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Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits

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On Mon, May 02, 2016 at 06:20:16AM -0400, George Spelvin wrote:
> Subject: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits

> +static __always_inline u64 hash_64(u64 val, unsigned bits)
> +{
>  	/* High bits are more random, so use them. */
> +	return __hash_64(val) >> (64 - bits);
>  }

Is the subject stale or the above a mistake? Because hash_64() still
very much seems to return u64.

Also, I think I would prefer to keep it like this, I would like to use
it for kernel/locking/lockdep.c:iterate_chain_key(), which currently is
a somewhat crap hash.

Something like:

static inline u64 iterate_chain_key(u64 key1, u64 key2)
{
	return hash_64(key1 ^ key2, 64);
}

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Re: [patch 2/7] lib/hashmod: Add modulo based hash mechanism "George Spelvin" <linux@horizon.com> - 2016-04-30 23:00 +0200
  Re: [patch 2/7] lib/hashmod: Add modulo based hash mechanism Thomas Gleixner <tglx@linutronix.de> - 2016-05-01 10:40 +0200
    Re: [patch 2/7] lib/hashmod: Add modulo based hash mechanism "George Spelvin" <linux@horizon.com> - 2016-05-01 11:50 +0200
      Re: [patch 2/7] lib/hashmod: Add modulo based hash mechanism Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-01 19:00 +0200
      Re: [patch 2/7] lib/hashmod: Add modulo based hash mechanism Thomas Gleixner <tglx@linutronix.de> - 2016-05-02 09:20 +0200
        [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits "George Spelvin" <linux@horizon.com> - 2016-05-02 12:30 +0200
          [PATCH 2/2] <linux/hash.h>: Fix hash_64()'s horrible collision problem "George Spelvin" <linux@horizon.com> - 2016-05-02 12:30 +0200
            Re: [PATCH 2/2] <linux/hash.h>: Fix hash_64()'s horrible collision problem Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-02 22:10 +0200
          [RFC PATCH 3/2] (Rant) Fix various hash abuses "George Spelvin" <linux@horizon.com> - 2016-05-02 12:30 +0200
          [RFC PATCH 4/2] namei: Improve hash mixing if CONFIG_DCACHE_WORD_ACCESS "George Spelvin" <linux@horizon.com> - 2016-05-02 12:40 +0200
          Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32  bits Peter Zijlstra <peterz@infradead.org> - 2016-05-02 15:30 +0200
            Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits "George Spelvin" <linux@horizon.com> - 2016-05-02 21:10 +0200
          Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-02 18:30 +0200
            Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits "George Spelvin" <linux@horizon.com> - 2016-05-02 22:30 +0200
              Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-02 23:20 +0200
                Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-02 23:50 +0200
                Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits "George Spelvin" <linux@horizon.com> - 2016-05-03 04:00 +0200
                Re: [PATCH 1/2] <linux/hash.h>: Make hash_64(), hash_ptr() return 32 bits Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-03 05:10 +0200

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