From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A229EC79F82 for ; Tue, 8 Sep 2026 08:46:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 64C056B008A; Tue, 8 Sep 2026 04:46:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5FCEB6B008C; Tue, 8 Sep 2026 04:46:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 512296B0092; Tue, 8 Sep 2026 04:46:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 2FA926B008A for ; Tue, 8 Sep 2026 04:46:41 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 87663120462 for ; Tue, 8 Sep 2026 08:46:40 +0000 (UTC) X-FDA: 85189964160.10.60D9E48 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf24.hostedemail.com (Postfix) with ESMTP id ECC77180002 for ; Tue, 8 Sep 2026 08:46:38 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PFVEN8Jg; spf=pass (imf24.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788857199; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pi6DH3h9BVaC49RRQjlI0O6aYCIlCAFAZNGWG1WvFkY=; b=xlPmyNeWrgwNVhGOdVmPQU3jpsFUseUs3bpGBcDTQsZ0hAIrp0SDg75oZrrc0GtYsTDvH8 lQTc77Rc7gUayR9VZgvJNeTdNn4Q5DWS+xgCOiGEvAVjarku2s7IlmratFawKh7OsXKLzW WGzdTxCR7JHknplMGrbT39mGFSUoAc8= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788857199; b=FNTDAUfTld+I9xTuaT2pSAOtSQquBwwUDLx/28gEuMV5vJXXYH19u3D7ugjg5BRv4Tko0I DXgnqmwl2pOMkbjBELdOAm/CG1gTnu4hZtxTVxC+0knfMzZUa24cCXe0BQF3SpxzU2l0kv 0UkW8um+7QV+l/nurrhhQ4ZoQtW0C7c= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=PFVEN8Jg; spf=pass (imf24.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0F3BF40BD3; Tue, 8 Sep 2026 08:46:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 865B01F00A3A; Tue, 8 Sep 2026 08:46:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788857197; bh=pi6DH3h9BVaC49RRQjlI0O6aYCIlCAFAZNGWG1WvFkY=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=PFVEN8JgyzdpOjdG910dp2qyUJAFTPtXr0iNqWNr5MagH+H0QrDfVOBmEq6qipxbZ ++krRlOTWT+r0W+aWIpso/p7i548JDpWtUPeoJ33EH1oE/mskhWZ/+AqLSPidspNYi Dkv//LMEhgIc1fNBR0aGJJlJPMvUIAZR5n69gc2lMfZBqn8PFIqfVk0MjJvjjM2kwP tHcZLmXVCGfVFqK07+qnTf1iKO93NehQ/JPShF2pvFi+2TDN4voi2YR/aZhtQVRz6F FRfIzr2sG6JwXZHfdvK6GP+pqy0lc6TPJtcNCiQI143SWohY2E+jlZWsZWNmiOZXvr l1DDLcjvqttJA== Date: Tue, 8 Sep 2026 09:46:30 +0100 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , "Matthew Wilcox (Oracle)" , Jan Kara , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH 3/6] mm/vma: only permit MAP_PRIVATE /dev/zero to be mapped anonymous Message-ID: References: <20260902-map-private-dev-zero-v1-0-a578c730cec7@kernel.org> <20260902-map-private-dev-zero-v1-3-a578c730cec7@kernel.org> <8f797f01-e958-404e-bcdf-283da960e95c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8f797f01-e958-404e-bcdf-283da960e95c@kernel.org> X-Stat-Signature: o64wuas48f6byuwtsgt3qczmgdffyiym X-Rspamd-Queue-Id: ECC77180002 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1788857198-568772 X-HE-Meta: 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 5o2CbGnr rvvbM/WxuCPtYBc/6VgsBxLGe5H8MsH2FAgzaLnSgneSb9fxpb9pBdtScKE1UFOzxFr897Ys/C1PcpNoJtiKWj7fILGEZH24RCGPfmlz1pMT18XLHV4368P8vywBzzrW7bhrx8iuDQAGvAkE1BUwkJiRKjJtDYwh6C4EtHVZEQx9XDhodQ1GcMGhQtPv9Du9LaBBJgHLB4dyDRIzdH9yJJ+crGoWJx9Dxmh908AR4wW4J0SolwLSmCQhx2GaoI9R6iZzJETOTz4Iiy1gZA01RWBlexEVP700xoFAC7MbFjmz5f9A= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 07, 2026 at 09:54:04PM +0200, David Hildenbrand (Arm) wrote: > Yes, but my point is that the comment > > "cannot mark themselves anonymous" > > will not really be correct after the next patch, no? Ah ok ack I get your point. I will update this comment in the next patch. > >>> set_vma_user_defined_fields(vma, &map); > >> > >> Ah, we have mmap_zero_prepare() for handling the shmem_zero_setup_desc(). I was > >> just about to ask whether we can just get rid of this here. > >> > >> > >> But, hold on, do we now even need that? Could core-mm now take care of that as > >> well, and we could just remove mmap_zero_prepare() entirely? > >> > >> That is, we'd make shmem_zero_setup() in __mmap_new_vma() take care of this? > >> Then we might not even need shmem_zero_setup_desc() anymore. > >> > >> Maybe harder than it sounds at first. > > > > I think I'd rather that be a follow up :) this series is about eliminiating the > > one last (I hope?) corner case for anon VMAs. > Right; having to deal with anonymous mappings that have mmap_prepare is rather > suboptimal. Ideally we'd just handle the odd dev-zero special-casing early in > the mmap path also for MAP_SHARED, and avoid messing with mmap_prepare entirely. > > So agreed that this can be done separately. Yeah, really life will be easier once the mmap path is gone in general :) > > -- > Cheers, > > David -- Cheers, Lorenzo