xref: /linux/fs/minix/dir.c (revision 14b42963f64b98ab61fa9723c03d71aa5ef4f862)
1 /*
2  *  linux/fs/minix/dir.c
3  *
4  *  Copyright (C) 1991, 1992 Linus Torvalds
5  *
6  *  minix directory handling functions
7  */
8 
9 #include "minix.h"
10 #include <linux/highmem.h>
11 #include <linux/smp_lock.h>
12 
13 typedef struct minix_dir_entry minix_dirent;
14 
15 static int minix_readdir(struct file *, void *, filldir_t);
16 
17 const struct file_operations minix_dir_operations = {
18 	.read		= generic_read_dir,
19 	.readdir	= minix_readdir,
20 	.fsync		= minix_sync_file,
21 };
22 
23 static inline void dir_put_page(struct page *page)
24 {
25 	kunmap(page);
26 	page_cache_release(page);
27 }
28 
29 /*
30  * Return the offset into page `page_nr' of the last valid
31  * byte in that page, plus one.
32  */
33 static unsigned
34 minix_last_byte(struct inode *inode, unsigned long page_nr)
35 {
36 	unsigned last_byte = PAGE_CACHE_SIZE;
37 
38 	if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
39 		last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
40 	return last_byte;
41 }
42 
43 static inline unsigned long dir_pages(struct inode *inode)
44 {
45 	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
46 }
47 
48 static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)
49 {
50 	struct inode *dir = (struct inode *)page->mapping->host;
51 	int err = 0;
52 	page->mapping->a_ops->commit_write(NULL, page, from, to);
53 	if (IS_DIRSYNC(dir))
54 		err = write_one_page(page, 1);
55 	else
56 		unlock_page(page);
57 	return err;
58 }
59 
60 static struct page * dir_get_page(struct inode *dir, unsigned long n)
61 {
62 	struct address_space *mapping = dir->i_mapping;
63 	struct page *page = read_mapping_page(mapping, n, NULL);
64 	if (!IS_ERR(page)) {
65 		wait_on_page_locked(page);
66 		kmap(page);
67 		if (!PageUptodate(page))
68 			goto fail;
69 	}
70 	return page;
71 
72 fail:
73 	dir_put_page(page);
74 	return ERR_PTR(-EIO);
75 }
76 
77 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
78 {
79 	return (void*)((char*)de + sbi->s_dirsize);
80 }
81 
82 static int minix_readdir(struct file * filp, void * dirent, filldir_t filldir)
83 {
84 	unsigned long pos = filp->f_pos;
85 	struct inode *inode = filp->f_dentry->d_inode;
86 	struct super_block *sb = inode->i_sb;
87 	unsigned offset = pos & ~PAGE_CACHE_MASK;
88 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
89 	unsigned long npages = dir_pages(inode);
90 	struct minix_sb_info *sbi = minix_sb(sb);
91 	unsigned chunk_size = sbi->s_dirsize;
92 
93 	lock_kernel();
94 
95 	pos = (pos + chunk_size-1) & ~(chunk_size-1);
96 	if (pos >= inode->i_size)
97 		goto done;
98 
99 	for ( ; n < npages; n++, offset = 0) {
100 		char *p, *kaddr, *limit;
101 		struct page *page = dir_get_page(inode, n);
102 
103 		if (IS_ERR(page))
104 			continue;
105 		kaddr = (char *)page_address(page);
106 		p = kaddr+offset;
107 		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
108 		for ( ; p <= limit ; p = minix_next_entry(p, sbi)) {
109 			minix_dirent *de = (minix_dirent *)p;
110 			if (de->inode) {
111 				int over;
112 				unsigned l = strnlen(de->name,sbi->s_namelen);
113 
114 				offset = p - kaddr;
115 				over = filldir(dirent, de->name, l,
116 						(n<<PAGE_CACHE_SHIFT) | offset,
117 						de->inode, DT_UNKNOWN);
118 				if (over) {
119 					dir_put_page(page);
120 					goto done;
121 				}
122 			}
123 		}
124 		dir_put_page(page);
125 	}
126 
127 done:
128 	filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
129 	unlock_kernel();
130 	return 0;
131 }
132 
133 static inline int namecompare(int len, int maxlen,
134 	const char * name, const char * buffer)
135 {
136 	if (len < maxlen && buffer[len])
137 		return 0;
138 	return !memcmp(name, buffer, len);
139 }
140 
141 /*
142  *	minix_find_entry()
143  *
144  * finds an entry in the specified directory with the wanted name. It
145  * returns the cache buffer in which the entry was found, and the entry
146  * itself (as a parameter - res_dir). It does NOT read the inode of the
147  * entry - you'll have to do that yourself if you want to.
148  */
149 minix_dirent *minix_find_entry(struct dentry *dentry, struct page **res_page)
150 {
151 	const char * name = dentry->d_name.name;
152 	int namelen = dentry->d_name.len;
153 	struct inode * dir = dentry->d_parent->d_inode;
154 	struct super_block * sb = dir->i_sb;
155 	struct minix_sb_info * sbi = minix_sb(sb);
156 	unsigned long n;
157 	unsigned long npages = dir_pages(dir);
158 	struct page *page = NULL;
159 	struct minix_dir_entry *de;
160 
161 	*res_page = NULL;
162 
163 	for (n = 0; n < npages; n++) {
164 		char *kaddr;
165 		page = dir_get_page(dir, n);
166 		if (IS_ERR(page))
167 			continue;
168 
169 		kaddr = (char*)page_address(page);
170 		de = (struct minix_dir_entry *) kaddr;
171 		kaddr += minix_last_byte(dir, n) - sbi->s_dirsize;
172 		for ( ; (char *) de <= kaddr ; de = minix_next_entry(de,sbi)) {
173 			if (!de->inode)
174 				continue;
175 			if (namecompare(namelen,sbi->s_namelen,name,de->name))
176 				goto found;
177 		}
178 		dir_put_page(page);
179 	}
180 	return NULL;
181 
182 found:
183 	*res_page = page;
184 	return de;
185 }
186 
187 int minix_add_link(struct dentry *dentry, struct inode *inode)
188 {
189 	struct inode *dir = dentry->d_parent->d_inode;
190 	const char * name = dentry->d_name.name;
191 	int namelen = dentry->d_name.len;
192 	struct super_block * sb = dir->i_sb;
193 	struct minix_sb_info * sbi = minix_sb(sb);
194 	struct page *page = NULL;
195 	struct minix_dir_entry * de;
196 	unsigned long npages = dir_pages(dir);
197 	unsigned long n;
198 	char *kaddr;
199 	unsigned from, to;
200 	int err;
201 
202 	/*
203 	 * We take care of directory expansion in the same loop
204 	 * This code plays outside i_size, so it locks the page
205 	 * to protect that region.
206 	 */
207 	for (n = 0; n <= npages; n++) {
208 		char *dir_end;
209 
210 		page = dir_get_page(dir, n);
211 		err = PTR_ERR(page);
212 		if (IS_ERR(page))
213 			goto out;
214 		lock_page(page);
215 		kaddr = (char*)page_address(page);
216 		dir_end = kaddr + minix_last_byte(dir, n);
217 		de = (minix_dirent *)kaddr;
218 		kaddr += PAGE_CACHE_SIZE - sbi->s_dirsize;
219 		while ((char *)de <= kaddr) {
220 			if ((char *)de == dir_end) {
221 				/* We hit i_size */
222 				de->inode = 0;
223 				goto got_it;
224 			}
225 			if (!de->inode)
226 				goto got_it;
227 			err = -EEXIST;
228 			if (namecompare(namelen,sbi->s_namelen,name,de->name))
229 				goto out_unlock;
230 			de = minix_next_entry(de, sbi);
231 		}
232 		unlock_page(page);
233 		dir_put_page(page);
234 	}
235 	BUG();
236 	return -EINVAL;
237 
238 got_it:
239 	from = (char*)de - (char*)page_address(page);
240 	to = from + sbi->s_dirsize;
241 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
242 	if (err)
243 		goto out_unlock;
244 	memcpy (de->name, name, namelen);
245 	memset (de->name + namelen, 0, sbi->s_dirsize - namelen - 2);
246 	de->inode = inode->i_ino;
247 	err = dir_commit_chunk(page, from, to);
248 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
249 	mark_inode_dirty(dir);
250 out_put:
251 	dir_put_page(page);
252 out:
253 	return err;
254 out_unlock:
255 	unlock_page(page);
256 	goto out_put;
257 }
258 
259 int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
260 {
261 	struct address_space *mapping = page->mapping;
262 	struct inode *inode = (struct inode*)mapping->host;
263 	char *kaddr = page_address(page);
264 	unsigned from = (char*)de - kaddr;
265 	unsigned to = from + minix_sb(inode->i_sb)->s_dirsize;
266 	int err;
267 
268 	lock_page(page);
269 	err = mapping->a_ops->prepare_write(NULL, page, from, to);
270 	if (err == 0) {
271 		de->inode = 0;
272 		err = dir_commit_chunk(page, from, to);
273 	} else {
274 		unlock_page(page);
275 	}
276 	dir_put_page(page);
277 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
278 	mark_inode_dirty(inode);
279 	return err;
280 }
281 
282 int minix_make_empty(struct inode *inode, struct inode *dir)
283 {
284 	struct address_space *mapping = inode->i_mapping;
285 	struct page *page = grab_cache_page(mapping, 0);
286 	struct minix_sb_info * sbi = minix_sb(inode->i_sb);
287 	struct minix_dir_entry * de;
288 	char *kaddr;
289 	int err;
290 
291 	if (!page)
292 		return -ENOMEM;
293 	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * sbi->s_dirsize);
294 	if (err) {
295 		unlock_page(page);
296 		goto fail;
297 	}
298 
299 	kaddr = kmap_atomic(page, KM_USER0);
300 	memset(kaddr, 0, PAGE_CACHE_SIZE);
301 
302 	de = (struct minix_dir_entry *)kaddr;
303 	de->inode = inode->i_ino;
304 	strcpy(de->name,".");
305 	de = minix_next_entry(de, sbi);
306 	de->inode = dir->i_ino;
307 	strcpy(de->name,"..");
308 	kunmap_atomic(kaddr, KM_USER0);
309 
310 	err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
311 fail:
312 	page_cache_release(page);
313 	return err;
314 }
315 
316 /*
317  * routine to check that the specified directory is empty (for rmdir)
318  */
319 int minix_empty_dir(struct inode * inode)
320 {
321 	struct page *page = NULL;
322 	unsigned long i, npages = dir_pages(inode);
323 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
324 
325 	for (i = 0; i < npages; i++) {
326 		char *kaddr;
327 		minix_dirent * de;
328 		page = dir_get_page(inode, i);
329 
330 		if (IS_ERR(page))
331 			continue;
332 
333 		kaddr = (char *)page_address(page);
334 		de = (minix_dirent *)kaddr;
335 		kaddr += minix_last_byte(inode, i) - sbi->s_dirsize;
336 
337 		while ((char *)de <= kaddr) {
338 			if (de->inode != 0) {
339 				/* check for . and .. */
340 				if (de->name[0] != '.')
341 					goto not_empty;
342 				if (!de->name[1]) {
343 					if (de->inode != inode->i_ino)
344 						goto not_empty;
345 				} else if (de->name[1] != '.')
346 					goto not_empty;
347 				else if (de->name[2])
348 					goto not_empty;
349 			}
350 			de = minix_next_entry(de, sbi);
351 		}
352 		dir_put_page(page);
353 	}
354 	return 1;
355 
356 not_empty:
357 	dir_put_page(page);
358 	return 0;
359 }
360 
361 /* Releases the page */
362 void minix_set_link(struct minix_dir_entry *de, struct page *page,
363 	struct inode *inode)
364 {
365 	struct inode *dir = (struct inode*)page->mapping->host;
366 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
367 	unsigned from = (char *)de-(char*)page_address(page);
368 	unsigned to = from + sbi->s_dirsize;
369 	int err;
370 
371 	lock_page(page);
372 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
373 	if (err == 0) {
374 		de->inode = inode->i_ino;
375 		err = dir_commit_chunk(page, from, to);
376 	} else {
377 		unlock_page(page);
378 	}
379 	dir_put_page(page);
380 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
381 	mark_inode_dirty(dir);
382 }
383 
384 struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
385 {
386 	struct page *page = dir_get_page(dir, 0);
387 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
388 	struct minix_dir_entry *de = NULL;
389 
390 	if (!IS_ERR(page)) {
391 		de = minix_next_entry(page_address(page), sbi);
392 		*p = page;
393 	}
394 	return de;
395 }
396 
397 ino_t minix_inode_by_name(struct dentry *dentry)
398 {
399 	struct page *page;
400 	struct minix_dir_entry *de = minix_find_entry(dentry, &page);
401 	ino_t res = 0;
402 
403 	if (de) {
404 		res = de->inode;
405 		dir_put_page(page);
406 	}
407 	return res;
408 }
409