Commit 5f14daa6 authored by Yury Norov's avatar Yury Norov Committed by Zeng Heng
Browse files

lib: extend the scope of small_const_nbits() macro 

mainline inclusion
from mainline-v5.13-rc1
commit 586eaebe
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6VS35

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=586eaebea5988302c5a8b018096dd6c6f4564940

--------------------------------

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
Acked-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: default avatarAndy Shevchenko <andy.shevchenko@gmail.com>
Cc: Alexey Klimov <aklimov@redhat.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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarZeng Heng <zengheng4@huawei.com>
parent 50612a26

include/asm-generic/bitsperlong.h

+12 −0
Original line number Diff line number Diff line
@@ -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 */

include/linux/bitmap.h

+0 −8
Original line number Diff line number Diff line
@@ -234,14 +234,6 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf, 
#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);