Merge branch 'master' into next

Merge master back into next, this allows us to resolve some conflicts in
arch/powerpc/Kconfig, and also re-sort the symbols under config PPC so
that they are in alphabetical order again.

1 files changed, 17 insertions, 5 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3b2205741048..0d53eba1c383 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -55,7 +55,7 @@ enum migratetype {
 	 * pageblocks to MIGRATE_CMA which can be done by
 	 * __free_pageblock_cma() function.  What is important though
 	 * is that a range of pageblocks must be aligned to
-	 * MAX_ORDER_NR_PAGES should biggest page be bigger then
+	 * MAX_ORDER_NR_PAGES should biggest page be bigger than
 	 * a single pageblock.
 	 */
 	MIGRATE_CMA,
@@ -407,8 +407,13 @@ enum zone_type {
 	 * to increase the number of THP/huge pages. Notable special cases are:
 	 *
 	 * 1. Pinned pages: (long-term) pinning of movable pages might
-	 *    essentially turn such pages unmovable. Memory offlining might
-	 *    retry a long time.
+	 *    essentially turn such pages unmovable. Therefore, we do not allow
+	 *    pinning long-term pages in ZONE_MOVABLE. When pages are pinned and
+	 *    faulted, they come from the right zone right away. However, it is
+	 *    still possible that address space already has pages in
+	 *    ZONE_MOVABLE at the time when pages are pinned (i.e. user has
+	 *    touches that memory before pinning). In such case we migrate them
+	 *    to a different zone. When migration fails - pinning fails.
 	 * 2. memblock allocations: kernelcore/movablecore setups might create
 	 *    situations where ZONE_MOVABLE contains unmovable allocations
 	 *    after boot. Memory offlining and allocations fail early.
@@ -427,6 +432,15 @@ enum zone_type {
 	 *    techniques might use alloc_contig_range() to hide previously
 	 *    exposed pages from the buddy again (e.g., to implement some sort
 	 *    of memory unplug in virtio-mem).
+	 * 6. ZERO_PAGE(0), kernelcore/movablecore setups might create
+	 *    situations where ZERO_PAGE(0) which is allocated differently
+	 *    on different platforms may end up in a movable zone. ZERO_PAGE(0)
+	 *    cannot be migrated.
+	 * 7. Memory-hotplug: when using memmap_on_memory and onlining the
+	 *    memory to the MOVABLE zone, the vmemmap pages are also placed in
+	 *    such zone. Such pages cannot be really moved around as they are
+	 *    self-stored in the range, but they are treated as movable when
+	 *    the range they describe is about to be offlined.
 	 *
 	 * In general, no unmovable allocations that degrade memory offlining
 	 * should end up in ZONE_MOVABLE. Allocators (like alloc_contig_range())
@@ -1383,10 +1397,8 @@ static inline int online_section_nr(unsigned long nr)
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
-#ifdef CONFIG_MEMORY_HOTREMOVE
 void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn);
 #endif
-#endif
 
 static inline struct mem_section *__pfn_to_section(unsigned long pfn)
 {