From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9289F42E00C; Tue, 20 Jan 2026 13:40:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768916456; cv=none; b=KvqIsG+yvwQByiaTMVmsbEwz5B0qJ/t1VkeWVyfPDYBZo0AAuDLy5jld0ad3j5VJe/drMItbTFiQ+WxPCH31jJ1wzBFEh6GjqByUN0Sjy9BkLtBJfR+LL30cq9FhnJTqApvdpWidtNLqxePSJp9kY2eu2ivKPsrGXuVAIMjF6ME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768916456; c=relaxed/simple; bh=Ww2vxfC7ZENAqiEwBP0gWFkYN0X8gY0coLCd/8tmAYk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=jBERAzdR+5bH926L0+mVG7VQruMqcM9GxMNSR9HimMxFC4CXb30qYvQxOGf4KItQkZTBQaSab4y9Li2wTTWT4Bp5jM5QxtfwtrcRF3IN2QYmwHiFpZahXbxDFui/9nTik2h6P026/bjE5QOhM5b2J+3m/8QSqjGu/lbfUK1Y6rA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IgaYm6RF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IgaYm6RF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E950C16AAE; Tue, 20 Jan 2026 13:40:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768916456; bh=Ww2vxfC7ZENAqiEwBP0gWFkYN0X8gY0coLCd/8tmAYk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IgaYm6RFfv8Nv1drQJ6ITXMxHwPX49R+TMVL22Q6Xyi7XsPox85wvP3cDsYLvkgHv 01z5GLkgSrOEMm0sxBTDsWkRPGhnKRkEj74rWtV3eu74uyZ7IC4ZrvLZbIU5zIjtGQ DWteKGqT4O52aDMm0GE0kgrPR7uVoFX/5G3OF44t3hgqeqNgNc05XNWC8yKXcFjD/Z FOtoQ3WRbFJOW0ORiZSc3uQGRWPtwGFbY+aji3MLhOqG1/XSIeJSVL7yEY9IfVp/i7 mNPx6PvfC3yqJa+7OAl8ERFZnWHHNE3Fr6HTsrcQD03LOUCOtWSLgnOyy3M+E5X+fw 1VDIm1TAgbA1A== Date: Tue, 20 Jan 2026 14:40:50 +0100 From: Christian Brauner To: Christoph Hellwig Cc: Gao Xiang , Hongbo Li , chao@kernel.org, djwong@kernel.org, amir73il@gmail.com, linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, Linus Torvalds , oliver.yang@linux.alibaba.com Subject: Re: [PATCH v15 5/9] erofs: introduce the page cache share feature Message-ID: <20260120-neuland-rastplatz-31cc7d61a196@brauner> References: <20260116154623.GC21174@lst.de> <20260119072932.GB2562@lst.de> <8e30bc4b-c97f-4ab2-a7ce-27f399ae7462@linux.alibaba.com> <20260119083251.GA5257@lst.de> <20260119092220.GA9140@lst.de> <73f2c243-e029-4f95-aa8e-285c7affacac@linux.alibaba.com> <50db56b8-4cf9-4d62-b242-c982a260a330@linux.alibaba.com> <20260120065242.GA3436@lst.de> 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=utf-8 Content-Disposition: inline In-Reply-To: <20260120065242.GA3436@lst.de> On Tue, Jan 20, 2026 at 07:52:42AM +0100, Christoph Hellwig wrote: > On Tue, Jan 20, 2026 at 11:07:48AM +0800, Gao Xiang wrote: > > > > Hi Christoph, > > > > Sorry I didn't phrase things clearly earlier, but I'd still > > like to explain the whole idea, as this feature is clearly > > useful for containerization. I hope we can reach agreement > > on the page cache sharing feature: Christian agreed on this > > feature (and I hope still): > > > > https://lore.kernel.org/linux-fsdevel/20260112-begreifbar-hasten-da396ac2759b@brauner > > He has to ultimatively decide. I do have an uneasy feeling about this. > It's not super informed as I can keep up, and I'm not the one in charge, > but I hope it is helpful to share my perspective. It always is helpful, Christoph! I appreciate your input. I'm fine with this feature. But as I've said in person: I still oppose making any block-based filesystem mountable in unprivileged containers without any sort of trust mechanism. I am however open in the future for block devices protected by dm-verity with the root hash signed by a sufficiently trusted key to be mountable in unprivileged containers.