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Change hash_64() return value to 32 bits

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That's all that's ever asked for, and it makes the return
type of hash_long() consistent.

It also allows (upcoming patch) an optimized implementation
of hash_64 on 32-bit machines.

I tried adding a BUILD_BUG_ON to ensure the number of bits requested
was never more than 32 (most callers use a compile-time constant), but
adding <linux/bug.h> to <linux/hash.h> breaks the tools/perf compiler
unless tools/perf/MANIFEST is updated, and understanding that code base
well enough to update it is too much trouble.  I did the rest of an
allyesconfig build with such a check, and nothing tripped.

Signed-off-by: George Spelvin <linux@sciencehorizons.net>
This commit is contained in:
George Spelvin 2016-05-26 22:22:01 -04:00
parent 917ea166f4
commit 92d567740f
1 changed files with 3 additions and 3 deletions
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6
include/linux/hash.h
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@ -48,7 +48,7 @@
#define GOLDEN_RATIO_32 0x61C88647
#define GOLDEN_RATIO_64 0x61C8864680B583EBull
static __always_inline u64 hash_64(u64 val, unsigned int bits)
static __always_inline u32 hash_64(u64 val, unsigned int bits)
{
u64 hash = val;
@ -72,7 +72,7 @@ static __always_inline u64 hash_64(u64 val, unsigned int bits)
#endif
/* High bits are more random, so use them. */
return hash >> (64 - bits);
return (u32)(hash >> (64 - bits));
}
static inline u32 hash_32(u32 val, unsigned int bits)
@ -84,7 +84,7 @@ static inline u32 hash_32(u32 val, unsigned int bits)
return hash >> (32 - bits);
}
static inline unsigned long hash_ptr(const void *ptr, unsigned int bits)
static inline u32 hash_ptr(const void *ptr, unsigned int bits)
{
return hash_long((unsigned long)ptr, bits);
}