// SPDX-License-Identifier: GPL-2.0-only

  /*
   * lib/bitmap.c
   * Helper functions for bitmap.h.

   */

  #include <linux/export.h>
  #include <linux/thread_info.h>

  #include <linux/ctype.h>
  #include <linux/errno.h>
  #include <linux/bitmap.h>
  #include <linux/bitops.h>

  #include <linux/bug.h>

  #include <linux/kernel.h>

  #include <linux/mm.h>

  #include <linux/slab.h>

  #include <linux/string.h>

  #include <linux/uaccess.h>

  
  #include <asm/page.h>

  #include "kstrtox.h"

  /**
   * DOC: bitmap introduction
   *

   * bitmaps provide an array of bits, implemented using an an
   * array of unsigned longs.  The number of valid bits in a
   * given bitmap does _not_ need to be an exact multiple of
   * BITS_PER_LONG.
   *
   * The possible unused bits in the last, partially used word
   * of a bitmap are 'don't care'.  The implementation makes
   * no particular effort to keep them zero.  It ensures that
   * their value will not affect the results of any operation.
   * The bitmap operations that return Boolean (bitmap_empty,
   * for example) or scalar (bitmap_weight, for example) results
   * carefully filter out these unused bits from impacting their
   * results.
   *

   * The byte ordering of bitmaps is more natural on little
   * endian architectures.  See the big-endian headers
   * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
   * for the best explanations of this ordering.
   */

  int __bitmap_equal(const unsigned long *bitmap1,

  		const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k, lim = bits/BITS_PER_LONG;

  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] != bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_equal);

  void __bitmap_complement(unsigned long *dst, const unsigned long *src, unsigned int bits)

  {

  	unsigned int k, lim = BITS_TO_LONGS(bits);

  	for (k = 0; k < lim; ++k)
  		dst[k] = ~src[k];

  }
  EXPORT_SYMBOL(__bitmap_complement);

  /**

   * __bitmap_shift_right - logical right shift of the bits in a bitmap

   *   @dst : destination bitmap
   *   @src : source bitmap
   *   @shift : shift by this many bits

   *   @nbits : bitmap size, in bits

   *
   * Shifting right (dividing) means moving bits in the MS -> LS bit
   * direction.  Zeros are fed into the vacated MS positions and the
   * LS bits shifted off the bottom are lost.
   */

  void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
  			unsigned shift, unsigned nbits)

  {

  	unsigned k, lim = BITS_TO_LONGS(nbits);

  	unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;

  	unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);

  	for (k = 0; off + k < lim; ++k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take lower rem bits of
  		 * word above and make them the top rem bits of result.
  		 */
  		if (!rem || off + k + 1 >= lim)
  			upper = 0;
  		else {
  			upper = src[off + k + 1];

  			if (off + k + 1 == lim - 1)

  				upper &= mask;

  			upper <<= (BITS_PER_LONG - rem);

  		}
  		lower = src[off + k];

  		if (off + k == lim - 1)

  			lower &= mask;

  		lower >>= rem;
  		dst[k] = lower | upper;

  	}
  	if (off)
  		memset(&dst[lim - off], 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_right);

  /**

   * __bitmap_shift_left - logical left shift of the bits in a bitmap

   *   @dst : destination bitmap
   *   @src : source bitmap
   *   @shift : shift by this many bits

   *   @nbits : bitmap size, in bits

   *
   * Shifting left (multiplying) means moving bits in the LS -> MS
   * direction.  Zeros are fed into the vacated LS bit positions
   * and those MS bits shifted off the top are lost.
   */

  void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
  			unsigned int shift, unsigned int nbits)

  {

  	int k;

  	unsigned int lim = BITS_TO_LONGS(nbits);

  	unsigned int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;

  	for (k = lim - off - 1; k >= 0; --k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take upper rem bits of
  		 * word below and make them the bottom rem bits of result.
  		 */
  		if (rem && k > 0)

  			lower = src[k - 1] >> (BITS_PER_LONG - rem);

  		else
  			lower = 0;

  		upper = src[k] << rem;

  		dst[k + off] = lower | upper;

  	}
  	if (off)
  		memset(dst, 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_left);

  int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k;

  	unsigned int lim = bits/BITS_PER_LONG;

  	unsigned long result = 0;

  	for (k = 0; k < lim; k++)

  		result |= (dst[k] = bitmap1[k] & bitmap2[k]);

  	if (bits % BITS_PER_LONG)
  		result |= (dst[k] = bitmap1[k] & bitmap2[k] &
  			   BITMAP_LAST_WORD_MASK(bits));

  	return result != 0;

  }
  EXPORT_SYMBOL(__bitmap_and);
  
  void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k;
  	unsigned int nr = BITS_TO_LONGS(bits);

  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] | bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_or);
  
  void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k;
  	unsigned int nr = BITS_TO_LONGS(bits);

  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] ^ bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_xor);

  int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,

  				const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k;

  	unsigned int lim = bits/BITS_PER_LONG;

  	unsigned long result = 0;

  	for (k = 0; k < lim; k++)

  		result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);

  	if (bits % BITS_PER_LONG)
  		result |= (dst[k] = bitmap1[k] & ~bitmap2[k] &
  			   BITMAP_LAST_WORD_MASK(bits));

  	return result != 0;

  }
  EXPORT_SYMBOL(__bitmap_andnot);
  
  int __bitmap_intersects(const unsigned long *bitmap1,

  			const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k, lim = bits/BITS_PER_LONG;

  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & bitmap2[k])
  			return 1;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 1;
  	return 0;
  }
  EXPORT_SYMBOL(__bitmap_intersects);
  
  int __bitmap_subset(const unsigned long *bitmap1,

  		    const unsigned long *bitmap2, unsigned int bits)

  {

  	unsigned int k, lim = bits/BITS_PER_LONG;

  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & ~bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_subset);

  int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)

  {

  	unsigned int k, lim = bits/BITS_PER_LONG;
  	int w = 0;

  
  	for (k = 0; k < lim; k++)

  		w += hweight_long(bitmap[k]);

  
  	if (bits % BITS_PER_LONG)

  		w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));

  
  	return w;
  }

  EXPORT_SYMBOL(__bitmap_weight);

  void __bitmap_set(unsigned long *map, unsigned int start, int len)

  {
  	unsigned long *p = map + BIT_WORD(start);

  	const unsigned int size = start + len;

  	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);

  	while (len - bits_to_set >= 0) {

  		*p |= mask_to_set;

  		len -= bits_to_set;

  		bits_to_set = BITS_PER_LONG;
  		mask_to_set = ~0UL;
  		p++;
  	}

  	if (len) {

  		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
  		*p |= mask_to_set;
  	}
  }

  EXPORT_SYMBOL(__bitmap_set);

  void __bitmap_clear(unsigned long *map, unsigned int start, int len)

  {
  	unsigned long *p = map + BIT_WORD(start);

  	const unsigned int size = start + len;

  	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
  	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);

  	while (len - bits_to_clear >= 0) {

  		*p &= ~mask_to_clear;

  		len -= bits_to_clear;

  		bits_to_clear = BITS_PER_LONG;
  		mask_to_clear = ~0UL;
  		p++;
  	}

  	if (len) {

  		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
  		*p &= ~mask_to_clear;
  	}
  }

  EXPORT_SYMBOL(__bitmap_clear);

  /**
   * bitmap_find_next_zero_area_off - find a contiguous aligned zero area

   * @map: The address to base the search on
   * @size: The bitmap size in bits
   * @start: The bitnumber to start searching at
   * @nr: The number of zeroed bits we're looking for
   * @align_mask: Alignment mask for zero area

   * @align_offset: Alignment offset for zero area.

   *
   * The @align_mask should be one less than a power of 2; the effect is that

   * the bit offset of all zero areas this function finds plus @align_offset
   * is multiple of that power of 2.

   */

  unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
  					     unsigned long size,
  					     unsigned long start,
  					     unsigned int nr,
  					     unsigned long align_mask,
  					     unsigned long align_offset)

  {
  	unsigned long index, end, i;
  again:
  	index = find_next_zero_bit(map, size, start);
  
  	/* Align allocation */

  	index = __ALIGN_MASK(index + align_offset, align_mask) - align_offset;

  
  	end = index + nr;
  	if (end > size)
  		return end;
  	i = find_next_bit(map, end, index);
  	if (i < end) {
  		start = i + 1;
  		goto again;
  	}
  	return index;
  }

  EXPORT_SYMBOL(bitmap_find_next_zero_area_off);

  /*

   * Bitmap printing & parsing functions: first version by Nadia Yvette Chambers,

   * second version by Paul Jackson, third by Joe Korty.
   */
  
  #define CHUNKSZ				32
  #define nbits_to_hold_value(val)	fls(val)

  #define BASEDEC 10		/* fancier cpuset lists input in decimal */
  
  /**

   * __bitmap_parse - convert an ASCII hex string into a bitmap.
   * @buf: pointer to buffer containing string.
   * @buflen: buffer size in bytes.  If string is smaller than this

   *    then it must be terminated with a \0.

   * @is_user: location of buffer, 0 indicates kernel space

   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Commas group hex digits into chunks.  Each chunk defines exactly 32
   * bits of the resultant bitmask.  No chunk may specify a value larger

   * than 32 bits (%-EOVERFLOW), and if a chunk specifies a smaller value
   * then leading 0-bits are prepended.  %-EINVAL is returned for illegal

   * characters and for grouping errors such as "1,,5", ",44", "," and "".
   * Leading and trailing whitespace accepted, but not embedded whitespace.
   */

  int __bitmap_parse(const char *buf, unsigned int buflen,
  		int is_user, unsigned long *maskp,
  		int nmaskbits)

  {
  	int c, old_c, totaldigits, ndigits, nchunks, nbits;
  	u32 chunk;

  	const char __user __force *ubuf = (const char __user __force *)buf;

  
  	bitmap_zero(maskp, nmaskbits);
  
  	nchunks = nbits = totaldigits = c = 0;
  	do {

  		chunk = 0;
  		ndigits = totaldigits;

  
  		/* Get the next chunk of the bitmap */

  		while (buflen) {

  			old_c = c;

  			if (is_user) {
  				if (__get_user(c, ubuf++))
  					return -EFAULT;
  			}
  			else
  				c = *buf++;
  			buflen--;

  			if (isspace(c))
  				continue;
  
  			/*
  			 * If the last character was a space and the current
  			 * character isn't '\0', we've got embedded whitespace.
  			 * This is a no-no, so throw an error.
  			 */
  			if (totaldigits && c && isspace(old_c))
  				return -EINVAL;
  
  			/* A '\0' or a ',' signal the end of the chunk */
  			if (c == '\0' || c == ',')
  				break;
  
  			if (!isxdigit(c))
  				return -EINVAL;
  
  			/*
  			 * Make sure there are at least 4 free bits in 'chunk'.
  			 * If not, this hexdigit will overflow 'chunk', so
  			 * throw an error.
  			 */
  			if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
  				return -EOVERFLOW;

  			chunk = (chunk << 4) | hex_to_bin(c);

  			totaldigits++;

  		}

  		if (ndigits == totaldigits)

  			return -EINVAL;
  		if (nchunks == 0 && chunk == 0)
  			continue;
  
  		__bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
  		*maskp |= chunk;
  		nchunks++;
  		nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
  		if (nbits > nmaskbits)
  			return -EOVERFLOW;

  	} while (buflen && c == ',');

  
  	return 0;
  }

  EXPORT_SYMBOL(__bitmap_parse);
  
  /**

   * bitmap_parse_user - convert an ASCII hex string in a user buffer into a bitmap

   *
   * @ubuf: pointer to user buffer containing string.
   * @ulen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Wrapper for __bitmap_parse(), providing it with user buffer.
   *
   * We cannot have this as an inline function in bitmap.h because it needs
   * linux/uaccess.h to get the access_ok() declaration and this causes
   * cyclic dependencies.
   */
  int bitmap_parse_user(const char __user *ubuf,
  			unsigned int ulen, unsigned long *maskp,
  			int nmaskbits)
  {

  	if (!access_ok(ubuf, ulen))

  		return -EFAULT;

  	return __bitmap_parse((const char __force *)ubuf,
  				ulen, 1, maskp, nmaskbits);

  }
  EXPORT_SYMBOL(bitmap_parse_user);

  /**

   * bitmap_print_to_pagebuf - convert bitmap to list or hex format ASCII string
   * @list: indicates whether the bitmap must be list
   * @buf: page aligned buffer into which string is placed
   * @maskp: pointer to bitmap to convert
   * @nmaskbits: size of bitmap, in bits
   *
   * Output format is a comma-separated list of decimal numbers and
   * ranges if list is specified or hex digits grouped into comma-separated
   * sets of 8 digits/set. Returns the number of characters written to buf.

   *

   * It is assumed that @buf is a pointer into a PAGE_SIZE, page-aligned
   * area and that sufficient storage remains at @buf to accommodate the
   * bitmap_print_to_pagebuf() output. Returns the number of characters
   * actually printed to @buf, excluding terminating '\0'.

   */
  int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
  			    int nmaskbits)
  {

  	ptrdiff_t len = PAGE_SIZE - offset_in_page(buf);

  	return list ? scnprintf(buf, len, "%*pbl
  ", nmaskbits, maskp) :
  		      scnprintf(buf, len, "%*pb
  ", nmaskbits, maskp);

  }
  EXPORT_SYMBOL(bitmap_print_to_pagebuf);

  /*
   * Region 9-38:4/10 describes the following bitmap structure:
   * 0	   9  12    18			38
   * .........****......****......****......
   *	    ^  ^     ^			 ^
   *      start  off   group_len	       end
   */
  struct region {
  	unsigned int start;
  	unsigned int off;
  	unsigned int group_len;
  	unsigned int end;
  };
  
  static int bitmap_set_region(const struct region *r,
  				unsigned long *bitmap, int nbits)
  {
  	unsigned int start;
  
  	if (r->end >= nbits)
  		return -ERANGE;
  
  	for (start = r->start; start <= r->end; start += r->group_len)
  		bitmap_set(bitmap, start, min(r->end - start + 1, r->off));
  
  	return 0;
  }
  
  static int bitmap_check_region(const struct region *r)
  {
  	if (r->start > r->end || r->group_len == 0 || r->off > r->group_len)
  		return -EINVAL;
  
  	return 0;
  }
  
  static const char *bitmap_getnum(const char *str, unsigned int *num)
  {
  	unsigned long long n;
  	unsigned int len;
  
  	len = _parse_integer(str, 10, &n);
  	if (!len)
  		return ERR_PTR(-EINVAL);
  	if (len & KSTRTOX_OVERFLOW || n != (unsigned int)n)
  		return ERR_PTR(-EOVERFLOW);
  
  	*num = n;
  	return str + len;
  }
  
  static inline bool end_of_str(char c)
  {
  	return c == '\0' || c == '
  ';
  }
  
  static inline bool __end_of_region(char c)
  {
  	return isspace(c) || c == ',';
  }
  
  static inline bool end_of_region(char c)
  {
  	return __end_of_region(c) || end_of_str(c);
  }
  
  /*
   * The format allows commas and whitespases at the beginning
   * of the region.
   */
  static const char *bitmap_find_region(const char *str)
  {
  	while (__end_of_region(*str))
  		str++;
  
  	return end_of_str(*str) ? NULL : str;
  }
  
  static const char *bitmap_parse_region(const char *str, struct region *r)
  {
  	str = bitmap_getnum(str, &r->start);
  	if (IS_ERR(str))
  		return str;
  
  	if (end_of_region(*str))
  		goto no_end;
  
  	if (*str != '-')
  		return ERR_PTR(-EINVAL);
  
  	str = bitmap_getnum(str + 1, &r->end);
  	if (IS_ERR(str))
  		return str;
  
  	if (end_of_region(*str))
  		goto no_pattern;
  
  	if (*str != ':')
  		return ERR_PTR(-EINVAL);
  
  	str = bitmap_getnum(str + 1, &r->off);
  	if (IS_ERR(str))
  		return str;
  
  	if (*str != '/')
  		return ERR_PTR(-EINVAL);
  
  	return bitmap_getnum(str + 1, &r->group_len);
  
  no_end:
  	r->end = r->start;
  no_pattern:
  	r->off = r->end + 1;
  	r->group_len = r->end + 1;
  
  	return end_of_str(*str) ? NULL : str;
  }

  /**

   * bitmap_parselist - convert list format ASCII string to bitmap
   * @buf: read user string from this buffer; must be terminated
   *    with a \0 or 
  .

   * @maskp: write resulting mask here

   * @nmaskbits: number of bits in mask to be written
   *
   * Input format is a comma-separated list of decimal numbers and
   * ranges.  Consecutively set bits are shown as two hyphen-separated
   * decimal numbers, the smallest and largest bit numbers set in
   * the range.

   * Optionally each range can be postfixed to denote that only parts of it
   * should be set. The range will divided to groups of specific size.
   * From each group will be used only defined amount of bits.
   * Syntax: range:used_size/group_size
   * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769

   *

   * Returns: 0 on success, -errno on invalid input strings. Error values:
   *

   *   - ``-EINVAL``: wrong region format

   *   - ``-EINVAL``: invalid character in string
   *   - ``-ERANGE``: bit number specified too large for mask

   *   - ``-EOVERFLOW``: integer overflow in the input parameters

   */

  int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)

  {

  	struct region r;
  	long ret;

  
  	bitmap_zero(maskp, nmaskbits);

  	while (buf) {
  		buf = bitmap_find_region(buf);
  		if (buf == NULL)
  			return 0;

  		buf = bitmap_parse_region(buf, &r);
  		if (IS_ERR(buf))
  			return PTR_ERR(buf);

  		ret = bitmap_check_region(&r);
  		if (ret)
  			return ret;

  		ret = bitmap_set_region(&r, maskp, nmaskbits);
  		if (ret)
  			return ret;
  	}

  	return 0;
  }
  EXPORT_SYMBOL(bitmap_parselist);

  
  /**
   * bitmap_parselist_user()
   *
   * @ubuf: pointer to user buffer containing string.
   * @ulen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Wrapper for bitmap_parselist(), providing it with user buffer.

   */
  int bitmap_parselist_user(const char __user *ubuf,
  			unsigned int ulen, unsigned long *maskp,
  			int nmaskbits)
  {

  	char *buf;
  	int ret;
  
  	buf = memdup_user_nul(ubuf, ulen);
  	if (IS_ERR(buf))
  		return PTR_ERR(buf);
  
  	ret = bitmap_parselist(buf, maskp, nmaskbits);
  
  	kfree(buf);
  	return ret;

  }
  EXPORT_SYMBOL(bitmap_parselist_user);

  #ifdef CONFIG_NUMA

  /**

   * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap

   *	@buf: pointer to a bitmap

   *	@pos: a bit position in @buf (0 <= @pos < @nbits)
   *	@nbits: number of valid bit positions in @buf

   *

   * Map the bit at position @pos in @buf (of length @nbits) to the

   * ordinal of which set bit it is.  If it is not set or if @pos

   * is not a valid bit position, map to -1.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @pos
   * values 4 through 7 will get mapped to 0 through 3, respectively,

   * and other @pos values will get mapped to -1.  When @pos value 7

   * gets mapped to (returns) @ord value 3 in this example, that means
   * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
   *
   * The bit positions 0 through @bits are valid positions in @buf.
   */

  static int bitmap_pos_to_ord(const unsigned long *buf, unsigned int pos, unsigned int nbits)

  {

  	if (pos >= nbits || !test_bit(pos, buf))

  		return -1;

  	return __bitmap_weight(buf, pos);

  }
  
  /**

   * bitmap_ord_to_pos - find position of n-th set bit in bitmap

   *	@buf: pointer to bitmap
   *	@ord: ordinal bit position (n-th set bit, n >= 0)

   *	@nbits: number of valid bit positions in @buf

   *
   * Map the ordinal offset of bit @ord in @buf to its position in @buf.

   * Value of @ord should be in range 0 <= @ord < weight(buf). If @ord
   * >= weight(buf), returns @nbits.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @ord
   * values 0 through 3 will get mapped to 4 through 7, respectively,

   * and all other @ord values returns @nbits.  When @ord value 3

   * gets mapped to (returns) @pos value 7 in this example, that means
   * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
   *

   * The bit positions 0 through @nbits-1 are valid positions in @buf.

   */

  unsigned int bitmap_ord_to_pos(const unsigned long *buf, unsigned int ord, unsigned int nbits)

  {

  	unsigned int pos;

  	for (pos = find_first_bit(buf, nbits);
  	     pos < nbits && ord;
  	     pos = find_next_bit(buf, nbits, pos + 1))
  		ord--;

  
  	return pos;
  }
  
  /**
   * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap

   *	@dst: remapped result

   *	@src: subset to be remapped

   *	@old: defines domain of map
   *	@new: defines range of map

   *	@nbits: number of bits in each of these bitmaps

   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * If either of the @old and @new bitmaps are empty, or if @src and
   * @dst point to the same location, then this routine copies @src
   * to @dst.

   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to @src, placing the result in
   * @dst, clearing any bits previously set in @dst.
   *

   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @src comes into this routine
   * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
   * 13 and 15 set.

   */
  void bitmap_remap(unsigned long *dst, const unsigned long *src,
  		const unsigned long *old, const unsigned long *new,

  		unsigned int nbits)

  {

  	unsigned int oldbit, w;

  	if (dst == src)		/* following doesn't handle inplace remaps */
  		return;

  	bitmap_zero(dst, nbits);

  	w = bitmap_weight(new, nbits);
  	for_each_set_bit(oldbit, src, nbits) {
  		int n = bitmap_pos_to_ord(old, oldbit, nbits);

  		if (n < 0 || w == 0)
  			set_bit(oldbit, dst);	/* identity map */
  		else

  			set_bit(bitmap_ord_to_pos(new, n % w, nbits), dst);

  	}
  }

  
  /**
   * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit

   *	@oldbit: bit position to be mapped
   *	@old: defines domain of map
   *	@new: defines range of map
   *	@bits: number of bits in each of these bitmaps

   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to bit position @oldbit, returning
   * the new bit position.
   *
   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @oldbit is 5, then this routine
   * returns 13.

   */
  int bitmap_bitremap(int oldbit, const unsigned long *old,
  				const unsigned long *new, int bits)
  {

  	int w = bitmap_weight(new, bits);
  	int n = bitmap_pos_to_ord(old, oldbit, bits);
  	if (n < 0 || w == 0)
  		return oldbit;
  	else
  		return bitmap_ord_to_pos(new, n % w, bits);

  }

  /**
   * bitmap_onto - translate one bitmap relative to another
   *	@dst: resulting translated bitmap
   * 	@orig: original untranslated bitmap
   * 	@relmap: bitmap relative to which translated
   *	@bits: number of bits in each of these bitmaps
   *
   * Set the n-th bit of @dst iff there exists some m such that the
   * n-th bit of @relmap is set, the m-th bit of @orig is set, and
   * the n-th bit of @relmap is also the m-th _set_ bit of @relmap.
   * (If you understood the previous sentence the first time your
   * read it, you're overqualified for your current job.)
   *
   * In other words, @orig is mapped onto (surjectively) @dst,

   * using the map { <n, m> | the n-th bit of @relmap is the

   * m-th set bit of @relmap }.
   *
   * Any set bits in @orig above bit number W, where W is the
   * weight of (number of set bits in) @relmap are mapped nowhere.
   * In particular, if for all bits m set in @orig, m >= W, then
   * @dst will end up empty.  In situations where the possibility
   * of such an empty result is not desired, one way to avoid it is
   * to use the bitmap_fold() operator, below, to first fold the
   * @orig bitmap over itself so that all its set bits x are in the
   * range 0 <= x < W.  The bitmap_fold() operator does this by
   * setting the bit (m % W) in @dst, for each bit (m) set in @orig.
   *
   * Example [1] for bitmap_onto():
   *  Let's say @relmap has bits 30-39 set, and @orig has bits
   *  1, 3, 5, 7, 9 and 11 set.  Then on return from this routine,
   *  @dst will have bits 31, 33, 35, 37 and 39 set.
   *
   *  When bit 0 is set in @orig, it means turn on the bit in
   *  @dst corresponding to whatever is the first bit (if any)
   *  that is turned on in @relmap.  Since bit 0 was off in the
   *  above example, we leave off that bit (bit 30) in @dst.
   *
   *  When bit 1 is set in @orig (as in the above example), it
   *  means turn on the bit in @dst corresponding to whatever
   *  is the second bit that is turned on in @relmap.  The second
   *  bit in @relmap that was turned on in the above example was
   *  bit 31, so we turned on bit 31 in @dst.
   *
   *  Similarly, we turned on bits 33, 35, 37 and 39 in @dst,
   *  because they were the 4th, 6th, 8th and 10th set bits
   *  set in @relmap, and the 4th, 6th, 8th and 10th bits of
   *  @orig (i.e. bits 3, 5, 7 and 9) were also set.
   *
   *  When bit 11 is set in @orig, it means turn on the bit in

   *  @dst corresponding to whatever is the twelfth bit that is

   *  turned on in @relmap.  In the above example, there were
   *  only ten bits turned on in @relmap (30..39), so that bit
   *  11 was set in @orig had no affect on @dst.
   *
   * Example [2] for bitmap_fold() + bitmap_onto():

   *  Let's say @relmap has these ten bits set::
   *

   *		40 41 42 43 45 48 53 61 74 95

   *

   *  (for the curious, that's 40 plus the first ten terms of the
   *  Fibonacci sequence.)
   *
   *  Further lets say we use the following code, invoking
   *  bitmap_fold() then bitmap_onto, as suggested above to

   *  avoid the possibility of an empty @dst result::

   *
   *	unsigned long *tmp;	// a temporary bitmap's bits
   *
   *	bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits);
   *	bitmap_onto(dst, tmp, relmap, bits);
   *
   *  Then this table shows what various values of @dst would be, for
   *  various @orig's.  I list the zero-based positions of each set bit.
   *  The tmp column shows the intermediate result, as computed by
   *  using bitmap_fold() to fold the @orig bitmap modulo ten

   *  (the weight of @relmap):

   *

   *      =============== ============== =================

   *      @orig           tmp            @dst
   *      0                0             40
   *      1                1             41
   *      9                9             95

   *      10               0             40 [#f1]_

   *      1 3 5 7          1 3 5 7       41 43 48 61
   *      0 1 2 3 4        0 1 2 3 4     40 41 42 43 45
   *      0 9 18 27        0 9 8 7       40 61 74 95
   *      0 10 20 30       0             40
   *      0 11 22 33       0 1 2 3       40 41 42 43
   *      0 12 24 36       0 2 4 6       40 42 45 53

   *      78 102 211       1 2 8         41 42 74 [#f1]_
   *      =============== ============== =================
   *
   * .. [#f1]

   *

   *     For these marked lines, if we hadn't first done bitmap_fold()

   *     into tmp, then the @dst result would have been empty.
   *
   * If either of @orig or @relmap is empty (no set bits), then @dst
   * will be returned empty.
   *
   * If (as explained above) the only set bits in @orig are in positions
   * m where m >= W, (where W is the weight of @relmap) then @dst will
   * once again be returned empty.
   *
   * All bits in @dst not set by the above rule are cleared.
   */
  void bitmap_onto(unsigned long *dst, const unsigned long *orig,

  			const unsigned long *relmap, unsigned int bits)

  {

  	unsigned int n, m;	/* same meaning as in above comment */

  
  	if (dst == orig)	/* following doesn't handle inplace mappings */
  		return;
  	bitmap_zero(dst, bits);
  
  	/*
  	 * The following code is a more efficient, but less
  	 * obvious, equivalent to the loop:
  	 *	for (m = 0; m < bitmap_weight(relmap, bits); m++) {
  	 *		n = bitmap_ord_to_pos(orig, m, bits);
  	 *		if (test_bit(m, orig))
  	 *			set_bit(n, dst);
  	 *	}
  	 */
  
  	m = 0;

  	for_each_set_bit(n, relmap, bits) {

  		/* m == bitmap_pos_to_ord(relmap, n, bits) */
  		if (test_bit(m, orig))
  			set_bit(n, dst);
  		m++;
  	}
  }

  
  /**
   * bitmap_fold - fold larger bitmap into smaller, modulo specified size
   *	@dst: resulting smaller bitmap
   *	@orig: original larger bitmap
   *	@sz: specified size

   *	@nbits: number of bits in each of these bitmaps

   *
   * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst.
   * Clear all other bits in @dst.  See further the comment and
   * Example [2] for bitmap_onto() for why and how to use this.
   */
  void bitmap_fold(unsigned long *dst, const unsigned long *orig,

  			unsigned int sz, unsigned int nbits)

  {

  	unsigned int oldbit;

  
  	if (dst == orig)	/* following doesn't handle inplace mappings */
  		return;

  	bitmap_zero(dst, nbits);

  	for_each_set_bit(oldbit, orig, nbits)

  		set_bit(oldbit % sz, dst);
  }

  #endif /* CONFIG_NUMA */

  /*
   * Common code for bitmap_*_region() routines.
   *	bitmap: array of unsigned longs corresponding to the bitmap
   *	pos: the beginning of the region
   *	order: region size (log base 2 of number of bits)
   *	reg_op: operation(s) to perform on that region of bitmap

   *

   * Can set, verify and/or release a region of bits in a bitmap,
   * depending on which combination of REG_OP_* flag bits is set.

   *

   * A region of a bitmap is a sequence of bits in the bitmap, of
   * some size '1 << order' (a power of two), aligned to that same
   * '1 << order' power of two.
   *
   * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits).
   * Returns 0 in all other cases and reg_ops.

   */

  
  enum {
  	REG_OP_ISFREE,		/* true if region is all zero bits */
  	REG_OP_ALLOC,		/* set all bits in region */
  	REG_OP_RELEASE,		/* clear all bits in region */
  };

  static int __reg_op(unsigned long *bitmap, unsigned int pos, int order, int reg_op)

  {

  	int nbits_reg;		/* number of bits in region */
  	int index;		/* index first long of region in bitmap */
  	int offset;		/* bit offset region in bitmap[index] */
  	int nlongs_reg;		/* num longs spanned by region in bitmap */

  	int nbitsinlong;	/* num bits of region in each spanned long */

  	unsigned long mask;	/* bitmask for one long of region */

  	int i;			/* scans bitmap by longs */

  	int ret = 0;		/* return value */

  	/*
  	 * Either nlongs_reg == 1 (for small orders that fit in one long)
  	 * or (offset == 0 && mask == ~0UL) (for larger multiword orders.)
  	 */
  	nbits_reg = 1 << order;
  	index = pos / BITS_PER_LONG;
  	offset = pos - (index * BITS_PER_LONG);
  	nlongs_reg = BITS_TO_LONGS(nbits_reg);
  	nbitsinlong = min(nbits_reg,  BITS_PER_LONG);

  	/*
  	 * Can't do "mask = (1UL << nbitsinlong) - 1", as that
  	 * overflows if nbitsinlong == BITS_PER_LONG.
  	 */

  	mask = (1UL << (nbitsinlong - 1));

  	mask += mask - 1;

  	mask <<= offset;

  	switch (reg_op) {
  	case REG_OP_ISFREE:
  		for (i = 0; i < nlongs_reg; i++) {
  			if (bitmap[index + i] & mask)
  				goto done;
  		}
  		ret = 1;	/* all bits in region free (zero) */
  		break;
  
  	case REG_OP_ALLOC:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] |= mask;
  		break;
  
  	case REG_OP_RELEASE:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] &= ~mask;
  		break;

  	}

  done:
  	return ret;
  }
  
  /**
   * bitmap_find_free_region - find a contiguous aligned mem region
   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@bits: number of bits in the bitmap
   *	@order: region size (log base 2 of number of bits) to find
   *
   * Find a region of free (zero) bits in a @bitmap of @bits bits and
   * allocate them (set them to one).  Only consider regions of length
   * a power (@order) of two, aligned to that power of two, which
   * makes the search algorithm much faster.
   *
   * Return the bit offset in bitmap of the allocated region,
   * or -errno on failure.
   */

  int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int order)

  {

  	unsigned int pos, end;		/* scans bitmap by regions of size order */

  	for (pos = 0 ; (end = pos + (1U << order)) <= bits; pos = end) {

  		if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  			continue;
  		__reg_op(bitmap, pos, order, REG_OP_ALLOC);
  		return pos;
  	}
  	return -ENOMEM;

  }
  EXPORT_SYMBOL(bitmap_find_free_region);
  
  /**

   * bitmap_release_region - release allocated bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to release
   *	@order: region size (log base 2 of number of bits) to release

   *

   * This is the complement to __bitmap_find_free_region() and releases

   * the found region (by clearing it in the bitmap).

   *
   * No return value.

   */

  void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order)

  {

  	__reg_op(bitmap, pos, order, REG_OP_RELEASE);

  }
  EXPORT_SYMBOL(bitmap_release_region);

  /**
   * bitmap_allocate_region - allocate bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to allocate
   *	@order: region size (log base 2 of number of bits) to allocate

   *
   * Allocate (set bits in) a specified region of a bitmap.

   *

   * Return 0 on success, or %-EBUSY if specified region wasn't

   * free (not all bits were zero).
   */

  int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order)

  {

  	if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  		return -EBUSY;

  	return __reg_op(bitmap, pos, order, REG_OP_ALLOC);

  }
  EXPORT_SYMBOL(bitmap_allocate_region);

  
  /**
   * bitmap_copy_le - copy a bitmap, putting the bits into little-endian order.
   * @dst:   destination buffer
   * @src:   bitmap to copy
   * @nbits: number of bits in the bitmap
   *
   * Require nbits % BITS_PER_LONG == 0.
   */

  #ifdef __BIG_ENDIAN

  void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int nbits)

  {

  	unsigned int i;

  
  	for (i = 0; i < nbits/BITS_PER_LONG; i++) {
  		if (BITS_PER_LONG == 64)

  			dst[i] = cpu_to_le64(src[i]);

  		else

  			dst[i] = cpu_to_le32(src[i]);

  	}
  }
  EXPORT_SYMBOL(bitmap_copy_le);

  #endif

  unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags)
  {
  	return kmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long),
  			     flags);
  }
  EXPORT_SYMBOL(bitmap_alloc);
  
  unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags)
  {
  	return bitmap_alloc(nbits, flags | __GFP_ZERO);
  }
  EXPORT_SYMBOL(bitmap_zalloc);
  
  void bitmap_free(const unsigned long *bitmap)
  {
  	kfree(bitmap);
  }
  EXPORT_SYMBOL(bitmap_free);

  #if BITS_PER_LONG == 64
  /**
   * bitmap_from_arr32 - copy the contents of u32 array of bits to bitmap
   *	@bitmap: array of unsigned longs, the destination bitmap
   *	@buf: array of u32 (in host byte order), the source bitmap
   *	@nbits: number of bits in @bitmap
   */

  void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, unsigned int nbits)

  {
  	unsigned int i, halfwords;

  	halfwords = DIV_ROUND_UP(nbits, 32);
  	for (i = 0; i < halfwords; i++) {
  		bitmap[i/2] = (unsigned long) buf[i];
  		if (++i < halfwords)
  			bitmap[i/2] |= ((unsigned long) buf[i]) << 32;
  	}
  
  	/* Clear tail bits in last word beyond nbits. */
  	if (nbits % BITS_PER_LONG)
  		bitmap[(halfwords - 1) / 2] &= BITMAP_LAST_WORD_MASK(nbits);
  }
  EXPORT_SYMBOL(bitmap_from_arr32);
  
  /**
   * bitmap_to_arr32 - copy the contents of bitmap to a u32 array of bits
   *	@buf: array of u32 (in host byte order), the dest bitmap
   *	@bitmap: array of unsigned longs, the source bitmap
   *	@nbits: number of bits in @bitmap
   */
  void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits)
  {
  	unsigned int i, halfwords;

  	halfwords = DIV_ROUND_UP(nbits, 32);
  	for (i = 0; i < halfwords; i++) {
  		buf[i] = (u32) (bitmap[i/2] & UINT_MAX);
  		if (++i < halfwords)
  			buf[i] = (u32) (bitmap[i/2] >> 32);
  	}
  
  	/* Clear tail bits in last element of array beyond nbits. */
  	if (nbits % BITS_PER_LONG)
  		buf[halfwords - 1] &= (u32) (UINT_MAX >> ((-nbits) & 31));
  }
  EXPORT_SYMBOL(bitmap_to_arr32);
  
  #endif