From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Moyer Subject: Re: [PATCH v5 17/21] libnvdimm: infrastructure for btt devices Date: Wed, 17 Jun 2015 12:47:23 -0400 Message-ID: References: <20150602001134.4506.45867.stgit@dwillia2-desk3.amr.corp.intel.com> <20150602001541.4506.90125.stgit@dwillia2-desk3.amr.corp.intel.com> <20150609064200.GE9804@lst.de> <20150610184616.GL2729@linux.intel.com> <20150611072812.GB1905@lst.de> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <20150611072812.GB1905-jcswGhMUV9g@public.gmane.org> (Christoph Hellwig's message of "Thu, 11 Jun 2015 09:28:12 +0200") Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig , Dan Williams Cc: Matthew Wilcox , axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, sfr-3FnU+UHB4dNDw9hX6IcOSA@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, neilb-l3A5Bk7waGM@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org Christoph Hellwig writes: > On Wed, Jun 10, 2015 at 02:46:16PM -0400, Matthew Wilcox wrote: >> Don't screw up rw_page. The point of rw_page is to read or write a page >> cache page. It can sleep, and it indicates success by using the page >> flags. Don't try and scqueeze rw_bytes into it. If you want rw_bytes >> to be a queue operation, that's one thing, but don't mess with rw_page. > > Oh, I forgot about the page manipulating nature. Yes, we'll need a different > operation in this case. I didn't see this addressed in the new patch set. I'm also concerned about the layering, but I haven't put enough time into it to really make a better suggestion. I really dislike the idea of yet another device stacking model in the kernel and I'm worried the code will go in, and the sysfs interface will end up as a "user abi" and we won't be able to change it in the future. Dan, have you made any progress on this, or do you have plans to? Cheers, Jeff