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Subject: Re: [RFC][PATCH v1 02/11] mm: soft-offline: add missing error check
 of set_hwpoison_free_buddy_page()
To:     Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Michal Hocko <mhocko@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        xishi.qiuxishi@alibaba-inc.com,
        Laurent Dufour <ldufour@linux.vnet.ibm.com>
References: <1541746035-13408-1-git-send-email-n-horiguchi@ah.jp.nec.com>
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From:   Anshuman Khandual <anshuman.khandual@arm.com>
Message-ID: <9ea93154-4843-231d-d72b-bf12c8807c24@arm.com>
Date:   Fri, 9 Nov 2018 15:50:41 +0530
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On 11/09/2018 12:17 PM, Naoya Horiguchi wrote:
> set_hwpoison_free_buddy_page() could fail, then the target page is
> finally not isolated, so it's better to report -EBUSY for userspace
> to know the failure and chance of retry.
> 

IIUC set_hwpoison_free_buddy_page() could only fail if the page is not
free in the buddy. At least for soft_offline_huge_page() that wont be
the case otherwise dissolve_free_huge_page() would have returned non
zero -EBUSY. Is there any other reason set_hwpoison_free_buddy_page()
would not succeed ?

> And for consistency, this patch moves set_hwpoison_free_buddy_page()
> in unmap_and_move() to __soft_offline_page().

Yeah this check should be handled in soft offline functions not inside
migrations they trigger.