On Fri, Jan 21, 2022 at 09:26:52AM +0800, Shiyang Ruan wrote: > > > 在 2022/1/20 16:46, Christoph Hellwig 写道: > > On Wed, Jan 05, 2022 at 04:12:04PM -0800, Dan Williams wrote: > > > We ended up with explicit callbacks after hch balked at a notifier > > > call-chain, but I think we're back to that now. The partition mistake > > > might be unfixable, but at least bdev_dax_pgoff() is dead. Notifier > > > call chains have their own locking so, Ruan, this still does not need > > > to touch dax_read_lock(). > > > > I think we have a few options here: > > > > (1) don't allow error notifications on partitions. And error return from > > the holder registration with proper error handling in the file > > system would give us that Hm, so that means XFS can only support dax+pmem when there aren't partitions in use? Ew. > > (2) extent the holder mechanism to cover a rangeo I don't think I was around for the part where "hch balked at a notifier call chain" -- what were the objections there, specifically? I would hope that pmem problems would be infrequent enough that the locking contention (or rcu expiration) wouldn't be an issue...? > > (3) bite the bullet and create a new stacked dax_device for each > > partition > > > > I think (1) is the best option for now. If people really do need > > partitions we'll have to go for (3) > > Yes, I agree. I'm doing it the first way right now. > > I think that since we can use namespace to divide a big NVDIMM into multiple > pmems, partition on a pmem seems not so meaningful. I'll try to find out what will happen if pmem suddenly stops supporting partitions... --D > > -- > Thanks, > Ruan. > >
