On Tue, Jun 26, 2018 at 2:23 PM, Kani, Toshi <toshi.kani@xxxxxxx> wrote: > On Tue, 2018-06-26 at 14:02 -0700, Dan Williams wrote: >> On Tue, Jun 26, 2018 at 1:54 PM, Kani, Toshi <toshi.kani@xxxxxxx> wrote: [..] >> > When this dm change was made, the pmem driver supported DAX for both raw >> > and memory modes (note: sector mode does not use the pmem driver). I >> > think the issue was introduced when we dropped DAX support from raw >> > mode. >> >> Still DAX with raw mode never really worked any way. It was also >> something that was broken from day one. So what happens to someone who >> happened to avoid all the problems with page-less DAX and enabled >> device-mapper on top? That failure mode detail needs to be added to >> this changelog if we want to propose this for -stable. > > My point is that the behavior should be consistent between pmem and > device-mapper. When -o dax succeeds on a pmem, then it should succeed > on a device-mapper on top of that pmem. > > Has the drop of dax support from raw mode made to -stable back to the > baseline accepted 545ed20e6df6? It will introduce inconsistency, > otherwise. That commit, 569d0365f571 "dax: require 'struct page' by default for filesystem dax", has not been tagged for -stable.
