bitmap: optimise bitmap_set and bitmap_clear of a single bit

We have eight users calling bitmap_clear for a single bit and seventeen
calling bitmap_set for a single bit.  Rather than fix all of them to
call __clear_bit or __set_bit, turn bitmap_clear and bitmap_set into
inline functions and make this special case efficient.

Link: http://lkml.kernel.org/r/20170628153221.11322-3-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>

1 files changed, 20 insertions, 3 deletions

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 3b77588a9360..4e0f0c8167af 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -112,9 +112,8 @@ extern int __bitmap_intersects(const unsigned long *bitmap1,
 extern int __bitmap_subset(const unsigned long *bitmap1,
                         const unsigned long *bitmap2, unsigned int nbits);
 extern int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
-
-extern void bitmap_set(unsigned long *map, unsigned int start, int len);
-extern void bitmap_clear(unsigned long *map, unsigned int start, int len);
+extern void __bitmap_set(unsigned long *map, unsigned int start, int len);
+extern void __bitmap_clear(unsigned long *map, unsigned int start, int len);
 
 extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
                                                     unsigned long size,
@@ -315,6 +314,24 @@ static __always_inline int bitmap_weight(const unsigned long *src, unsigned int
         return __bitmap_weight(src, nbits);
 }
 
+static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
+                unsigned int nbits)
+{
+        if (__builtin_constant_p(nbits) && nbits == 1)
+                __set_bit(start, map);
+        else
+                __bitmap_set(map, start, nbits);
+}
+
+static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
+                unsigned int nbits)
+{
+        if (__builtin_constant_p(nbits) && nbits == 1)
+                __clear_bit(start, map);
+        else
+                __bitmap_clear(map, start, nbits);
+}
+
 static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *src,
                                 unsigned int shift, int nbits)
 {