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Date:   Thu, 21 Mar 2019 09:07:02 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     Zi Yan <ziy@nvidia.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, mike.kravetz@oracle.com,
        osalvador@suse.de, akpm@linux-foundation.org
Subject: Re: [PATCH] mm/isolation: Remove redundant pfn_valid_within() in
 __first_valid_page()
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On Thu 21-03-19 11:03:18, Anshuman Khandual wrote:
> 
> 
> On 03/21/2019 10:31 AM, Zi Yan wrote:
> > On 20 Mar 2019, at 21:13, Anshuman Khandual wrote:
> > 
> >> pfn_valid_within() calls pfn_valid() when CONFIG_HOLES_IN_ZONE making it
> >> redundant for both definitions (w/wo CONFIG_MEMORY_HOTPLUG) of the helper
> >> pfn_to_online_page() which either calls pfn_valid() or pfn_valid_within().
> >> pfn_valid_within() being 1 when !CONFIG_HOLES_IN_ZONE is irrelevant either
> >> way. This does not change functionality.
> >>
> >> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
> > 
> > I would not say this patch fixes the commit 2ce13640b3f4 from 2017,
> > because the pfn_valid_within() in pfn_to_online_page() was introduced by
> > a recent commit b13bc35193d9e last month. :)
> 
> Right, will update the tag with this commit.

The patch is correct but I wouldn't bother to add Fixes tag at all. The
current code is obviously not incorrect. Do you see any actual
performance issue?
-- 
Michal Hocko
SUSE Labs