linux-kernel - [PATCH 18/18] lib: bitmap: Add missing mask in bitmap

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Message-Id: <1404427384-11422-19-git-send-email-linux@rasmusvillemoes.dk>
Date:	Fri,  4 Jul 2014 00:43:04 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	linux-kernel@...r.kernel.org
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH 18/18] lib: bitmap: Add missing mask in bitmap_andnot

Apparently, bitmap_andnot is supposed to return whether the new bitmap
is empty. But it didn't take potential garbage bits in the last word
into account.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 include/linux/bitmap.h | 2 +-
 lib/bitmap.c           | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 3399a9e..e1c8d08 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -217,7 +217,7 @@ static inline int bitmap_andnot(unsigned long *dst, const unsigned long *src1,
 			const unsigned long *src2, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
-		return (*dst = *src1 & ~(*src2)) != 0;
+		return (*dst = *src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
 	return __bitmap_andnot(dst, src1, src2, nbits);
 }
 
diff --git a/lib/bitmap.c b/lib/bitmap.c
index ce2ec80..1e031f2 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -223,11 +223,14 @@ int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 				const unsigned long *bitmap2, unsigned int bits)
 {
 	unsigned int k;
-	unsigned int nr = BITS_TO_LONGS(bits);
+	unsigned int lim = bits/BITS_PER_LONG;
 	unsigned long result = 0;
 
-	for (k = 0; k < nr; k++)
+	for (k = 0; k < lim; k++)
 		result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
+	if (bits % BITS_PER_LONG)
+		result |= (dst[k] = bitmap1[k] & ~bitmap2[k] &
+			   BITMAP_LAST_WORD_MASK(bits));
 	return result != 0;
 }
 EXPORT_SYMBOL(__bitmap_andnot);
-- 
1.9.2

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