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Subject: Re: [PATCH v7 2/7] mm,compaction: Let
 isolate_migratepages_{range,block} return error codes
To:     Oscar Salvador <osalvador@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Vlastimil Babka <vbabka@suse.cz>,
        David Hildenbrand <david@redhat.com>,
        Michal Hocko <mhocko@kernel.org>,
        Muchun Song <songmuchun@bytedance.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20210413104747.12177-1-osalvador@suse.de>
 <20210413104747.12177-3-osalvador@suse.de>
From:   Mike Kravetz <mike.kravetz@oracle.com>
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Date:   Tue, 13 Apr 2021 10:52:24 -0700
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On 4/13/21 3:47 AM, Oscar Salvador wrote:
> Currently, isolate_migratepages_{range,block} and their callers use
> a pfn == 0 vs pfn != 0 scheme to let the caller know whether there was
> any error during isolation.
> This does not work as soon as we need to start reporting different error
> codes and make sure we pass them down the chain, so they are properly
> interpreted by functions like e.g: alloc_contig_range.
> 
> Let us rework isolate_migratepages_{range,block} so we can report error
> codes.
> Since isolate_migratepages_block will stop returning the next pfn to be
> scanned, we reuse the cc->migrate_pfn field to keep track of that.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Mike Kravetz <mike.kravetz@oracle.com>

-- 
Mike Kravetz