linux-kernel - Re: [RFC][PATCH] kernel.h: Add generic roundup

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Date:   Fri, 24 May 2019 16:11:14 +0100
From:   Roger Willcocks <roger@...mlight.ltd.uk>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     roger@...mlight.ltd.uk, LKML <linux-kernel@...r.kernel.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau@...ts.freedesktop.org,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC][PATCH] kernel.h: Add generic roundup_64() macro


On 23/05/2019 16:27, Steven Rostedt wrote:
>
> I haven't yet tested this, but what about something like the following:
>
> ...perhaps forget about the constant check, and just force
> the power of two check:
>
> 							\
> 	if (!(__y & (__y >> 1))) {			\
> 		__x = round_up(x, y);			\
> 	} else {					\

You probably want

            if (!(__y & (__y - 1))

--

Roger