FreeBSD/Linux Kernel Cross Reference
sys/lib/bitmap.c

     /*
      * lib/bitmap.c
      * Helper functions for bitmap.h.
      *
      * This source code is licensed under the GNU General Public License,
      * Version 2.  See the file COPYING for more details.
      */
     #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 <asm/uaccess.h>
    
    /*
     * 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.
     *
     * These operations actually hold to a slightly stronger rule:
     * if you don't input any bitmaps to these ops that have some
     * unused bits set, then they won't output any set unused bits
     * in output bitmaps.
     *
     * 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_empty(const unsigned long *bitmap, int bits)
    {
            int k, lim = bits/BITS_PER_LONG;
            for (k = 0; k < lim; ++k)
                    if (bitmap[k])
                            return 0;
    
            if (bits % BITS_PER_LONG)
                    if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
                            return 0;
    
            return 1;
    }
    EXPORT_SYMBOL(__bitmap_empty);
    
    int __bitmap_full(const unsigned long *bitmap, int bits)
    {
            int k, lim = bits/BITS_PER_LONG;
            for (k = 0; k < lim; ++k)
                    if (~bitmap[k])
                            return 0;
    
            if (bits % BITS_PER_LONG)
                    if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
                            return 0;
    
            return 1;
    }
    EXPORT_SYMBOL(__bitmap_full);
    
    int __bitmap_equal(const unsigned long *bitmap1,
                    const unsigned long *bitmap2, int bits)
    {
            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, int bits)
    {
            int k, lim = bits/BITS_PER_LONG;
            for (k = 0; k < lim; ++k)
                    dst[k] = ~src[k];
    
            if (bits % BITS_PER_LONG)
                    dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
    }
    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
    *   @bits : 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, int shift, int bits)
   {
           int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
           int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
           unsigned long mask = (1UL << left) - 1;
           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 && left)
                                   upper &= mask;
                   }
                   lower = src[off + k];
                   if (left && off + k == lim - 1)
                           lower &= mask;
                   dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
                   if (left && k == lim - 1)
                           dst[k] &= mask;
           }
           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
    *   @bits : 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, int shift, int bits)
   {
           int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
           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];
                   else
                           lower = 0;
                   upper = src[k];
                   if (left && k == lim - 1)
                           upper &= (1UL << left) - 1;
                   dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
                   if (left && k + off == lim - 1)
                           dst[k + off] &= (1UL << left) - 1;
           }
           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, int bits)
   {
           int k;
           int nr = BITS_TO_LONGS(bits);
           unsigned long result = 0;
   
           for (k = 0; k < nr; k++)
                   result |= (dst[k] = bitmap1[k] & bitmap2[k]);
           return result != 0;
   }
   EXPORT_SYMBOL(__bitmap_and);
   
   void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
                                   const unsigned long *bitmap2, int bits)
   {
           int k;
           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, int bits)
   {
           int k;
           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, int bits)
   {
           int k;
           int nr = BITS_TO_LONGS(bits);
           unsigned long result = 0;
   
           for (k = 0; k < nr; k++)
                   result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
           return result != 0;
   }
   EXPORT_SYMBOL(__bitmap_andnot);
   
   int __bitmap_intersects(const unsigned long *bitmap1,
                                   const unsigned long *bitmap2, int bits)
   {
           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, int bits)
   {
           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, int bits)
   {
           int k, w = 0, lim = bits/BITS_PER_LONG;
   
           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, int start, int nr)
   {
           unsigned long *p = map + BIT_WORD(start);
           const int size = start + nr;
           int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
           unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
   
           while (nr - bits_to_set >= 0) {
                   *p |= mask_to_set;
                   nr -= bits_to_set;
                   bits_to_set = BITS_PER_LONG;
                   mask_to_set = ~0UL;
                   p++;
           }
           if (nr) {
                   mask_to_set &= BITMAP_LAST_WORD_MASK(size);
                   *p |= mask_to_set;
           }
   }
   EXPORT_SYMBOL(bitmap_set);
   
   void bitmap_clear(unsigned long *map, int start, int nr)
   {
           unsigned long *p = map + BIT_WORD(start);
           const int size = start + nr;
           int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
           unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
   
           while (nr - bits_to_clear >= 0) {
                   *p &= ~mask_to_clear;
                   nr -= bits_to_clear;
                   bits_to_clear = BITS_PER_LONG;
                   mask_to_clear = ~0UL;
                   p++;
           }
           if (nr) {
                   mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
                   *p &= ~mask_to_clear;
           }
   }
   EXPORT_SYMBOL(bitmap_clear);
   
   /*
    * bitmap_find_next_zero_area - 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
    *
    * 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 is multiples of that
    * power of 2. A @align_mask of 0 means no alignment is required.
    */
   unsigned long bitmap_find_next_zero_area(unsigned long *map,
                                            unsigned long size,
                                            unsigned long start,
                                            unsigned int nr,
                                            unsigned long align_mask)
   {
           unsigned long index, end, i;
   again:
           index = find_next_zero_bit(map, size, start);
   
           /* Align allocation */
           index = __ALIGN_MASK(index, align_mask);
   
           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);
   
   /*
    * 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_scnprintf - convert bitmap to an ASCII hex string.
    * @buf: byte buffer into which string is placed
    * @buflen: reserved size of @buf, in bytes
    * @maskp: pointer to bitmap to convert
    * @nmaskbits: size of bitmap, in bits
    *
    * Exactly @nmaskbits bits are displayed.  Hex digits are grouped into
    * comma-separated sets of eight digits per set.  Returns the number of
    * characters which were written to *buf, excluding the trailing \0.
    */
   int bitmap_scnprintf(char *buf, unsigned int buflen,
           const unsigned long *maskp, int nmaskbits)
   {
           int i, word, bit, len = 0;
           unsigned long val;
           const char *sep = "";
           int chunksz;
           u32 chunkmask;
   
           chunksz = nmaskbits & (CHUNKSZ - 1);
           if (chunksz == 0)
                   chunksz = CHUNKSZ;
   
           i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;
           for (; i >= 0; i -= CHUNKSZ) {
                   chunkmask = ((1ULL << chunksz) - 1);
                   word = i / BITS_PER_LONG;
                   bit = i % BITS_PER_LONG;
                   val = (maskp[word] >> bit) & chunkmask;
                   len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
                           (chunksz+3)/4, val);
                   chunksz = CHUNKSZ;
                   sep = ",";
           }
           return len;
   }
   EXPORT_SYMBOL(bitmap_scnprintf);
   
   /**
    * __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 = ndigits = 0;
   
                   /* 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);
                           ndigits++; totaldigits++;
                   }
                   if (ndigits == 0)
                           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(VERIFY_READ, ubuf, ulen))
                   return -EFAULT;
           return __bitmap_parse((const char __force *)ubuf,
                                   ulen, 1, maskp, nmaskbits);
   
   }
   EXPORT_SYMBOL(bitmap_parse_user);
   
   /*
    * bscnl_emit(buf, buflen, rbot, rtop, bp)
    *
    * Helper routine for bitmap_scnlistprintf().  Write decimal number
    * or range to buf, suppressing output past buf+buflen, with optional
    * comma-prefix.  Return len of what was written to *buf, excluding the
    * trailing \0.
    */
   static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
   {
           if (len > 0)
                   len += scnprintf(buf + len, buflen - len, ",");
           if (rbot == rtop)
                   len += scnprintf(buf + len, buflen - len, "%d", rbot);
           else
                   len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
           return len;
   }
   
   /**
    * bitmap_scnlistprintf - convert bitmap to list format ASCII string
    * @buf: byte buffer into which string is placed
    * @buflen: reserved size of @buf, in bytes
    * @maskp: pointer to bitmap to convert
    * @nmaskbits: size of bitmap, in bits
    *
    * Output 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.  Output format is compatible with the format
    * accepted as input by bitmap_parselist().
    *
    * The return value is the number of characters which were written to *buf
    * excluding the trailing '\0', as per ISO C99's scnprintf.
    */
   int bitmap_scnlistprintf(char *buf, unsigned int buflen,
           const unsigned long *maskp, int nmaskbits)
   {
           int len = 0;
           /* current bit is 'cur', most recently seen range is [rbot, rtop] */
           int cur, rbot, rtop;
   
           if (buflen == 0)
                   return 0;
           buf[0] = 0;
   
           rbot = cur = find_first_bit(maskp, nmaskbits);
           while (cur < nmaskbits) {
                   rtop = cur;
                   cur = find_next_bit(maskp, nmaskbits, cur+1);
                   if (cur >= nmaskbits || cur > rtop + 1) {
                           len = bscnl_emit(buf, buflen, rbot, rtop, len);
                           rbot = cur;
                   }
           }
           return len;
   }
   EXPORT_SYMBOL(bitmap_scnlistprintf);
   
   /**
    * __bitmap_parselist - convert list format ASCII string to bitmap
    * @buf: read nul-terminated user string from this buffer
    * @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: 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.
    *
    * Returns 0 on success, -errno on invalid input strings.
    * Error values:
    *    %-EINVAL: second number in range smaller than first
    *    %-EINVAL: invalid character in string
    *    %-ERANGE: bit number specified too large for mask
    */
   static int __bitmap_parselist(const char *buf, unsigned int buflen,
                   int is_user, unsigned long *maskp,
                   int nmaskbits)
   {
           unsigned a, b;
           int c, old_c, totaldigits;
           const char __user __force *ubuf = (const char __user __force *)buf;
           int exp_digit, in_range;
   
           totaldigits = c = 0;
           bitmap_zero(maskp, nmaskbits);
           do {
                   exp_digit = 1;
                   in_range = 0;
                   a = b = 0;
   
                   /* Get the next cpu# or a range of cpu#'s */
                   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 a cpu# or range */
                           if (c == '\0' || c == ',')
                                   break;
   
                           if (c == '-') {
                                   if (exp_digit || in_range)
                                           return -EINVAL;
                                   b = 0;
                                   in_range = 1;
                                   exp_digit = 1;
                                   continue;
                           }
   
                           if (!isdigit(c))
                                   return -EINVAL;
   
                           b = b * 10 + (c - '');
                           if (!in_range)
                                   a = b;
                           exp_digit = 0;
                           totaldigits++;
                   }
                   if (!(a <= b))
                           return -EINVAL;
                   if (b >= nmaskbits)
                           return -ERANGE;
                   while (a <= b) {
                           set_bit(a, maskp);
                           a++;
                   }
           } while (buflen && c == ',');
           return 0;
   }
   
   int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
   {
           char *nl  = strchr(bp, '\n');
           int len;
   
           if (nl)
                   len = nl - bp;
           else
                   len = strlen(bp);
   
           return __bitmap_parselist(bp, len, 0, maskp, nmaskbits);
   }
   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.
    *
    * 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_parselist_user(const char __user *ubuf,
                           unsigned int ulen, unsigned long *maskp,
                           int nmaskbits)
   {
           if (!access_ok(VERIFY_READ, ubuf, ulen))
                   return -EFAULT;
           return __bitmap_parselist((const char __force *)ubuf,
                                           ulen, 1, maskp, nmaskbits);
   }
   EXPORT_SYMBOL(bitmap_parselist_user);
   
   
   /**
    * 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 < @bits)
    *      @bits: number of valid bit positions in @buf
    *
    * Map the bit at position @pos in @buf (of length @bits) 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 0.  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, int pos, int bits)
   {
           int i, ord;
   
           if (pos < 0 || pos >= bits || !test_bit(pos, buf))
                   return -1;
   
           i = find_first_bit(buf, bits);
           ord = 0;
           while (i < pos) {
                   i = find_next_bit(buf, bits, i + 1);
                   ord++;
           }
           BUG_ON(i != pos);
   
           return ord;
   }
   
   /**
    * 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)
    *      @bits: 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), else
    * results are undefined.
    *
    * 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 return undefined values.  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 @bits are valid positions in @buf.
    */
   int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
   {
           int pos = 0;
   
           if (ord >= 0 && ord < bits) {
                   int i;
   
                   for (i = find_first_bit(buf, bits);
                        i < bits && ord > 0;
                        i = find_next_bit(buf, bits, i + 1))
                           ord--;
                   if (i < bits && ord == 0)
                           pos = i;
           }
   
           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
    *      @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.
    *
    * 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,
                   int bits)
   {
           int oldbit, w;
   
           if (dst == src)         /* following doesn't handle inplace remaps */
                   return;
           bitmap_zero(dst, bits);
   
           w = bitmap_weight(new, bits);
           for_each_set_bit(oldbit, src, bits) {
                   int n = bitmap_pos_to_ord(old, oldbit, bits);
   
                   if (n < 0 || w == 0)
                           set_bit(oldbit, dst);   /* identity map */
                   else
                           set_bit(bitmap_ord_to_pos(new, n % w, bits), dst);
           }
   }
   EXPORT_SYMBOL(bitmap_remap);
   
   /**
    * 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);
   }
   EXPORT_SYMBOL(bitmap_bitremap);
   
   /**
    * 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 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 possitility 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 (*)
    *      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 (*)
    *
    * (*) 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, int bits)
   {
           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++;
           }
   }
   EXPORT_SYMBOL(bitmap_onto);
   
  /**
   * bitmap_fold - fold larger bitmap into smaller, modulo specified size
   *      @dst: resulting smaller bitmap
   *      @orig: original larger bitmap
   *      @sz: specified size
   *      @bits: 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,
                          int sz, int bits)
  {
          int oldbit;
  
          if (dst == orig)        /* following doesn't handle inplace mappings */
                  return;
          bitmap_zero(dst, bits);
  
          for_each_set_bit(oldbit, orig, bits)
                  set_bit(oldbit % sz, dst);
  }
  EXPORT_SYMBOL(bitmap_fold);
  
  /*
   * 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, 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, int bits, int order)
  {
          int pos, end;           /* scans bitmap by regions of size order */
  
          for (pos = 0 ; (end = pos + (1 << 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, 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, int pos, int order)
  {
          if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
                  return -EBUSY;
          __reg_op(bitmap, pos, order, REG_OP_ALLOC);
          return 0;
  }
  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.
   */
  void bitmap_copy_le(void *dst, const unsigned long *src, int nbits)
  {
          unsigned long *d = dst;
          int i;
  
          for (i = 0; i < nbits/BITS_PER_LONG; i++) {
                  if (BITS_PER_LONG == 64)
                          d[i] = cpu_to_le64(src[i]);
                  else
                          d[i] = cpu_to_le32(src[i]);
          }
  }
  EXPORT_SYMBOL(bitmap_copy_le);

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