[PATCH v2 0/7] mm/hotplug: Only use subsection map in VMEMMAP case

From: Baoquan He
Date: Wed Feb 19 2020 - 23:33:41 EST

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. 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.

Move the hot remove fixing patch to the front so that people can
back port it to easier. Suggested by David.

Split the old patch which invalidate the sub-section map in
!VMEMMAP case into two patches, patch 4/7, and patch 6/7. This
makes patch reviewing easier. David by David.

Take Wei Yang's fixing patch out to post alone, since it has been
reviewed and acked by people. Suggested by Andrew.

Fix a code comment mistake in the current patch 2/7. Found out by
Wei Yang during reviewing.

Baoquan He (7):
mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case
mm/sparse.c: introduce new function fill_subsection_map()
mm/sparse.c: introduce a new function clear_subsection_map()
mm/sparse.c: only use subsection map in VMEMMAP case
mm/sparse.c: add code comment about sub-section hotplug
mm/sparse.c: move subsection_map related codes together
mm/sparse.c: Use __get_free_pages() instead in

include/linux/mmzone.h | 2 +
mm/sparse.c | 178 +++++++++++++++++++++++++++++------------
2 files changed, 127 insertions(+), 53 deletions(-)