From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="QoBl/5Qa" Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA684B8 for ; Mon, 27 Nov 2023 09:19:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=izdgl9OMTrve/VgGaU+Po2+ZToRQOkGAUt7Q3g9emHo=; b=QoBl/5QaMQ4O9f6rWlWCe0H7Xi aQHJKlqr43Tq/59Bxj5+KP6T7zHQ4s+dwhkggnLx0LOE/wtnMGowvkpjk8XVbtvXlGAMPfK1u1DlF 79ADzYf+rWMEDIHEvgjq1CH4YGr99QvohuVvd0sb/druzoqYxDAE6yB98RSUAx1aQZC63O9uHIgpK bd8P3rA4jZvUkPvN7H3mzPQnAtKluNvhyiqxW3MZo2u0EPqx9gElTAtCKcQsLdjCoKZVyM3efuoQK D5gew1UGEc0YYlzQhuwtEz3W9FaX9+y56eycuRG0Ifv5o9nxvzJ+Gf2IJ4Mj+qBVUatynylU9BAsC +xFORQtg==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1r7fGh-0037KU-3D; Mon, 27 Nov 2023 17:19:36 +0000 Date: Mon, 27 Nov 2023 09:19:35 -0800 From: "hch@infradead.org" To: Trond Myklebust Cc: "hch@infradead.org" , "tao.lyu@epfl.ch" , "linux-nfs@vger.kernel.org" Subject: Re: Question about O_APPEND | O_DIRECT Message-ID: References: <2d948b43fa625952e50589e4bedf9551df7ee112.camel@hammerspace.com> <7d2d17e4d3904d29b75fadcfd916b2a3@epfl.ch> <20107e878f185628a8d498ebb046e55618abfd4f.camel@hammerspace.com> Precedence: bulk X-Mailing-List: linux-nfs@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: <20107e878f185628a8d498ebb046e55618abfd4f.camel@hammerspace.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Nov 27, 2023 at 05:08:22PM +0000, Trond Myklebust wrote: > Note that APPEND would only really work with O_DIRECT, since it is > anathema to cached I/O to not be able to control the placement of the > data. Yes. > In addition, the model will always break down if someone decides they > want to write a log entry of size > wsize. Once you have to split up > the data, you (obviously) lose the atomicity you need in order to write > a contiguous record. Yes. Note that there is work going on to define atomic I/O limits on the various Linux lists currently. Although in the block layer we also have a separate limit for the maximum append size already.