From: "hch@infradead.org" Subject: Re: [PATCH v4 5/7] fs: prioritize and separate direct_io from dax_io Date: Sun, 8 May 2016 02:01:15 -0700 Message-ID: <20160508090115.GE15458@infradead.org> References: <1461878218-3844-1-git-send-email-vishal.l.verma@intel.com> <1461878218-3844-6-git-send-email-vishal.l.verma@intel.com> <5727753F.6090104@plexistor.com> <20160505142433.GA4557@infradead.org> <20160505152230.GA3994@infradead.org> <1462484695.29294.7.camel@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Williams, Dan J" , "hch@infradead.org" , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "xfs@oss.sgi.com" , "linux-nvdimm@ml01.01.org" , "linux-mm@kvack.org" , "viro@zeniv.linux.org.uk" , "axboe@fb.com" , "akpm@linux-foundation.org" , "linux-fsdevel@vger.kernel.org" , "linux-ext4@vger.kernel.org" , "david@fromorbit.com" , "jack@suse.cz" , "matthew@wil.cx" To: "Verma, Vishal L" Return-path: Content-Disposition: inline In-Reply-To: <1462484695.29294.7.camel@intel.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu, May 05, 2016 at 09:45:07PM +0000, Verma, Vishal L wrote: > I'm not sure I completely understand how this will work? Can you explain > a bit? Would we have to export rw_bytes up to layers above the pmem > driver? Where does get_user_pages come in? A DAX filesystem can directly use the nvdimm layer the same way btt doe,s what's the problem? Re get_user_pages my idea was to simply use that to lock down the user pages so that we can call rw_bytes on it. How else would you do it? Do a kmalloc, copy_from_user and then another memcpy?