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From:   "Huang\, Ying" <ying.huang@intel.com>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        David Rientjes <rientjes@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
        Minchan Kim <minchan@kernel.org>,
        "Hugh Dickins" <hughd@google.com>, Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH] mm: Code cleanup for MADV_FREE
References: <20200313090056.2104105-1-ying.huang@intel.com>
        <20200313154110.GH21007@dhcp22.suse.cz>
Date:   Mon, 16 Mar 2020 09:42:06 +0800
In-Reply-To: <20200313154110.GH21007@dhcp22.suse.cz> (Michal Hocko's message
        of "Fri, 13 Mar 2020 16:41:10 +0100")
Message-ID: <87lfo1rs7l.fsf@yhuang-dev.intel.com>
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Michal Hocko <mhocko@kernel.org> writes:

> On Fri 13-03-20 17:00:56, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> Some comments for MADV_FREE is revised and added to help people understand the
>> MADV_FREE code, especially the page flag, PG_swapbacked.  This makes
>> page_is_file_cache() isn't consistent with its comments.  So the function is
>> renamed to page_is_file_lru() to make them consistent again.  All these are put
>> in one patch as one logical change.
>> 
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> Suggested-by: David Hildenbrand <david@redhat.com>
>> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
>> Suggested-by: David Rientjes <rientjes@google.com>
>> Cc: Michal Hocko <mhocko@kernel.org>
>> Cc: Dave Hansen <dave.hansen@linux.intel.com>
>> Cc: Mel Gorman <mgorman@suse.de>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Minchan Kim <minchan@kernel.org>
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: Rik van Riel <riel@surriel.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> Although I would rephrased this a bit
>> + * PG_swapbacked is cleared if the page is page cache page backed by a regular
>> + * file system or anonymous page lazily freed (e.g. via MADV_FREE).  It is set
>> + * if the page is normal anonymous page, tmpfs or otherwise RAM or swap backed.
>> + *
>
> PG_swapbacked is set when a page uses swap as a backing storage. This
> are usually PageAnon or shmem pages but please note that even anonymous
> pages might lose their PG_swapbacked flag when they simply can be
> dropped (e.g. as a result of MADV_FREE).

This looks better, Thanks!  I will send a new version with this.

Best Regards,
Huang, Ying