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/swap.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 	.llseek		= generic_file_llseek,
25 	.read		= generic_read_dir,
26 	.readdir	= sysv_readdir,
27 	.fsync		= generic_file_fsync,
28 };
29 
dir_put_page(struct page * page)30 static inline void dir_put_page(struct page *page)
31 {
32 	kunmap(page);
33 	page_cache_release(page);
34 }
35 
dir_pages(struct inode * inode)36 static inline unsigned long dir_pages(struct inode *inode)
37 {
38 	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
39 }
40 
dir_commit_chunk(struct page * page,loff_t pos,unsigned len)41 static int dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
42 {
43 	struct address_space *mapping = page->mapping;
44 	struct inode *dir = mapping->host;
45 	int err = 0;
46 
47 	block_write_end(NULL, mapping, pos, len, len, page, NULL);
48 	if (pos+len > dir->i_size) {
49 		i_size_write(dir, pos+len);
50 		mark_inode_dirty(dir);
51 	}
52 	if (IS_DIRSYNC(dir))
53 		err = write_one_page(page, 1);
54 	else
55 		unlock_page(page);
56 	return err;
57 }
58 
dir_get_page(struct inode * dir,unsigned long n)59 static struct page * dir_get_page(struct inode *dir, unsigned long n)
60 {
61 	struct address_space *mapping = dir->i_mapping;
62 	struct page *page = read_mapping_page(mapping, n, NULL);
63 	if (!IS_ERR(page))
64 		kmap(page);
65 	return page;
66 }
67 
sysv_readdir(struct file * filp,void * dirent,filldir_t filldir)68 static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
69 {
70 	unsigned long pos = filp->f_pos;
71 	struct inode *inode = filp->f_path.dentry->d_inode;
72 	struct super_block *sb = inode->i_sb;
73 	unsigned offset = pos & ~PAGE_CACHE_MASK;
74 	unsigned long n = pos >> PAGE_CACHE_SHIFT;
75 	unsigned long npages = dir_pages(inode);
76 
77 	pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
78 	if (pos >= inode->i_size)
79 		goto done;
80 
81 	for ( ; n < npages; n++, offset = 0) {
82 		char *kaddr, *limit;
83 		struct sysv_dir_entry *de;
84 		struct page *page = dir_get_page(inode, n);
85 
86 		if (IS_ERR(page))
87 			continue;
88 		kaddr = (char *)page_address(page);
89 		de = (struct sysv_dir_entry *)(kaddr+offset);
90 		limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
91 		for ( ;(char*)de <= limit; de++) {
92 			char *name = de->name;
93 			int over;
94 
95 			if (!de->inode)
96 				continue;
97 
98 			offset = (char *)de - kaddr;
99 
100 			over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
101 					((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
102 					fs16_to_cpu(SYSV_SB(sb), de->inode),
103 					DT_UNKNOWN);
104 			if (over) {
105 				dir_put_page(page);
106 				goto done;
107 			}
108 		}
109 		dir_put_page(page);
110 	}
111 
112 done:
113 	filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
114 	return 0;
115 }
116 
117 /* compare strings: name[0..len-1] (not zero-terminated) and
118  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
119  */
namecompare(int len,int maxlen,const char * name,const char * buffer)120 static inline int namecompare(int len, int maxlen,
121 	const char * name, const char * buffer)
122 {
123 	if (len < maxlen && buffer[len])
124 		return 0;
125 	return !memcmp(name, buffer, len);
126 }
127 
128 /*
129  *	sysv_find_entry()
130  *
131  * finds an entry in the specified directory with the wanted name. It
132  * returns the cache buffer in which the entry was found, and the entry
133  * itself (as a parameter - res_dir). It does NOT read the inode of the
134  * entry - you'll have to do that yourself if you want to.
135  */
sysv_find_entry(struct dentry * dentry,struct page ** res_page)136 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
137 {
138 	const char * name = dentry->d_name.name;
139 	int namelen = dentry->d_name.len;
140 	struct inode * dir = dentry->d_parent->d_inode;
141 	unsigned long start, n;
142 	unsigned long npages = dir_pages(dir);
143 	struct page *page = NULL;
144 	struct sysv_dir_entry *de;
145 
146 	*res_page = NULL;
147 
148 	start = SYSV_I(dir)->i_dir_start_lookup;
149 	if (start >= npages)
150 		start = 0;
151 	n = start;
152 
153 	do {
154 		char *kaddr;
155 		page = dir_get_page(dir, n);
156 		if (!IS_ERR(page)) {
157 			kaddr = (char*)page_address(page);
158 			de = (struct sysv_dir_entry *) kaddr;
159 			kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
160 			for ( ; (char *) de <= kaddr ; de++) {
161 				if (!de->inode)
162 					continue;
163 				if (namecompare(namelen, SYSV_NAMELEN,
164 							name, de->name))
165 					goto found;
166 			}
167 			dir_put_page(page);
168 		}
169 
170 		if (++n >= npages)
171 			n = 0;
172 	} while (n != start);
173 
174 	return NULL;
175 
176 found:
177 	SYSV_I(dir)->i_dir_start_lookup = n;
178 	*res_page = page;
179 	return de;
180 }
181 
sysv_add_link(struct dentry * dentry,struct inode * inode)182 int sysv_add_link(struct dentry *dentry, struct inode *inode)
183 {
184 	struct inode *dir = dentry->d_parent->d_inode;
185 	const char * name = dentry->d_name.name;
186 	int namelen = dentry->d_name.len;
187 	struct page *page = NULL;
188 	struct sysv_dir_entry * de;
189 	unsigned long npages = dir_pages(dir);
190 	unsigned long n;
191 	char *kaddr;
192 	loff_t pos;
193 	int err;
194 
195 	/* We take care of directory expansion in the same loop */
196 	for (n = 0; n <= npages; n++) {
197 		page = dir_get_page(dir, n);
198 		err = PTR_ERR(page);
199 		if (IS_ERR(page))
200 			goto out;
201 		kaddr = (char*)page_address(page);
202 		de = (struct sysv_dir_entry *)kaddr;
203 		kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
204 		while ((char *)de <= kaddr) {
205 			if (!de->inode)
206 				goto got_it;
207 			err = -EEXIST;
208 			if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
209 				goto out_page;
210 			de++;
211 		}
212 		dir_put_page(page);
213 	}
214 	BUG();
215 	return -EINVAL;
216 
217 got_it:
218 	pos = page_offset(page) +
219 			(char*)de - (char*)page_address(page);
220 	lock_page(page);
221 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
222 	if (err)
223 		goto out_unlock;
224 	memcpy (de->name, name, namelen);
225 	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
226 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
227 	err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
228 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
229 	mark_inode_dirty(dir);
230 out_page:
231 	dir_put_page(page);
232 out:
233 	return err;
234 out_unlock:
235 	unlock_page(page);
236 	goto out_page;
237 }
238 
sysv_delete_entry(struct sysv_dir_entry * de,struct page * page)239 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
240 {
241 	struct inode *inode = page->mapping->host;
242 	char *kaddr = (char*)page_address(page);
243 	loff_t pos = page_offset(page) + (char *)de - kaddr;
244 	int err;
245 
246 	lock_page(page);
247 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
248 	BUG_ON(err);
249 	de->inode = 0;
250 	err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
251 	dir_put_page(page);
252 	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
253 	mark_inode_dirty(inode);
254 	return err;
255 }
256 
sysv_make_empty(struct inode * inode,struct inode * dir)257 int sysv_make_empty(struct inode *inode, struct inode *dir)
258 {
259 	struct page *page = grab_cache_page(inode->i_mapping, 0);
260 	struct sysv_dir_entry * de;
261 	char *base;
262 	int err;
263 
264 	if (!page)
265 		return -ENOMEM;
266 	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
267 	if (err) {
268 		unlock_page(page);
269 		goto fail;
270 	}
271 	kmap(page);
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 	kunmap(page);
284 	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
285 fail:
286 	page_cache_release(page);
287 	return err;
288 }
289 
290 /*
291  * routine to check that the specified directory is empty (for rmdir)
292  */
sysv_empty_dir(struct inode * inode)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 */
sysv_set_link(struct sysv_dir_entry * de,struct page * page,struct inode * inode)336 void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
337 	struct inode *inode)
338 {
339 	struct inode *dir = page->mapping->host;
340 	loff_t pos = page_offset(page) +
341 			(char *)de-(char*)page_address(page);
342 	int err;
343 
344 	lock_page(page);
345 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
346 	BUG_ON(err);
347 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
348 	err = dir_commit_chunk(page, pos, SYSV_DIRSIZE);
349 	dir_put_page(page);
350 	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
351 	mark_inode_dirty(dir);
352 }
353 
sysv_dotdot(struct inode * dir,struct page ** p)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 
sysv_inode_by_name(struct dentry * dentry)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