linux-kernel - [PATCH 4/7] lib: bitmap: Yet another simplification in __bitmap_shift

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Date:	Fri, 28 Nov 2014 17:01:07 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 4/7] 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: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 lib/bitmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 20bb314..0d78c96 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -111,9 +111,9 @@ 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;
 
@@ -125,12 +125,12 @@ 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;
-- 
2.0.4

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