From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 E37A233CEA2; Mon, 19 Jan 2026 08:32:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768811578; cv=none; b=YDA+hUZmqZWoIEkRDi822UxgdRtgCNnppihlrRtae8806ZeYNitJSRzED8OQDbmzwyXIE7rKw2JWxPwe0HNGRadkDm1F1AqPkzSMlIWDrVBokJNoX1miBKzMlZ3vQrCnfzXkaq44hVD4ZiktOZ6VNsoQJp9II+l+tIzgfgireSI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768811578; c=relaxed/simple; bh=blKTkVXbfR4T3/PtCN0leNvZZa9/BJgRBGhK2T6VzFY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bMb+KpTk1z9vy10qkyiYqH+1rDQgiu6EOxIX5bFOybdlv2PS4NM9Cy5UFGCe2EIVx/vDidJotMf9gKTZKH6q6A1uVRfXexai8xLjbDCro3WKVA1h14ohsFk17+2whieOiv2S79RBJzcAqnEuwcDerTILSdVGkqtRkvkw/9/OU3I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id F41E4227A88; Mon, 19 Jan 2026 09:32:51 +0100 (CET) Date: Mon, 19 Jan 2026 09:32:51 +0100 From: Christoph Hellwig To: Gao Xiang Cc: Christoph Hellwig , Hongbo Li , chao@kernel.org, brauner@kernel.org, djwong@kernel.org, amir73il@gmail.com, linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v15 5/9] erofs: introduce the page cache share feature Message-ID: <20260119083251.GA5257@lst.de> References: <20260116095550.627082-1-lihongbo22@huawei.com> <20260116095550.627082-6-lihongbo22@huawei.com> <20260116154623.GC21174@lst.de> <20260119072932.GB2562@lst.de> <8e30bc4b-c97f-4ab2-a7ce-27f399ae7462@linux.alibaba.com> 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: <8e30bc4b-c97f-4ab2-a7ce-27f399ae7462@linux.alibaba.com> User-Agent: Mutt/1.5.17 (2007-11-01) On Mon, Jan 19, 2026 at 03:53:21PM +0800, Gao Xiang wrote: > I just tried to say EROFS doesn't limit what's > the real meaning of `fingerprint` (they can be serialized > integer numbers for example defined by a specific image > publisher, or a specific secure hash. Currently, > "mkfs.erofs" will generate sha256 for each files), but > left them to the image builders: To me this sounds pretty scary, as we have code in the kernel's trust domain that heavily depends on arbitrary userspace policy decisions. Similarly the sharing of blocks between different file system instances opens a lot of questions about trust boundaries and life time rules. I don't really have good answers, but writing up the lifetime and threat models would really help.