// SPDX-License-Identifier: GPL-2.0

  /*
   * QNX6 file system, Linux implementation.
   *
   * Version : 1.0.0
   *
   * History :
   *
   * 01-02-2012 by Kai Bankett (chaosman@ontika.net) : first release.
   * 16-02-2012 pagemap extension by Al Viro
   *
   */
  
  #include "qnx6.h"
  
  static unsigned qnx6_lfile_checksum(char *name, unsigned size)
  {
  	unsigned crc = 0;
  	char *end = name + size;
  	while (name < end) {
  		crc = ((crc >> 1) + *(name++)) ^
  			((crc & 0x00000001) ? 0x80000000 : 0);
  	}
  	return crc;
  }
  
  static struct page *qnx6_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 unsigned last_entry(struct inode *inode, unsigned long page_nr)
  {
  	unsigned long last_byte = inode->i_size;

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

  	return last_byte / QNX6_DIR_ENTRY_SIZE;
  }
  
  static struct qnx6_long_filename *qnx6_longname(struct super_block *sb,
  					 struct qnx6_long_dir_entry *de,
  					 struct page **p)
  {
  	struct qnx6_sb_info *sbi = QNX6_SB(sb);
  	u32 s = fs32_to_cpu(sbi, de->de_long_inode); /* in block units */

  	u32 n = s >> (PAGE_SHIFT - sb->s_blocksize_bits); /* in pages */

  	/* within page */

  	u32 offs = (s << sb->s_blocksize_bits) & ~PAGE_MASK;

  	struct address_space *mapping = sbi->longfile->i_mapping;
  	struct page *page = read_mapping_page(mapping, n, NULL);
  	if (IS_ERR(page))
  		return ERR_CAST(page);
  	kmap(*p = page);
  	return (struct qnx6_long_filename *)(page_address(page) + offs);
  }
  
  static int qnx6_dir_longfilename(struct inode *inode,
  			struct qnx6_long_dir_entry *de,

  			struct dir_context *ctx,
  			unsigned de_inode)

  {
  	struct qnx6_long_filename *lf;
  	struct super_block *s = inode->i_sb;
  	struct qnx6_sb_info *sbi = QNX6_SB(s);
  	struct page *page;
  	int lf_size;
  
  	if (de->de_size != 0xff) {
  		/* error - long filename entries always have size 0xff
  		   in direntry */

  		pr_err("invalid direntry size (%i).
  ", de->de_size);

  		return 0;
  	}
  	lf = qnx6_longname(s, de, &page);
  	if (IS_ERR(lf)) {

  		pr_err("Error reading longname
  ");

  		return 0;
  	}
  
  	lf_size = fs16_to_cpu(sbi, lf->lf_size);
  
  	if (lf_size > QNX6_LONG_NAME_MAX) {

  		pr_debug("file %s
  ", lf->lf_fname);

  		pr_err("Filename too long (%i)
  ", lf_size);

  		qnx6_put_page(page);
  		return 0;
  	}
  
  	/* calc & validate longfilename checksum
  	   mmi 3g filesystem does not have that checksum */
  	if (!test_opt(s, MMI_FS) && fs32_to_cpu(sbi, de->de_checksum) !=
  			qnx6_lfile_checksum(lf->lf_fname, lf_size))

  		pr_info("long filename checksum error.
  ");

  	pr_debug("qnx6_readdir:%.*s inode:%u
  ",
  		 lf_size, lf->lf_fname, de_inode);

  	if (!dir_emit(ctx, lf->lf_fname, lf_size, de_inode, DT_UNKNOWN)) {

  		qnx6_put_page(page);
  		return 0;
  	}
  
  	qnx6_put_page(page);
  	/* success */
  	return 1;
  }

  static int qnx6_readdir(struct file *file, struct dir_context *ctx)

  {

  	struct inode *inode = file_inode(file);

  	struct super_block *s = inode->i_sb;
  	struct qnx6_sb_info *sbi = QNX6_SB(s);

  	loff_t pos = ctx->pos & ~(QNX6_DIR_ENTRY_SIZE - 1);

  	unsigned long npages = dir_pages(inode);

  	unsigned long n = pos >> PAGE_SHIFT;
  	unsigned start = (pos & ~PAGE_MASK) / QNX6_DIR_ENTRY_SIZE;

  	bool done = false;

  	ctx->pos = pos;
  	if (ctx->pos >= inode->i_size)

  		return 0;
  
  	for ( ; !done && n < npages; n++, start = 0) {
  		struct page *page = qnx6_get_page(inode, n);
  		int limit = last_entry(inode, n);
  		struct qnx6_dir_entry *de;
  		int i = start;
  
  		if (IS_ERR(page)) {

  			pr_err("%s(): read failed
  ", __func__);

  			ctx->pos = (n + 1) << PAGE_SHIFT;

  			return PTR_ERR(page);
  		}
  		de = ((struct qnx6_dir_entry *)page_address(page)) + start;

  		for (; i < limit; i++, de++, ctx->pos += QNX6_DIR_ENTRY_SIZE) {

  			int size = de->de_size;
  			u32 no_inode = fs32_to_cpu(sbi, de->de_inode);
  
  			if (!no_inode || !size)
  				continue;
  
  			if (size > QNX6_SHORT_NAME_MAX) {
  				/* long filename detected
  				   get the filename from long filename
  				   structure / block */
  				if (!qnx6_dir_longfilename(inode,
  					(struct qnx6_long_dir_entry *)de,

  					ctx, no_inode)) {

  					done = true;
  					break;
  				}
  			} else {

  				pr_debug("%s():%.*s inode:%u
  ",
  					 __func__, size, de->de_fname,
  					 no_inode);

  				if (!dir_emit(ctx, de->de_fname, size,
  				      no_inode, DT_UNKNOWN)) {

  					done = true;
  					break;
  				}
  			}
  		}
  		qnx6_put_page(page);
  	}

  	return 0;
  }
  
  /*
   * check if the long filename is correct.
   */
  static unsigned qnx6_long_match(int len, const char *name,
  			struct qnx6_long_dir_entry *de, struct inode *dir)
  {
  	struct super_block *s = dir->i_sb;
  	struct qnx6_sb_info *sbi = QNX6_SB(s);
  	struct page *page;
  	int thislen;
  	struct qnx6_long_filename *lf = qnx6_longname(s, de, &page);
  
  	if (IS_ERR(lf))
  		return 0;
  
  	thislen = fs16_to_cpu(sbi, lf->lf_size);
  	if (len != thislen) {
  		qnx6_put_page(page);
  		return 0;
  	}
  	if (memcmp(name, lf->lf_fname, len) == 0) {
  		qnx6_put_page(page);
  		return fs32_to_cpu(sbi, de->de_inode);
  	}
  	qnx6_put_page(page);
  	return 0;
  }
  
  /*
   * check if the filename is correct.
   */
  static unsigned qnx6_match(struct super_block *s, int len, const char *name,
  			struct qnx6_dir_entry *de)
  {
  	struct qnx6_sb_info *sbi = QNX6_SB(s);
  	if (memcmp(name, de->de_fname, len) == 0)
  		return fs32_to_cpu(sbi, de->de_inode);
  	return 0;
  }
  
  
  unsigned qnx6_find_entry(int len, struct inode *dir, const char *name,
  			 struct page **res_page)
  {
  	struct super_block *s = dir->i_sb;
  	struct qnx6_inode_info *ei = QNX6_I(dir);
  	struct page *page = NULL;
  	unsigned long start, n;
  	unsigned long npages = dir_pages(dir);
  	unsigned ino;
  	struct qnx6_dir_entry *de;
  	struct qnx6_long_dir_entry *lde;
  
  	*res_page = NULL;
  
  	if (npages == 0)
  		return 0;
  	start = ei->i_dir_start_lookup;
  	if (start >= npages)
  		start = 0;
  	n = start;
  
  	do {
  		page = qnx6_get_page(dir, n);
  		if (!IS_ERR(page)) {
  			int limit = last_entry(dir, n);
  			int i;
  
  			de = (struct qnx6_dir_entry *)page_address(page);
  			for (i = 0; i < limit; i++, de++) {
  				if (len <= QNX6_SHORT_NAME_MAX) {
  					/* short filename */
  					if (len != de->de_size)
  						continue;
  					ino = qnx6_match(s, len, name, de);
  					if (ino)
  						goto found;
  				} else if (de->de_size == 0xff) {
  					/* deal with long filename */
  					lde = (struct qnx6_long_dir_entry *)de;
  					ino = qnx6_long_match(len,
  								name, lde, dir);
  					if (ino)
  						goto found;
  				} else

  					pr_err("undefined filename size in inode.
  ");

  			}
  			qnx6_put_page(page);
  		}
  
  		if (++n >= npages)
  			n = 0;
  	} while (n != start);
  	return 0;
  
  found:
  	*res_page = page;
  	ei->i_dir_start_lookup = n;
  	return ino;
  }
  
  const struct file_operations qnx6_dir_operations = {
  	.llseek		= generic_file_llseek,
  	.read		= generic_read_dir,

  	.iterate_shared	= qnx6_readdir,

  	.fsync		= generic_file_fsync,
  };
  
  const struct inode_operations qnx6_dir_inode_operations = {
  	.lookup		= qnx6_lookup,
  };