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blockgroup_lock.h: simplify definition of NR_BG_LOCKS

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We can use ilog2() to more easily produce the desired NR_BG_LOCKS.  This
works because ilog2() is evaluated at compile-time when its argument is
a compile-time constant.

I did not change the chosen NR_BG_LOCKS values.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
This commit is contained in:
Eric Biggers 2016-09-15 18:29:06 -04:00 • committed by Theodore Ts'o
parent 9e5ab85deb
commit 7c5f6b320b
1 changed files with 2 additions and 20 deletions
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22
include/linux/blockgroup_lock.h
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@ -10,28 +10,10 @@
#include <linux/cache.h> #include <linux/cache.h>
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
#define NR_BG_LOCKS (4 << ilog2(NR_CPUS < 32 ? NR_CPUS : 32))
/*
* We want a power-of-two. Is there a better way than this?
*/
#if NR_CPUS >= 32
#define NR_BG_LOCKS 128
#elif NR_CPUS >= 16
#define NR_BG_LOCKS 64
#elif NR_CPUS >= 8
#define NR_BG_LOCKS 32
#elif NR_CPUS >= 4
#define NR_BG_LOCKS 16
#elif NR_CPUS >= 2
#define NR_BG_LOCKS 8
#else #else
#define NR_BG_LOCKS 4
#endif
#else /* CONFIG_SMP */
#define NR_BG_LOCKS 1 #define NR_BG_LOCKS 1
#endif /* CONFIG_SMP */ #endif
struct bgl_lock { struct bgl_lock {
spinlock_t lock; spinlock_t lock;