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include/linux/bitmap.h: turn bitmap_set and bitmap_clear into memset when possible 

Several callers have constant 'start' and an 'nbits' that is a multiple
of 8, so we can turn them into calls to memset.  We don't need the
entirety of 'start' and 'nbits' to be constant, we just need to know
whether they're divisible by 8.

Link: http://lkml.kernel.org/r/20170628153221.11322-4-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox 2017-07-10 15:51:32 -07:00 committed by Linus Torvalds
parent e5af323c9b
commit 2a98dc028f
1 changed files with 6 additions and 0 deletions
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6
include/linux/bitmap.h
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@ -319,6 +319,9 @@ 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))
memset((char *)map + start / 8, 0xff, nbits / 8);
else
__bitmap_set(map, start, nbits);
}
@ -328,6 +331,9 @@ 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))
memset((char *)map + start / 8, 0, nbits / 8);
else
__bitmap_clear(map, start, nbits);
}