linux-kernel - Re: [GIT PULL] iscsi-target merge for v3.1-rc1

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Message-Id: <1311665161.17766.234.camel@haakon2.linux-iscsi.org>
Date:	Tue, 26 Jul 2011 00:26:01 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	target-devel <target-devel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>,
	Andy Grover <agrover@...hat.com>,
	Hannes Reinecke <hare@...e.de>,
	Roland Dreier <roland@...estorage.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	Boaz Harrosh <openosd@...il.com>,
	Mike Christie <michaelc@...wisc.edu>
Subject: Re: [GIT PULL] iscsi-target merge for v3.1-rc1

On Tue, 2011-07-26 at 00:09 -0700, Linus Torvalds wrote:
> On Mon, Jul 25, 2011 at 11:51 PM, Nicholas A. Bellinger
> <nab@...ux-iscsi.org> wrote:
> >
> > How about the following to add a new DIV_ROUND_UP_ULL macro
> 
> Hmm.
> 
> >  #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
> > +#define DIV_ROUND_UP_ULL(n,d) (                                \
> > +{                                                      \
> > +       unsigned long long _tmp = n, _off;              \
> > +       int _res;                                       \
> > +       /* Round up using asm/div64.h:do_div */         \
> > +       _off = do_div(_tmp, d);                         \
> > +       if (_off != 0)                                  \
> > +               _tmp++;                                 \
> > +       _res = _tmp;                                    \
> > +}                                                      \
> > +)
> 
> That looks buggy. Why the "_res = _tmp" there? All that does is to
> truncate the result to "int", which looks bogus.
> 
> And it just looks unnecessarily complicated. Just a simple
> 
> #define DIV_ROUND_UP_ULL(ll,d) \
>   ({ unsigned long long _tmp = (ll)+(d)-1; do_div(_tmp, d); _tmp; })
> 
> looks like it would work and be simpler. Avoid the conditional, do the
> same "add 'd-1' thing as the regular ROUND_UP().
> 
> Untested. And not much thinking involved.
> 

Fixing this up in lio-core-2.6.git now and pushing out into
target-pending.git/for-next now unless you have any other concerns.

Thank you,

--nab


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