linux-kernel - Re: [PATCH 3/3] bitops.h: set_mask

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Message-ID: <693b30a9-96dc-a5e6-9708-c215b90146b0@oracle.com>
Date:   Thu, 10 Jan 2019 20:25:09 -0800
From:   Anthony Yznaga <anthony.yznaga@...cle.com>
To:     Vineet Gupta <vineet.gupta1@...opsys.com>,
        linux-kernel@...r.kernel.org
Cc:     linux-snps-arc@...ts.infradead.org, linux-mm@...ck.org,
        peterz@...radead.org, Miklos Szeredi <mszeredi@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Jani Nikula <jani.nikula@...el.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH 3/3] bitops.h: set_mask_bits() to return old value



On 1/10/19 4:26 PM, Vineet Gupta wrote:
> | > Also, set_mask_bits is used in fs quite a bit and we can possibly come up
> | > with a generic llsc based implementation (w/o the cmpxchg loop)
> |
> | May I also suggest changing the return value of set_mask_bits() to old.
> |
> | You can compute the new value given old, but you cannot compute the old
> | value given new, therefore old is the better return value. Also, no
> | current user seems to use the return value, so changing it is without
> | risk.
>
> Link: http://lkml.kernel.org/g/20150807110955.GH16853@twins.programming.kicks-ass.net
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Cc: Miklos Szeredi <mszeredi@...hat.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Jani Nikula <jani.nikula@...el.com>
> Cc: Chris Wilson <chris@...is-wilson.co.uk>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Will Deacon <will.deacon@....com>
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
>

Reviewed-by: Anthony Yznaga <anthony.yznaga@...cle.com>