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Message-ID: <1365536528.32127.56.camel@misato.fc.hp.com>
Subject: Re: [UPDATE][PATCH v2 2/3] resource: Add
 release_mem_region_adjustable()
From: Toshi Kani <toshi.kani@hp.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Ram Pai <linuxram@us.ibm.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>,
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Date: Tue, 09 Apr 2013 13:42:08 -0600
In-Reply-To: <20130409125141.bfe6e26142e5bb2ff229ed29@linux-foundation.org>
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On Tue, 2013-04-09 at 12:51 -0700, Andrew Morton wrote:
> On Tue, 09 Apr 2013 13:02:30 -0600 Toshi Kani <toshi.kani@hp.com> wrote:
> 
> > > > +		/* look for the next resource if it does not fit into */
> > > > +		if (res->start > start || res->end < end) {
> > > > +			p = &res->sibling;
> > > > +			continue;
> > > > +		}
> > > 
> > > What if the resource overlaps. In other words, the res->start > start 
> > > but res->end > end  ? 
> > > 
> > > Also do you handle the case where the range <start,end> spans
> > > across multiple adjacent resources?
> > 
> > Good questions!  The two cases above are handled as error cases
> > (-EINVAL) by design.  A requested region must either match exactly or
> > fit into a single resource entry.  There are basically two design
> > choices in release -- restrictive or non-restrictive.  Restrictive only
> > releases under certain conditions, and non-restrictive releases under
> > any conditions.  Since the existing release interfaces,
> > __release_region() and __release_resource(), are restrictive, I intend
> > to follow the same policy and made this new interface restrictive as
> > well.  This new interface handles the common scenarios of memory
> > hot-plug operations well.  I think your example cases are non-typical
> > scenarios for memory hot-plug, and I am not sure if they happen under
> > normal cases at this point.  Hence, they are handled as error cases for
> > now.  We can always enhance this interface when we find them necessary
> > to support as this interface is dedicated for memory hot-plug.  In other
> > words, we should make such enhancement after we understand their
> > scenarios well.  Does it make sense?
> 
> Can you please update the comment to describe the above?  Because if
> one reviewer was wondering then later readers will also wonder.

Yes, I will update the comment and send an updated patch again.

Thanks,
-Toshi