+ lib-extend-the-scope-of-small_const_nbits-macro.patch added to -mm tree

+ lib-extend-the-scope-of-small_const_nbits-macro.patch added to -mm tree

[akpm]

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@gmail.com>
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@gmail.com
Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Alexey Klimov <aklimov@redhat.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Sterba <dsterba@suse.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jianpeng Ma <jianpeng.ma@intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Stefano Brivio <sbrivio@redhat.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Yoshinori Sato <ysato@users.osdn.me>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@gmail.com 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