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