From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AE3E1477299; Mon, 7 Sep 2026 16:29:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788798554; cv=none; b=gi9kpV75IFRAHUFRuAFwnrepuI9CDviA3XItRLKZAY/NlXi3ErP1D24fLzNASmEYAt1s1xuPnXsugI8T1n3XZruTw3S27yQ78MFm8wRhLuvQCdQ/PGVbXPpk/87IjT/NzngifpLFXnxt4IZzrkN1AtMrR1yM0IzqJ/a+FGI8AgE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788798554; c=relaxed/simple; bh=6Mi0KexjACT8EM1oYAJ+w+kZqAp8kzJ2mApTUd50940=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=doKGXMS+ezM7+Gzj3wOEYWLrsvyxgaGp2eCk2IcRHXPIbH7KA22osRgxc8kSesMxHEUEB/O9DEw51d73au2FGOIxpA6lo2YfVKZtWkzRVw7s0KxEwfvRwzAHOAfrYNhI3GkiFylClzcmXQwRR560f3LRxjoRYPwMA3pKYlNF990= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AA9jvqee; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AA9jvqee" 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <292b27a7-94d1-4a2e-8346-a53e80fd2ed0@kernel.org> 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