omfs_inode *) bh->b_data;
195		entry = &oi->i_sibling;
196	}
197
198	*entry = next;
199	mark_buffer_dirty(bh);
200
201	if (prev != ~0) {
202		dirty = omfs_iget(dir->i_sb, prev);
203		if (!IS_ERR(dirty)) {
204			mark_inode_dirty(dirty);
205			iput(dirty);
206		}
207	}
208
209	err = 0;
210out_free_bh:
211	brelse(bh);
212out:
213	return err;
214}
215
216static int omfs_dir_is_empty(struct inode *inode)
217{
218	int nbuckets = (inode->i_size - OMFS_DIR_START) / 8;
219	struct buffer_head *bh;
220	u64 *ptr;
221	int i;
222
223	bh = omfs_bread(inode->i_sb, inode->i_ino);
224
225	if (!bh)
226		return 0;
227
228	ptr = (u64 *) &bh->b_data[OMFS_DIR_START];
229
230	for (i = 0; i < nbuckets; i++, ptr++)
231		if (*ptr != ~0)
232			break;
233
234	brelse(bh);
235	return *ptr != ~0;
236}
237
238static int omfs_remove(struct inode *dir, struct dentry *dentry)
239{
240	struct inode *inode = d_inode(dentry);
241	int ret;
242
243
244	if (S_ISDIR(inode->i_mode) &&
245	    !omfs_dir_is_empty(inode))
246		return -ENOTEMPTY;
247
248	ret = omfs_delete_entry(dentry);
249	if (ret)
250		return ret;
251
252	clear_nlink(inode);
253	mark_inode_dirty(inode);
254	mark_inode_dirty(dir);
255	return 0;
256}
257
258static int omfs_add_node(struct inode *dir, struct dentry *dentry, umode_t mode)
259{
260	int err;
261	struct inode *inode = omfs_new_inode(dir, mode);
262
263	if (IS_ERR(inode))
264		return PTR_ERR(inode);
265
266	err = omfs_make_empty(inode, dir->i_sb);
267	if (err)
268		goto out_free_inode;
269
270	err = omfs_add_link(dentry, inode);
271	if (err)
272		goto out_free_inode;
273
274	d_instantiate(dentry, inode);
275	return 0;
276
277out_free_inode:
278	iput(inode);
279	return err;
280}
281
282static int omfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
283{
284	return omfs_add_node(dir, dentry, mode | S_IFDIR);
285}
286
287static int omfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
288		bool excl)
289{
290	return omfs_add_node(dir, dentry, mode | S_IFREG);
291}
292
293static struct dentry *omfs_lookup(struct inode *dir, struct dentry *dentry,
294				  unsigned int flags)
295{
296	struct buffer_head *bh;
297	struct inode *inode = NULL;
298
299	if (dentry->d_name.len > OMFS_NAMELEN)
300		return ERR_PTR(-ENAMETOOLONG);
301
302	bh = omfs_find_entry(dir, dentry->d_name.name, dentry->d_name.len);
303	if (!IS_ERR(bh)) {
304		struct omfs_inode *oi = (struct omfs_inode *)bh->b_data;
305		ino_t ino = be64_to_cpu(oi->i_head.h_self);
306		brelse(bh);
307		inode = omfs_iget(dir->i_sb, ino);
308	} else if (bh != ERR_PTR(-ENOENT)) {
309		inode = ERR_CAST(bh);
310	}
311	return d_splice_alias(inode, dentry);
312}
313
314/* sanity check block's self pointer */
315int omfs_is_bad(struct omfs_sb_info *sbi, struct omfs_header *header,
316	u64 fsblock)
317{
318	int is_bad;
319	u64 ino = be64_to_cpu(header->h_self);
320	is_bad = ((ino != fsblock) || (ino < sbi->s_root_ino) ||
321		(ino > sbi->s_num_blocks));
322
323	if (is_bad)
324		printk(KERN_WARNING "omfs: bad hash chain detected\n");
325
326	return is_bad;
327}
328
329static bool omfs_fill_chain(struct inode *dir, struct dir_context *ctx,
330		u64 fsblock, int hindex)
331{
332	/* follow chain in this bucket */
333	while (fsblock != ~0) {
334		struct buffer_head *bh = omfs_bread(dir->i_sb, fsblock);
335		struct omfs_inode *oi;
336		u64 self;
337		unsigned char d_type;
338
339		if (!bh)
340			return true;
341
342		oi = (struct omfs_inode *) bh->b_data;
343		if (omfs_is_bad(OMFS_SB(dir->i_sb), &oi->i_head, fsblock)) {
344			brelse(bh);
345			return true;
346		}
347
348		self = fsblock;
349		fsblock = be64_to_cpu(oi->i_sibling);
350
351		/* skip visited nodes */
352		if (hindex) {
353			hindex--;
354			brelse(bh);
355			continue;
356		}
357
358		d_type = (oi->i_type == OMFS_DIR) ? DT_DIR : DT_REG;
359
360		if (!dir_emit(ctx, oi->i_name,
361			      strnlen(oi->i_name, OMFS_NAMELEN),
362			      self, d_type)) {
363			brelse(bh);
364			return false;
365		}
366		brelse(bh);
367		ctx->pos++;
368	}
369	return true;
370}
371
372static int omfs_rename(struct inode *old_dir, struct dentry *old_dentry,
373		       struct inode *new_dir, struct dentry *new_dentry,
374		       unsigned int flags)
375{
376	struct inode *new_inode = d_inode(new_dentry);
377	struct inode *old_inode = d_inode(old_dentry);
378	int err;
379
380	if (flags & ~RENAME_NOREPLACE)
381		return -EINVAL;
382
383	if (new_inode) {
384		/* overwriting existing file/dir */
385		err = omfs_remove(new_dir, new_dentry);
386		if (err)
387			goto out;
388	}
389
390	/* since omfs locates files by name, we need to unlink _before_
391	 * adding the new link or we won't find the old one */
392	err = omfs_delete_entry(old_dentry);
393	if (err)
394		goto out;
395
396	mark_inode_dirty(old_dir);
397	err = omfs_add_link(new_dentry, old_inode);
398	if (err)
399		goto out;
400
401	old_inode->i_ctime = current_time(old_inode);
402	mark_inode_dirty(old_inode);
403out:
404	return err;
405}
406
407static int omfs_readdir(struct file *file, struct dir_context *ctx)
408{
409	struct inode *dir = file_inode(file);
410	struct buffer_head *bh;
411	__be64 *p;
412	unsigned int hchain, hindex;
413	int nbuckets;
414
415	if (ctx->pos >> 32)
416		return -EINVAL;
417
418	if (ctx->pos < 1 << 20) {
419		if (!dir_emit_dots(file, ctx))
420			return 0;
421		ctx->pos = 1 << 20;
422	}
423
424	nbuckets = (dir->i_size - OMFS_DIR_START) / 8;
425
426	/* high 12 bits store bucket + 1 and low 20 bits store hash index */
427	hchain = (ctx->pos >> 20) - 1;
428	hindex = ctx->pos & 0xfffff;
429
430	bh = omfs_bread(dir->i_sb, dir->i_ino);
431	if (!bh)
432		return -EINVAL;
433
434	p = (__be64 *)(bh->b_data + OMFS_DIR_START) + hchain;
435
436	for (; hchain < nbuckets; hchain++) {
437		__u64 fsblock = be64_to_cpu(*p++);
438		if (!omfs_fill_chain(dir, ctx, fsblock, hindex))
439			break;
440		hindex = 0;
441		ctx->pos = (hchain+2) << 20;
442	}
443	brelse(bh);
444	return 0;
445}
446
447const struct inode_operations omfs_dir_inops = {
448	.lookup = omfs_lookup,
449	.mkdir = omfs_mkdir,
450	.rename = omfs_rename,
451	.create = omfs_create,
452	.unlink = omfs_remove,
453	.rmdir = omfs_remove,
454};
455
456const struct file_operations omfs_dir_operations = {
457	.read = generic_read_dir,
458	.iterate_shared = omfs_readdir,
459	.llseek = generic_file_llseek,
460};
461