lib: bitmap: remove redundant code from __bitmap_shift_left (7f590657) · Commits · 戴 / test

The first of these conditionals is completely redundant: If k == lim-1, we must have off==0, so the second conditional will also trigger and then it wouldn't matter if upper had some high bits set. But the second conditional is in fact also redundant, since it only serves to clear out some high-order "don't care" bits of dst, about which no guarantee is made. Signed-off-by:

Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

lib/bitmap.c

+2 −7

Original line number	Diff line number	Diff line
		@@ -159,7 +159,7 @@ 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), left = nbits % BITS_PER_LONG;
		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;
		@@ -172,13 +172,8 @@ void __bitmap_shift_left(unsigned long dst, const unsigned long src,
		lower = src[k - 1] >> (BITS_PER_LONG - rem);
		else
		lower = 0;
		upper = src[k];
		if (left && k == lim - 1)
		upper &= (1UL << left) - 1;
		upper <<= rem;
		upper = src[k] << rem;
		dst[k + off] = lower \| upper;
		if (left && k + off == lim - 1)
		dst[k + off] &= (1UL << left) - 1;
		}
		if (off)
		memset(dst, 0, off*sizeof(unsigned long));

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