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Subject: Re: [PATCH] mm: change may_enter_fs check condition
From: yalin wang <yalin.wang2010@gmail.com>
In-Reply-To: <20151113153615.GE2632@dhcp22.suse.cz>
Date: Mon, 16 Nov 2015 09:38:32 +0800
Cc: Vlastimil Babka <vbabka@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>, vdavydov@parallels.com,
        hannes@cmpxchg.org, mgorman@techsingularity.net, tj@kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
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References: <1447415255-832-1-git-send-email-yalin.wang2010@gmail.com> <5645D10C.701@suse.cz> <20151113153615.GE2632@dhcp22.suse.cz>
To: Michal Hocko <mhocko@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Nov 13, 2015, at 23:36, Michal Hocko <mhocko@kernel.org> wrote:
> 
> On Fri 13-11-15 13:01:16, Vlastimil Babka wrote:
>> On 11/13/2015 12:47 PM, yalin wang wrote:
>>> Add page_is_file_cache() for __GFP_FS check,
>>> otherwise, a Pageswapcache() && PageDirty() page can always be write
>>> back if the gfp flag is __GFP_FS, this is not the expected behavior.
>> 
>> I'm not sure I understand your point correctly *), but you seem to imply
>> that there would be an allocation that has __GFP_FS but doesn't have
>> __GFP_IO? Are there such allocations and does it make sense?
> 
> No it doesn't. There is a natural layering here and __GFP_FS allocations
> should contain __GFP_IO.
> 
> The patch as is makes only little sense to me. Are you seeing any issue
> which this is trying to fix?
mm..
i don’t see issue for this part ,
just feel confuse when i see code about this part ,
then i make a patch for this .
i am not sure if __GFP_FS will make sure __GFP_IO flag must be always set.
if it is ,  i think can add comment here to make people clear . :)

Thanks

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