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
21static int sysv_readdir(struct file *, void *, filldir_t);
22
23const struct file_operations sysv_dir_operations = {
24	.read		= generic_read_dir,
25	.readdir	= sysv_readdir,
26	.fsync		= sysv_sync_file,
27};
28
29static inline void dir_put_page(struct page *page)
30{
31	kunmap(page);
32	page_cache_release(page);
33}
34
35static inline unsigned long dir_pages(struct inode *inode)
36{
37	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
38}
39
40static 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
53static 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
62static 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
108done:
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 */
117static 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 */
133struct 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
173found:
174	SYSV_I(dir)->i_dir_start_lookup = n;
175	*res_page = page;
176	return de;
177}
178
179int 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
214got_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);
227out_page:
228	dir_put_page(page);
229out:
230	return err;
231out_unlock:
232	unlock_page(page);
233	goto out_page;
234}
235
236int 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
256int 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);
284fail:
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 */
293int 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
330not_empty:
331	dir_put_page(page);
332	return 0;
333}
334
335/* Releases the page */
336void 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
354struct 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
366ino_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