On Mon, Jun 22, 2015 at 09:36:50AM -0700, Dan Williams wrote: > In that case "don't stack" is too coarse of a hammer. I see this as a > request to hide the subordinate ULD which is a new capability that DM > and MD might benefit from as well. We already have the case in MD > where it internally holds a reference to bdev that has been hot > removed, it seems not much of a stretch to have stacking drivers be > able to hide device nodes for bdevs that they are holding. I don't see why you're comparing with MD and DM here. MD and DM sit cleanly ontop of any block device. If btt was independent of libnvdimm and just used ->rw_bytes we could see it as this. But it's all a giant entangled mess, where btt for example is probed by libnvdimm. At the same time pmem.c isn't really a true block driver, it's really just a trivial shim between the block API and pmem-style memcpy. Especially with the proper pmem API btt would become cleaner just calling that directly. > Yes, if they want to use DAX they should do it consciously and audit > their application to be sure it is safe to abandon atomic sector > guarantees. With the current flexibility to do BTT on a partition > they can do this conversion piecemeal and, for example, keep metadata > on BTT and data on DAX. By that logic you'd want to attach BTT by default and allow opt-out at some level. This could be a libnvmdimm-level partitioning scheme, which would also allow storing the bit if BTT is used or not persistently. Or it could be on fine grained boundaries which might be more useful. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
