From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH 5/9] block: add ability to flag write back caching on a device To: Christoph Hellwig References: <1459350477-16404-1-git-send-email-axboe@fb.com> <1459350477-16404-6-git-send-email-axboe@fb.com> <20160330154241.GA13131@infradead.org> CC: , , From: Jens Axboe Message-ID: <56FBF4D8.9000203@fb.com> Date: Wed, 30 Mar 2016 09:46:32 -0600 MIME-Version: 1.0 In-Reply-To: <20160330154241.GA13131@infradead.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: On 03/30/2016 09:42 AM, Christoph Hellwig wrote: > 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 :)) That's fine, I don't mind making that change, just didn't do it for this version. I prefer if we change the cache flagging to be the primary way to signal it, it's more intuitive than REQ_FLUSH. It'll be in the next version. -- Jens Axboe