On Thu, 2018-06-28 at 13:48 -0400, Mike Snitzer wrote: > On Thu, Jun 28 2018 at 1:42pm -0400, > Kani, Toshi <[email protected]> wrote: > > > On Tue, 2018-06-26 at 16:04 -0600, Ross Zwisler wrote: > > > On Tue, Jun 26, 2018 at 02:51:52PM -0700, Dan Williams wrote: > > > > On Tue, Jun 26, 2018 at 2:31 PM, Kani, Toshi <[email protected]> wrote: > > > > > On Tue, 2018-06-26 at 14:28 -0700, Dan Williams wrote: > > > > > > On Tue, Jun 26, 2018 at 2:23 PM, Kani, Toshi <[email protected]> > > > > > > wrote: > > > > > > > On Tue, 2018-06-26 at 14:02 -0700, Dan Williams wrote: > > > > > > > > On Tue, Jun 26, 2018 at 1:54 PM, Kani, Toshi > > > > > > > > <[email protected]> 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. > > > > > > > > > > Then, Fixes tag should be set to 569d0365f571 to keep the behavior > > > > > consistent. > > > > > > > > Sure, and the failure mode is...? I'm thinking the commit log should > > > > say: > > > > > > > > "Starting with commit 569d0365f571 "dax: require 'struct page' by > > > > default for filesystem dax", dax is no longer supported for page-less > > > > configurations. However, device-mapper sees the QUEUE_FLAG_DAX still > > > > being set and falsely assumes that DAX is enabled, this leads to > > > > <insert user visible failure mode details here>" > > > > > > Dan is correct that there is no user visible change for this. It is the > > > right > > > thing to do for consistency and sanity, but it doesn't actually have user > > > visible behavior that needs to be backported to stable. > > > > > > Toshi is correct that this change is only for raw mode namespaces, not btt > > > namespaces. > > > > > > I'll adjust the changelog and remove the stable flag for v5, and I'll add > > > a > > > Fixes: tag for patch 2. > > > > Hi Ross, > > > > Your patches look good. But I am still not clear about the Fixes & > > stable handling. Talking about user visible behavior, I do not think we > > had any issue until dax support was dropped from raw mode. Until then, > > the pmem driver supported dax for all modes, and the check for > > direct_access worked. > > I've staged the changes to send to Linus shortly. > > The first patch has: > > Fixes: 569d0365f571 ("dax: require 'struct page' by default for filesystem > dax") > Cc: [email protected] > > As that is the right thing to do given the other 2 patches are marked > for stable. We don't want to have a stable kernel with the last 2 > patches but not the first.
Agreed. Technically, all 3 patches may have "Fixes: 569d0365f571 dax..", but I think having "Fixes 545ed20e6df6 dm.." for patch 2 & 3 provide a protection in case 569d0365f571 gets backported in future. For the series: Reviewed-by: Toshi Kani <[email protected]> Thanks, -Toshi _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
