The patch titled
Subject: lib: extend the scope of small_const_nbits() macro
has been added to the -mm tree. Its filename is
lib-extend-the-scope-of-small_const_nbits-macro.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/lib-extend-the-scope-of-small_const_nbits-macro.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/lib-extend-the-scope-of-small_const_nbits-macro.patch
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From: Yury Norov <yury.norov@xxxxxxxxx>
Subject: lib: extend the scope of small_const_nbits() macro
find_bit would also benefit from small_const_nbits() optimizations. The
detailed comment is provided by Rasmus Villemoes.
Link: https://lkml.kernel.org/r/20210401003153.97325-6-yury.norov@xxxxxxxxx
Suggested-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
Acked-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Alexey Klimov <aklimov@xxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: Dennis Zhou <dennis@xxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Jianpeng Ma <jianpeng.ma@xxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxx>
Cc: Stefano Brivio <sbrivio@xxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Cc: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/asm-generic/bitsperlong.h | 12 ++++++++++++
include/linux/bitmap.h | 8 --------
2 files changed, 12 insertions(+), 8 deletions(-)
--- a/include/asm-generic/bitsperlong.h~lib-extend-the-scope-of-small_const_nbits-macro
+++ a/include/asm-generic/bitsperlong.h
@@ -23,4 +23,16 @@
#define BITS_PER_LONG_LONG 64
#endif
+/*
+ * small_const_nbits(n) is true precisely when it is known at compile-time
+ * that BITMAP_SIZE(n) is 1, i.e. 1 <= n <= BITS_PER_LONG. This allows
+ * various bit/bitmap APIs to provide a fast inline implementation. Bitmaps
+ * of size 0 are very rare, and a compile-time-known-size 0 is most likely
+ * a sign of error. They will be handled correctly by the bit/bitmap APIs,
+ * but using the out-of-line functions, so that the inline implementations
+ * can unconditionally dereference the pointer(s).
+ */
+#define small_const_nbits(nbits) \
+ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
+
#endif /* __ASM_GENERIC_BITS_PER_LONG */
--- a/include/linux/bitmap.h~lib-extend-the-scope-of-small_const_nbits-macro
+++ a/include/linux/bitmap.h
@@ -223,14 +223,6 @@ extern int bitmap_print_to_pagebuf(bool
#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
-/*
- * The static inlines below do not handle constant nbits==0 correctly,
- * so make such users (should any ever turn up) call the out-of-line
- * versions.
- */
-#define small_const_nbits(nbits) \
- (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
-
static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
{
unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
_
Patches currently in -mm which might be from yury.norov@xxxxxxxxx are
tools-disable-wno-type-limits.patch
tools-bitmap-sync-function-declarations-with-the-kernel.patch
tools-sync-bitmap_last_word_mask-macro-with-the-kernel.patch
arch-rearrange-headers-inclusion-order-in-asm-bitops-for-m68k-and-sh.patch
lib-extend-the-scope-of-small_const_nbits-macro.patch
tools-sync-small_const_nbits-macro-with-the-kernel.patch
lib-inline-_find_next_bit-wrappers.patch
tools-sync-find_next_bit-implementation.patch
lib-add-fast-path-for-find_next__bit.patch
lib-add-fast-path-for-find_first__bit-and-find_last_bit.patch
tools-sync-lib-find_bit-implementation.patch
maintainers-add-entry-for-the-bitmap-api.patch
