On Thu 20-02-20 12:33:09, Baoquan He wrote: > Memory sub-section hotplug was added to fix the issue that nvdimm could > be mapped at non-section aligned starting address. A subsection map is > added into struct mem_section_usage to implement it. However, sub-section > is only supported in VMEMMAP case. Why? Is there any fundamental reason or just a lack of implementation? VMEMMAP should be really only an implementation detail unless I am missing something subtle. > Hence there's no need to operate > subsection map in SPARSEMEM|!VMEMMAP case. In this patchset, change > codes to make sub-section map and the relevant operation only available > in VMEMMAP case. > > And since sub-section hotplug added, the hot add/remove functionality > have been broken in SPARSEMEM|!VMEMMAP case. Wei Yang and I, each of us > make one patch to fix one of the failures. In this patchset, the patch > 1/7 from me is used to fix the hot remove failure. Wei Yang's patch has > been merged by Andrew. Not sure I understand. Are there more issues to be fixed? > include/linux/mmzone.h | 2 + > mm/sparse.c | 178 +++++++++++++++++++++++++++++------------ > 2 files changed, 127 insertions(+), 53 deletions(-) Why do we need to add so much code to remove a functionality from one memory model? -- Michal Hocko SUSE Labs
