// SPDX-License-Identifier: GPL-2.0

  /*
   *  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 "ext2.h"

  #include <linux/buffer_head.h>

  #include <linux/pagemap.h>

  #include <linux/swap.h>

  #include <linux/iversion.h>

  
  typedef struct ext2_dir_entry_2 ext2_dirent;

  /*
   * Tests against MAX_REC_LEN etc were put in place for 64k block
   * sizes; if that is not possible on this arch, we can skip
   * those tests and speed things up.
   */

  static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
  {
  	unsigned len = le16_to_cpu(dlen);

  #if (PAGE_SIZE >= 65536)

  	if (len == EXT2_MAX_REC_LEN)
  		return 1 << 16;

  #endif

  	return len;
  }
  
  static inline __le16 ext2_rec_len_to_disk(unsigned len)
  {

  #if (PAGE_SIZE >= 65536)

  	if (len == (1 << 16))
  		return cpu_to_le16(EXT2_MAX_REC_LEN);

  	else
  		BUG_ON(len > (1 << 16));

  #endif

  	return cpu_to_le16(len);
  }

  /*
   * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
   * more robust, but we have what we have
   */
  static inline unsigned ext2_chunk_size(struct inode *inode)
  {
  	return inode->i_sb->s_blocksize;
  }
  
  static inline void ext2_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
  ext2_last_byte(struct inode *inode, unsigned long page_nr)
  {
  	unsigned 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 ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)

  {

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

  	int err = 0;

  	inode_inc_iversion(dir);

  	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);

  		if (!err)

  			err = sync_inode_metadata(dir, 1);

  	} else {

  		unlock_page(page);

  	}

  	return err;
  }

  static bool ext2_check_page(struct page *page, int quiet)

  {
  	struct inode *dir = page->mapping->host;
  	struct super_block *sb = dir->i_sb;
  	unsigned chunk_size = ext2_chunk_size(dir);
  	char *kaddr = page_address(page);
  	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
  	unsigned offs, rec_len;

  	unsigned limit = PAGE_SIZE;

  	ext2_dirent *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 - EXT2_DIR_REC_LEN(1); offs += rec_len) {
  		p = (ext2_dirent *)(kaddr + offs);

  		rec_len = ext2_rec_len_from_disk(p->rec_len);

  		if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))

  			goto Eshort;

  		if (unlikely(rec_len & 3))

  			goto Ealign;

  		if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))

  			goto Enamelen;

  		if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))

  			goto Espan;

  		if (unlikely(le32_to_cpu(p->inode) > max_inumber))

  			goto Einumber;
  	}
  	if (offs != limit)
  		goto Eend;
  out:
  	SetPageChecked(page);

  	return true;

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

  	if (!quiet)
  		ext2_error(sb, __func__,
  			"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";
  	goto bad_entry;
  Einumber:
  	error = "inode out of bounds";
  bad_entry:

  	if (!quiet)
  		ext2_error(sb, __func__, "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) le32_to_cpu(p->inode),
  			rec_len, p->name_len);

  	goto fail;
  Eend:

  	if (!quiet) {
  		p = (ext2_dirent *)(kaddr + offs);
  		ext2_error(sb, "ext2_check_page",
  			"entry in directory #%lu spans the page boundary"
  			"offset=%lu, inode=%lu",

  			dir->i_ino, (page->index<<PAGE_SHIFT)+offs,

  			(unsigned long) le32_to_cpu(p->inode));
  	}

  fail:

  	SetPageError(page);

  	return false;

  }

  static struct page * ext2_get_page(struct inode *dir, unsigned long n,
  				   int quiet)

  {
  	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) || !ext2_check_page(page, quiet))
  				goto fail;
  		}

  	}
  	return page;
  
  fail:
  	ext2_put_page(page);
  	return ERR_PTR(-EIO);
  }
  
  /*
   * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
   *
   * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller.
   */
  static inline int ext2_match (int len, const char * const name,
  					struct ext2_dir_entry_2 * 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 inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
  {

  	return (ext2_dirent *)((char *)p +
  			ext2_rec_len_from_disk(p->rec_len));

  }
  
  static inline unsigned 
  ext2_validate_entry(char *base, unsigned offset, unsigned mask)
  {
  	ext2_dirent *de = (ext2_dirent*)(base + offset);
  	ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));
  	while ((char*)p < (char*)de) {
  		if (p->rec_len == 0)
  			break;
  		p = ext2_next_entry(p);
  	}
  	return (char *)p - base;
  }

  static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
  {

  	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))

  		de->file_type = fs_umode_to_ftype(inode->i_mode);

  	else
  		de->file_type = 0;
  }
  
  static int

  ext2_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);
  	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);

  	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);

  	bool has_filetype;

  
  	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))

  		return 0;

  	has_filetype =
  		EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE);

  
  	for ( ; n < npages; n++, offset = 0) {
  		char *kaddr, *limit;
  		ext2_dirent *de;

  		struct page *page = ext2_get_page(inode, n, 0);

  
  		if (IS_ERR(page)) {

  			ext2_error(sb, __func__,

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

  			ctx->pos += PAGE_SIZE - offset;

  			return PTR_ERR(page);

  		}
  		kaddr = page_address(page);

  		if (unlikely(need_revalidate)) {
  			if (offset) {
  				offset = ext2_validate_entry(kaddr, offset, chunk_mask);

  				ctx->pos = (n<<PAGE_SHIFT) + offset;

  			}

  			file->f_version = inode_query_iversion(inode);
  			need_revalidate = false;

  		}
  		de = (ext2_dirent *)(kaddr+offset);
  		limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
  		for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
  			if (de->rec_len == 0) {

  				ext2_error(sb, __func__,

  					"zero-length directory entry");

  				ext2_put_page(page);

  				return -EIO;

  			}
  			if (de->inode) {

  				unsigned char d_type = DT_UNKNOWN;

  				if (has_filetype)
  					d_type = fs_ftype_to_dtype(de->file_type);

  				if (!dir_emit(ctx, de->name, de->name_len,
  						le32_to_cpu(de->inode),
  						d_type)) {

  					ext2_put_page(page);

  					return 0;

  				}
  			}

  			ctx->pos += ext2_rec_len_from_disk(de->rec_len);

  		}
  		ext2_put_page(page);
  	}

  	return 0;

  }
  
  /*
   *	ext2_find_entry()
   *
   * finds an entry in the specified directory with the wanted name. It

   * returns the page in which the entry was found (as a parameter - res_page),
   * and the entry itself. Page is returned mapped and unlocked.

   * Entry is guaranteed to be valid.
   */

  struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
  			const struct qstr *child, struct page **res_page)

  {

  	const char *name = child->name;
  	int namelen = child->len;

  	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
  	unsigned long start, n;
  	unsigned long npages = dir_pages(dir);
  	struct page *page = NULL;
  	struct ext2_inode_info *ei = EXT2_I(dir);
  	ext2_dirent * de;

  	int dir_has_error = 0;

  
  	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 = ext2_get_page(dir, n, dir_has_error);

  		if (!IS_ERR(page)) {
  			kaddr = page_address(page);
  			de = (ext2_dirent *) kaddr;
  			kaddr += ext2_last_byte(dir, n) - reclen;
  			while ((char *) de <= kaddr) {
  				if (de->rec_len == 0) {

  					ext2_error(dir->i_sb, __func__,

  						"zero-length directory entry");
  					ext2_put_page(page);
  					goto out;
  				}
  				if (ext2_match (namelen, name, de))
  					goto found;
  				de = ext2_next_entry(de);
  			}
  			ext2_put_page(page);

  		} else
  			dir_has_error = 1;

  		if (++n >= npages)
  			n = 0;

  		/* next page is past the blocks we've got */

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

  			ext2_error(dir->i_sb, __func__,

  				"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 ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
  {

  	struct page *page = ext2_get_page(dir, 0, 0);

  	ext2_dirent *de = NULL;
  
  	if (!IS_ERR(page)) {
  		de = ext2_next_entry((ext2_dirent *) page_address(page));
  		*p = page;
  	}
  	return de;
  }

  ino_t ext2_inode_by_name(struct inode *dir, const struct qstr *child)

  {
  	ino_t res = 0;

  	struct ext2_dir_entry_2 *de;

  	struct page *page;
  	

  	de = ext2_find_entry (dir, child, &page);

  	if (de) {
  		res = le32_to_cpu(de->inode);

  		ext2_put_page(page);

  	}
  	return res;
  }

  static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
  {

  	return __block_write_begin(page, pos, len, ext2_get_block);

  }

  /* Releases the page */
  void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,

  		   struct page *page, struct inode *inode, int update_times)

  {

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

  	unsigned len = ext2_rec_len_from_disk(de->rec_len);

  	int err;
  
  	lock_page(page);

  	err = ext2_prepare_chunk(page, pos, len);

  	BUG_ON(err);

  	de->inode = cpu_to_le32(inode->i_ino);

  	ext2_set_de_type(de, inode);
  	err = ext2_commit_chunk(page, pos, len);

  	ext2_put_page(page);

  	if (update_times)

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

  	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
  	mark_inode_dirty(dir);
  }
  
  /*
   *	Parent is locked.
   */
  int ext2_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;
  	unsigned chunk_size = ext2_chunk_size(dir);
  	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
  	unsigned short rec_len, name_len;
  	struct page *page = NULL;
  	ext2_dirent * 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.
  	 * 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 = ext2_get_page(dir, n, 0);

  		err = PTR_ERR(page);
  		if (IS_ERR(page))
  			goto out;
  		lock_page(page);
  		kaddr = page_address(page);
  		dir_end = kaddr + ext2_last_byte(dir, n);
  		de = (ext2_dirent *)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 = ext2_rec_len_to_disk(chunk_size);

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

  				ext2_error(dir->i_sb, __func__,

  					"zero-length directory entry");
  				err = -EIO;
  				goto out_unlock;
  			}
  			err = -EEXIST;
  			if (ext2_match (namelen, name, de))
  				goto out_unlock;
  			name_len = EXT2_DIR_REC_LEN(de->name_len);

  			rec_len = ext2_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 = (ext2_dirent *) ((char *) de + rec_len);
  		}
  		unlock_page(page);
  		ext2_put_page(page);
  	}
  	BUG();
  	return -EINVAL;
  
  got_it:

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

  	err = ext2_prepare_chunk(page, pos, rec_len);

  	if (err)
  		goto out_unlock;
  	if (de->inode) {
  		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);

  		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
  		de->rec_len = ext2_rec_len_to_disk(name_len);

  		de = de1;
  	}
  	de->name_len = namelen;

  	memcpy(de->name, name, namelen);

  	de->inode = cpu_to_le32(inode->i_ino);
  	ext2_set_de_type (de, inode);

  	err = ext2_commit_chunk(page, pos, rec_len);

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

  	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
  	mark_inode_dirty(dir);
  	/* OFFSET_CACHE */
  out_put:
  	ext2_put_page(page);
  out:
  	return err;
  out_unlock:
  	unlock_page(page);
  	goto out_put;
  }
  
  /*
   * ext2_delete_entry deletes a directory entry by merging it with the
   * previous entry. Page is up-to-date. Releases the page.
   */
  int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
  {

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

  	char *kaddr = page_address(page);
  	unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);

  	unsigned to = ((char *)dir - kaddr) +
  				ext2_rec_len_from_disk(dir->rec_len);

  	loff_t pos;

  	ext2_dirent * pde = NULL;
  	ext2_dirent * de = (ext2_dirent *) (kaddr + from);
  	int err;
  
  	while ((char*)de < (char*)dir) {
  		if (de->rec_len == 0) {

  			ext2_error(inode->i_sb, __func__,

  				"zero-length directory entry");
  			err = -EIO;
  			goto out;
  		}
  		pde = de;
  		de = ext2_next_entry(de);
  	}
  	if (pde)
  		from = (char*)pde - (char*)page_address(page);

  	pos = page_offset(page) + from;

  	lock_page(page);

  	err = ext2_prepare_chunk(page, pos, to - from);

  	BUG_ON(err);

  	if (pde)

  		pde->rec_len = ext2_rec_len_to_disk(to - from);

  	dir->inode = 0;

  	err = ext2_commit_chunk(page, pos, to - from);

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

  	EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
  	mark_inode_dirty(inode);
  out:
  	ext2_put_page(page);
  	return err;
  }
  
  /*
   * Set the first fragment of directory.
   */
  int ext2_make_empty(struct inode *inode, struct inode *parent)
  {

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

  	unsigned chunk_size = ext2_chunk_size(inode);
  	struct ext2_dir_entry_2 * de;
  	int err;
  	void *kaddr;
  
  	if (!page)
  		return -ENOMEM;

  	err = ext2_prepare_chunk(page, 0, chunk_size);

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

  	kaddr = kmap_atomic(page);

  	memset(kaddr, 0, chunk_size);

  	de = (struct ext2_dir_entry_2 *)kaddr;
  	de->name_len = 1;

  	de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));

  	memcpy (de->name, ".\0\0", 4);
  	de->inode = cpu_to_le32(inode->i_ino);
  	ext2_set_de_type (de, inode);
  
  	de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
  	de->name_len = 2;

  	de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));

  	de->inode = cpu_to_le32(parent->i_ino);
  	memcpy (de->name, "..\0", 4);
  	ext2_set_de_type (de, inode);

  	kunmap_atomic(kaddr);

  	err = ext2_commit_chunk(page, 0, chunk_size);
  fail:

  	put_page(page);

  	return err;
  }
  
  /*
   * routine to check that the specified directory is empty (for rmdir)
   */
  int ext2_empty_dir (struct inode * inode)
  {
  	struct page *page = NULL;
  	unsigned long i, npages = dir_pages(inode);

  	int dir_has_error = 0;

  
  	for (i = 0; i < npages; i++) {
  		char *kaddr;
  		ext2_dirent * de;

  		page = ext2_get_page(inode, i, dir_has_error);

  		if (IS_ERR(page)) {
  			dir_has_error = 1;

  			continue;

  		}

  
  		kaddr = page_address(page);
  		de = (ext2_dirent *)kaddr;
  		kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
  
  		while ((char *)de <= kaddr) {
  			if (de->rec_len == 0) {

  				ext2_error(inode->i_sb, __func__,

  					"zero-length directory entry");
  				printk("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_le32(inode->i_ino))
  						goto not_empty;
  				} else if (de->name[1] != '.')
  					goto not_empty;
  			}
  			de = ext2_next_entry(de);
  		}
  		ext2_put_page(page);
  	}
  	return 1;
  
  not_empty:
  	ext2_put_page(page);
  	return 0;
  }

  const struct file_operations ext2_dir_operations = {

  	.llseek		= generic_file_llseek,
  	.read		= generic_read_dir,

  	.iterate_shared	= ext2_readdir,

  	.unlocked_ioctl = ext2_ioctl,

  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= ext2_compat_ioctl,
  #endif

  	.fsync		= ext2_fsync,

  };