fs/minix/dir.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/minix/dir.c
  *
  *  Copyright (C) 1991, 1992 Linus Torvalds
  *
  *  minix directory handling functions
  *
  *  Updated to filesystem version 3 by Daniel Aragones
  */

 #include "minix.h"
 #include <linux/buffer_head.h>
 #include <linux/highmem.h>
 #include <linux/swap.h>

 typedef struct minix_dir_entry minix_dirent;
 typedef struct minix3_dir_entry minix3_dirent;

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

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

 /*
  * Return the offset into page `page_nr' of the last valid
  * byte in that page, plus one.
  */
 static unsigned
 minix_last_byte(struct inode *inode, unsigned long page_nr)
 {
 	unsigned last_byte = PAGE_SIZE;

 	if (page_nr == (inode->i_size >> PAGE_SHIFT))
 		last_byte = inode->i_size & (PAGE_SIZE - 1);
 	return last_byte;
 }

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

 	block_write_end(NULL, mapping, pos, len, len, folio, NULL);

 	if (pos+len > dir->i_size) {
 		i_size_write(dir, pos+len);
 		mark_inode_dirty(dir);
 	}
 	folio_unlock(folio);
 }

 static int minix_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;
 }

 static void *dir_get_folio(struct inode *dir, unsigned long n,
 		struct folio **foliop)
 {
 	struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);

 	if (IS_ERR(folio))
 		return ERR_CAST(folio);
 	*foliop = folio;
 	return kmap_local_folio(folio, 0);
 }

 static inline void *minix_next_entry(void *de, struct minix_sb_info *sbi)
 {
 	return (void*)((char*)de + sbi->s_dirsize);
 }

 static int minix_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	struct minix_sb_info *sbi = minix_sb(sb);
 	unsigned chunk_size = sbi->s_dirsize;
 	unsigned long npages = dir_pages(inode);
 	unsigned long pos = ctx->pos;
 	unsigned offset;
 	unsigned long n;

 	ctx->pos = pos = ALIGN(pos, chunk_size);
 	if (pos >= inode->i_size)
 		return 0;

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

 	for ( ; n < npages; n++, offset = 0) {
 		char *p, *kaddr, *limit;
 		struct folio *folio;

 		kaddr = dir_get_folio(inode, n, &folio);
 		if (IS_ERR(kaddr))
 			continue;
 		p = kaddr+offset;
 		limit = kaddr + minix_last_byte(inode, n) - chunk_size;
 		for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
 			const char *name;
 			__u32 inumber;
 			if (sbi->s_version == MINIX_V3) {
 				minix3_dirent *de3 = (minix3_dirent *)p;
 				name = de3->name;
 				inumber = de3->inode;
 	 		} else {
 				minix_dirent *de = (minix_dirent *)p;
 				name = de->name;
 				inumber = de->inode;
 			}
 			if (inumber) {
 				unsigned l = strnlen(name, sbi->s_namelen);
 				if (!dir_emit(ctx, name, l,
 					      inumber, DT_UNKNOWN)) {
 					folio_release_kmap(folio, p);
 					return 0;
 				}
 			}
 			ctx->pos += chunk_size;
 		}
 		folio_release_kmap(folio, kaddr);
 	}
 	return 0;
 }

 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);
 }

 /*
  *	minix_find_entry()
  *
  * finds an entry in the specified directory with the wanted name.
  * It does NOT read the inode of the
  * entry - you'll have to do that yourself if you want to.
  *
  * On Success folio_release_kmap() should be called on *foliop.
  */
 minix_dirent *minix_find_entry(struct dentry *dentry, struct folio **foliop)
 {
 	const char * name = dentry->d_name.name;
 	int namelen = dentry->d_name.len;
 	struct inode * dir = d_inode(dentry->d_parent);
 	struct super_block * sb = dir->i_sb;
 	struct minix_sb_info * sbi = minix_sb(sb);
 	unsigned long n;
 	unsigned long npages = dir_pages(dir);
 	char *p;

 	char *namx;
 	__u32 inumber;

 	for (n = 0; n < npages; n++) {
 		char *kaddr, *limit;

 		kaddr = dir_get_folio(dir, n, foliop);
 		if (IS_ERR(kaddr))
 			continue;

 		limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 			if (sbi->s_version == MINIX_V3) {
 				minix3_dirent *de3 = (minix3_dirent *)p;
 				namx = de3->name;
 				inumber = de3->inode;
  			} else {
 				minix_dirent *de = (minix_dirent *)p;
 				namx = de->name;
 				inumber = de->inode;
 			}
 			if (!inumber)
 				continue;
 			if (namecompare(namelen, sbi->s_namelen, name, namx))
 				goto found;
 		}
 		folio_release_kmap(*foliop, kaddr);
 	}
 	return NULL;

 found:
 	return (minix_dirent *)p;
 }

 int minix_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 super_block * sb = dir->i_sb;
 	struct minix_sb_info * sbi = minix_sb(sb);
 	struct folio *folio = NULL;
 	unsigned long npages = dir_pages(dir);
 	unsigned long n;
 	char *kaddr, *p;
 	minix_dirent *de;
 	minix3_dirent *de3;
 	loff_t pos;
 	int err;
 	char *namx = NULL;
 	__u32 inumber;

 	/*
 	 * We take care of directory expansion in the same loop
 	 * This code plays outside i_size, so it locks the page
 	 * to protect that region.
 	 */
 	for (n = 0; n <= npages; n++) {
 		char *limit, *dir_end;

 		kaddr = dir_get_folio(dir, n, &folio);
 		if (IS_ERR(kaddr))
 			return PTR_ERR(kaddr);
 		folio_lock(folio);
 		dir_end = kaddr + minix_last_byte(dir, n);
 		limit = kaddr + PAGE_SIZE - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 			de = (minix_dirent *)p;
 			de3 = (minix3_dirent *)p;
 			if (sbi->s_version == MINIX_V3) {
 				namx = de3->name;
 				inumber = de3->inode;
 		 	} else {
   				namx = de->name;
 				inumber = de->inode;
 			}
 			if (p == dir_end) {
 				/* We hit i_size */
 				if (sbi->s_version == MINIX_V3)
 					de3->inode = 0;
 		 		else
 					de->inode = 0;
 				goto got_it;
 			}
 			if (!inumber)
 				goto got_it;
 			err = -EEXIST;
 			if (namecompare(namelen, sbi->s_namelen, name, namx))
 				goto out_unlock;
 		}
 		folio_unlock(folio);
 		folio_release_kmap(folio, kaddr);
 	}
 	BUG();
 	return -EINVAL;

 got_it:
 	pos = folio_pos(folio) + offset_in_folio(folio, p);
 	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
 	if (err)
 		goto out_unlock;
 	memcpy (namx, name, namelen);
 	if (sbi->s_version == MINIX_V3) {
 		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
 		de3->inode = inode->i_ino;
 	} else {
 		memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
 		de->inode = inode->i_ino;
 	}
 	dir_commit_chunk(folio, pos, sbi->s_dirsize);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	mark_inode_dirty(dir);
 	err = minix_handle_dirsync(dir);
 out_put:
 	folio_release_kmap(folio, kaddr);
 	return err;
 out_unlock:
 	folio_unlock(folio);
 	goto out_put;
 }

 int minix_delete_entry(struct minix_dir_entry *de, struct folio *folio)
 {
 	struct inode *inode = folio->mapping->host;
 	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 	unsigned len = sbi->s_dirsize;
 	int err;

 	folio_lock(folio);
 	err = minix_prepare_chunk(folio, pos, len);
 	if (err) {
 		folio_unlock(folio);
 		return err;
 	}
 	if (sbi->s_version == MINIX_V3)
 		((minix3_dirent *)de)->inode = 0;
 	else
 		de->inode = 0;
 	dir_commit_chunk(folio, pos, len);
 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
 	mark_inode_dirty(inode);
 	return minix_handle_dirsync(inode);
 }

 int minix_make_empty(struct inode *inode, struct inode *dir)
 {
 	struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);
 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 	char *kaddr;
 	int err;

 	if (IS_ERR(folio))
 		return PTR_ERR(folio);
 	err = minix_prepare_chunk(folio, 0, 2 * sbi->s_dirsize);
 	if (err) {
 		folio_unlock(folio);
 		goto fail;
 	}

 	kaddr = kmap_local_folio(folio, 0);
 	memset(kaddr, 0, folio_size(folio));

 	if (sbi->s_version == MINIX_V3) {
 		minix3_dirent *de3 = (minix3_dirent *)kaddr;

 		de3->inode = inode->i_ino;
 		strcpy(de3->name, ".");
 		de3 = minix_next_entry(de3, sbi);
 		de3->inode = dir->i_ino;
 		strcpy(de3->name, "..");
 	} else {
 		minix_dirent *de = (minix_dirent *)kaddr;

 		de->inode = inode->i_ino;
 		strcpy(de->name, ".");
 		de = minix_next_entry(de, sbi);
 		de->inode = dir->i_ino;
 		strcpy(de->name, "..");
 	}
 	kunmap_local(kaddr);

 	dir_commit_chunk(folio, 0, 2 * sbi->s_dirsize);
 	err = minix_handle_dirsync(inode);
 fail:
 	folio_put(folio);
 	return err;
 }

 /*
  * routine to check that the specified directory is empty (for rmdir)
  */
 int minix_empty_dir(struct inode * inode)
 {
 	struct folio *folio = NULL;
 	unsigned long i, npages = dir_pages(inode);
 	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
 	char *name, *kaddr;
 	__u32 inumber;

 	for (i = 0; i < npages; i++) {
 		char *p, *limit;

 		kaddr = dir_get_folio(inode, i, &folio);
 		if (IS_ERR(kaddr))
 			continue;

 		limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
 		for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
 			if (sbi->s_version == MINIX_V3) {
 				minix3_dirent *de3 = (minix3_dirent *)p;
 				name = de3->name;
 				inumber = de3->inode;
 			} else {
 				minix_dirent *de = (minix_dirent *)p;
 				name = de->name;
 				inumber = de->inode;
 			}

 			if (inumber != 0) {
 				/* check for . and .. */
 				if (name[0] != '.')
 					goto not_empty;
 				if (!name[1]) {
 					if (inumber != inode->i_ino)
 						goto not_empty;
 				} else if (name[1] != '.')
 					goto not_empty;
 				else if (name[2])
 					goto not_empty;
 			}
 		}
 		folio_release_kmap(folio, kaddr);
 	}
 	return 1;

 not_empty:
 	folio_release_kmap(folio, kaddr);
 	return 0;
 }

 /* Releases the page */
 int minix_set_link(struct minix_dir_entry *de, struct folio *folio,
 		struct inode *inode)
 {
 	struct inode *dir = folio->mapping->host;
 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
 	int err;

 	folio_lock(folio);
 	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
 	if (err) {
 		folio_unlock(folio);
 		return err;
 	}
 	if (sbi->s_version == MINIX_V3)
 		((minix3_dirent *)de)->inode = inode->i_ino;
 	else
 		de->inode = inode->i_ino;
 	dir_commit_chunk(folio, pos, sbi->s_dirsize);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	mark_inode_dirty(dir);
 	return minix_handle_dirsync(dir);
 }

 struct minix_dir_entry *minix_dotdot(struct inode *dir, struct folio **foliop)
 {
 	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
 	struct minix_dir_entry *de = dir_get_folio(dir, 0, foliop);

 	if (!IS_ERR(de))
 		return minix_next_entry(de, sbi);
 	return NULL;
 }

 ino_t minix_inode_by_name(struct dentry *dentry)
 {
 	struct folio *folio;
 	struct minix_dir_entry *de = minix_find_entry(dentry, &folio);
 	ino_t res = 0;

 	if (de) {
 		struct inode *inode = folio->mapping->host;
 		struct minix_sb_info *sbi = minix_sb(inode->i_sb);

 		if (sbi->s_version == MINIX_V3)
 			res = ((minix3_dirent *) de)->inode;
 		else
 			res = de->inode;
 		folio_release_kmap(folio, de);
 	}
 	return res;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/minix/dir.c
	*
	* Copyright (C) 1991, 1992 Linus Torvalds
	*
	* minix directory handling functions
	*
	* Updated to filesystem version 3 by Daniel Aragones
	*/

	#include "minix.h"
	#include <linux/buffer_head.h>
	#include <linux/highmem.h>
	#include <linux/swap.h>

	typedef struct minix_dir_entry minix_dirent;
	typedef struct minix3_dir_entry minix3_dirent;

	static int minix_readdir(struct file , struct dir_context );

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

	/*
	* Return the offset into page `page_nr' of the last valid
	* byte in that page, plus one.
	*/
	static unsigned
	minix_last_byte(struct inode *inode, unsigned long page_nr)
	{
	unsigned last_byte = PAGE_SIZE;

	if (page_nr == (inode->i_size >> PAGE_SHIFT))
	last_byte = inode->i_size & (PAGE_SIZE - 1);
	return last_byte;
	}

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

	block_write_end(NULL, mapping, pos, len, len, folio, NULL);

	if (pos+len > dir->i_size) {
	i_size_write(dir, pos+len);
	mark_inode_dirty(dir);
	}
	folio_unlock(folio);
	}

	static int minix_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;
	}

	static void dir_get_folio(struct inode dir, unsigned long n,
	struct folio **foliop)
	{
	struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);

	if (IS_ERR(folio))
	return ERR_CAST(folio);
	*foliop = folio;
	return kmap_local_folio(folio, 0);
	}

	static inline void minix_next_entry(void de, struct minix_sb_info *sbi)
	{
	return (void)((char)de + sbi->s_dirsize);
	}

	static int minix_readdir(struct file file, struct dir_context ctx)
	{
	struct inode *inode = file_inode(file);
	struct super_block *sb = inode->i_sb;
	struct minix_sb_info *sbi = minix_sb(sb);
	unsigned chunk_size = sbi->s_dirsize;
	unsigned long npages = dir_pages(inode);
	unsigned long pos = ctx->pos;
	unsigned offset;
	unsigned long n;

	ctx->pos = pos = ALIGN(pos, chunk_size);
	if (pos >= inode->i_size)
	return 0;

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

	for ( ; n < npages; n++, offset = 0) {
	char p, kaddr, *limit;
	struct folio *folio;

	kaddr = dir_get_folio(inode, n, &folio);
	if (IS_ERR(kaddr))
	continue;
	p = kaddr+offset;
	limit = kaddr + minix_last_byte(inode, n) - chunk_size;
	for ( ; p <= limit; p = minix_next_entry(p, sbi)) {
	const char *name;
	__u32 inumber;
	if (sbi->s_version == MINIX_V3) {
	minix3_dirent de3 = (minix3_dirent )p;
	name = de3->name;
	inumber = de3->inode;
	} else {
	minix_dirent de = (minix_dirent )p;
	name = de->name;
	inumber = de->inode;
	}
	if (inumber) {
	unsigned l = strnlen(name, sbi->s_namelen);
	if (!dir_emit(ctx, name, l,
	inumber, DT_UNKNOWN)) {
	folio_release_kmap(folio, p);
	return 0;
	}
	}
	ctx->pos += chunk_size;
	}
	folio_release_kmap(folio, kaddr);
	}
	return 0;
	}

	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);
	}

	/*
	* minix_find_entry()
	*
	* finds an entry in the specified directory with the wanted name.
	* It does NOT read the inode of the
	* entry - you'll have to do that yourself if you want to.
	*
	* On Success folio_release_kmap() should be called on *foliop.
	*/
	minix_dirent minix_find_entry(struct dentry dentry, struct folio **foliop)
	{
	const char * name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct inode * dir = d_inode(dentry->d_parent);
	struct super_block * sb = dir->i_sb;
	struct minix_sb_info * sbi = minix_sb(sb);
	unsigned long n;
	unsigned long npages = dir_pages(dir);
	char *p;

	char *namx;
	__u32 inumber;

	for (n = 0; n < npages; n++) {
	char kaddr, limit;

	kaddr = dir_get_folio(dir, n, foliop);
	if (IS_ERR(kaddr))
	continue;

	limit = kaddr + minix_last_byte(dir, n) - sbi->s_dirsize;
	for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
	if (sbi->s_version == MINIX_V3) {
	minix3_dirent de3 = (minix3_dirent )p;
	namx = de3->name;
	inumber = de3->inode;
	} else {
	minix_dirent de = (minix_dirent )p;
	namx = de->name;
	inumber = de->inode;
	}
	if (!inumber)
	continue;
	if (namecompare(namelen, sbi->s_namelen, name, namx))
	goto found;
	}
	folio_release_kmap(*foliop, kaddr);
	}
	return NULL;

	found:
	return (minix_dirent *)p;
	}

	int minix_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 super_block * sb = dir->i_sb;
	struct minix_sb_info * sbi = minix_sb(sb);
	struct folio *folio = NULL;
	unsigned long npages = dir_pages(dir);
	unsigned long n;
	char kaddr, p;
	minix_dirent *de;
	minix3_dirent *de3;
	loff_t pos;
	int err;
	char *namx = NULL;
	__u32 inumber;

	/*
	* We take care of directory expansion in the same loop
	* This code plays outside i_size, so it locks the page
	* to protect that region.
	*/
	for (n = 0; n <= npages; n++) {
	char limit, dir_end;

	kaddr = dir_get_folio(dir, n, &folio);
	if (IS_ERR(kaddr))
	return PTR_ERR(kaddr);
	folio_lock(folio);
	dir_end = kaddr + minix_last_byte(dir, n);
	limit = kaddr + PAGE_SIZE - sbi->s_dirsize;
	for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
	de = (minix_dirent *)p;
	de3 = (minix3_dirent *)p;
	if (sbi->s_version == MINIX_V3) {
	namx = de3->name;
	inumber = de3->inode;
	} else {
	namx = de->name;
	inumber = de->inode;
	}
	if (p == dir_end) {
	/* We hit i_size */
	if (sbi->s_version == MINIX_V3)
	de3->inode = 0;
	else
	de->inode = 0;
	goto got_it;
	}
	if (!inumber)
	goto got_it;
	err = -EEXIST;
	if (namecompare(namelen, sbi->s_namelen, name, namx))
	goto out_unlock;
	}
	folio_unlock(folio);
	folio_release_kmap(folio, kaddr);
	}
	BUG();
	return -EINVAL;

	got_it:
	pos = folio_pos(folio) + offset_in_folio(folio, p);
	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
	if (err)
	goto out_unlock;
	memcpy (namx, name, namelen);
	if (sbi->s_version == MINIX_V3) {
	memset (namx + namelen, 0, sbi->s_dirsize - namelen - 4);
	de3->inode = inode->i_ino;
	} else {
	memset (namx + namelen, 0, sbi->s_dirsize - namelen - 2);
	de->inode = inode->i_ino;
	}
	dir_commit_chunk(folio, pos, sbi->s_dirsize);
	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
	mark_inode_dirty(dir);
	err = minix_handle_dirsync(dir);
	out_put:
	folio_release_kmap(folio, kaddr);
	return err;
	out_unlock:
	folio_unlock(folio);
	goto out_put;
	}

	int minix_delete_entry(struct minix_dir_entry de, struct folio folio)
	{
	struct inode *inode = folio->mapping->host;
	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
	unsigned len = sbi->s_dirsize;
	int err;

	folio_lock(folio);
	err = minix_prepare_chunk(folio, pos, len);
	if (err) {
	folio_unlock(folio);
	return err;
	}
	if (sbi->s_version == MINIX_V3)
	((minix3_dirent *)de)->inode = 0;
	else
	de->inode = 0;
	dir_commit_chunk(folio, pos, len);
	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
	mark_inode_dirty(inode);
	return minix_handle_dirsync(inode);
	}

	int minix_make_empty(struct inode inode, struct inode dir)
	{
	struct folio *folio = filemap_grab_folio(inode->i_mapping, 0);
	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
	char *kaddr;
	int err;

	if (IS_ERR(folio))
	return PTR_ERR(folio);
	err = minix_prepare_chunk(folio, 0, 2 * sbi->s_dirsize);
	if (err) {
	folio_unlock(folio);
	goto fail;
	}

	kaddr = kmap_local_folio(folio, 0);
	memset(kaddr, 0, folio_size(folio));

	if (sbi->s_version == MINIX_V3) {
	minix3_dirent de3 = (minix3_dirent )kaddr;

	de3->inode = inode->i_ino;
	strcpy(de3->name, ".");
	de3 = minix_next_entry(de3, sbi);
	de3->inode = dir->i_ino;
	strcpy(de3->name, "..");
	} else {
	minix_dirent de = (minix_dirent )kaddr;

	de->inode = inode->i_ino;
	strcpy(de->name, ".");
	de = minix_next_entry(de, sbi);
	de->inode = dir->i_ino;
	strcpy(de->name, "..");
	}
	kunmap_local(kaddr);

	dir_commit_chunk(folio, 0, 2 * sbi->s_dirsize);
	err = minix_handle_dirsync(inode);
	fail:
	folio_put(folio);
	return err;
	}

	/*
	* routine to check that the specified directory is empty (for rmdir)
	*/
	int minix_empty_dir(struct inode * inode)
	{
	struct folio *folio = NULL;
	unsigned long i, npages = dir_pages(inode);
	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
	char name, kaddr;
	__u32 inumber;

	for (i = 0; i < npages; i++) {
	char p, limit;

	kaddr = dir_get_folio(inode, i, &folio);
	if (IS_ERR(kaddr))
	continue;

	limit = kaddr + minix_last_byte(inode, i) - sbi->s_dirsize;
	for (p = kaddr; p <= limit; p = minix_next_entry(p, sbi)) {
	if (sbi->s_version == MINIX_V3) {
	minix3_dirent de3 = (minix3_dirent )p;
	name = de3->name;
	inumber = de3->inode;
	} else {
	minix_dirent de = (minix_dirent )p;
	name = de->name;
	inumber = de->inode;
	}

	if (inumber != 0) {
	/* check for . and .. */
	if (name[0] != '.')
	goto not_empty;
	if (!name[1]) {
	if (inumber != inode->i_ino)
	goto not_empty;
	} else if (name[1] != '.')
	goto not_empty;
	else if (name[2])
	goto not_empty;
	}
	}
	folio_release_kmap(folio, kaddr);
	}
	return 1;

	not_empty:
	folio_release_kmap(folio, kaddr);
	return 0;
	}

	/* Releases the page */
	int minix_set_link(struct minix_dir_entry de, struct folio folio,
	struct inode *inode)
	{
	struct inode *dir = folio->mapping->host;
	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
	loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
	int err;

	folio_lock(folio);
	err = minix_prepare_chunk(folio, pos, sbi->s_dirsize);
	if (err) {
	folio_unlock(folio);
	return err;
	}
	if (sbi->s_version == MINIX_V3)
	((minix3_dirent *)de)->inode = inode->i_ino;
	else
	de->inode = inode->i_ino;
	dir_commit_chunk(folio, pos, sbi->s_dirsize);
	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
	mark_inode_dirty(dir);
	return minix_handle_dirsync(dir);
	}

	struct minix_dir_entry minix_dotdot(struct inode dir, struct folio **foliop)
	{
	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
	struct minix_dir_entry *de = dir_get_folio(dir, 0, foliop);

	if (!IS_ERR(de))
	return minix_next_entry(de, sbi);
	return NULL;
	}

	ino_t minix_inode_by_name(struct dentry *dentry)
	{
	struct folio *folio;
	struct minix_dir_entry *de = minix_find_entry(dentry, &folio);
	ino_t res = 0;

	if (de) {
	struct inode *inode = folio->mapping->host;
	struct minix_sb_info *sbi = minix_sb(inode->i_sb);

	if (sbi->s_version == MINIX_V3)
	res = ((minix3_dirent *) de)->inode;
	else
	res = de->inode;
	folio_release_kmap(folio, de);
	}
	return res;
	}