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Date:   Wed, 13 Apr 2022 17:15:33 +0800
From:   Chao Peng <chao.p.peng@linux.intel.com>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     Sean Christopherson <seanjc@google.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
        qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
        Hugh Dickins <hughd@google.com>,
        Jeff Layton <jlayton@kernel.org>,
        "J . Bruce Fields" <bfields@fieldses.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@kernel.org>,
        Steven Price <steven.price@arm.com>,
        "Maciej S . Szmigiero" <mail@maciej.szmigiero.name>,
        Vlastimil Babka <vbabka@suse.cz>,
        Vishal Annapurve <vannapurve@google.com>,
        Yu Zhang <yu.c.zhang@linux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        luto@kernel.org, jun.nakajima@intel.com, dave.hansen@intel.com,
        ak@linux.intel.com, david@redhat.com
Subject: Re: [PATCH v5 04/13] mm/shmem: Restrict MFD_INACCESSIBLE memory
 against RLIMIT_MEMLOCK
Message-ID: <20220413091533.GC10041@chaop.bj.intel.com>
Reply-To: Chao Peng <chao.p.peng@linux.intel.com>
References: <20220310140911.50924-1-chao.p.peng@linux.intel.com>
 <20220310140911.50924-5-chao.p.peng@linux.intel.com>
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 <20220411153233.54ljmi7zgqovhgsn@box.shutemov.name>
 <20220412133925.GG8013@chaop.bj.intel.com>
 <20220412192821.xliop57sblvjx4t4@box.shutemov.name>
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On Tue, Apr 12, 2022 at 10:28:21PM +0300, Kirill A. Shutemov wrote:
> On Tue, Apr 12, 2022 at 09:39:25PM +0800, Chao Peng wrote:
> > On Mon, Apr 11, 2022 at 06:32:33PM +0300, Kirill A. Shutemov wrote:
> > > On Thu, Apr 07, 2022 at 04:05:36PM +0000, Sean Christopherson wrote:
> > > > Hmm, shmem_writepage() already handles SHM_F_INACCESSIBLE by rejecting the swap, so
> > > > maybe it's just the page migration path that needs to be updated?
> > > 
> > > My early version prevented migration with -ENOTSUPP for
> > > address_space_operations::migratepage().
> > > 
> > > What's wrong with that approach?
> > 
> > I previously thought migratepage will not be called since we already
> > marked the pages as UNMOVABLE, sounds not correct?
> 
> Do you mean missing __GFP_MOVABLE?

Yes.

> I can be wrong, but I don't see that it
> direclty affects if the page is migratable. It is a hint to page allocator
> to group unmovable pages to separate page block and impove availablity of
> higher order pages this way. Page allocator tries to allocate unmovable
> pages from pages blocks that already have unmovable pages.

OK, thanks.

Chao
> 
> -- 
>  Kirill A. Shutemov