/*
   * bitmap.c - NTFS kernel bitmap handling.  Part of the Linux-NTFS project.
   *
   * Copyright (c) 2004-2005 Anton Altaparmakov
   *
   * This program/include file 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/include file 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.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program (in the main directory of the Linux-NTFS
   * distribution in the file COPYING); if not, write to the Free Software
   * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #ifdef NTFS_RW
  
  #include <linux/pagemap.h>
  
  #include "bitmap.h"
  #include "debug.h"
  #include "aops.h"
  #include "ntfs.h"
  
  /**
   * __ntfs_bitmap_set_bits_in_run - set a run of bits in a bitmap to a value
   * @vi:			vfs inode describing the bitmap
   * @start_bit:		first bit to set
   * @count:		number of bits to set
   * @value:		value to set the bits to (i.e. 0 or 1)
   * @is_rollback:	if 'true' this is a rollback operation
   *
   * Set @count bits starting at bit @start_bit in the bitmap described by the
   * vfs inode @vi to @value, where @value is either 0 or 1.
   *
   * @is_rollback should always be 'false', it is for internal use to rollback
   * errors.  You probably want to use ntfs_bitmap_set_bits_in_run() instead.
   *
   * Return 0 on success and -errno on error.
   */
  int __ntfs_bitmap_set_bits_in_run(struct inode *vi, const s64 start_bit,
  		const s64 count, const u8 value, const bool is_rollback)
  {
  	s64 cnt = count;
  	pgoff_t index, end_index;
  	struct address_space *mapping;
  	struct page *page;
  	u8 *kaddr;
  	int pos, len;
  	u8 bit;
  
  	BUG_ON(!vi);
  	ntfs_debug("Entering for i_ino 0x%lx, start_bit 0x%llx, count 0x%llx, "
  			"value %u.%s", vi->i_ino, (unsigned long long)start_bit,
  			(unsigned long long)cnt, (unsigned int)value,
  			is_rollback ? " (rollback)" : "");
  	BUG_ON(start_bit < 0);
  	BUG_ON(cnt < 0);
  	BUG_ON(value > 1);
  	/*
  	 * Calculate the indices for the pages containing the first and last
  	 * bits, i.e. @start_bit and @start_bit + @cnt - 1, respectively.
  	 */
  	index = start_bit >> (3 + PAGE_CACHE_SHIFT);
  	end_index = (start_bit + cnt - 1) >> (3 + PAGE_CACHE_SHIFT);
  
  	/* Get the page containing the first bit (@start_bit). */
  	mapping = vi->i_mapping;
  	page = ntfs_map_page(mapping, index);
  	if (IS_ERR(page)) {
  		if (!is_rollback)
  			ntfs_error(vi->i_sb, "Failed to map first page (error "
  					"%li), aborting.", PTR_ERR(page));
  		return PTR_ERR(page);
  	}
  	kaddr = page_address(page);
  
  	/* Set @pos to the position of the byte containing @start_bit. */
  	pos = (start_bit >> 3) & ~PAGE_CACHE_MASK;
  
  	/* Calculate the position of @start_bit in the first byte. */
  	bit = start_bit & 7;
  
  	/* If the first byte is partial, modify the appropriate bits in it. */
  	if (bit) {
  		u8 *byte = kaddr + pos;
  		while ((bit & 7) && cnt) {
  			cnt--;
  			if (value)
  				*byte |= 1 << bit++;
  			else
  				*byte &= ~(1 << bit++);
  		}
  		/* If we are done, unmap the page and return success. */
  		if (!cnt)
  			goto done;
  
  		/* Update @pos to the new position. */
  		pos++;
  	}
  	/*
  	 * Depending on @value, modify all remaining whole bytes in the page up
  	 * to @cnt.
  	 */
  	len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE - pos);
  	memset(kaddr + pos, value ? 0xff : 0, len);
  	cnt -= len << 3;
  
  	/* Update @len to point to the first not-done byte in the page. */
  	if (cnt < 8)
  		len += pos;
  
  	/* If we are not in the last page, deal with all subsequent pages. */
  	while (index < end_index) {
  		BUG_ON(cnt <= 0);
  
  		/* Update @index and get the next page. */
  		flush_dcache_page(page);
  		set_page_dirty(page);
  		ntfs_unmap_page(page);
  		page = ntfs_map_page(mapping, ++index);
  		if (IS_ERR(page))
  			goto rollback;
  		kaddr = page_address(page);
  		/*
  		 * Depending on @value, modify all remaining whole bytes in the
  		 * page up to @cnt.
  		 */
  		len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE);
  		memset(kaddr, value ? 0xff : 0, len);
  		cnt -= len << 3;
  	}
  	/*
  	 * The currently mapped page is the last one.  If the last byte is
  	 * partial, modify the appropriate bits in it.  Note, @len is the
  	 * position of the last byte inside the page.
  	 */
  	if (cnt) {
  		u8 *byte;
  
  		BUG_ON(cnt > 7);
  
  		bit = cnt;
  		byte = kaddr + len;
  		while (bit--) {
  			if (value)
  				*byte |= 1 << bit;
  			else
  				*byte &= ~(1 << bit);
  		}
  	}
  done:
  	/* We are done.  Unmap the page and return success. */
  	flush_dcache_page(page);
  	set_page_dirty(page);
  	ntfs_unmap_page(page);
  	ntfs_debug("Done.");
  	return 0;
  rollback:
  	/*
  	 * Current state:
  	 *	- no pages are mapped
  	 *	- @count - @cnt is the number of bits that have been modified
  	 */
  	if (is_rollback)
  		return PTR_ERR(page);
  	if (count != cnt)
  		pos = __ntfs_bitmap_set_bits_in_run(vi, start_bit, count - cnt,
  				value ? 0 : 1, true);
  	else
  		pos = 0;
  	if (!pos) {
  		/* Rollback was successful. */
  		ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
  				"%li), aborting.", PTR_ERR(page));
  	} else {
  		/* Rollback failed. */
  		ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
  				"%li) and rollback failed (error %i).  "
  				"Aborting and leaving inconsistent metadata.  "
  				"Unmount and run chkdsk.", PTR_ERR(page), pos);
  		NVolSetErrors(NTFS_SB(vi->i_sb));
  	}
  	return PTR_ERR(page);
  }
  
  #endif /* NTFS_RW */