[linux.git] / fs / sysv / dir.c

/*
 *  linux/fs/sysv/dir.c
 *
 *  minix/dir.c
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  coh/dir.c
 *  Copyright (C) 1993  Pascal Haible, Bruno Haible
 *
 *  sysv/dir.c
 *  Copyright (C) 1993  Bruno Haible
 *
 *  SystemV/Coherent directory handling functions
 */

#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include "sysv.h"

static int sysv_readdir(struct file *, void *, filldir_t);

const struct file_operations sysv_dir_operations = {
	.read		= generic_read_dir,
	.readdir	= sysv_readdir,
	.fsync		= sysv_sync_file,
};

static inline void dir_put_page(struct page *page)
{
	kunmap(page);
	page_cache_release(page);
}

static inline unsigned long dir_pages(struct inode *inode)
{
	return (inode->i_size+PAGE_CACHE_SIZE-1)>>PAGE_CACHE_SHIFT;
}

static int dir_commit_chunk(struct page *page, unsigned from, unsigned to)
{
	struct inode *dir = (struct inode *)page->mapping->host;
	int err = 0;

	page->mapping->a_ops->commit_write(NULL, page, from, to);
	if (IS_DIRSYNC(dir))
		err = write_one_page(page, 1);
	else
		unlock_page(page);
	return err;
}

static struct page * dir_get_page(struct inode *dir, unsigned long n)
{
	struct address_space *mapping = dir->i_mapping;
	struct page *page = read_cache_page(mapping, n,
				(filler_t*)mapping->a_ops->readpage, NULL);
	if (!IS_ERR(page)) {
		wait_on_page_locked(page);
		kmap(page);
		if (!PageUptodate(page))
			goto fail;
	}
	return page;

fail:
	dir_put_page(page);
	return ERR_PTR(-EIO);
}

static int sysv_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
	unsigned long pos = filp->f_pos;
	struct inode *inode = filp->f_dentry->d_inode;
	struct super_block *sb = inode->i_sb;
	unsigned offset = pos & ~PAGE_CACHE_MASK;
	unsigned long n = pos >> PAGE_CACHE_SHIFT;
	unsigned long npages = dir_pages(inode);

	lock_kernel();

	pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
	if (pos >= inode->i_size)
		goto done;

	for ( ; n < npages; n++, offset = 0) {
		char *kaddr, *limit;
		struct sysv_dir_entry *de;
		struct page *page = dir_get_page(inode, n);

		if (IS_ERR(page))
			continue;
		kaddr = (char *)page_address(page);
		de = (struct sysv_dir_entry *)(kaddr+offset);
		limit = kaddr + PAGE_CACHE_SIZE - SYSV_DIRSIZE;
		for ( ;(char*)de <= limit; de++) {
			char *name = de->name;
			int over;

			if (!de->inode)
				continue;

			offset = (char *)de - kaddr;

			over = filldir(dirent, name, strnlen(name,SYSV_NAMELEN),
					((loff_t)n<<PAGE_CACHE_SHIFT) | offset,
					fs16_to_cpu(SYSV_SB(sb), de->inode),
					DT_UNKNOWN);
			if (over) {
				dir_put_page(page);
				goto done;
			}
		}
		dir_put_page(page);
	}

done:
	filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) | offset;
	unlock_kernel();
	return 0;
}

/* compare strings: name[0..len-1] (not zero-terminated) and
 * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
 */
static inline int namecompare(int len, int maxlen,
	const char * name, const char * buffer)
{
	if (len < maxlen && buffer[len])
		return 0;
	return !memcmp(name, buffer, len);
}

/*
 *	sysv_find_entry()
 *
 * finds an entry in the specified directory with the wanted name. It
 * returns the cache buffer in which the entry was found, and the entry
 * itself (as a parameter - res_dir). It does NOT read the inode of the
 * entry - you'll have to do that yourself if you want to.
 */
struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
{
	const char * name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct inode * dir = dentry->d_parent->d_inode;
	unsigned long start, n;
	unsigned long npages = dir_pages(dir);
	struct page *page = NULL;
	struct sysv_dir_entry *de;

	*res_page = NULL;

	start = SYSV_I(dir)->i_dir_start_lookup;
	if (start >= npages)
		start = 0;
	n = start;

	do {
		char *kaddr;
		page = dir_get_page(dir, n);
		if (!IS_ERR(page)) {
			kaddr = (char*)page_address(page);
			de = (struct sysv_dir_entry *) kaddr;
			kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
			for ( ; (char *) de <= kaddr ; de++) {
				if (!de->inode)
					continue;
				if (namecompare(namelen, SYSV_NAMELEN,
							name, de->name))
					goto found;
			}
		}
		dir_put_page(page);

		if (++n >= npages)
			n = 0;
	} while (n != start);

	return NULL;

found:
	SYSV_I(dir)->i_dir_start_lookup = n;
	*res_page = page;
	return de;
}

int sysv_add_link(struct dentry *dentry, struct inode *inode)
{
	struct inode *dir = dentry->d_parent->d_inode;
	const char * name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct page *page = NULL;
	struct sysv_dir_entry * de;
	unsigned long npages = dir_pages(dir);
	unsigned long n;
	char *kaddr;
	unsigned from, to;
	int err;

	/* We take care of directory expansion in the same loop */
	for (n = 0; n <= npages; n++) {
		page = dir_get_page(dir, n);
		err = PTR_ERR(page);
		if (IS_ERR(page))
			goto out;
		kaddr = (char*)page_address(page);
		de = (struct sysv_dir_entry *)kaddr;
		kaddr += PAGE_CACHE_SIZE - SYSV_DIRSIZE;
		while ((char *)de <= kaddr) {
			if (!de->inode)
				goto got_it;
			err = -EEXIST;
			if (namecompare(namelen, SYSV_NAMELEN, name, de->name)) 
				goto out_page;
			de++;
		}
		dir_put_page(page);
	}
	BUG();
	return -EINVAL;

got_it:
	from = (char*)de - (char*)page_address(page);
	to = from + SYSV_DIRSIZE;
	lock_page(page);
	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
	if (err)
		goto out_unlock;
	memcpy (de->name, name, namelen);
	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	err = dir_commit_chunk(page, from, to);
	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
	mark_inode_dirty(dir);
out_page:
	dir_put_page(page);
out:
	return err;
out_unlock:
	unlock_page(page);
	goto out_page;
}

int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
{
	struct address_space *mapping = page->mapping;
	struct inode *inode = (struct inode*)mapping->host;
	char *kaddr = (char*)page_address(page);
	unsigned from = (char*)de - kaddr;
	unsigned to = from + SYSV_DIRSIZE;
	int err;

	lock_page(page);
	err = mapping->a_ops->prepare_write(NULL, page, from, to);
	BUG_ON(err);
	de->inode = 0;
	err = dir_commit_chunk(page, from, to);
	dir_put_page(page);
	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
	mark_inode_dirty(inode);
	return err;
}

int sysv_make_empty(struct inode *inode, struct inode *dir)
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page = grab_cache_page(mapping, 0);
	struct sysv_dir_entry * de;
	char *base;
	int err;

	if (!page)
		return -ENOMEM;
	kmap(page);
	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
	if (err) {
		unlock_page(page);
		goto fail;
	}

	base = (char*)page_address(page);
	memset(base, 0, PAGE_CACHE_SIZE);

	de = (struct sysv_dir_entry *) base;
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	strcpy(de->name,".");
	de++;
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
	strcpy(de->name,"..");

	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
fail:
	kunmap(page);
	page_cache_release(page);
	return err;
}

/*
 * routine to check that the specified directory is empty (for rmdir)
 */
int sysv_empty_dir(struct inode * inode)
{
	struct super_block *sb = inode->i_sb;
	struct page *page = NULL;
	unsigned long i, npages = dir_pages(inode);

	for (i = 0; i < npages; i++) {
		char *kaddr;
		struct sysv_dir_entry * de;
		page = dir_get_page(inode, i);

		if (IS_ERR(page))
			continue;

		kaddr = (char *)page_address(page);
		de = (struct sysv_dir_entry *)kaddr;
		kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;

		for ( ;(char *)de <= kaddr; de++) {
			if (!de->inode)
				continue;
			/* check for . and .. */
			if (de->name[0] != '.')
				goto not_empty;
			if (!de->name[1]) {
				if (de->inode == cpu_to_fs16(SYSV_SB(sb),
							inode->i_ino))
					continue;
				goto not_empty;
			}
			if (de->name[1] != '.' || de->name[2])
				goto not_empty;
		}
		dir_put_page(page);
	}
	return 1;

not_empty:
	dir_put_page(page);
	return 0;
}

/* Releases the page */
void sysv_set_link(struct sysv_dir_entry *de, struct page *page,
	struct inode *inode)
{
	struct inode *dir = (struct inode*)page->mapping->host;
	unsigned from = (char *)de-(char*)page_address(page);
	unsigned to = from + SYSV_DIRSIZE;
	int err;

	lock_page(page);
	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
	BUG_ON(err);
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	err = dir_commit_chunk(page, from, to);
	dir_put_page(page);
	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
	mark_inode_dirty(dir);
}

struct sysv_dir_entry * sysv_dotdot (struct inode *dir, struct page **p)
{
	struct page *page = dir_get_page(dir, 0);
	struct sysv_dir_entry *de = NULL;

	if (!IS_ERR(page)) {
		de = (struct sysv_dir_entry*) page_address(page) + 1;
		*p = page;
	}
	return de;
}

ino_t sysv_inode_by_name(struct dentry *dentry)
{
	struct page *page;
	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
	ino_t res = 0;
	
	if (de) {
		res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
		dir_put_page(page);
	}
	return res;
}
Commit	Line	Data
1da177e4 LT	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
4b6f5d20	23	const struct file_operations sysv_dir_operations = {
1da177e4 LT	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),
54b21a79	106	((loff_t)n<<PAGE_CACHE_SHIFT) \| offset,
1da177e4 LT	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:
54b21a79	118	filp->f_pos = ((loff_t)n << PAGE_CACHE_SHIFT) \| offset;
1da177e4 LT	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);
d6735bfc	256	BUG_ON(err);
1da177e4 LT	257	de->inode = 0;
	258	err = dir_commit_chunk(page, from, to);
	259	dir_put_page(page);
	260	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
	261	mark_inode_dirty(inode);
	262	return err;
	263	}
	264
	265	int sysv_make_empty(struct inode inode, struct inode dir)
	266	{
	267	struct address_space *mapping = inode->i_mapping;
	268	struct page *page = grab_cache_page(mapping, 0);
	269	struct sysv_dir_entry * de;
	270	char *base;
	271	int err;
	272
	273	if (!page)
	274	return -ENOMEM;
	275	kmap(page);
	276	err = mapping->a_ops->prepare_write(NULL, page, 0, 2 * SYSV_DIRSIZE);
	277	if (err) {
	278	unlock_page(page);
	279	goto fail;
	280	}
	281
	282	base = (char*)page_address(page);
	283	memset(base, 0, PAGE_CACHE_SIZE);
	284
	285	de = (struct sysv_dir_entry *) base;
	286	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	287	strcpy(de->name,".");
	288	de++;
	289	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
	290	strcpy(de->name,"..");
	291
	292	err = dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
	293	fail:
	294	kunmap(page);
	295	page_cache_release(page);
	296	return err;
	297	}
	298
	299	/*
	300	* routine to check that the specified directory is empty (for rmdir)
	301	*/
	302	int sysv_empty_dir(struct inode * inode)
	303	{
	304	struct super_block *sb = inode->i_sb;
	305	struct page *page = NULL;
	306	unsigned long i, npages = dir_pages(inode);
	307
	308	for (i = 0; i < npages; i++) {
	309	char *kaddr;
	310	struct sysv_dir_entry * de;
	311	page = dir_get_page(inode, i);
	312
	313	if (IS_ERR(page))
	314	continue;
	315
	316	kaddr = (char *)page_address(page);
	317	de = (struct sysv_dir_entry *)kaddr;
	318	kaddr += PAGE_CACHE_SIZE-SYSV_DIRSIZE;
	319
	320	for ( ;(char *)de <= kaddr; de++) {
321	if (!de->inode)
322	continue;
323	/* check for . and .. */
324	if (de->name[0] != '.')
325	goto not_empty;
326	if (!de->name[1]) {
327	if (de->inode == cpu_to_fs16(SYSV_SB(sb),
328	inode->i_ino))
329	continue;
330	goto not_empty;
331	}
332	if (de->name[1] != '.' \|\| de->name[2])
333	goto not_empty;
334	}
335	dir_put_page(page);
336	}
337	return 1;
338
339	not_empty:
340	dir_put_page(page);
341	return 0;
342	}
343
344	/* Releases the page */
345	void sysv_set_link(struct sysv_dir_entry de, struct page page,
346	struct inode *inode)
347	{
348	struct inode dir = (struct inode)page->mapping->host;
349	unsigned from = (char )de-(char)page_address(page);
350	unsigned to = from + SYSV_DIRSIZE;
351	int err;
352
353	lock_page(page);
354	err = page->mapping->a_ops->prepare_write(NULL, page, from, to);
d6735bfc	355	BUG_ON(err);
1da177e4 LT	356	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	357	err = dir_commit_chunk(page, from, to);
	358	dir_put_page(page);
	359	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
	360	mark_inode_dirty(dir);
	361	}
	362
	363	struct sysv_dir_entry * sysv_dotdot (struct inode dir, struct page *p)
	364	{
	365	struct page *page = dir_get_page(dir, 0);
	366	struct sysv_dir_entry *de = NULL;
	367
	368	if (!IS_ERR(page)) {
	369	de = (struct sysv_dir_entry*) page_address(page) + 1;
	370	*p = page;
	371	}
	372	return de;
	373	}
	374
	375	ino_t sysv_inode_by_name(struct dentry *dentry)
	376	{
	377	struct page *page;
	378	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
	379	ino_t res = 0;
	380
	381	if (de) {
	382	res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
	383	dir_put_page(page);
	384	}
	385	return res;
	386	}