Commit dba94c25 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds
Browse files

lib: bitmap: change bitmap_shift_left to take unsigned parameters 



gcc can generate slightly better code for stuff like "nbits %
BITS_PER_LONG" when it knows nbits is not negative.  Since negative size
bitmaps or shift amounts don't make sense, change these parameters of
bitmap_shift_right to unsigned.

If off >= lim (which requires shift >= nbits), k is initialized with a
large positive value, but since I've let k continue to be signed, the loop
will never run and dst will be zeroed as expected.  Inside the loop, k is
guaranteed to be non-negative, so the fact that it is promoted to unsigned
in the various expressions it appears in is harmless.

Also use "shift" and "nbits" consistently for the parameter names.

Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cfac1d08

include/linux/bitmap.h

+6 −6
Original line number Diff line number Diff line
@@ -98,8 +98,8 @@ extern void __bitmap_complement(unsigned long *dst, const unsigned long *src, 
			unsigned int nbits);

extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,

				unsigned int shift, unsigned int nbits);

extern void __bitmap_shift_left(unsigned long *dst,

                        const unsigned long *src, int shift, int bits);

extern void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,

				unsigned int shift, unsigned int nbits);

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

			const unsigned long *bitmap2, unsigned int nbits);

extern void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
@@ -322,13 +322,13 @@ static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *s 
		__bitmap_shift_right(dst, src, shift, nbits);

}



static inline void bitmap_shift_left(unsigned long *dst,

			const unsigned long *src, int n, int nbits)

static inline void bitmap_shift_left(unsigned long *dst, const unsigned long *src,

				unsigned int shift, unsigned int nbits)

{

	if (small_const_nbits(nbits))

		*dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits);

		*dst = (*src << shift) & BITMAP_LAST_WORD_MASK(nbits);

	else

		__bitmap_shift_left(dst, src, n, nbits);

		__bitmap_shift_left(dst, src, shift, nbits);

}



static inline int bitmap_parse(const char *buf, unsigned int buflen,

lib/bitmap.c

+6 −5
Original line number Diff line number Diff line
@@ -148,18 +148,19 @@ EXPORT_SYMBOL(__bitmap_shift_right); 
 *   @dst : destination bitmap

 *   @src : source bitmap

 *   @shift : shift by this many bits

 *   @bits : bitmap size, in 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, int shift, int bits)

void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,

			unsigned int shift, unsigned int nbits)

{

	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;

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

	int k;

	unsigned int lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG;

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

	for (k = lim - off - 1; k >= 0; --k) {

		unsigned long upper, lower;

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