Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753893AbcC3Pmn (ORCPT ); Wed, 30 Mar 2016 11:42:43 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:56608 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752388AbcC3Pmm (ORCPT ); Wed, 30 Mar 2016 11:42:42 -0400 Date: Wed, 30 Mar 2016 08:42:41 -0700 From: Christoph Hellwig To: Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [PATCH 5/9] block: add ability to flag write back caching on a device Message-ID: <20160330154241.GA13131@infradead.org> References: <1459350477-16404-1-git-send-email-axboe@fb.com> <1459350477-16404-6-git-send-email-axboe@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1459350477-16404-6-git-send-email-axboe@fb.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 661 Lines: 12 On Wed, Mar 30, 2016 at 09:07:53AM -0600, Jens Axboe wrote: > Add an internal helper and flag for setting whether a queue has > write back caching, or write through (or none). Add a sysfs file > to show this as well, and make it changeable from user space. As per previous discussion: I don't really care about the way how we tell the block layer we have a writeback cache, but a NAK to having each driver call two interfaces to convey the same information. Please just look at q->flush_flag & REQ_FLUSH for now, and then improvem the interface if you don't like it (I don't particularly like it, but not to the point that I'm motivated enough to fix it :))