Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Wed, 12 Sep 2018 11:16:39 +0200
From:   Roger Pau =?utf-8?B?TW9ubsOp?= <roger.pau@citrix.com>
To:     Julien Grall <julien.grall@arm.com>
CC:     Jan Beulich <JBeulich@suse.com>, Jens Axboe <axboe@kernel.dk>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        <linux-kernel@vger.kernel.org>, <linux-block@vger.kernel.org>,
        xen-devel <xen-devel@lists.xenproject.org>,
        zhong jiang <zhongjiang@huawei.com>
Subject: Re: [Xen-devel] [PATCH] drivers/block/xen-blkback/common.h: use
 DIV_ROUND_UP instead of reimplementing its function
Message-ID: <20180912091639.oynlvdo6pghnqfvt@mac.bytemobile.com>
References: <1536731100-56054-1-git-send-email-zhongjiang@huawei.com>
 <5B98CAE202000078001E79CC@prv1-mh.provo.novell.com>
 <20180912091350.6wuvt2jkvzg6wruo@mac.bytemobile.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20180912091350.6wuvt2jkvzg6wruo@mac.bytemobile.com>
User-Agent: NeoMutt/20180716
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Sorry, I've failed to add Julien in my previous reply.

On Wed, Sep 12, 2018 at 11:13:50AM +0200, Roger Pau Monn? wrote:
> Adding Julien how did the work to support XEN_PAGE_SIZE != PAGE_SIZE.
> 
> On Wed, Sep 12, 2018 at 02:14:26AM -0600, Jan Beulich wrote:
> > >>> On 12.09.18 at 07:45, <zhongjiang@huawei.com> wrote:
> > > --- a/drivers/block/xen-blkback/common.h
> > > +++ b/drivers/block/xen-blkback/common.h
> > > @@ -65,7 +65,7 @@
> > >  	(XEN_PAGES_PER_INDIRECT_FRAME / XEN_PAGES_PER_SEGMENT)
> > >  
> > >  #define MAX_INDIRECT_PAGES \
> > > -	((MAX_INDIRECT_SEGMENTS + SEGS_PER_INDIRECT_FRAME - 1)/SEGS_PER_INDIRECT_FRAME)
> > > +		DIV_ROUND_UP(MAX_INDIRECT_SEGMENTS, SEGS_PER_INDIRECT_FRAME)
> > >  #define INDIRECT_PAGES(_segs) DIV_ROUND_UP(_segs, XEN_PAGES_PER_INDIRECT_FRAME)
> > 
> > My first reaction was to suggest
> > 
> > #define MAX_INDIRECT_PAGES INDIRECT_PAGES(MAX_INDIRECT_SEGMENTS)
> > 
> > but that wouldn't match what's there currently (note the two different
> > divisors). I can't really decide whether that's just unfortunate naming
> > of the two macros, or an actual bug.
> 
> I think there's indeed a bug here.
> 
> AFAICT, MAX_INDIRECT_PAGES should use XEN_PAGES_PER_INDIRECT_FRAME and
> then it could be changed as Jan suggested.
> 
> Current MAX_INDIRECT_PAGES is misnamed and should instead be
> MAX_INDIRECT_SEGS (which on x86 is exactly the same because PAGE_SIZE
> == XEN_PAGE_SIZE).
> 
> Roger.
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xenproject.org
> https://lists.xenproject.org/mailman/listinfo/xen-devel