xref: /openbmc/linux/fs/sysv/dir.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  *  linux/fs/sysv/dir.c
3  *
4  *  minix/dir.c
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  *
7  *  coh/dir.c
8  *  Copyright (C) 1993  Pascal Haible, Bruno Haible
9  *
10  *  sysv/dir.c
11  *  Copyright (C) 1993  Bruno Haible
12  *
13  *  SystemV/Coherent directory handling functions
14  */
15 
16 #include <linux/pagemap.h>
17 #include <linux/highmem.h>
18 #include <linux/smp_lock.h>
19 #include "sysv.h"
20 
21 static int sysv_readdir(struct file *, void *, filldir_t);
22 
23 struct file_operations sysv_dir_operations = {
24 	.read		= generic_read_dir,
25 	.readdir	= sysv_readdir,
26 	.fsync		= sysv_sync_file,
27 };
28 
29 static inline void dir_put_page(struct page *page)
30 {
31 	kunmap(page);
32 	page_cache_release(page);
33 }
34 
35 static inline unsigned long dir_pages(struct inode *inode)
36 {
37 	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
38 }
39 
40 static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)
41 {
42 	struct inode *dir = (struct inode *)page->mapping->host;
43 	int err = 0;
44 
45 	page->mapping->a_ops->commit_write(NULL, page, from, to);
46 	if (IS_DIRSYNC(dir))
47 		err = write_one_page(page, 1);
48 	else
49 		unlock_page(page);
50 	return err;
51 }
52 
53 static struct page * dir_get_page(struct inode *dir, unsigned long n)
54 {
55 	struct address_space *mapping = dir->i_mapping;
56 	struct page *page = read_cache_page(mapping, n,
57 				(filler_t*)mapping->a_ops->readpage, NULL);
58 	if (!IS_ERR(page)) {
59 		wait_on_page_locked(page);
60 		kmap(page);
61 		if (!PageUptodate(page))
62 			goto fail;
63 	}
64 	return page;
65 
66 fail:
67 	dir_put_page(page);
68 	return ERR_PTR(-EIO);
69 }
70 
71 static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
72 {
73 	unsigned long pos = filp->f_pos;
74 	struct inode *inode = filp->f_dentry->d_inode;
75 	struct super_block *sb = inode->i_sb;
76 	unsigned offset = pos & ~PAGE_CACHE_MASK;
77 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
78 	unsigned long npages = dir_pages(inode);
79 
80 	lock_kernel();
81 
82 	pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
83 	if (pos >= inode->i_size)
84 		goto done;
85 
86 	for ( ; n < npages; n++, offset = 0) {
87 		char *kaddr, *limit;
88 		struct sysv_dir_entry *de;
89 		struct page *page = dir_get_page(inode, n);
90 
91 		if (IS_ERR(page))
92 			continue;
93 		kaddr = (char *)page_address(page);
94 		de = (struct sysv_dir_entry *)(kaddr+offset);
95 		limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
96 		for ( ;(char*)de <= limit; de++) {
97 			char *name = de->name;
98 			int over;
99 
100 			if (!de->inode)
101 				continue;
102 
103 			offset = (char *)de - kaddr;
104 
105 			over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
106 					(n<<PAGE_CACHE_SHIFT) | offset,
107 					fs16_to_cpu(SYSV_SB(sb), de->inode),
108 					DT_UNKNOWN);
109 			if (over) {
110 				dir_put_page(page);
111 				goto done;
112 			}
113 		}
114 		dir_put_page(page);
115 	}
116 
117 done:
118 	filp->f_pos = (n << PAGE_CACHE_SHIFT) | offset;
119 	unlock_kernel();
120 	return 0;
121 }
122 
123 /* compare strings: name[0..len-1] (not zero-terminated) and
124  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
125  */
126 static inline int namecompare(int len, int maxlen,
127 	const char * name, const char * buffer)
128 {
129 	if (len < maxlen && buffer[len])
130 		return 0;
131 	return !memcmp(name, buffer, len);
132 }
133 
134 /*
135  *	sysv_find_entry()
136  *
137  * finds an entry in the specified directory with the wanted name. It
138  * returns the cache buffer in which the entry was found, and the entry
139  * itself (as a parameter - res_dir). It does NOT read the inode of the
140  * entry - you'll have to do that yourself if you want to.
141  */
142 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
143 {
144 	const char * name = dentry->d_name.name;
145 	int namelen = dentry->d_name.len;
146 	struct inode * dir = dentry->d_parent->d_inode;
147 	unsigned long start, n;
148 	unsigned long npages = dir_pages(dir);
149 	struct page *page = NULL;
150 	struct sysv_dir_entry *de;
151 
152 	*res_page = NULL;
153 
154 	start = SYSV_I(dir)->i_dir_start_lookup;
155 	if (start >= npages)
156 		start = 0;
157 	n = start;
158 
159 	do {
160 		char *kaddr;
161 		page = dir_get_page(dir, n);
162 		if (!IS_ERR(page)) {
163 			kaddr = (char*)page_address(page);
164 			de = (struct sysv_dir_entry *) kaddr;
165 			kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
166 			for ( ; (char *) de <= kaddr ; de++) {
167 				if (!de->inode)
168 					continue;
169 				if (namecompare(namelen, SYSV_NAMELEN,
170 							name, de->name))
171 					goto found;
172 			}
173 		}
174 		dir_put_page(page);
175 
176 		if (++n >= npages)
177 			n = 0;
178 	} while (n != start);
179 
180 	return NULL;
181 
182 found:
183 	SYSV_I(dir)->i_dir_start_lookup = n;
184 	*res_page = page;
185 	return de;
186 }
187 
188 int sysv_add_link(struct dentry *dentry, struct inode *inode)
189 {
190 	struct inode *dir = dentry->d_parent->d_inode;
191 	const char * name = dentry->d_name.name;
192 	int namelen = dentry->d_name.len;
193 	struct page *page = NULL;
194 	struct sysv_dir_entry * de;
195 	unsigned long npages = dir_pages(dir);
196 	unsigned long n;
197 	char *kaddr;
198 	unsigned from, to;
199 	int err;
200 
201 	/* We take care of directory expansion in the same loop */
202 	for (n = 0; n <= npages; n++) {
203 		page = dir_get_page(dir, n);
204 		err = PTR_ERR(page);
205 		if (IS_ERR(page))
206 			goto out;
207 		kaddr = (char*)page_address(page);
208 		de = (struct sysv_dir_entry *)kaddr;
209 		kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
210 		while ((char *)de <= kaddr) {
211 			if (!de->inode)
212 				goto got_it;
213 			err = -EEXIST;
214 			if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
215 				goto out_page;
216 			de++;
217 		}
218 		dir_put_page(page);
219 	}
220 	BUG();
221 	return -EINVAL;
222 
223 got_it:
224 	from = (char*)de - (char*)page_address(page);
225 	to = from + SYSV_DIRSIZE;
226 	lock_page(page);
227 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
228 	if (err)
229 		goto out_unlock;
230 	memcpy (de->name, name, namelen);
231 	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
232 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
233 	err = dir_commit_chunk(page, from, to);
234 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
235 	mark_inode_dirty(dir);
236 out_page:
237 	dir_put_page(page);
238 out:
239 	return err;
240 out_unlock:
241 	unlock_page(page);
242 	goto out_page;
243 }
244 
245 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
246 {
247 	struct address_space *mapping = page->mapping;
248 	struct inode *inode = (struct inode*)mapping->host;
249 	char *kaddr = (char*)page_address(page);
250 	unsigned from = (char*)de - kaddr;
251 	unsigned to = from + SYSV_DIRSIZE;
252 	int err;
253 
254 	lock_page(page);
255 	err = mapping->a_ops->prepare_write(NULL, page, from, to);
256 	if (err)
257 		BUG();
258 	de->inode = 0;
259 	err = dir_commit_chunk(page, from, to);
260 	dir_put_page(page);
261 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
262 	mark_inode_dirty(inode);
263 	return err;
264 }
265 
266 int sysv_make_empty(struct inode *inode, struct inode *dir)
267 {
268 	struct address_space *mapping = inode->i_mapping;
269 	struct page *page = grab_cache_page(mapping, 0);
270 	struct sysv_dir_entry * de;
271 	char *base;
272 	int err;
273 
274 	if (!page)
275 		return -ENOMEM;
276 	kmap(page);
277 	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
278 	if (err) {
279 		unlock_page(page);
280 		goto fail;
281 	}
282 
283 	base = (char*)page_address(page);
284 	memset(base, 0, PAGE_CACHE_SIZE);
285 
286 	de = (struct sysv_dir_entry *) base;
287 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
288 	strcpy(de->name,".");
289 	de++;
290 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
291 	strcpy(de->name,"..");
292 
293 	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
294 fail:
295 	kunmap(page);
296 	page_cache_release(page);
297 	return err;
298 }
299 
300 /*
301  * routine to check that the specified directory is empty (for rmdir)
302  */
303 int sysv_empty_dir(struct inode * inode)
304 {
305 	struct super_block *sb = inode->i_sb;
306 	struct page *page = NULL;
307 	unsigned long i, npages = dir_pages(inode);
308 
309 	for (i = 0; i < npages; i++) {
310 		char *kaddr;
311 		struct sysv_dir_entry * de;
312 		page = dir_get_page(inode, i);
313 
314 		if (IS_ERR(page))
315 			continue;
316 
317 		kaddr = (char *)page_address(page);
318 		de = (struct sysv_dir_entry *)kaddr;
319 		kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
320 
321 		for ( ;(char *)de <= kaddr; de++) {
322 			if (!de->inode)
323 				continue;
324 			/* check for . and .. */
325 			if (de->name[0] != '.')
326 				goto not_empty;
327 			if (!de->name[1]) {
328 				if (de->inode == cpu_to_fs16(SYSV_SB(sb),
329 							inode->i_ino))
330 					continue;
331 				goto not_empty;
332 			}
333 			if (de->name[1] != '.' || de->name[2])
334 				goto not_empty;
335 		}
336 		dir_put_page(page);
337 	}
338 	return 1;
339 
340 not_empty:
341 	dir_put_page(page);
342 	return 0;
343 }
344 
345 /* Releases the page */
346 void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
347 	struct inode *inode)
348 {
349 	struct inode *dir = (struct inode*)page->mapping->host;
350 	unsigned from = (char *)de-(char*)page_address(page);
351 	unsigned to = from + SYSV_DIRSIZE;
352 	int err;
353 
354 	lock_page(page);
355 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
356 	if (err)
357 		BUG();
358 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
359 	err = dir_commit_chunk(page, from, to);
360 	dir_put_page(page);
361 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
362 	mark_inode_dirty(dir);
363 }
364 
365 struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
366 {
367 	struct page *page = dir_get_page(dir, 0);
368 	struct sysv_dir_entry *de = NULL;
369 
370 	if (!IS_ERR(page)) {
371 		de = (struct sysv_dir_entry*) page_address(page) + 1;
372 		*p = page;
373 	}
374 	return de;
375 }
376 
377 ino_t sysv_inode_by_name(struct dentry *dentry)
378 {
379 	struct page *page;
380 	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
381 	ino_t res = 0;
382 
383 	if (de) {
384 		res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
385 		dir_put_page(page);
386 	}
387 	return res;
388 }
389