提交 cfac1d08 编写于 作者: R Rasmus Villemoes 提交者: Linus Torvalds

lib: bitmap: yet another simplification in __bitmap_shift_right

If left is 0, we can just let mask be ~0UL, so that anding with it is a
no-op.  Conveniently, BITMAP_LAST_WORD_MASK provides precisely what we
need, and we can eliminate left.
Signed-off-by: NRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
上级 97fb8e94
......@@ -113,9 +113,9 @@ EXPORT_SYMBOL(__bitmap_complement);
void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
unsigned shift, unsigned nbits)
{
unsigned k, lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG;
unsigned k, lim = BITS_TO_LONGS(nbits);
unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
unsigned long mask = (1UL << left) - 1;
unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
for (k = 0; off + k < lim; ++k) {
unsigned long upper, lower;
......@@ -127,12 +127,12 @@ void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
upper = 0;
else {
upper = src[off + k + 1];
if (off + k + 1 == lim - 1 && left)
if (off + k + 1 == lim - 1)
upper &= mask;
upper <<= (BITS_PER_LONG - rem);
}
lower = src[off + k];
if (left && off + k == lim - 1)
if (off + k == lim - 1)
lower &= mask;
lower >>= rem;
dst[k] = lower | upper;
......
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