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