/*
   *  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	= minix_readdir,

  	.fsync		= generic_file_fsync,

  };
  
  static inline void dir_put_page(struct page *page)
  {
  	kunmap(page);
  	page_cache_release(page);
  }
  
  /*
   * 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_CACHE_SIZE;
  
  	if (page_nr == (inode->i_size >> PAGE_CACHE_SHIFT))
  		last_byte = inode->i_size & (PAGE_CACHE_SIZE - 1);
  	return last_byte;
  }
  
  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, loff_t pos, unsigned len)

  {

  	struct address_space *mapping = page->mapping;
  	struct inode *dir = mapping->host;

  	int err = 0;

  	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);
  	}

  	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_mapping_page(mapping, n, NULL);

  	if (!IS_ERR(page))

  		kmap(page);

  	return page;

  }
  
  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_CACHE_MASK;
  	n = pos >> PAGE_CACHE_SHIFT;

  
  	for ( ; n < npages; n++, offset = 0) {
  		char *p, *kaddr, *limit;
  		struct page *page = dir_get_page(inode, n);
  
  		if (IS_ERR(page))
  			continue;
  		kaddr = (char *)page_address(page);
  		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)) {

  					dir_put_page(page);

  					return 0;

  				}
  			}

  			ctx->pos += chunk_size;

  		}
  		dir_put_page(page);
  	}

  	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
   * 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.
   */
  minix_dirent *minix_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;
  	struct super_block * sb = dir->i_sb;
  	struct minix_sb_info * sbi = minix_sb(sb);
  	unsigned long n;
  	unsigned long npages = dir_pages(dir);
  	struct page *page = NULL;

  	char *p;

  	char *namx;
  	__u32 inumber;

  	*res_page = NULL;
  
  	for (n = 0; n < npages; n++) {

  		char *kaddr, *limit;

  		page = dir_get_page(dir, n);
  		if (IS_ERR(page))
  			continue;
  
  		kaddr = (char*)page_address(page);

  		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;
  		}
  		dir_put_page(page);
  	}
  	return NULL;
  
  found:
  	*res_page = page;

  	return (minix_dirent *)p;

  }
  
  int minix_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 super_block * sb = dir->i_sb;
  	struct minix_sb_info * sbi = minix_sb(sb);
  	struct page *page = 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;

  
  		page = dir_get_page(dir, n);
  		err = PTR_ERR(page);
  		if (IS_ERR(page))
  			goto out;
  		lock_page(page);
  		kaddr = (char*)page_address(page);
  		dir_end = kaddr + minix_last_byte(dir, n);

  		limit = kaddr + PAGE_CACHE_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;

  		}
  		unlock_page(page);
  		dir_put_page(page);
  	}
  	BUG();
  	return -EINVAL;
  
  got_it:

  	pos = page_offset(page) + p - (char *)page_address(page);

  	err = minix_prepare_chunk(page, 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;
  	}

  	err = dir_commit_chunk(page, pos, sbi->s_dirsize);

  	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
  	mark_inode_dirty(dir);
  out_put:
  	dir_put_page(page);
  out:
  	return err;
  out_unlock:
  	unlock_page(page);
  	goto out_put;
  }
  
  int minix_delete_entry(struct minix_dir_entry *de, struct page *page)
  {

  	struct inode *inode = page->mapping->host;

  	char *kaddr = page_address(page);

  	loff_t pos = page_offset(page) + (char*)de - kaddr;

  	struct minix_sb_info *sbi = minix_sb(inode->i_sb);
  	unsigned len = sbi->s_dirsize;

  	int err;
  
  	lock_page(page);

  	err = minix_prepare_chunk(page, pos, len);

  	if (err == 0) {

  		if (sbi->s_version == MINIX_V3)
  			((minix3_dirent *) de)->inode = 0;
  		else
  			de->inode = 0;

  		err = dir_commit_chunk(page, pos, len);

  	} else {
  		unlock_page(page);
  	}
  	dir_put_page(page);
  	inode->i_ctime = inode->i_mtime = CURRENT_TIME_SEC;
  	mark_inode_dirty(inode);
  	return err;
  }
  
  int minix_make_empty(struct inode *inode, struct inode *dir)
  {

  	struct page *page = grab_cache_page(inode->i_mapping, 0);

  	struct minix_sb_info *sbi = minix_sb(inode->i_sb);

  	char *kaddr;
  	int err;
  
  	if (!page)
  		return -ENOMEM;

  	err = minix_prepare_chunk(page, 0, 2 * sbi->s_dirsize);

  	if (err) {
  		unlock_page(page);
  		goto fail;
  	}

  	kaddr = kmap_atomic(page);

  	memset(kaddr, 0, PAGE_CACHE_SIZE);

  	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_atomic(kaddr);

  
  	err = dir_commit_chunk(page, 0, 2 * sbi->s_dirsize);
  fail:
  	page_cache_release(page);
  	return err;
  }
  
  /*
   * routine to check that the specified directory is empty (for rmdir)
   */
  int minix_empty_dir(struct inode * inode)
  {
  	struct page *page = NULL;
  	unsigned long i, npages = dir_pages(inode);
  	struct minix_sb_info *sbi = minix_sb(inode->i_sb);

  	char *name;
  	__u32 inumber;

  
  	for (i = 0; i < npages; i++) {

  		char *p, *kaddr, *limit;

  		page = dir_get_page(inode, i);

  		if (IS_ERR(page))
  			continue;
  
  		kaddr = (char *)page_address(page);

  		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;
  			}

  		}
  		dir_put_page(page);
  	}
  	return 1;
  
  not_empty:
  	dir_put_page(page);
  	return 0;
  }
  
  /* Releases the page */
  void minix_set_link(struct minix_dir_entry *de, struct page *page,
  	struct inode *inode)
  {

  	struct inode *dir = page->mapping->host;

  	struct minix_sb_info *sbi = minix_sb(dir->i_sb);

  	loff_t pos = page_offset(page) +
  			(char *)de-(char*)page_address(page);

  	int err;
  
  	lock_page(page);

  	err = minix_prepare_chunk(page, pos, sbi->s_dirsize);

  	if (err == 0) {

  		if (sbi->s_version == MINIX_V3)
  			((minix3_dirent *) de)->inode = inode->i_ino;
  		else
  			de->inode = inode->i_ino;

  		err = dir_commit_chunk(page, pos, sbi->s_dirsize);

  	} else {
  		unlock_page(page);
  	}
  	dir_put_page(page);
  	dir->i_mtime = dir->i_ctime = CURRENT_TIME_SEC;
  	mark_inode_dirty(dir);
  }
  
  struct minix_dir_entry * minix_dotdot (struct inode *dir, struct page **p)
  {
  	struct page *page = dir_get_page(dir, 0);
  	struct minix_sb_info *sbi = minix_sb(dir->i_sb);
  	struct minix_dir_entry *de = NULL;
  
  	if (!IS_ERR(page)) {
  		de = minix_next_entry(page_address(page), sbi);
  		*p = page;
  	}
  	return de;
  }
  
  ino_t minix_inode_by_name(struct dentry *dentry)
  {
  	struct page *page;
  	struct minix_dir_entry *de = minix_find_entry(dentry, &page);
  	ino_t res = 0;
  
  	if (de) {

  		struct address_space *mapping = page->mapping;
  		struct inode *inode = 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;

  		dir_put_page(page);
  	}
  	return res;
  }