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

// SPDX-License-Identifier: GPL-2.0
/*
 *  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/swap.h>
#include "sysv.h"

static int sysv_readdir(struct file *, struct dir_context *);

const struct file_operations sysv_dir_operations = {
	.llseek		= generic_file_llseek,
	.read		= generic_read_dir,
	.iterate_shared	= sysv_readdir,
	.fsync		= generic_file_fsync,
};

inline void dir_put_page(struct page *page, void *page_addr)
{
	kunmap_local((void *)((unsigned long)page_addr & PAGE_MASK));
	put_page(page);
}

static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
{
	struct address_space *mapping = page->mapping;
	struct inode *dir = mapping->host;

	block_write_end(NULL, mapping, pos, len, len, page, NULL);
	if (pos+len > dir->i_size) {
		i_size_write(dir, pos+len);
		mark_inode_dirty(dir);
	}
	unlock_page(page);
}

static int sysv_handle_dirsync(struct inode *dir)
{
	int err;

	err = filemap_write_and_wait(dir->i_mapping);
	if (!err)
		err = sync_inode_metadata(dir, 1);
	return err;
}

/*
 * Calls to dir_get_page()/dir_put_page() must be nested according to the
 * rules documented in mm/highmem.rst.
 *
 * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
 * and must be treated accordingly for nesting purposes.
 */
static void *dir_get_page(struct inode *dir, unsigned long n, struct page **p)
{
	struct address_space *mapping = dir->i_mapping;
	struct page *page = read_mapping_page(mapping, n, NULL);
	if (IS_ERR(page))
		return ERR_CAST(page);
	*p = page;
	return kmap_local_page(page);
}

static int sysv_readdir(struct file *file, struct dir_context *ctx)
{
	unsigned long pos = ctx->pos;
	struct inode *inode = file_inode(file);
	struct super_block *sb = inode->i_sb;
	unsigned long npages = dir_pages(inode);
	unsigned offset;
	unsigned long n;

	ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
	if (pos >= inode->i_size)
		return 0;

	offset = pos & ~PAGE_MASK;
	n = pos >> PAGE_SHIFT;

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

		kaddr = dir_get_page(inode, n, &page);
		if (IS_ERR(kaddr))
			continue;
		de = (struct sysv_dir_entry *)(kaddr+offset);
		limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
		for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
			char *name = de->name;

			if (!de->inode)
				continue;

			if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
					fs16_to_cpu(SYSV_SB(sb), de->inode),
					DT_UNKNOWN)) {
				dir_put_page(page, kaddr);
				return 0;
			}
		}
		dir_put_page(page, kaddr);
	}
	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.
 *
 * On Success dir_put_page() should be called on *res_page.
 *
 * sysv_find_entry() acts as a call to dir_get_page() and must be treated
 * accordingly for nesting purposes.
 */
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 = d_inode(dentry->d_parent);
	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 = dir_get_page(dir, n, &page);

		if (!IS_ERR(kaddr)) {
			de = (struct sysv_dir_entry *)kaddr;
			kaddr += PAGE_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, kaddr);
		}

		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 = d_inode(dentry->d_parent);
	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;
	loff_t pos;
	int err;

	/* We take care of directory expansion in the same loop */
	for (n = 0; n <= npages; n++) {
		kaddr = dir_get_page(dir, n, &page);
		if (IS_ERR(kaddr))
			return PTR_ERR(kaddr);
		de = (struct sysv_dir_entry *)kaddr;
		kaddr += PAGE_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, kaddr);
	}
	BUG();
	return -EINVAL;

got_it:
	pos = page_offset(page) + offset_in_page(de);
	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	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);
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	dir->i_mtime = dir->i_ctime = current_time(dir);
	mark_inode_dirty(dir);
	err = sysv_handle_dirsync(dir);
out_page:
	dir_put_page(page, kaddr);
	return err;
out_unlock:
	unlock_page(page);
	goto out_page;
}

int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
{
	struct inode *inode = page->mapping->host;
	loff_t pos = page_offset(page) + offset_in_page(de);
	int err;

	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	if (err) {
		unlock_page(page);
		return err;
	}
	de->inode = 0;
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	inode->i_ctime = inode->i_mtime = current_time(inode);
	mark_inode_dirty(inode);
	return sysv_handle_dirsync(inode);
}

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

	if (!page)
		return -ENOMEM;
	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
	if (err) {
		unlock_page(page);
		goto fail;
	}
	base = kmap_local_page(page);
	memset(base, 0, PAGE_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,"..");

	kunmap_local(base);
	dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
	err = sysv_handle_dirsync(inode);
fail:
	put_page(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);
	char *kaddr;

	for (i = 0; i < npages; i++) {
		struct sysv_dir_entry *de;

		kaddr = dir_get_page(inode, i, &page);
		if (IS_ERR(kaddr))
			continue;

		de = (struct sysv_dir_entry *)kaddr;
		kaddr += PAGE_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, kaddr);
	}
	return 1;

not_empty:
	dir_put_page(page, kaddr);
	return 0;
}

/* Releases the page */
int sysv_set_link(struct sysv_dir_entry *de, struct page *page,
	struct inode *inode)
{
	struct inode *dir = page->mapping->host;
	loff_t pos = page_offset(page) + offset_in_page(de);
	int err;

	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	if (err) {
		unlock_page(page);
		return err;
	}
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	dir->i_mtime = dir->i_ctime = current_time(dir);
	mark_inode_dirty(dir);
	return sysv_handle_dirsync(inode);
}

/*
 * Calls to dir_get_page()/dir_put_page() must be nested according to the
 * rules documented in mm/highmem.rst.
 *
 * sysv_dotdot() acts as a call to dir_get_page() and must be treated
 * accordingly for nesting purposes.
 */
struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct page **p)
{
	struct sysv_dir_entry *de = dir_get_page(dir, 0, p);

	if (IS_ERR(de))
		return NULL;
	/* ".." is the second directory entry */
	return de + 1;
}

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, de);
	}
	return res;
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	2	/*
	3	* linux/fs/sysv/dir.c
	4	*
	5	* minix/dir.c
	6	* Copyright (C) 1991, 1992 Linus Torvalds
	7	*
	8	* coh/dir.c
	9	* Copyright (C) 1993 Pascal Haible, Bruno Haible
	10	*
	11	* sysv/dir.c
	12	* Copyright (C) 1993 Bruno Haible
	13	*
	14	* SystemV/Coherent directory handling functions
	15	*/
	16
	17	#include <linux/pagemap.h>
	18	#include <linux/highmem.h>
26a6441a	19	#include <linux/swap.h>
1da177e4 LT	20	#include "sysv.h"
1da177e4 LT	21
80886298	22	static int sysv_readdir(struct file , struct dir_context );
1da177e4	23
4b6f5d20	24	const struct file_operations sysv_dir_operations = {
5ac3455a	25	.llseek = generic_file_llseek,
1da177e4	26	.read = generic_read_dir,
3b0a3c1a	27	.iterate_shared = sysv_readdir,
1b061d92	28	.fsync = generic_file_fsync,
1da177e4 LT	29	};
1da177e4 LT	30
83005276	31	inline void dir_put_page(struct page page, void page_addr)
1da177e4	32	{
83005276	33	kunmap_local((void *)((unsigned long)page_addr & PAGE_MASK));
09cbfeaf	34	put_page(page);
1da177e4 LT	35	}
1da177e4 LT	36
4309093e	37	static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
1da177e4	38	{
26a6441a NP	39	struct address_space *mapping = page->mapping;
26a6441a NP	40	struct inode *dir = mapping->host;
1da177e4	41
26a6441a NP	42	block_write_end(NULL, mapping, pos, len, len, page, NULL);
	43	if (pos+len > dir->i_size) {
	44	i_size_write(dir, pos+len);
	45	mark_inode_dirty(dir);
	46	}
4309093e CH	47	unlock_page(page);
	48	}
	49
	50	static int sysv_handle_dirsync(struct inode *dir)
	51	{
	52	int err;
	53
	54	err = filemap_write_and_wait(dir->i_mapping);
	55	if (!err)
	56	err = sync_inode_metadata(dir, 1);
1da177e4 LT	57	return err;
	58	}
	59
83005276 FDF	60	/*
	61	* Calls to dir_get_page()/dir_put_page() must be nested according to the
	62	* rules documented in mm/highmem.rst.
	63	*
	64	* NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
	65	* and must be treated accordingly for nesting purposes.
	66	*/
8dd6c7b2	67	static void dir_get_page(struct inode dir, unsigned long n, struct page **p)
1da177e4 LT	68	{
1da177e4 LT	69	struct address_space *mapping = dir->i_mapping;
090d2b18	70	struct page *page = read_mapping_page(mapping, n, NULL);
8dd6c7b2 FDF	71	if (IS_ERR(page))
8dd6c7b2 FDF	72	return ERR_CAST(page);
8dd6c7b2	73	*p = page;
83005276	74	return kmap_local_page(page);
1da177e4 LT	75	}
1da177e4 LT	76
80886298	77	static int sysv_readdir(struct file file, struct dir_context ctx)
1da177e4	78	{
80886298 AV	79	unsigned long pos = ctx->pos;
80886298 AV	80	struct inode *inode = file_inode(file);
1da177e4	81	struct super_block *sb = inode->i_sb;
1da177e4	82	unsigned long npages = dir_pages(inode);
80886298 AV	83	unsigned offset;
80886298 AV	84	unsigned long n;
1da177e4	85
80886298	86	ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
1da177e4	87	if (pos >= inode->i_size)
80886298 AV	88	return 0;
80886298 AV	89
09cbfeaf KS	90	offset = pos & ~PAGE_MASK;
09cbfeaf KS	91	n = pos >> PAGE_SHIFT;
1da177e4 LT	92
	93	for ( ; n < npages; n++, offset = 0) {
	94	char kaddr, limit;
	95	struct sysv_dir_entry *de;
8dd6c7b2	96	struct page *page;
1da177e4	97
8dd6c7b2 FDF	98	kaddr = dir_get_page(inode, n, &page);
8dd6c7b2 FDF	99	if (IS_ERR(kaddr))
1da177e4	100	continue;
1da177e4	101	de = (struct sysv_dir_entry *)(kaddr+offset);
09cbfeaf	102	limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
80886298	103	for ( ;(char)de <= limit; de++, ctx->pos += sizeof(de)) {
1da177e4	104	char *name = de->name;
1da177e4 LT	105
	106	if (!de->inode)
	107	continue;
	108
80886298	109	if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
1da177e4	110	fs16_to_cpu(SYSV_SB(sb), de->inode),
80886298	111	DT_UNKNOWN)) {
83005276	112	dir_put_page(page, kaddr);
80886298	113	return 0;
1da177e4 LT	114	}
1da177e4 LT	115	}
83005276	116	dir_put_page(page, kaddr);
1da177e4	117	}
1da177e4 LT	118	return 0;
	119	}
	120
	121	/* compare strings: name[0..len-1] (not zero-terminated) and
	122	* buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
	123	*/
	124	static inline int namecompare(int len, int maxlen,
	125	const char * name, const char * buffer)
	126	{
	127	if (len < maxlen && buffer[len])
	128	return 0;
	129	return !memcmp(name, buffer, len);
	130	}
	131
	132	/*
	133	* sysv_find_entry()
	134	*
	135	* finds an entry in the specified directory with the wanted name. It
	136	* returns the cache buffer in which the entry was found, and the entry
	137	* itself (as a parameter - res_dir). It does NOT read the inode of the
	138	* entry - you'll have to do that yourself if you want to.
83005276 FDF	139	*
	140	* On Success dir_put_page() should be called on *res_page.
	141	*
	142	* sysv_find_entry() acts as a call to dir_get_page() and must be treated
	143	* accordingly for nesting purposes.
1da177e4 LT	144	*/
	145	struct sysv_dir_entry sysv_find_entry(struct dentry dentry, struct page **res_page)
	146	{
	147	const char * name = dentry->d_name.name;
	148	int namelen = dentry->d_name.len;
2b0143b5	149	struct inode * dir = d_inode(dentry->d_parent);
1da177e4 LT	150	unsigned long start, n;
	151	unsigned long npages = dir_pages(dir);
	152	struct page *page = NULL;
	153	struct sysv_dir_entry *de;
	154
	155	*res_page = NULL;
	156
	157	start = SYSV_I(dir)->i_dir_start_lookup;
	158	if (start >= npages)
	159	start = 0;
	160	n = start;
	161
	162	do {
8dd6c7b2 FDF	163	char *kaddr = dir_get_page(dir, n, &page);
	164
	165	if (!IS_ERR(kaddr)) {
	166	de = (struct sysv_dir_entry *)kaddr;
09cbfeaf	167	kaddr += PAGE_SIZE - SYSV_DIRSIZE;
1da177e4 LT	168	for ( ; (char *) de <= kaddr ; de++) {
	169	if (!de->inode)
	170	continue;
	171	if (namecompare(namelen, SYSV_NAMELEN,
	172	name, de->name))
	173	goto found;
	174	}
83005276	175	dir_put_page(page, kaddr);
1da177e4	176	}
1da177e4 LT	177
	178	if (++n >= npages)
	179	n = 0;
	180	} while (n != start);
	181
	182	return NULL;
	183
	184	found:
	185	SYSV_I(dir)->i_dir_start_lookup = n;
	186	*res_page = page;
	187	return de;
	188	}
	189
	190	int sysv_add_link(struct dentry dentry, struct inode inode)
	191	{
2b0143b5	192	struct inode *dir = d_inode(dentry->d_parent);
1da177e4 LT	193	const char * name = dentry->d_name.name;
	194	int namelen = dentry->d_name.len;
	195	struct page *page = NULL;
	196	struct sysv_dir_entry * de;
	197	unsigned long npages = dir_pages(dir);
	198	unsigned long n;
	199	char *kaddr;
26a6441a	200	loff_t pos;
1da177e4 LT	201	int err;
	202
	203	/* We take care of directory expansion in the same loop */
	204	for (n = 0; n <= npages; n++) {
8dd6c7b2 FDF	205	kaddr = dir_get_page(dir, n, &page);
	206	if (IS_ERR(kaddr))
	207	return PTR_ERR(kaddr);
1da177e4	208	de = (struct sysv_dir_entry *)kaddr;
09cbfeaf	209	kaddr += PAGE_SIZE - SYSV_DIRSIZE;
1da177e4 LT	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	}
83005276	218	dir_put_page(page, kaddr);
1da177e4 LT	219	}
	220	BUG();
	221	return -EINVAL;
	222
	223	got_it:
4bb1a137	224	pos = page_offset(page) + offset_in_page(de);
1da177e4	225	lock_page(page);
f4e420dc	226	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
1da177e4 LT	227	if (err)
	228	goto out_unlock;
	229	memcpy (de->name, name, namelen);
	230	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
	231	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
4309093e	232	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
02027d42	233	dir->i_mtime = dir->i_ctime = current_time(dir);
1da177e4	234	mark_inode_dirty(dir);
4309093e	235	err = sysv_handle_dirsync(dir);
1da177e4	236	out_page:
83005276	237	dir_put_page(page, kaddr);
1da177e4 LT	238	return err;
	239	out_unlock:
	240	unlock_page(page);
	241	goto out_page;
	242	}
	243
	244	int sysv_delete_entry(struct sysv_dir_entry de, struct page page)
	245	{
f4e420dc	246	struct inode *inode = page->mapping->host;
4bb1a137	247	loff_t pos = page_offset(page) + offset_in_page(de);
1da177e4 LT	248	int err;
	249
	250	lock_page(page);
f4e420dc	251	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
abb7c742 AV	252	if (err) {
	253	unlock_page(page);
	254	return err;
	255	}
1da177e4	256	de->inode = 0;
4309093e	257	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
02027d42	258	inode->i_ctime = inode->i_mtime = current_time(inode);
1da177e4	259	mark_inode_dirty(inode);
4309093e	260	return sysv_handle_dirsync(inode);
1da177e4 LT	261	}
	262
	263	int sysv_make_empty(struct inode inode, struct inode dir)
	264	{
f4e420dc	265	struct page *page = grab_cache_page(inode->i_mapping, 0);
1da177e4 LT	266	struct sysv_dir_entry * de;
	267	char *base;
	268	int err;
	269
	270	if (!page)
	271	return -ENOMEM;
f4e420dc	272	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
1da177e4 LT	273	if (err) {
	274	unlock_page(page);
	275	goto fail;
	276	}
83005276	277	base = kmap_local_page(page);
09cbfeaf	278	memset(base, 0, PAGE_SIZE);
1da177e4 LT	279
	280	de = (struct sysv_dir_entry *) base;
	281	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	282	strcpy(de->name,".");
	283	de++;
	284	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
	285	strcpy(de->name,"..");
	286
83005276	287	kunmap_local(base);
4309093e CH	288	dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
4309093e CH	289	err = sysv_handle_dirsync(inode);
1da177e4	290	fail:
09cbfeaf	291	put_page(page);
1da177e4 LT	292	return err;
	293	}
	294
	295	/*
	296	* routine to check that the specified directory is empty (for rmdir)
	297	*/
	298	int sysv_empty_dir(struct inode * inode)
	299	{
	300	struct super_block *sb = inode->i_sb;
	301	struct page *page = NULL;
	302	unsigned long i, npages = dir_pages(inode);
83005276	303	char *kaddr;
1da177e4 LT	304
1da177e4 LT	305	for (i = 0; i < npages; i++) {
83005276	306	struct sysv_dir_entry *de;
1da177e4	307
8dd6c7b2 FDF	308	kaddr = dir_get_page(inode, i, &page);
8dd6c7b2 FDF	309	if (IS_ERR(kaddr))
1da177e4 LT	310	continue;
1da177e4 LT	311
1da177e4	312	de = (struct sysv_dir_entry *)kaddr;
09cbfeaf	313	kaddr += PAGE_SIZE-SYSV_DIRSIZE;
1da177e4 LT	314
	315	for ( ;(char *)de <= kaddr; de++) {
	316	if (!de->inode)
	317	continue;
	318	/* check for . and .. */
	319	if (de->name[0] != '.')
	320	goto not_empty;
	321	if (!de->name[1]) {
	322	if (de->inode == cpu_to_fs16(SYSV_SB(sb),
	323	inode->i_ino))
	324	continue;
	325	goto not_empty;
	326	}
	327	if (de->name[1] != '.' \|\| de->name[2])
	328	goto not_empty;
	329	}
83005276	330	dir_put_page(page, kaddr);
1da177e4 LT	331	}
	332	return 1;
	333
	334	not_empty:
83005276	335	dir_put_page(page, kaddr);
1da177e4 LT	336	return 0;
	337	}
	338
	339	/* Releases the page */
abb7c742	340	int sysv_set_link(struct sysv_dir_entry de, struct page page,
1da177e4 LT	341	struct inode *inode)
1da177e4 LT	342	{
f4e420dc	343	struct inode *dir = page->mapping->host;
4bb1a137	344	loff_t pos = page_offset(page) + offset_in_page(de);
1da177e4 LT	345	int err;
	346
	347	lock_page(page);
f4e420dc	348	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
abb7c742 AV	349	if (err) {
	350	unlock_page(page);
	351	return err;
	352	}
1da177e4	353	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
4309093e	354	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
02027d42	355	dir->i_mtime = dir->i_ctime = current_time(dir);
1da177e4	356	mark_inode_dirty(dir);
abb7c742	357	return sysv_handle_dirsync(inode);
1da177e4 LT	358	}
1da177e4 LT	359
83005276 FDF	360	/*
	361	* Calls to dir_get_page()/dir_put_page() must be nested according to the
	362	* rules documented in mm/highmem.rst.
	363	*
	364	* sysv_dotdot() acts as a call to dir_get_page() and must be treated
	365	* accordingly for nesting purposes.
	366	*/
8dd6c7b2	367	struct sysv_dir_entry sysv_dotdot(struct inode dir, struct page **p)
1da177e4	368	{
8dd6c7b2	369	struct sysv_dir_entry *de = dir_get_page(dir, 0, p);
1da177e4	370
8dd6c7b2 FDF	371	if (IS_ERR(de))
	372	return NULL;
	373	/* ".." is the second directory entry */
	374	return de + 1;
1da177e4 LT	375	}
	376
	377	ino_t sysv_inode_by_name(struct dentry *dentry)
	378	{
	379	struct page *page;
	380	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
	381	ino_t res = 0;
	382
	383	if (de) {
	384	res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
83005276	385	dir_put_page(page, de);
1da177e4 LT	386	}
	387	return res;
	388	}