1/*
2 *  linux/fs/minix/dir.c
3 *
4 *  Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 *  minix directory handling functions
7 *
8 *  Updated to filesystem version 3 by Daniel Aragones
9 */
10
11#include "minix.h"
12#include <linux/buffer_head.h>
13#include <linux/highmem.h>
14#include <linux/swap.h>
15
16typedef struct minix_dir_entry minix_dirent;
17typedef struct minix3_dir_entry minix3_dirent;
18
19static int minix_readdir(struct file *, struct dir_context *);
20
21const struct file_operations minix_dir_operations = {
22	.llseek		= generic_file_llseek,
23	.read		= generic_read_dir,
24	.iterate	= minix_readdir,
25	.fsync		= generic_file_fsync,
26};
27
28static inline void dir_put_page(struct page *page)
29{
30	kunmap(page);
31	page_cache_release(page);
32}
33
34/*
35 * Return the offset into page `page_nr' of the last valid
36 * byte in that page, plus one.
37 */
38static unsigned
39minix_last_byte(struct inode *inode, unsigned long page_nr)
40{
41	unsigned last_byte = PAGE_CACHE_SIZE;
42
43	if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
44		last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
45	return last_byte;
46}
47
48static inline unsigned long dir_pages(struct inode *inode)
49{
50	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
51}
52
53static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
54{
55	struct address_space *mapping = page->mapping;
56	struct inode *dir = mapping->host;
57	int err = 0;
58	block_write_end(NULL, mapping, pos, len, len, page, NULL);
59
60	if (pos+len > dir->i_size) {
61		i_size_write(dir, pos+len);
62		mark_inode_dirty(dir);
63	}
64	if (IS_DIRSYNC(dir))
65		err = write_one_page(page, 1);
66	else
67		unlock_page(page);
68	return err;
69}
70
71static struct page * dir_get_page(struct inode *dir, unsigned long n)
72{
73	struct address_space *mapping = dir->i_mapping;
74	struct page *page = read_mapping_page(mapping, n, NULL);
75	if (!IS_ERR(page))
76		kmap(page);
77	return page;
78}
79
80static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
81{
82	return (void*)((char*)de + sbi->s_dirsize);
83}
84
85static int minix_readdir(struct file *file, struct dir_context *ctx)
86{
87	struct inode *inode = file_inode(file);
88	struct super_block *sb = inode->i_sb;
89	struct minix_sb_info *sbi = minix_sb(sb);
90	unsigned chunk_size = sbi->s_dirsize;
91	unsigned long npages = dir_pages(inode);
92	unsigned long pos = ctx->pos;
93	unsigned offset;
94	unsigned long n;
95
96	ctx->pos = pos = ALIGN(pos, chunk_size);
97	if (pos >= inode->i_size)
98		return 0;
99
100	offset = pos & ~PAGE_CACHE_MASK;
101	n = pos >> PAGE_CACHE_SHIFT;
102
103	for ( ; n < npages; n++, offset = 0) {
104		char *p, *kaddr, *limit;
105		struct page *page = dir_get_page(inode, n);
106
107		if (IS_ERR(page))
108			continue;
109		kaddr = (char *)page_address(page);
110		p = kaddr+offset;
111		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
112		for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
113			const char *name;
114			__u32 inumber;
115			if (sbi->s_version == MINIX_V3) {
116				minix3_dirent *de3 = (minix3_dirent *)p;
117				name = de3->name;
118				inumber = de3->inode;
119	 		} else {
120				minix_dirent *de = (minix_dirent *)p;
121				name = de->name;
122				inumber = de->inode;
123			}
124			if (inumber) {
125				unsigned l = strnlen(name, sbi->s_namelen);
126				if (!dir_emit(ctx, name, l,
127					      inumber, DT_UNKNOWN)) {
128					dir_put_page(page);
129					return 0;
130				}
131			}
132			ctx->pos += chunk_size;
133		}
134		dir_put_page(page);
135	}
136	return 0;
137}
138
139static inline int namecompare(int len, int maxlen,
140	const char * name, const char * buffer)
141{
142	if (len < maxlen && buffer[len])
143		return 0;
144	return !memcmp(name, buffer, len);
145}
146
147/*
148 *	minix_find_entry()
149 *
150 * finds an entry in the specified directory with the wanted name. It
151 * returns the cache buffer in which the entry was found, and the entry
152 * itself (as a parameter - res_dir). It does NOT read the inode of the
153 * entry - you'll have to do that yourself if you want to.
154 */
155minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
156{
157	const char * name = dentry->d_name.name;
158	int namelen = dentry->d_name.len;
159	struct inode * dir = d_inode(dentry->d_parent);
160	struct super_block * sb = dir->i_sb;
161	struct minix_sb_info * sbi = minix_sb(sb);
162	unsigned long n;
163	unsigned long npages = dir_pages(dir);
164	struct page *page = NULL;
165	char *p;
166
167	char *namx;
168	__u32 inumber;
169	*res_page = NULL;
170
171	for (n = 0; n < npages; n++) {
172		char *kaddr, *limit;
173
174		page = dir_get_page(dir, n);
175		if (IS_ERR(page))
176			continue;
177
178		kaddr = (char*)page_address(page);
179		limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
180		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
181			if (sbi->s_version == MINIX_V3) {
182				minix3_dirent *de3 = (minix3_dirent *)p;
183				namx = de3->name;
184				inumber = de3->inode;
185 			} else {
186				minix_dirent *de = (minix_dirent *)p;
187				namx = de->name;
188				inumber = de->inode;
189			}
190			if (!inumber)
191				continue;
192			if (namecompare(namelen, sbi->s_namelen, name, namx))
193				goto found;
194		}
195		dir_put_page(page);
196	}
197	return NULL;
198
199found:
200	*res_page = page;
201	return (minix_dirent *)p;
202}
203
204int minix_add_link(struct dentry *dentry, struct inode *inode)
205{
206	struct inode *dir = d_inode(dentry->d_parent);
207	const char * name = dentry->d_name.name;
208	int namelen = dentry->d_name.len;
209	struct super_block * sb = dir->i_sb;
210	struct minix_sb_info * sbi = minix_sb(sb);
211	struct page *page = NULL;
212	unsigned long npages = dir_pages(dir);
213	unsigned long n;
214	char *kaddr, *p;
215	minix_dirent *de;
216	minix3_dirent *de3;
217	loff_t pos;
218	int err;
219	char *namx = NULL;
220	__u32 inumber;
221
222	/*
223	 * We take care of directory expansion in the same loop
224	 * This code plays outside i_size, so it locks the page
225	 * to protect that region.
226	 */
227	for (n = 0; n <= npages; n++) {
228		char *limit, *dir_end;
229
230		page = dir_get_page(dir, n);
231		err = PTR_ERR(page);
232		if (IS_ERR(page))
233			goto out;
234		lock_page(page);
235		kaddr = (char*)page_address(page);
236		dir_end = kaddr + minix_last_byte(dir, n);
237		limit = kaddr + PAGE_CACHE_SIZE - sbi->s_dirsize;
238		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
239			de = (minix_dirent *)p;
240			de3 = (minix3_dirent *)p;
241			if (sbi->s_version == MINIX_V3) {
242				namx = de3->name;
243				inumber = de3->inode;
244		 	} else {
245  				namx = de->name;
246				inumber = de->inode;
247			}
248			if (p == dir_end) {
249				/* We hit i_size */
250				if (sbi->s_version == MINIX_V3)
251					de3->inode = 0;
252		 		else
253					de->inode = 0;
254				goto got_it;
255			}
256			if (!inumber)
257				goto got_it;
258			err = -EEXIST;
259			if (namecompare(namelen, sbi->s_namelen, name, namx))
260				goto out_unlock;
261		}
262		unlock_page(page);
263		dir_put_page(page);
264	}
265	BUG();
266	return -EINVAL;
267
268got_it:
269	pos = page_offset(page) + p - (char *)page_address(page);
270	err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
271	if (err)
272		goto out_unlock;
273	memcpy (namx, name, namelen);
274	if (sbi->s_version == MINIX_V3) {
275		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
276		de3->inode = inode->i_ino;
277	} else {
278		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
279		de->inode = inode->i_ino;
280	}
281	err = dir_commit_chunk(page, pos, sbi->s_dirsize);
282	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
283	mark_inode_dirty(dir);
284out_put:
285	dir_put_page(page);
286out:
287	return err;
288out_unlock:
289	unlock_page(page);
290	goto out_put;
291}
292
293int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
294{
295	struct inode *inode = page->mapping->host;
296	char *kaddr = page_address(page);
297	loff_t pos = page_offset(page) + (char*)de - kaddr;
298	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
299	unsigned len = sbi->s_dirsize;
300	int err;
301
302	lock_page(page);
303	err = minix_prepare_chunk(page, pos, len);
304	if (err == 0) {
305		if (sbi->s_version == MINIX_V3)
306			((minix3_dirent *) de)->inode = 0;
307		else
308			de->inode = 0;
309		err = dir_commit_chunk(page, pos, len);
310	} else {
311		unlock_page(page);
312	}
313	dir_put_page(page);
314	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
315	mark_inode_dirty(inode);
316	return err;
317}
318
319int minix_make_empty(struct inode *inode, struct inode *dir)
320{
321	struct page *page = grab_cache_page(inode->i_mapping, 0);
322	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
323	char *kaddr;
324	int err;
325
326	if (!page)
327		return -ENOMEM;
328	err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize);
329	if (err) {
330		unlock_page(page);
331		goto fail;
332	}
333
334	kaddr = kmap_atomic(page);
335	memset(kaddr, 0, PAGE_CACHE_SIZE);
336
337	if (sbi->s_version == MINIX_V3) {
338		minix3_dirent *de3 = (minix3_dirent *)kaddr;
339
340		de3->inode = inode->i_ino;
341		strcpy(de3->name, ".");
342		de3 = minix_next_entry(de3, sbi);
343		de3->inode = dir->i_ino;
344		strcpy(de3->name, "..");
345	} else {
346		minix_dirent *de = (minix_dirent *)kaddr;
347
348		de->inode = inode->i_ino;
349		strcpy(de->name, ".");
350		de = minix_next_entry(de, sbi);
351		de->inode = dir->i_ino;
352		strcpy(de->name, "..");
353	}
354	kunmap_atomic(kaddr);
355
356	err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
357fail:
358	page_cache_release(page);
359	return err;
360}
361
362/*
363 * routine to check that the specified directory is empty (for rmdir)
364 */
365int minix_empty_dir(struct inode * inode)
366{
367	struct page *page = NULL;
368	unsigned long i, npages = dir_pages(inode);
369	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
370	char *name;
371	__u32 inumber;
372
373	for (i = 0; i < npages; i++) {
374		char *p, *kaddr, *limit;
375
376		page = dir_get_page(inode, i);
377		if (IS_ERR(page))
378			continue;
379
380		kaddr = (char *)page_address(page);
381		limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
382		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
383			if (sbi->s_version == MINIX_V3) {
384				minix3_dirent *de3 = (minix3_dirent *)p;
385				name = de3->name;
386				inumber = de3->inode;
387			} else {
388				minix_dirent *de = (minix_dirent *)p;
389				name = de->name;
390				inumber = de->inode;
391			}
392
393			if (inumber != 0) {
394				/* check for . and .. */
395				if (name[0] != '.')
396					goto not_empty;
397				if (!name[1]) {
398					if (inumber != inode->i_ino)
399						goto not_empty;
400				} else if (name[1] != '.')
401					goto not_empty;
402				else if (name[2])
403					goto not_empty;
404			}
405		}
406		dir_put_page(page);
407	}
408	return 1;
409
410not_empty:
411	dir_put_page(page);
412	return 0;
413}
414
415/* Releases the page */
416void minix_set_link(struct minix_dir_entry *de, struct page *page,
417	struct inode *inode)
418{
419	struct inode *dir = page->mapping->host;
420	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
421	loff_t pos = page_offset(page) +
422			(char *)de-(char*)page_address(page);
423	int err;
424
425	lock_page(page);
426
427	err = minix_prepare_chunk(page, pos, sbi->s_dirsize);
428	if (err == 0) {
429		if (sbi->s_version == MINIX_V3)
430			((minix3_dirent *) de)->inode = inode->i_ino;
431		else
432			de->inode = inode->i_ino;
433		err = dir_commit_chunk(page, pos, sbi->s_dirsize);
434	} else {
435		unlock_page(page);
436	}
437	dir_put_page(page);
438	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
439	mark_inode_dirty(dir);
440}
441
442struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
443{
444	struct page *page = dir_get_page(dir, 0);
445	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
446	struct minix_dir_entry *de = NULL;
447
448	if (!IS_ERR(page)) {
449		de = minix_next_entry(page_address(page), sbi);
450		*p = page;
451	}
452	return de;
453}
454
455ino_t minix_inode_by_name(struct dentry *dentry)
456{
457	struct page *page;
458	struct minix_dir_entry *de = minix_find_entry(dentry, &page);
459	ino_t res = 0;
460
461	if (de) {
462		struct address_space *mapping = page->mapping;
463		struct inode *inode = mapping->host;
464		struct minix_sb_info *sbi = minix_sb(inode->i_sb);
465
466		if (sbi->s_version == MINIX_V3)
467			res = ((minix3_dirent *) de)->inode;
468		else
469			res = de->inode;
470		dir_put_page(page);
471	}
472	return res;
473}
474