xref: /openbmc/linux/fs/minix/dir.c (revision 367b8112) 
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/smp_lock.h>
15 #include <linux/swap.h>
16 
17 typedef struct minix_dir_entry minix_dirent;
18 typedef struct minix3_dir_entry minix3_dirent;
19 
20 static int minix_readdir(struct file *, void *, filldir_t);
21 
22 const struct file_operations minix_dir_operations = {
23 	.read		= generic_read_dir,
24 	.readdir	= minix_readdir,
25 	.fsync		= minix_sync_file,
26 };
27 
28 static 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  */
38 static unsigned
39 minix_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 
48 static inline unsigned long dir_pages(struct inode *inode)
49 {
50 	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
51 }
52 
53 static 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 
71 static 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 		if (!PageUptodate(page))
78 			goto fail;
79 	}
80 	return page;
81 
82 fail:
83 	dir_put_page(page);
84 	return ERR_PTR(-EIO);
85 }
86 
87 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
88 {
89 	return (void*)((char*)de + sbi->s_dirsize);
90 }
91 
92 static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)
93 {
94 	unsigned long pos = filp->f_pos;
95 	struct inode *inode = filp->f_path.dentry->d_inode;
96 	struct super_block *sb = inode->i_sb;
97 	unsigned offset = pos & ~PAGE_CACHE_MASK;
98 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
99 	unsigned long npages = dir_pages(inode);
100 	struct minix_sb_info *sbi = minix_sb(sb);
101 	unsigned chunk_size = sbi->s_dirsize;
102 	char *name;
103 	__u32 inumber;
104 
105 	lock_kernel();
106 
107 	pos = (pos + chunk_size-1) & ~(chunk_size-1);
108 	if (pos >= inode->i_size)
109 		goto done;
110 
111 	for ( ; n < npages; n++, offset = 0) {
112 		char *p, *kaddr, *limit;
113 		struct page *page = dir_get_page(inode, n);
114 
115 		if (IS_ERR(page))
116 			continue;
117 		kaddr = (char *)page_address(page);
118 		p = kaddr+offset;
119 		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
120 		for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
121 			if (sbi->s_version == MINIX_V3) {
122 				minix3_dirent *de3 = (minix3_dirent *)p;
123 				name = de3->name;
124 				inumber = de3->inode;
125 	 		} else {
126 				minix_dirent *de = (minix_dirent *)p;
127 				name = de->name;
128 				inumber = de->inode;
129 			}
130 			if (inumber) {
131 				int over;
132 
133 				unsigned l = strnlen(name, sbi->s_namelen);
134 				offset = p - kaddr;
135 				over = filldir(dirent, name, l,
136 					(n << PAGE_CACHE_SHIFT) | offset,
137 					inumber, DT_UNKNOWN);
138 				if (over) {
139 					dir_put_page(page);
140 					goto done;
141 				}
142 			}
143 		}
144 		dir_put_page(page);
145 	}
146 
147 done:
148 	filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
149 	unlock_kernel();
150 	return 0;
151 }
152 
153 static inline int namecompare(int len, int maxlen,
154 	const char * name, const char * buffer)
155 {
156 	if (len < maxlen && buffer[len])
157 		return 0;
158 	return !memcmp(name, buffer, len);
159 }
160 
161 /*
162  *	minix_find_entry()
163  *
164  * finds an entry in the specified directory with the wanted name. It
165  * returns the cache buffer in which the entry was found, and the entry
166  * itself (as a parameter - res_dir). It does NOT read the inode of the
167  * entry - you'll have to do that yourself if you want to.
168  */
169 minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
170 {
171 	const char * name = dentry->d_name.name;
172 	int namelen = dentry->d_name.len;
173 	struct inode * dir = dentry->d_parent->d_inode;
174 	struct super_block * sb = dir->i_sb;
175 	struct minix_sb_info * sbi = minix_sb(sb);
176 	unsigned long n;
177 	unsigned long npages = dir_pages(dir);
178 	struct page *page = NULL;
179 	char *p;
180 
181 	char *namx;
182 	__u32 inumber;
183 	*res_page = NULL;
184 
185 	for (n = 0; n < npages; n++) {
186 		char *kaddr, *limit;
187 
188 		page = dir_get_page(dir, n);
189 		if (IS_ERR(page))
190 			continue;
191 
192 		kaddr = (char*)page_address(page);
193 		limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
194 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
195 			if (sbi->s_version == MINIX_V3) {
196 				minix3_dirent *de3 = (minix3_dirent *)p;
197 				namx = de3->name;
198 				inumber = de3->inode;
199  			} else {
200 				minix_dirent *de = (minix_dirent *)p;
201 				namx = de->name;
202 				inumber = de->inode;
203 			}
204 			if (!inumber)
205 				continue;
206 			if (namecompare(namelen, sbi->s_namelen, name, namx))
207 				goto found;
208 		}
209 		dir_put_page(page);
210 	}
211 	return NULL;
212 
213 found:
214 	*res_page = page;
215 	return (minix_dirent *)p;
216 }
217 
218 int minix_add_link(struct dentry *dentry, struct inode *inode)
219 {
220 	struct inode *dir = dentry->d_parent->d_inode;
221 	const char * name = dentry->d_name.name;
222 	int namelen = dentry->d_name.len;
223 	struct super_block * sb = dir->i_sb;
224 	struct minix_sb_info * sbi = minix_sb(sb);
225 	struct page *page = NULL;
226 	unsigned long npages = dir_pages(dir);
227 	unsigned long n;
228 	char *kaddr, *p;
229 	minix_dirent *de;
230 	minix3_dirent *de3;
231 	loff_t pos;
232 	int err;
233 	char *namx = NULL;
234 	__u32 inumber;
235 
236 	/*
237 	 * We take care of directory expansion in the same loop
238 	 * This code plays outside i_size, so it locks the page
239 	 * to protect that region.
240 	 */
241 	for (n = 0; n <= npages; n++) {
242 		char *limit, *dir_end;
243 
244 		page = dir_get_page(dir, n);
245 		err = PTR_ERR(page);
246 		if (IS_ERR(page))
247 			goto out;
248 		lock_page(page);
249 		kaddr = (char*)page_address(page);
250 		dir_end = kaddr + minix_last_byte(dir, n);
251 		limit = kaddr + PAGE_CACHE_SIZE - sbi->s_dirsize;
252 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
253 			de = (minix_dirent *)p;
254 			de3 = (minix3_dirent *)p;
255 			if (sbi->s_version == MINIX_V3) {
256 				namx = de3->name;
257 				inumber = de3->inode;
258 		 	} else {
259   				namx = de->name;
260 				inumber = de->inode;
261 			}
262 			if (p == dir_end) {
263 				/* We hit i_size */
264 				if (sbi->s_version == MINIX_V3)
265 					de3->inode = 0;
266 		 		else
267 					de->inode = 0;
268 				goto got_it;
269 			}
270 			if (!inumber)
271 				goto got_it;
272 			err = -EEXIST;
273 			if (namecompare(namelen, sbi->s_namelen, name, namx))
274 				goto out_unlock;
275 		}
276 		unlock_page(page);
277 		dir_put_page(page);
278 	}
279 	BUG();
280 	return -EINVAL;
281 
282 got_it:
283 	pos = (page->index >> PAGE_CACHE_SHIFT) + p - (char*)page_address(page);
284 	err = __minix_write_begin(NULL, page->mapping, pos, sbi->s_dirsize,
285 					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
286 	if (err)
287 		goto out_unlock;
288 	memcpy (namx, name, namelen);
289 	if (sbi->s_version == MINIX_V3) {
290 		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
291 		de3->inode = inode->i_ino;
292 	} else {
293 		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
294 		de->inode = inode->i_ino;
295 	}
296 	err = dir_commit_chunk(page, pos, sbi->s_dirsize);
297 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
298 	mark_inode_dirty(dir);
299 out_put:
300 	dir_put_page(page);
301 out:
302 	return err;
303 out_unlock:
304 	unlock_page(page);
305 	goto out_put;
306 }
307 
308 int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
309 {
310 	struct address_space *mapping = page->mapping;
311 	struct inode *inode = (struct inode*)mapping->host;
312 	char *kaddr = page_address(page);
313 	loff_t pos = page_offset(page) + (char*)de - kaddr;
314 	unsigned len = minix_sb(inode->i_sb)->s_dirsize;
315 	int err;
316 
317 	lock_page(page);
318 	err = __minix_write_begin(NULL, mapping, pos, len,
319 					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
320 	if (err == 0) {
321 		de->inode = 0;
322 		err = dir_commit_chunk(page, pos, len);
323 	} else {
324 		unlock_page(page);
325 	}
326 	dir_put_page(page);
327 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
328 	mark_inode_dirty(inode);
329 	return err;
330 }
331 
332 int minix_make_empty(struct inode *inode, struct inode *dir)
333 {
334 	struct address_space *mapping = inode->i_mapping;
335 	struct page *page = grab_cache_page(mapping, 0);
336 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
337 	char *kaddr;
338 	int err;
339 
340 	if (!page)
341 		return -ENOMEM;
342 	err = __minix_write_begin(NULL, mapping, 0, 2 * sbi->s_dirsize,
343 					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
344 	if (err) {
345 		unlock_page(page);
346 		goto fail;
347 	}
348 
349 	kaddr = kmap_atomic(page, KM_USER0);
350 	memset(kaddr, 0, PAGE_CACHE_SIZE);
351 
352 	if (sbi->s_version == MINIX_V3) {
353 		minix3_dirent *de3 = (minix3_dirent *)kaddr;
354 
355 		de3->inode = inode->i_ino;
356 		strcpy(de3->name, ".");
357 		de3 = minix_next_entry(de3, sbi);
358 		de3->inode = dir->i_ino;
359 		strcpy(de3->name, "..");
360 	} else {
361 		minix_dirent *de = (minix_dirent *)kaddr;
362 
363 		de->inode = inode->i_ino;
364 		strcpy(de->name, ".");
365 		de = minix_next_entry(de, sbi);
366 		de->inode = dir->i_ino;
367 		strcpy(de->name, "..");
368 	}
369 	kunmap_atomic(kaddr, KM_USER0);
370 
371 	err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
372 fail:
373 	page_cache_release(page);
374 	return err;
375 }
376 
377 /*
378  * routine to check that the specified directory is empty (for rmdir)
379  */
380 int minix_empty_dir(struct inode * inode)
381 {
382 	struct page *page = NULL;
383 	unsigned long i, npages = dir_pages(inode);
384 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
385 	char *name;
386 	__u32 inumber;
387 
388 	for (i = 0; i < npages; i++) {
389 		char *p, *kaddr, *limit;
390 
391 		page = dir_get_page(inode, i);
392 		if (IS_ERR(page))
393 			continue;
394 
395 		kaddr = (char *)page_address(page);
396 		limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
397 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
398 			if (sbi->s_version == MINIX_V3) {
399 				minix3_dirent *de3 = (minix3_dirent *)p;
400 				name = de3->name;
401 				inumber = de3->inode;
402 			} else {
403 				minix_dirent *de = (minix_dirent *)p;
404 				name = de->name;
405 				inumber = de->inode;
406 			}
407 
408 			if (inumber != 0) {
409 				/* check for . and .. */
410 				if (name[0] != '.')
411 					goto not_empty;
412 				if (!name[1]) {
413 					if (inumber != inode->i_ino)
414 						goto not_empty;
415 				} else if (name[1] != '.')
416 					goto not_empty;
417 				else if (name[2])
418 					goto not_empty;
419 			}
420 		}
421 		dir_put_page(page);
422 	}
423 	return 1;
424 
425 not_empty:
426 	dir_put_page(page);
427 	return 0;
428 }
429 
430 /* Releases the page */
431 void minix_set_link(struct minix_dir_entry *de, struct page *page,
432 	struct inode *inode)
433 {
434 	struct address_space *mapping = page->mapping;
435 	struct inode *dir = mapping->host;
436 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
437 	loff_t pos = page_offset(page) +
438 			(char *)de-(char*)page_address(page);
439 	int err;
440 
441 	lock_page(page);
442 
443 	err = __minix_write_begin(NULL, mapping, pos, sbi->s_dirsize,
444 					AOP_FLAG_UNINTERRUPTIBLE, &page, NULL);
445 	if (err == 0) {
446 		de->inode = inode->i_ino;
447 		err = dir_commit_chunk(page, pos, sbi->s_dirsize);
448 	} else {
449 		unlock_page(page);
450 	}
451 	dir_put_page(page);
452 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
453 	mark_inode_dirty(dir);
454 }
455 
456 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
457 {
458 	struct page *page = dir_get_page(dir, 0);
459 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
460 	struct minix_dir_entry *de = NULL;
461 
462 	if (!IS_ERR(page)) {
463 		de = minix_next_entry(page_address(page), sbi);
464 		*p = page;
465 	}
466 	return de;
467 }
468 
469 ino_t minix_inode_by_name(struct dentry *dentry)
470 {
471 	struct page *page;
472 	struct minix_dir_entry *de = minix_find_entry(dentry, &page);
473 	ino_t res = 0;
474 
475 	if (de) {
476 		res = de->inode;
477 		dir_put_page(page);
478 	}
479 	return res;
480 }
481