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Date:   Fri, 18 Jun 2021 09:53:33 +0200
From:   Oscar Salvador <osalvador@suse.de>
To:     Huang Ying <ying.huang@intel.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Yang Shi <shy828301@gmail.com>, Michal Hocko <mhocko@suse.com>,
        Wei Xu <weixugc@google.com>,
        Dan Williams <dan.j.williams@intel.com>,
        David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH -V8 04/10] mm/migrate: make migrate_pages() return
 nr_succeeded
Message-ID: <20210618075328.GA23470@linux>
References: <20210618061537.434999-1-ying.huang@intel.com>
 <20210618061537.434999-5-ying.huang@intel.com>
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On Fri, Jun 18, 2021 at 02:15:31PM +0800, Huang Ying wrote:
> From: Yang Shi <yang.shi@linux.alibaba.com>
> 
> The migrate_pages() returns the number of pages that were not migrated,
> or an error code.  When returning an error code, there is no way to know
> how many pages were migrated or not migrated.
> 
> In the following patch, migrate_pages() is used to demote pages to PMEM
> node, we need account how many pages are reclaimed (demoted) since page
> reclaim behavior depends on this.  Add *nr_succeeded parameter to make
> migrate_pages() return how many pages are demoted successfully for all
> cases.
> 
> Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Reviewed-by: Yang Shi <shy828301@gmail.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Wei Xu <weixugc@google.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: osalvador <osalvador@suse.de>

I thought we all agreed on making nr_succeed an optional argument [1].
It reduced the churn quite a lot.

[1] https://patchwork.kernel.org/comment/24104453/


-- 
Oscar Salvador
SUSE L3