On Sun, Jun 21, 2015 at 08:11:25AM -0700, Dan Williams wrote: > The labels only allow allocation of persistent media between pmem and > blk. For a given dimm you may access in either mode and the label > records the decision. We can have a btt on either the pmem or > blk-mode disk type, or partition thereof. Sounds like the spec should allow a btt type as well insteaad of requiring the OS to work around it, as that seems to be one of the few useful things to do with a run-time label. Either way, partitions are trivial things and we could add them to the nvdimm layer. > Yes, it's this hybrid thing that mostly fits into the existing block > device model save for two new block_device_operations > ->direct_access() and ->rw_bytes(). We then use property of a > block_device that allows it to be claimed for exclusive ownership by a > filesystem or another block_device to layer storage semantics on top > be it files+directories, raid, caching, or atomic sectors. NVDIMM > devices don't present the same complexity as MTD devices. The only > complexity they present is byte-address-ability, not erase-block-size, > wear-leveling, etc... I didn't say they show the same complexities, but the same layering. > Good to hear that we don't need BTT for XFS v5, can we make the > guarantee for all filesystems that may want to support DAX? I still > think stacking is a natural fit for this problem. I can't make any guarantees, especially not without verification. But if correctly implemented any filesystems that does out of place metadata writes (and that includes a traditional log) and uses checksum to ensure the integrity of these updates it should be fine. You'd still have the issue of sector atomicy of file I/O though. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
