Change hash_64() return value to 32 bits (92d56774) · Commits · 戴 / test

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>

include/linux/hash.h

+3 −3

Original line number	Diff line number	Diff line
		@@ -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);
		}

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