linux-kernel - Re: [PATCH 03/13] mm: meminit: Only set page reserved in the memblock region

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Message-ID: <BY2PR0301MB16558D99EC6729AE515B6E64D88B0@BY2PR0301MB1655.namprd03.prod.outlook.com>
Date:	Thu, 30 Jul 2015 23:41:49 +0000
From:	"Alex Ng (LIS)" <alexng@...rosoft.com>
To:	Nathan Zimmer <nzimmer@....com>
CC:	Mel Gorman <mgorman@...e.de>, Robin Holt <holt@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/13] mm: meminit: Only set page reserved in the memblock
 region

Hi,

While testing builds containing this change (commit id: 92923ca3aacef63c92dc297a75ad0c6dfe4eab37), I've observed that memory fails to come online in the hotplug case. When attempting to bring the hot added pages online (via udev rules or manually writing to sysfs); it's failing with -EBUSY error because the hot added pages no longer have the Reserved flag set.

The reserved bit is being checked in memory_block_action() in drivers/base/memory.c:

                switch (action) {
                case MEM_ONLINE:
                                if (!pages_correctly_reserved(start_pfn))
                                                return -EBUSY;

Should the reserved bit be set in some other place? Or should the above test be removed from sysfs memory device?

--
Alex Ng
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