From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 288444B487D for ; Mon, 21 Sep 2026 21:19:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790025600; cv=none; b=AoIVs1lAwqb0AxSVKYPcdNJ0IMzxl7juzTqqkeAZJntdtl2vtl9khCo0Q4dzjQ2W8fPkteYvXhiIiLcCMVVvayxvc0J7HxQJN861xVEidmPa9Rmhb1Uf2iKvCARaQJASOu77eys/gP/yhcnlMavxfOegwH1JCyWDD7caqNN5bwI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790025600; c=relaxed/simple; bh=xVGQt5MuV3cUiZxUeOR9+A+ce+0m4H6k5p7si+ipYfA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=TRH6hStzeQRzmiTa/cHghY/TDLM0Ws1g1JSqeohlEXM/VTILU/KCIJ0JUhDw0SsiSpDwDIiVGgZXz8/huYzEdQyPPUW3RQ5se5hYMoQcCEC5ne6O1vPRv+dJuvjMowJT+cvqFe/OqdweT8dEM2fnBxna93MgRNEQ4fl2eSAwGVY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=BGqiyqf6; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="BGqiyqf6" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=RsKa6xtGpVrKjIKV82En0dvWYXbJt5+yoZDKyIsIQkI=; b=BGqiyqf6xDxb3nrgigpwzr6zw0 TsULh7HP4rRDfVuvJZdXyMBCWNYoLFwJiSlbb8HEl/J0WO3r6BYhGCrzTBGM1dmzVPFYwffeddwew LOapQ2TrqU5dhgRK/8UbAPF0yTfcj7GtckO7RxKUx/lsw6dI3Hd45zbaJ0xTLFy4ryv2ZQMe0OfQi 83tGp3Q96YEkmcZ05AySXfFa8mIn3HFEbWVXWyqaqi2rVRKGyPZMhT2Flx3KpsU2VMe3qA9MR2Bof J5ImoJnfCyBOL7PuiDVZnLRRoPYg7g5OeoL1RdcRrfoZY/dZtqK7ZUYjfnrHibyUTrA24W4U76tiK r8cHKrhQ==; Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8lQM-00000005Xnu-4A8c; Mon, 21 Sep 2026 21:19:43 +0000 Date: Mon, 21 Sep 2026 22:19:42 +0100 From: Matthew Wilcox To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Jane Chu , linux-mm@kvack.org, Muchun Song , Oscar Salvador , Miaohe Lin , Naoya Horiguchi , Jan Kara , linux-fsdevel@vger.kernel.org, Christian Brauner , Jiaqi Yan Subject: Re: [PATCH v9 14/15] filemap: Add support for authoritative mappings Message-ID: References: <20260805210557.1118966-1-willy@infradead.org> <20260805210557.1118966-15-willy@infradead.org> <0e0a0908-8e5d-4cee-9fbb-ce730bb662e1@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@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: <0e0a0908-8e5d-4cee-9fbb-ce730bb662e1@kernel.org> On Fri, Sep 18, 2026 at 03:51:59PM +0200, David Hildenbrand (Arm) wrote: > On 8/5/26 23:05, Matthew Wilcox (Oracle) wrote: > > +++ b/include/linux/pagemap.h > > @@ -210,6 +210,7 @@ enum mapping_flags { > > AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM = 9, > > AS_KERNEL_FILE = 10, /* mapping for a fake kernel file that shouldn't > > account usage to user cgroups */ > > + AS_AUTHORITATIVE = 11, /* If we miss in the page cache, it's a hole */ > > Just curious if "in-memory file system" would be a different way of looking at > it. There, a hole in the page cache always expresses a hole in the file. > > AS_IN_MEMORY_FILE > > Just an idea, because that's why I always had in mind regarding that (all state > in memory). I suspect that's always going to be the case, but I don't want to be quite so prescriptive. I'd rather describe the property than the user.