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 82684C79FA1 for ; Mon, 7 Sep 2026 16:29:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9F1A56B0098; Mon, 7 Sep 2026 12:29:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9CA326B0099; Mon, 7 Sep 2026 12:29:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 907526B009B; Mon, 7 Sep 2026 12:29:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 73D476B0098 for ; Mon, 7 Sep 2026 12:29:14 -0400 (EDT) Received: from smtpin24.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 069BA1C07EA for ; Mon, 7 Sep 2026 16:29:14 +0000 (UTC) X-FDA: 85187501028.24.83B10F9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf11.hostedemail.com (Postfix) with ESMTP id 68AF540011 for ; Mon, 7 Sep 2026 16:29:12 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=AA9jvqee; spf=pass (imf11.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=1788798552; 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=6Mi0KexjACT8EM1oYAJ+w+kZqAp8kzJ2mApTUd50940=; b=Vxrxt9D/WZUgxIgw8Wn8kudE6x2AhjNnB5e8m7uLm0VQduJNuza3VdjlmgNRhHAnPp6Pdw xBbFi9CqLgZdDQnAdqDFFtOdVL/V7IBrwPoRh68gBHnjX3CDD2vCaKbHyoDLTRUzoRJwqa vKdn2szWvyVLdksfg1Vyd0H+QFq91YU= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788798552; b=YoA68G3tL1J+A7fWnA9DCcCN5aKSiE7gIEQBFaQakkVMdADnWxCn0INWTOtYm8Ai7DRM3l T+UpO+HU8AFFIhvNdJCqDPRJFfSnygSxE+zMywhHB8KVNb4TxcT5eAjWsi2NGcDXSiGPnz vy0K/6k6UFkSvbEPP6COU45R+95vp4s= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=AA9jvqee; spf=pass (imf11.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 88FAF40541; Mon, 7 Sep 2026 16:29:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F52A1F00A3D; Mon, 7 Sep 2026 16:29:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788798551; bh=6Mi0KexjACT8EM1oYAJ+w+kZqAp8kzJ2mApTUd50940=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=AA9jvqeelrtgtADkk5mv9JMok2q4G/kVWhwLejDCvh7k6Bjosp16ast2eQbe8z3wZ 32Jq8QsukZsY6MQEnZXPOrmXS1S6Gz4mRLAd0yCXI322sqt7HacOuSQEuoQ9Cby0q4 Dmt6Z3Mr4zOK4ejpTbMgDIjkWmh9oM7y22gbIwFDLlAfoz3qjh46jLWvdQFuLC3sWG pI68lEya2SWOP9mM3qUldcXe9u+fiVXEre9AsJ0BDUIni2CL+AUGL18eQkIlyqkmAy GB49tJWtBs46+5TjG9ft7p1HGBBc0FzrEnhdIGPOMYzsSuOPma6Dy9P8sz0/ko/HuM Jn0ywdYBjHvUg== Date: Mon, 7 Sep 2026 17:29:04 +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 2/6] mm: implement file_is_dev_zero() to uniquely identify /dev/zero Message-ID: References: <20260902-map-private-dev-zero-v1-0-a578c730cec7@kernel.org> <20260902-map-private-dev-zero-v1-2-a578c730cec7@kernel.org> <292b27a7-94d1-4a2e-8346-a53e80fd2ed0@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <292b27a7-94d1-4a2e-8346-a53e80fd2ed0@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 68AF540011 X-Stat-Signature: qgjmducjg7yda8h44s587e3xst5motij X-HE-Tag: 1788798552-877011 X-HE-Meta: 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 VVnB6ani DWUlSM+CDl1OAfx053lPCQczz64e8aw1svjtWCfw3POugXxnEEuwD19kWZSW6BLBOSih2v4wRgh4WFR7/BagHvPaZniXlP4uExQ9gTqnJUSQncm90k+r4hELf+qHFCrRY6H9NgMzlXkRzoo+5aBnYWaRQiTLVpMu1srUxqTa1kIqxMfA+v27jjpHDoV/MrKyL5wRSAnDHUsjC7/nTP2fAbfIRmFHNmVtH/SrXNivc44D3fVxpRT5HlJTZ4AqsVFlAQ7X4G1T0XxaXFumjeeb8pJ3PsK/MxvWZTpEPSZLsTxROQol7u3KWlB5Uk7VetR1JPTCs 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 06:21:27PM +0200, David Hildenbrand (Arm) wrote: > On 9/2/26 20:00, Lorenzo Stoakes (ARM) wrote: > > To lay the foundation for a future change that converts > > MAP_PRIVATE-/dev/zero mappings to be truly anonymous, add the ability to > > uniquely identify these mappings. > > > > With the memory character device now part of mm/ this is trivially > > achievable through a file_is_dev_zero() predicate that simply tests that > > the file operation hooks are zero_fops. > > > > Also update userland VMA tests to expose file_is_dev_zero() and provide > > a stub zero_fops for testing. > > > > Signed-off-by: Lorenzo Stoakes (ARM) > > --- > > yes! > > Acked-by: David Hildenbrand (Arm) I thought you might like these ;) Thanks for pushing back last cycle, this is MUCH better. Struck me that actually that it's trivial + requires no fugliness the second we have it mm/. > > -- > Cheers, > > David -- Cheers, Lorenzo