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[198.145.29.99]) by mx.google.com with ESMTPS id v21si28980276pgb.560.2019.05.23.09.19.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 May 2019 09:19:17 -0700 (PDT) Received-SPF: pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b="m8wcPZW/"; spf=pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mail-wr1-f41.google.com (mail-wr1-f41.google.com [209.85.221.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C256B2189D for ; Thu, 23 May 2019 16:19:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558628357; bh=Wv0O6tMsqxBwrYSLzxmAH+HjOtWLDhHqgQXa2NMoUIM=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=m8wcPZW/M5eX6YmtPExOOjXbCs1Fo1YueQMdcV589nhOSyRRfgxcT1t4ux70n1ALe sdXuQDKIaa0saOhmp7SlCZBenDx2VVUEyRbkHBeLGunh1nk+LkWLYGyCdNi3rQp4CK WzeOTXr3vBI3tiirMj/acZjWjunbW3S/efBcfh08= Received: by mail-wr1-f41.google.com with SMTP id d9so6973982wrx.0 for ; Thu, 23 May 2019 09:19:16 -0700 (PDT) X-Received: by 2002:adf:e90b:: with SMTP id f11mr4069510wrm.291.1558628353521; Thu, 23 May 2019 09:19:13 -0700 (PDT) MIME-Version: 1.0 References: <155836064844.2441.10911127801797083064.stgit@localhost.localdomain> <9638a51c-4295-924f-1852-1783c7f3e82d@virtuozzo.com> <67d1321e-ffd6-24a3-407f-cd26c82e46b8@virtuozzo.com> In-Reply-To: <67d1321e-ffd6-24a3-407f-cd26c82e46b8@virtuozzo.com> From: Andy Lutomirski Date: Thu, 23 May 2019 09:19:01 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 0/7] mm: process_vm_mmap() -- syscall for duplication a process mapping To: Kirill Tkhai Cc: Andy Lutomirski , Andrew Morton , Dan Williams , Michal Hocko , Keith Busch , "Kirill A. Shutemov" , alexander.h.duyck@linux.intel.com, Weiny Ira , Andrey Konovalov , arunks@codeaurora.org, Vlastimil Babka , Christoph Lameter , Rik van Riel , Kees Cook , Johannes Weiner , Nicholas Piggin , Mathieu Desnoyers , Shakeel Butt , Roman Gushchin , Andrea Arcangeli , Hugh Dickins , Jerome Glisse , Mel Gorman , daniel.m.jordan@oracle.com, Jann Horn , Adam Borowski , Linux API , LKML , Linux-MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 21, 2019 at 10:44 AM Kirill Tkhai wrote: > > On 21.05.2019 19:43, Andy Lutomirski wrote: > > On Tue, May 21, 2019 at 8:52 AM Kirill Tkhai wrote: > >> > >> On 21.05.2019 17:43, Andy Lutomirski wrote: > > Do you mean that the code you sent rejects this case? If so, please > > document it. In any case, I looked at the code, and it seems to be > > trying to handle MAP_SHARED and MAP_ANONYMOUS. I don't see where it > > would reject copying a vDSO. > > I prohibit all the VMAs, which contain on of flags: VM_HUGETLB|VM_DONTEXPAND|VM_PFNMAP|VM_IO. > I'll check carefully, whether it's enough for vDSO. I think you could make the new syscall a lot more comprehensible bg restricting it to just MAP_ANONYMOUS, by making it unmap the source, or possibly both. If the new syscall unmaps the source (in order so that the source is gone before the newly mapped pages become accessible), then you avoid issues in which you need to define sensible semantics for what happens if both copies are accessed simultaneously. --Andy