On Thu, 2016-05-05 at 08:22 -0700, Christoph Hellwig wrote: > On Thu, May 05, 2016 at 08:15:32AM -0700, Dan Williams wrote: > > > > > > > > Agreed - makig O_DIRECT less direct than not having it is plain > > > stupid, > > > and I somehow missed this initially. > > Of course I disagree because like Dave argues in the msync case we > > should do the correct thing first and make it fast later, but also > > like Dave this arguing in circles is getting tiresome. > We should do the right thing first, and make it fast later. But this > proposal is not getting it right - it still does not handle errors > for the fast path, but magically makes it work for direct I/O by > in general using a less optional path for O_DIRECT. It's getting the > worst of all choices. > > As far as I can tell the only sensible option is to: > > - always try dax-like I/O first > - have a custom get_user_pages + rw_bytes fallback handles bad blocks > when hitting EIO 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? > > And then we need to sort out the concurrent write synchronization. > Again there I think we absolutely have to obey Posix for the !O_DIRECT > case and can avoid it for O_DIRECT, similar to the existing non-DAX > semantics. If we want any special additional semantics we _will_ need > a special O_DAX flag. > _______________________________________________ > Linux-nvdimm mailing list > Linux-nvdimm@xxxxxxxxxxxx > https://lists.01.org/mailman/listinfo/linux-nvdimm��.n��������+%����;��w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
