linux-kernel - Re: [UPDATE][PATCH v2 2/3] resource: Add release_mem_region

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Message-ID: <1365536528.32127.56.camel@misato.fc.hp.com>
Date:	Tue, 09 Apr 2013 13:42:08 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ram Pai <linuxram@...ibm.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"guz.fnst@...fujitsu.com" <guz.fnst@...fujitsu.com>,
	"Makphaibulchoke, Thavatchai" <thavatchai.makpahibulchoke@...com>,
	"isimatu.yasuaki@...fujitsu.com" <isimatu.yasuaki@...fujitsu.com>,
	"wency@...fujitsu.com" <wency@...fujitsu.com>,
	"tangchen@...fujitsu.com" <tangchen@...fujitsu.com>,
	"jiang.liu@...wei.com" <jiang.liu@...wei.com>
Subject: Re: [UPDATE][PATCH v2 2/3] resource: Add
 release_mem_region_adjustable()

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@...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


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