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Date: Wed, 11 May 2016 14:23:26 -0500
From: Reza Arbab <arbab@linux.vnet.ibm.com>
To: Yasuaki Ishimatsu <yasu.isimatu@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Daniel Kiper <daniel.kiper@oracle.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Vlastimil Babka <vbabka@suse.cz>, Tang Chen <tangchen@cn.fujitsu.com>,
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        Chen Yucong <slaoub@gmail.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Subject: Re: [PATCH 2/3] memory-hotplug: more general validation of zone
 during online
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On Wed, May 11, 2016 at 08:17:41AM -0700, Yasuaki Ishimatsu wrote:
>On Tue, 10 May 2016 15:39:43 -0500
>Reza Arbab <arbab@linux.vnet.ibm.com> wrote:
><snip>
>> +	if (idx < target) {
>> +		/* pages must be at end of current zone */
>> +		if (pfn + nr_pages != zone_end_pfn(zone))
>> +			return 0;
><snip>
>> +	if (target < idx) {
>> +		/* pages must be at beginning of current zone */
>> +		if (pfn != zone->zone_start_pfn)
>> +			return 0;
>
>According your patch, memory address must be continuous for changing zone.
>So if memory address is uncontinuous as follows, memory address 0x180000000-0x1FFFFFFFF
>can be changed from ZONE_NORMAL to ZONE_MOVABLE. But memory address 0x80000000-0xFFFFFFFF
>can not be changed from ZONE_NORMAL to ZONE_MOVABLE since it does not meet
>above condition.
>
>Memory address
>  0x80000000 -  0xFFFFFFFF
> 0x180000000 - 0x1FFFFFFFF

Ah, I see. What do you think of this instead?

<snip>
+	if (idx < target) {
+		/* must be the last pages present in current zone */
+		for (i = pfn + nr_pages; i < zone_end_pfn(zone); i++)
+			if (pfn_present(i))
+				return 0;
<snip>
+	if (target < idx) {
+		/* must be the first pages present in current zone */
+		for (i = zone->zone_start_pfn; i < pfn; i++)
+			if (pfn_present(i))
+				return 0;

-- 
Reza Arbab