On Fri, Sep 17, 2021 at 5:57 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > On Thu, Sep 16, 2021 at 11:40:28AM -0700, Dan Williams wrote: > > > That was my gut feeling. If everyone feels 100% comfortable with > > > zeroingas the mechanism to clear poisoning I'll cave in. The most > > > important bit is that we do that through a dedicated DAX path instead > > > of abusing the block layer even more. > > > > ...or just rename dax_zero_page_range() to dax_reset_page_range()? > > Where reset == "zero + clear-poison"? > > I'd say that naming is more confusing than overloading zero. Ok, I see Darrick has a better suggestion for the shed color. > > > > I'm really worried about both patartitions on DAX and DM passing through > > > DAX because they deeply bind DAX to the block layer, which is just a bad > > > idea. I think we also need to sort that whole story out before removing > > > the EXPERIMENTAL tags. > > > > I do think it was a mistake to allow for DAX on partitions of a pmemX > > block-device. > > > > DAX-reflink support may be the opportunity to start deprecating that > > support. Only enable DAX-reflink for direct mounting on /dev/pmemX > > without partitions (later add dax-device direct mounting), > > I think we need to fully or almost fully sort this out. > > Here is my bold suggestions: > > 1) drop no drop the EXPERMINTAL on the current block layer overload > at all s/drop no drop/do not drop/? > 2) add direct mounting of the nvdimm namespaces ASAP. Because all > the filesystem currently also need the /dev/pmem0 device add a way > to open the block device by the dax_device instead of our current > way of doing the reverse Oh, interesting. I can get on board with that. There's currently no /dev entry for namespaces. It's either /dev/pmemX, or /dev/daxX.Y as a child of /sys/bus/nd/devices/namespaceX.Y. However, I see nothing glaringly wrong with having /dev/daxX.Y always published regardless of whether /dev/pmemX is also present. > 3) deprecate DAX support through block layer mounts with a say 2 year > deprecation period > 4) add DAX remapping devices as needed > > I'll volunteer to write the initial code for 2). And I think we should > not allow DAX+reflink on the block device shim at all. Yeah, I think this can fly.
