On Sun, 2016-05-08 at 02:01 -0700, hch@xxxxxxxxxxxxx wrote: > 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? The BTT does rw_bytes through an internal-to-libnvdimm mechanism, but rw_bytes isn't exported to the filesystem, currently.. To do this we'd have to either add an rw_bytes to block device operations...or something. Another thing is rw_bytes currently doesn't do error clearing either. We store badblocks at sector granularity, and like Dan said earlier, that hides the clear_error alignment requirements and upper layers don't have to be aware of it. To make rw_bytes clear sub-sector errors, we'd have to change the granularity of bad-blocks, and make upper layers aware of the clearing alignment requirements. Using a block-write semantic for clearing hides all this away. > > 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?��.n������g��� �a��� �&ޖ)���)��h���&������梷���� �Ǟ�m������)������^�����������v���O��zf������