[PATCH v4 0/6] mm / virtio-mem: support ZONE_MOVABLE

From: David Hildenbrand
Date: Tue Aug 04 2020 - 15:42:03 EST

@Andrew can we give this a churn and consider it for v5.9 in case there
are no more comments?

Patch #1-#4,#6 have RBss or ACKs, patch #5 is virtio-mem stuff maintained
by me (and MST is aware).


When introducing virtio-mem, the semantics of ZONE_MOVABLE were rather
unclear, which is why we special-cased ZONE_MOVABLE such that partially
plugged blocks would never end up in ZONE_MOVABLE.

Now that the semantics are much clearer (and are documented in patch #6),
let's support partially plugged memory blocks in ZONE_MOVABLE, allowing
partially plugged memory blocks to be online to ZONE_MOVABLE and also
unplugging from such memory blocks. This avoids surprises when onlining
of memory blocks suddenly fails, just because they are not completely
populated by virtio-mem (yet).

This is especially helpful for testing, but also paves the way for
virtio-mem optimizations, allowing more memory to get reliably unplugged.

Cleanup has_unmovable_pages() and set_migratetype_isolate(), providing
better documentation of how ZONE_MOVABLE interacts with different kind of
unmovable pages (memory offlining vs. alloc_contig_range()).

v3 -> v4:
- "mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()"
-- Fix typo in description
- "virtio-mem: don't special-case ZONE_MOVABLE"
-- Add more details why we initialli special-cased ZONE_MOVABLE (via MST)
- "mm: document semantics of ZONE_MOVABLE"
-- Rephrase some parts of documentation (via Mike)

v2 -> v3:
- "mm: document semantics of ZONE_MOVABLE"
-- Fix a typo

v1 -> v2:
- "mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate()"
-- Move to position 1, add Fixes: tag
-- Drop unused "out:" label
- "mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()"
-- Keep curly braces on "else" case
- Replace "[PATCH v1 5/6] mm/page_alloc: restrict ZONE_MOVABLE optimization
in has_unmovable_pages() to memory offlining"
by "mm: document semantics of ZONE_MOVABLE"
-- Brain dump of what I know about ZONE_MOVABLE

David Hildenbrand (6):
mm/page_isolation: don't dump_page(NULL) in set_migratetype_isolate()
mm/page_alloc: tweak comments in has_unmovable_pages()
mm/page_isolation: drop WARN_ON_ONCE() in set_migratetype_isolate()
mm/page_isolation: cleanup set_migratetype_isolate()
virtio-mem: don't special-case ZONE_MOVABLE
mm: document semantics of ZONE_MOVABLE

drivers/virtio/virtio_mem.c | 47 +++++++------------------------------
include/linux/mmzone.h | 35 +++++++++++++++++++++++++++
mm/page_alloc.c | 22 +++++------------
mm/page_isolation.c | 39 ++++++++++++++----------------
4 files changed, 66 insertions(+), 77 deletions(-)