1/*
2 * bitmap.c - NTFS kernel bitmap handling.  Part of the Linux-NTFS project.
3 *
4 * Copyright (c) 2004-2005 Anton Altaparmakov
5 *
6 * This program/include file is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as published
8 * by the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program/include file is distributed in the hope that it will be
12 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program (in the main directory of the Linux-NTFS
18 * distribution in the file COPYING); if not, write to the Free Software
19 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20 */
21
22#ifdef NTFS_RW
23
24#include <linux/pagemap.h>
25
26#include "bitmap.h"
27#include "debug.h"
28#include "aops.h"
29#include "ntfs.h"
30
31/**
32 * __ntfs_bitmap_set_bits_in_run - set a run of bits in a bitmap to a value
33 * @vi:			vfs inode describing the bitmap
34 * @start_bit:		first bit to set
35 * @count:		number of bits to set
36 * @value:		value to set the bits to (i.e. 0 or 1)
37 * @is_rollback:	if 'true' this is a rollback operation
38 *
39 * Set @count bits starting at bit @start_bit in the bitmap described by the
40 * vfs inode @vi to @value, where @value is either 0 or 1.
41 *
42 * @is_rollback should always be 'false', it is for internal use to rollback
43 * errors.  You probably want to use ntfs_bitmap_set_bits_in_run() instead.
44 *
45 * Return 0 on success and -errno on error.
46 */
47int __ntfs_bitmap_set_bits_in_run(struct inode *vi, const s64 start_bit,
48		const s64 count, const u8 value, const bool is_rollback)
49{
50	s64 cnt = count;
51	pgoff_t index, end_index;
52	struct address_space *mapping;
53	struct page *page;
54	u8 *kaddr;
55	int pos, len;
56	u8 bit;
57
58	BUG_ON(!vi);
59	ntfs_debug("Entering for i_ino 0x%lx, start_bit 0x%llx, count 0x%llx, "
60			"value %u.%s", vi->i_ino, (unsigned long long)start_bit,
61			(unsigned long long)cnt, (unsigned int)value,
62			is_rollback ? " (rollback)" : "");
63	BUG_ON(start_bit < 0);
64	BUG_ON(cnt < 0);
65	BUG_ON(value > 1);
66	/*
67	 * Calculate the indices for the pages containing the first and last
68	 * bits, i.e. @start_bit and @start_bit + @cnt - 1, respectively.
69	 */
70	index = start_bit >> (3 + PAGE_CACHE_SHIFT);
71	end_index = (start_bit + cnt - 1) >> (3 + PAGE_CACHE_SHIFT);
72
73	/* Get the page containing the first bit (@start_bit). */
74	mapping = vi->i_mapping;
75	page = ntfs_map_page(mapping, index);
76	if (IS_ERR(page)) {
77		if (!is_rollback)
78			ntfs_error(vi->i_sb, "Failed to map first page (error "
79					"%li), aborting.", PTR_ERR(page));
80		return PTR_ERR(page);
81	}
82	kaddr = page_address(page);
83
84	/* Set @pos to the position of the byte containing @start_bit. */
85	pos = (start_bit >> 3) & ~PAGE_CACHE_MASK;
86
87	/* Calculate the position of @start_bit in the first byte. */
88	bit = start_bit & 7;
89
90	/* If the first byte is partial, modify the appropriate bits in it. */
91	if (bit) {
92		u8 *byte = kaddr + pos;
93		while ((bit & 7) && cnt) {
94			cnt--;
95			if (value)
96				*byte |= 1 << bit++;
97			else
98				*byte &= ~(1 << bit++);
99		}
100		/* If we are done, unmap the page and return success. */
101		if (!cnt)
102			goto done;
103
104		/* Update @pos to the new position. */
105		pos++;
106	}
107	/*
108	 * Depending on @value, modify all remaining whole bytes in the page up
109	 * to @cnt.
110	 */
111	len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE - pos);
112	memset(kaddr + pos, value ? 0xff : 0, len);
113	cnt -= len << 3;
114
115	/* Update @len to point to the first not-done byte in the page. */
116	if (cnt < 8)
117		len += pos;
118
119	/* If we are not in the last page, deal with all subsequent pages. */
120	while (index < end_index) {
121		BUG_ON(cnt <= 0);
122
123		/* Update @index and get the next page. */
124		flush_dcache_page(page);
125		set_page_dirty(page);
126		ntfs_unmap_page(page);
127		page = ntfs_map_page(mapping, ++index);
128		if (IS_ERR(page))
129			goto rollback;
130		kaddr = page_address(page);
131		/*
132		 * Depending on @value, modify all remaining whole bytes in the
133		 * page up to @cnt.
134		 */
135		len = min_t(s64, cnt >> 3, PAGE_CACHE_SIZE);
136		memset(kaddr, value ? 0xff : 0, len);
137		cnt -= len << 3;
138	}
139	/*
140	 * The currently mapped page is the last one.  If the last byte is
141	 * partial, modify the appropriate bits in it.  Note, @len is the
142	 * position of the last byte inside the page.
143	 */
144	if (cnt) {
145		u8 *byte;
146
147		BUG_ON(cnt > 7);
148
149		bit = cnt;
150		byte = kaddr + len;
151		while (bit--) {
152			if (value)
153				*byte |= 1 << bit;
154			else
155				*byte &= ~(1 << bit);
156		}
157	}
158done:
159	/* We are done.  Unmap the page and return success. */
160	flush_dcache_page(page);
161	set_page_dirty(page);
162	ntfs_unmap_page(page);
163	ntfs_debug("Done.");
164	return 0;
165rollback:
166	/*
167	 * Current state:
168	 *	- no pages are mapped
169	 *	- @count - @cnt is the number of bits that have been modified
170	 */
171	if (is_rollback)
172		return PTR_ERR(page);
173	if (count != cnt)
174		pos = __ntfs_bitmap_set_bits_in_run(vi, start_bit, count - cnt,
175				value ? 0 : 1, true);
176	else
177		pos = 0;
178	if (!pos) {
179		/* Rollback was successful. */
180		ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
181				"%li), aborting.", PTR_ERR(page));
182	} else {
183		/* Rollback failed. */
184		ntfs_error(vi->i_sb, "Failed to map subsequent page (error "
185				"%li) and rollback failed (error %i).  "
186				"Aborting and leaving inconsistent metadata.  "
187				"Unmount and run chkdsk.", PTR_ERR(page), pos);
188		NVolSetErrors(NTFS_SB(vi->i_sb));
189	}
190	return PTR_ERR(page);
191}
192
193#endif /* NTFS_RW */
194