xref: /openbmc/linux/fs/sysv/dir.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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 const 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_mapping_page(mapping, n, NULL);
57 	if (!IS_ERR(page))
58 		kmap(page);
59 	return page;
60 }
61 
62 static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
63 {
64 	unsigned long pos = filp->f_pos;
65 	struct inode *inode = filp->f_path.dentry->d_inode;
66 	struct super_block *sb = inode->i_sb;
67 	unsigned offset = pos & ~PAGE_CACHE_MASK;
68 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
69 	unsigned long npages = dir_pages(inode);
70 
71 	lock_kernel();
72 
73 	pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
74 	if (pos >= inode->i_size)
75 		goto done;
76 
77 	for ( ; n < npages; n++, offset = 0) {
78 		char *kaddr, *limit;
79 		struct sysv_dir_entry *de;
80 		struct page *page = dir_get_page(inode, n);
81 
82 		if (IS_ERR(page))
83 			continue;
84 		kaddr = (char *)page_address(page);
85 		de = (struct sysv_dir_entry *)(kaddr+offset);
86 		limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
87 		for ( ;(char*)de <= limit; de++) {
88 			char *name = de->name;
89 			int over;
90 
91 			if (!de->inode)
92 				continue;
93 
94 			offset = (char *)de - kaddr;
95 
96 			over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
97 					((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
98 					fs16_to_cpu(SYSV_SB(sb), de->inode),
99 					DT_UNKNOWN);
100 			if (over) {
101 				dir_put_page(page);
102 				goto done;
103 			}
104 		}
105 		dir_put_page(page);
106 	}
107 
108 done:
109 	filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
110 	unlock_kernel();
111 	return 0;
112 }
113 
114 /* compare strings: name[0..len-1] (not zero-terminated) and
115  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
116  */
117 static inline int namecompare(int len, int maxlen,
118 	const char * name, const char * buffer)
119 {
120 	if (len < maxlen && buffer[len])
121 		return 0;
122 	return !memcmp(name, buffer, len);
123 }
124 
125 /*
126  *	sysv_find_entry()
127  *
128  * finds an entry in the specified directory with the wanted name. It
129  * returns the cache buffer in which the entry was found, and the entry
130  * itself (as a parameter - res_dir). It does NOT read the inode of the
131  * entry - you'll have to do that yourself if you want to.
132  */
133 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
134 {
135 	const char * name = dentry->d_name.name;
136 	int namelen = dentry->d_name.len;
137 	struct inode * dir = dentry->d_parent->d_inode;
138 	unsigned long start, n;
139 	unsigned long npages = dir_pages(dir);
140 	struct page *page = NULL;
141 	struct sysv_dir_entry *de;
142 
143 	*res_page = NULL;
144 
145 	start = SYSV_I(dir)->i_dir_start_lookup;
146 	if (start >= npages)
147 		start = 0;
148 	n = start;
149 
150 	do {
151 		char *kaddr;
152 		page = dir_get_page(dir, n);
153 		if (!IS_ERR(page)) {
154 			kaddr = (char*)page_address(page);
155 			de = (struct sysv_dir_entry *) kaddr;
156 			kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
157 			for ( ; (char *) de <= kaddr ; de++) {
158 				if (!de->inode)
159 					continue;
160 				if (namecompare(namelen, SYSV_NAMELEN,
161 							name, de->name))
162 					goto found;
163 			}
164 		}
165 		dir_put_page(page);
166 
167 		if (++n >= npages)
168 			n = 0;
169 	} while (n != start);
170 
171 	return NULL;
172 
173 found:
174 	SYSV_I(dir)->i_dir_start_lookup = n;
175 	*res_page = page;
176 	return de;
177 }
178 
179 int sysv_add_link(struct dentry *dentry, struct inode *inode)
180 {
181 	struct inode *dir = dentry->d_parent->d_inode;
182 	const char * name = dentry->d_name.name;
183 	int namelen = dentry->d_name.len;
184 	struct page *page = NULL;
185 	struct sysv_dir_entry * de;
186 	unsigned long npages = dir_pages(dir);
187 	unsigned long n;
188 	char *kaddr;
189 	unsigned from, to;
190 	int err;
191 
192 	/* We take care of directory expansion in the same loop */
193 	for (n = 0; n <= npages; n++) {
194 		page = dir_get_page(dir, n);
195 		err = PTR_ERR(page);
196 		if (IS_ERR(page))
197 			goto out;
198 		kaddr = (char*)page_address(page);
199 		de = (struct sysv_dir_entry *)kaddr;
200 		kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
201 		while ((char *)de <= kaddr) {
202 			if (!de->inode)
203 				goto got_it;
204 			err = -EEXIST;
205 			if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
206 				goto out_page;
207 			de++;
208 		}
209 		dir_put_page(page);
210 	}
211 	BUG();
212 	return -EINVAL;
213 
214 got_it:
215 	from = (char*)de - (char*)page_address(page);
216 	to = from + SYSV_DIRSIZE;
217 	lock_page(page);
218 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
219 	if (err)
220 		goto out_unlock;
221 	memcpy (de->name, name, namelen);
222 	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
223 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
224 	err = dir_commit_chunk(page, from, to);
225 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
226 	mark_inode_dirty(dir);
227 out_page:
228 	dir_put_page(page);
229 out:
230 	return err;
231 out_unlock:
232 	unlock_page(page);
233 	goto out_page;
234 }
235 
236 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
237 {
238 	struct address_space *mapping = page->mapping;
239 	struct inode *inode = (struct inode*)mapping->host;
240 	char *kaddr = (char*)page_address(page);
241 	unsigned from = (char*)de - kaddr;
242 	unsigned to = from + SYSV_DIRSIZE;
243 	int err;
244 
245 	lock_page(page);
246 	err = mapping->a_ops->prepare_write(NULL, page, from, to);
247 	BUG_ON(err);
248 	de->inode = 0;
249 	err = dir_commit_chunk(page, from, to);
250 	dir_put_page(page);
251 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
252 	mark_inode_dirty(inode);
253 	return err;
254 }
255 
256 int sysv_make_empty(struct inode *inode, struct inode *dir)
257 {
258 	struct address_space *mapping = inode->i_mapping;
259 	struct page *page = grab_cache_page(mapping, 0);
260 	struct sysv_dir_entry * de;
261 	char *base;
262 	int err;
263 
264 	if (!page)
265 		return -ENOMEM;
266 	kmap(page);
267 	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
268 	if (err) {
269 		unlock_page(page);
270 		goto fail;
271 	}
272 
273 	base = (char*)page_address(page);
274 	memset(base, 0, PAGE_CACHE_SIZE);
275 
276 	de = (struct sysv_dir_entry *) base;
277 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
278 	strcpy(de->name,".");
279 	de++;
280 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
281 	strcpy(de->name,"..");
282 
283 	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
284 fail:
285 	kunmap(page);
286 	page_cache_release(page);
287 	return err;
288 }
289 
290 /*
291  * routine to check that the specified directory is empty (for rmdir)
292  */
293 int sysv_empty_dir(struct inode * inode)
294 {
295 	struct super_block *sb = inode->i_sb;
296 	struct page *page = NULL;
297 	unsigned long i, npages = dir_pages(inode);
298 
299 	for (i = 0; i < npages; i++) {
300 		char *kaddr;
301 		struct sysv_dir_entry * de;
302 		page = dir_get_page(inode, i);
303 
304 		if (IS_ERR(page))
305 			continue;
306 
307 		kaddr = (char *)page_address(page);
308 		de = (struct sysv_dir_entry *)kaddr;
309 		kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
310 
311 		for ( ;(char *)de <= kaddr; de++) {
312 			if (!de->inode)
313 				continue;
314 			/* check for . and .. */
315 			if (de->name[0] != '.')
316 				goto not_empty;
317 			if (!de->name[1]) {
318 				if (de->inode == cpu_to_fs16(SYSV_SB(sb),
319 							inode->i_ino))
320 					continue;
321 				goto not_empty;
322 			}
323 			if (de->name[1] != '.' || de->name[2])
324 				goto not_empty;
325 		}
326 		dir_put_page(page);
327 	}
328 	return 1;
329 
330 not_empty:
331 	dir_put_page(page);
332 	return 0;
333 }
334 
335 /* Releases the page */
336 void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
337 	struct inode *inode)
338 {
339 	struct inode *dir = (struct inode*)page->mapping->host;
340 	unsigned from = (char *)de-(char*)page_address(page);
341 	unsigned to = from + SYSV_DIRSIZE;
342 	int err;
343 
344 	lock_page(page);
345 	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
346 	BUG_ON(err);
347 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
348 	err = dir_commit_chunk(page, from, to);
349 	dir_put_page(page);
350 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
351 	mark_inode_dirty(dir);
352 }
353 
354 struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
355 {
356 	struct page *page = dir_get_page(dir, 0);
357 	struct sysv_dir_entry *de = NULL;
358 
359 	if (!IS_ERR(page)) {
360 		de = (struct sysv_dir_entry*) page_address(page) + 1;
361 		*p = page;
362 	}
363 	return de;
364 }
365 
366 ino_t sysv_inode_by_name(struct dentry *dentry)
367 {
368 	struct page *page;
369 	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
370 	ino_t res = 0;
371 
372 	if (de) {
373 		res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
374 		dir_put_page(page);
375 	}
376 	return res;
377 }
378