/*
   * dir.c - NILFS directory entry operations
   *
   * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *

   * Modified for NILFS by Amagai Yoshiji.

   */
  /*
   *  linux/fs/ext2/dir.c
   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   *  from
   *
   *  linux/fs/minix/dir.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  ext2 directory handling functions
   *
   *  Big-endian to little-endian byte-swapping/bitmaps by
   *        David S. Miller (davem@caip.rutgers.edu), 1995
   *
   * All code that works with directory layout had been switched to pagecache
   * and moved here. AV
   */
  
  #include <linux/pagemap.h>

  #include "nilfs.h"
  #include "page.h"

  static inline unsigned int nilfs_rec_len_from_disk(__le16 dlen)
  {
  	unsigned int len = le16_to_cpu(dlen);
  
  #if (PAGE_SIZE >= 65536)
  	if (len == NILFS_MAX_REC_LEN)
  		return 1 << 16;
  #endif
  	return len;
  }
  
  static inline __le16 nilfs_rec_len_to_disk(unsigned int len)
  {
  #if (PAGE_SIZE >= 65536)
  	if (len == (1 << 16))
  		return cpu_to_le16(NILFS_MAX_REC_LEN);
  
  	BUG_ON(len > (1 << 16));
  #endif
  	return cpu_to_le16(len);
  }

  /*
   * nilfs uses block-sized chunks. Arguably, sector-sized ones would be
   * more robust, but we have what we have
   */

  static inline unsigned int nilfs_chunk_size(struct inode *inode)

  {
  	return inode->i_sb->s_blocksize;
  }
  
  static inline void nilfs_put_page(struct page *page)
  {
  	kunmap(page);

  	put_page(page);

  }

  /*
   * Return the offset into page `page_nr' of the last valid
   * byte in that page, plus one.
   */

  static unsigned int nilfs_last_byte(struct inode *inode, unsigned long page_nr)

  {

  	unsigned int last_byte = inode->i_size;

  	last_byte -= page_nr << PAGE_SHIFT;
  	if (last_byte > PAGE_SIZE)
  		last_byte = PAGE_SIZE;

  	return last_byte;
  }

  static int nilfs_prepare_chunk(struct page *page, unsigned int from,
  			       unsigned int to)

  {
  	loff_t pos = page_offset(page) + from;

  	return __block_write_begin(page, pos, to - from, nilfs_get_block);

  }

  static void nilfs_commit_chunk(struct page *page,
  			       struct address_space *mapping,

  			       unsigned int from, unsigned int to)

  {
  	struct inode *dir = mapping->host;

  	loff_t pos = page_offset(page) + from;

  	unsigned int len = to - from;
  	unsigned int nr_dirty, copied;

  	int err;
  
  	nr_dirty = nilfs_page_count_clean_buffers(page, from, to);
  	copied = block_write_end(NULL, mapping, pos, len, len, page, NULL);

  	if (pos + copied > dir->i_size)

  		i_size_write(dir, pos + copied);

  	if (IS_DIRSYNC(dir))
  		nilfs_set_transaction_flag(NILFS_TI_SYNC);

  	err = nilfs_set_file_dirty(dir, nr_dirty);

  	WARN_ON(err); /* do not happen */

  	unlock_page(page);

  }

  static bool nilfs_check_page(struct page *page)

  {
  	struct inode *dir = page->mapping->host;
  	struct super_block *sb = dir->i_sb;

  	unsigned int chunk_size = nilfs_chunk_size(dir);

  	char *kaddr = page_address(page);

  	unsigned int offs, rec_len;
  	unsigned int limit = PAGE_SIZE;

  	struct nilfs_dir_entry *p;
  	char *error;

  	if ((dir->i_size >> PAGE_SHIFT) == page->index) {
  		limit = dir->i_size & ~PAGE_MASK;

  		if (limit & (chunk_size - 1))
  			goto Ebadsize;
  		if (!limit)
  			goto out;
  	}
  	for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
  		p = (struct nilfs_dir_entry *)(kaddr + offs);

  		rec_len = nilfs_rec_len_from_disk(p->rec_len);

  
  		if (rec_len < NILFS_DIR_REC_LEN(1))
  			goto Eshort;
  		if (rec_len & 3)
  			goto Ealign;
  		if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
  			goto Enamelen;
  		if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
  			goto Espan;
  	}
  	if (offs != limit)
  		goto Eend;
  out:
  	SetPageChecked(page);

  	return true;

  
  	/* Too bad, we had an error */
  
  Ebadsize:

  	nilfs_error(sb,

  		    "size of directory #%lu is not a multiple of chunk size",

  		    dir->i_ino);

  	goto fail;
  Eshort:
  	error = "rec_len is smaller than minimal";
  	goto bad_entry;
  Ealign:
  	error = "unaligned directory entry";
  	goto bad_entry;
  Enamelen:
  	error = "rec_len is too small for name_len";
  	goto bad_entry;
  Espan:
  	error = "directory entry across blocks";
  bad_entry:

  	nilfs_error(sb,
  		    "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
  		    dir->i_ino, error, (page->index << PAGE_SHIFT) + offs,
  		    (unsigned long)le64_to_cpu(p->inode),

  		    rec_len, p->name_len);
  	goto fail;
  Eend:
  	p = (struct nilfs_dir_entry *)(kaddr + offs);

  	nilfs_error(sb,
  		    "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
  		    dir->i_ino, (page->index << PAGE_SHIFT) + offs,
  		    (unsigned long)le64_to_cpu(p->inode));

  fail:

  	SetPageError(page);

  	return false;

  }
  
  static struct page *nilfs_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);

  		if (unlikely(!PageChecked(page))) {
  			if (PageError(page) || !nilfs_check_page(page))
  				goto fail;
  		}

  	}
  	return page;
  
  fail:
  	nilfs_put_page(page);
  	return ERR_PTR(-EIO);
  }
  
  /*
   * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
   *
   * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
   */
  static int

  nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)

  {
  	if (len != de->name_len)
  		return 0;
  	if (!de->inode)
  		return 0;
  	return !memcmp(name, de->name, len);
  }
  
  /*
   * p is at least 6 bytes before the end of page
   */
  static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
  {

  	return (struct nilfs_dir_entry *)((char *)p +
  					  nilfs_rec_len_from_disk(p->rec_len));

  }
  
  static unsigned char
  nilfs_filetype_table[NILFS_FT_MAX] = {
  	[NILFS_FT_UNKNOWN]	= DT_UNKNOWN,
  	[NILFS_FT_REG_FILE]	= DT_REG,
  	[NILFS_FT_DIR]		= DT_DIR,
  	[NILFS_FT_CHRDEV]	= DT_CHR,
  	[NILFS_FT_BLKDEV]	= DT_BLK,
  	[NILFS_FT_FIFO]		= DT_FIFO,
  	[NILFS_FT_SOCK]		= DT_SOCK,
  	[NILFS_FT_SYMLINK]	= DT_LNK,
  };
  
  #define S_SHIFT 12
  static unsigned char
  nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
  	[S_IFREG >> S_SHIFT]	= NILFS_FT_REG_FILE,
  	[S_IFDIR >> S_SHIFT]	= NILFS_FT_DIR,
  	[S_IFCHR >> S_SHIFT]	= NILFS_FT_CHRDEV,
  	[S_IFBLK >> S_SHIFT]	= NILFS_FT_BLKDEV,
  	[S_IFIFO >> S_SHIFT]	= NILFS_FT_FIFO,
  	[S_IFSOCK >> S_SHIFT]	= NILFS_FT_SOCK,
  	[S_IFLNK >> S_SHIFT]	= NILFS_FT_SYMLINK,
  };
  
  static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
  {

  	umode_t mode = inode->i_mode;

  
  	de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
  }

  static int nilfs_readdir(struct file *file, struct dir_context *ctx)

  {

  	loff_t pos = ctx->pos;
  	struct inode *inode = file_inode(file);

  	struct super_block *sb = inode->i_sb;

  	unsigned int offset = pos & ~PAGE_MASK;
  	unsigned long n = pos >> PAGE_SHIFT;

  	unsigned long npages = dir_pages(inode);

  
  	if (pos > inode->i_size - NILFS_DIR_REC_LEN(1))

  		return 0;

  
  	for ( ; n < npages; n++, offset = 0) {
  		char *kaddr, *limit;
  		struct nilfs_dir_entry *de;
  		struct page *page = nilfs_get_page(inode, n);
  
  		if (IS_ERR(page)) {

  			nilfs_error(sb, "bad page in #%lu", inode->i_ino);

  			ctx->pos += PAGE_SIZE - offset;

  			return -EIO;

  		}
  		kaddr = page_address(page);
  		de = (struct nilfs_dir_entry *)(kaddr + offset);
  		limit = kaddr + nilfs_last_byte(inode, n) -
  			NILFS_DIR_REC_LEN(1);
  		for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
  			if (de->rec_len == 0) {

  				nilfs_error(sb, "zero-length directory entry");

  				nilfs_put_page(page);

  				return -EIO;

  			}
  			if (de->inode) {

  				unsigned char t;

  				if (de->file_type < NILFS_FT_MAX)
  					t = nilfs_filetype_table[de->file_type];
  				else
  					t = DT_UNKNOWN;

  				if (!dir_emit(ctx, de->name, de->name_len,
  						le64_to_cpu(de->inode), t)) {

  					nilfs_put_page(page);

  					return 0;

  				}
  			}

  			ctx->pos += nilfs_rec_len_from_disk(de->rec_len);

  		}
  		nilfs_put_page(page);
  	}

  	return 0;

  }
  
  /*
   *	nilfs_find_entry()
   *
   * finds an entry in the specified directory with the wanted name. It
   * returns the page in which the entry was found, and the entry itself
   * (as a parameter - res_dir). Page is returned mapped and unlocked.
   * Entry is guaranteed to be valid.
   */
  struct nilfs_dir_entry *

  nilfs_find_entry(struct inode *dir, const struct qstr *qstr,

  		 struct page **res_page)
  {

  	const unsigned char *name = qstr->name;
  	int namelen = qstr->len;

  	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);

  	unsigned long start, n;
  	unsigned long npages = dir_pages(dir);
  	struct page *page = NULL;
  	struct nilfs_inode_info *ei = NILFS_I(dir);
  	struct nilfs_dir_entry *de;
  
  	if (npages == 0)
  		goto out;
  
  	/* OFFSET_CACHE */
  	*res_page = NULL;
  
  	start = ei->i_dir_start_lookup;
  	if (start >= npages)
  		start = 0;
  	n = start;
  	do {
  		char *kaddr;

  		page = nilfs_get_page(dir, n);
  		if (!IS_ERR(page)) {
  			kaddr = page_address(page);
  			de = (struct nilfs_dir_entry *)kaddr;
  			kaddr += nilfs_last_byte(dir, n) - reclen;
  			while ((char *) de <= kaddr) {
  				if (de->rec_len == 0) {

  					nilfs_error(dir->i_sb,

  						"zero-length directory entry");
  					nilfs_put_page(page);
  					goto out;
  				}
  				if (nilfs_match(namelen, name, de))
  					goto found;
  				de = nilfs_next_entry(de);
  			}
  			nilfs_put_page(page);
  		}
  		if (++n >= npages)
  			n = 0;
  		/* next page is past the blocks we've got */

  		if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {

  			nilfs_error(dir->i_sb,

  			       "dir %lu size %lld exceeds block count %llu",

  			       dir->i_ino, dir->i_size,
  			       (unsigned long long)dir->i_blocks);
  			goto out;
  		}
  	} while (n != start);
  out:
  	return NULL;
  
  found:
  	*res_page = page;
  	ei->i_dir_start_lookup = n;
  	return de;
  }
  
  struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
  {
  	struct page *page = nilfs_get_page(dir, 0);
  	struct nilfs_dir_entry *de = NULL;
  
  	if (!IS_ERR(page)) {
  		de = nilfs_next_entry(
  			(struct nilfs_dir_entry *)page_address(page));
  		*p = page;
  	}
  	return de;
  }

  ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)

  {
  	ino_t res = 0;
  	struct nilfs_dir_entry *de;
  	struct page *page;

  	de = nilfs_find_entry(dir, qstr, &page);

  	if (de) {
  		res = le64_to_cpu(de->inode);
  		kunmap(page);

  		put_page(page);

  	}
  	return res;
  }
  
  /* Releases the page */
  void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
  		    struct page *page, struct inode *inode)
  {

  	unsigned int from = (char *)de - (char *)page_address(page);
  	unsigned int to = from + nilfs_rec_len_from_disk(de->rec_len);

  	struct address_space *mapping = page->mapping;
  	int err;
  
  	lock_page(page);

  	err = nilfs_prepare_chunk(page, from, to);

  	BUG_ON(err);
  	de->inode = cpu_to_le64(inode->i_ino);
  	nilfs_set_de_type(de, inode);

  	nilfs_commit_chunk(page, mapping, from, to);

  	nilfs_put_page(page);

  	dir->i_mtime = dir->i_ctime = current_time(dir);

  }
  
  /*
   *	Parent is locked.
   */
  int nilfs_add_link(struct dentry *dentry, struct inode *inode)
  {

  	struct inode *dir = d_inode(dentry->d_parent);

  	const unsigned char *name = dentry->d_name.name;

  	int namelen = dentry->d_name.len;

  	unsigned int chunk_size = nilfs_chunk_size(dir);
  	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);

  	unsigned short rec_len, name_len;
  	struct page *page = NULL;
  	struct nilfs_dir_entry *de;
  	unsigned long npages = dir_pages(dir);
  	unsigned long n;
  	char *kaddr;

  	unsigned int from, to;

  	int err;
  
  	/*
  	 * 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 *dir_end;
  
  		page = nilfs_get_page(dir, n);
  		err = PTR_ERR(page);
  		if (IS_ERR(page))
  			goto out;
  		lock_page(page);
  		kaddr = page_address(page);
  		dir_end = kaddr + nilfs_last_byte(dir, n);
  		de = (struct nilfs_dir_entry *)kaddr;

  		kaddr += PAGE_SIZE - reclen;

  		while ((char *)de <= kaddr) {
  			if ((char *)de == dir_end) {
  				/* We hit i_size */
  				name_len = 0;
  				rec_len = chunk_size;

  				de->rec_len = nilfs_rec_len_to_disk(chunk_size);

  				de->inode = 0;
  				goto got_it;
  			}
  			if (de->rec_len == 0) {

  				nilfs_error(dir->i_sb,

  					    "zero-length directory entry");
  				err = -EIO;
  				goto out_unlock;
  			}
  			err = -EEXIST;
  			if (nilfs_match(namelen, name, de))
  				goto out_unlock;
  			name_len = NILFS_DIR_REC_LEN(de->name_len);

  			rec_len = nilfs_rec_len_from_disk(de->rec_len);

  			if (!de->inode && rec_len >= reclen)
  				goto got_it;
  			if (rec_len >= name_len + reclen)
  				goto got_it;
  			de = (struct nilfs_dir_entry *)((char *)de + rec_len);
  		}
  		unlock_page(page);
  		nilfs_put_page(page);
  	}
  	BUG();
  	return -EINVAL;
  
  got_it:
  	from = (char *)de - (char *)page_address(page);
  	to = from + rec_len;

  	err = nilfs_prepare_chunk(page, from, to);

  	if (err)
  		goto out_unlock;
  	if (de->inode) {
  		struct nilfs_dir_entry *de1;
  
  		de1 = (struct nilfs_dir_entry *)((char *)de + name_len);

  		de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
  		de->rec_len = nilfs_rec_len_to_disk(name_len);

  		de = de1;
  	}
  	de->name_len = namelen;
  	memcpy(de->name, name, namelen);
  	de->inode = cpu_to_le64(inode->i_ino);
  	nilfs_set_de_type(de, inode);

  	nilfs_commit_chunk(page, page->mapping, from, to);

  	dir->i_mtime = dir->i_ctime = current_time(dir);

  	nilfs_mark_inode_dirty(dir);

  	/* OFFSET_CACHE */
  out_put:
  	nilfs_put_page(page);
  out:
  	return err;
  out_unlock:
  	unlock_page(page);
  	goto out_put;
  }
  
  /*
   * nilfs_delete_entry deletes a directory entry by merging it with the
   * previous entry. Page is up-to-date. Releases the page.
   */
  int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
  {
  	struct address_space *mapping = page->mapping;
  	struct inode *inode = mapping->host;
  	char *kaddr = page_address(page);

  	unsigned int from, to;
  	struct nilfs_dir_entry *de, *pde = NULL;

  	int err;

  	from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
  	to = ((char *)dir - kaddr) + nilfs_rec_len_from_disk(dir->rec_len);
  	de = (struct nilfs_dir_entry *)(kaddr + from);

  	while ((char *)de < (char *)dir) {
  		if (de->rec_len == 0) {

  			nilfs_error(inode->i_sb,

  				    "zero-length directory entry");
  			err = -EIO;
  			goto out;
  		}
  		pde = de;
  		de = nilfs_next_entry(de);
  	}
  	if (pde)
  		from = (char *)pde - (char *)page_address(page);
  	lock_page(page);

  	err = nilfs_prepare_chunk(page, from, to);

  	BUG_ON(err);
  	if (pde)

  		pde->rec_len = nilfs_rec_len_to_disk(to - from);

  	dir->inode = 0;

  	nilfs_commit_chunk(page, mapping, from, to);

  	inode->i_ctime = inode->i_mtime = current_time(inode);

  out:
  	nilfs_put_page(page);
  	return err;
  }
  
  /*
   * Set the first fragment of directory.
   */
  int nilfs_make_empty(struct inode *inode, struct inode *parent)
  {
  	struct address_space *mapping = inode->i_mapping;
  	struct page *page = grab_cache_page(mapping, 0);

  	unsigned int chunk_size = nilfs_chunk_size(inode);

  	struct nilfs_dir_entry *de;
  	int err;
  	void *kaddr;
  
  	if (!page)
  		return -ENOMEM;

  	err = nilfs_prepare_chunk(page, 0, chunk_size);

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

  	kaddr = kmap_atomic(page);

  	memset(kaddr, 0, chunk_size);
  	de = (struct nilfs_dir_entry *)kaddr;
  	de->name_len = 1;

  	de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));

  	memcpy(de->name, ".\0\0", 4);
  	de->inode = cpu_to_le64(inode->i_ino);
  	nilfs_set_de_type(de, inode);
  
  	de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
  	de->name_len = 2;

  	de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));

  	de->inode = cpu_to_le64(parent->i_ino);
  	memcpy(de->name, "..\0", 4);
  	nilfs_set_de_type(de, inode);

  	kunmap_atomic(kaddr);

  	nilfs_commit_chunk(page, mapping, 0, chunk_size);

  fail:

  	put_page(page);

  	return err;
  }
  
  /*
   * routine to check that the specified directory is empty (for rmdir)
   */
  int nilfs_empty_dir(struct inode *inode)
  {
  	struct page *page = NULL;
  	unsigned long i, npages = dir_pages(inode);
  
  	for (i = 0; i < npages; i++) {
  		char *kaddr;
  		struct nilfs_dir_entry *de;
  
  		page = nilfs_get_page(inode, i);
  		if (IS_ERR(page))
  			continue;
  
  		kaddr = page_address(page);
  		de = (struct nilfs_dir_entry *)kaddr;
  		kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);
  
  		while ((char *)de <= kaddr) {
  			if (de->rec_len == 0) {

  				nilfs_error(inode->i_sb,

  					    "zero-length directory entry (kaddr=%p, de=%p)",
  					    kaddr, de);

  				goto not_empty;
  			}
  			if (de->inode != 0) {
  				/* check for . and .. */
  				if (de->name[0] != '.')
  					goto not_empty;
  				if (de->name_len > 2)
  					goto not_empty;
  				if (de->name_len < 2) {
  					if (de->inode !=
  					    cpu_to_le64(inode->i_ino))
  						goto not_empty;
  				} else if (de->name[1] != '.')
  					goto not_empty;
  			}
  			de = nilfs_next_entry(de);
  		}
  		nilfs_put_page(page);
  	}
  	return 1;
  
  not_empty:
  	nilfs_put_page(page);
  	return 0;
  }

  const struct file_operations nilfs_dir_operations = {

  	.llseek		= generic_file_llseek,
  	.read		= generic_read_dir,

  	.iterate_shared	= nilfs_readdir,

  	.unlocked_ioctl	= nilfs_ioctl,

  #ifdef CONFIG_COMPAT

  	.compat_ioctl	= nilfs_compat_ioctl,

  #endif	/* CONFIG_COMPAT */
  	.fsync		= nilfs_sync_file,
  
  };