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authorOmar Sandoval <osandov@fb.com>2018-04-02 15:58:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-02 20:52:27 -0700
commit21035965f60b0502fc6537b232839389bb4ce664 (patch)
treeb4c969cd182d8e30dd9b0123c945f200ab50f14a /include/linux/bitmap.h
parentf5a8eb632b562bd9c16c389f5db3a5260fba4157 (diff)
bitmap: fix memset optimization on big-endian systems
Commit 2a98dc028f91 ("include/linux/bitmap.h: turn bitmap_set and bitmap_clear into memset when possible") introduced an optimization to bitmap_{set,clear}() which uses memset() when the start and length are constants aligned to a byte. This is wrong on big-endian systems; our bitmaps are arrays of unsigned long, so bit n is not at byte n / 8 in memory. This was caught by the Btrfs selftests, but the bitmap selftests also fail when run on a big-endian machine. We can still use memset if the start and length are aligned to an unsigned long, so do that on big-endian. The same problem applies to the memcmp in bitmap_equal(), so fix it there, too. Fixes: 2a98dc028f91 ("include/linux/bitmap.h: turn bitmap_set and bitmap_clear into memset when possible") Fixes: 2c6deb01525a ("bitmap: use memcmp optimisation in more situations") Cc: stable@kernel.org Reported-by: "Erhard F." <erhard_f@mailbox.org> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/bitmap.h')
-rw-r--r--include/linux/bitmap.h22
1 files changed, 17 insertions, 5 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 5f11fbdc27f8..1ee46f492267 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -302,12 +302,20 @@ static inline void bitmap_complement(unsigned long *dst, const unsigned long *sr
__bitmap_complement(dst, src, nbits);
}
+#ifdef __LITTLE_ENDIAN
+#define BITMAP_MEM_ALIGNMENT 8
+#else
+#define BITMAP_MEM_ALIGNMENT (8 * sizeof(unsigned long))
+#endif
+#define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1)
+
static inline int bitmap_equal(const unsigned long *src1,
const unsigned long *src2, unsigned int nbits)
{
if (small_const_nbits(nbits))
return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits));
- if (__builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))
+ if (__builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+ IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
return !memcmp(src1, src2, nbits / 8);
return __bitmap_equal(src1, src2, nbits);
}
@@ -358,8 +366,10 @@ static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
{
if (__builtin_constant_p(nbits) && nbits == 1)
__set_bit(start, map);
- else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) &&
- __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))
+ else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
+ IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
+ __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+ IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
memset((char *)map + start / 8, 0xff, nbits / 8);
else
__bitmap_set(map, start, nbits);
@@ -370,8 +380,10 @@ static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
{
if (__builtin_constant_p(nbits) && nbits == 1)
__clear_bit(start, map);
- else if (__builtin_constant_p(start & 7) && IS_ALIGNED(start, 8) &&
- __builtin_constant_p(nbits & 7) && IS_ALIGNED(nbits, 8))
+ else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
+ IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
+ __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
+ IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
memset((char *)map + start / 8, 0, nbits / 8);
else
__bitmap_clear(map, start, nbits);