[PATCH v3 21/24] mm/kconfig: make BALLOON_COMPACTION depend on MIGRATION

[David Hildenbrand (Red Hat)]

Migration support for balloon memory depends on MIGRATION not
COMPACTION. Compaction is simply another user of page migration.

The last dependency on compaction.c was effectively removed with
commit 3d388584d599 ("mm: convert "movable" flag in page->mapping to a
page flag"). Ever since, everything for handling movable_ops page
migration resides in core migration code.

So let's change the dependency and adjust the description +
help text.

We'll rename BALLOON_COMPACTION separately next.

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes at oracle.com>
Acked-by: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: David Hildenbrand (Red Hat) <david at kernel.org>
---
 mm/Kconfig | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 24a3ff149a1b0..0d13c1b36e1c1 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -599,17 +599,14 @@ config MEMORY_BALLOON
 #
 # support for memory balloon compaction
 config BALLOON_COMPACTION
-	bool "Allow for balloon memory compaction/migration"
+	bool "Allow for balloon memory migration"
 	default y
-	depends on COMPACTION && MEMORY_BALLOON
-	help
-	  Memory fragmentation introduced by ballooning might reduce
-	  significantly the number of 2MB contiguous memory blocks that can be
-	  used within a guest, thus imposing performance penalties associated
-	  with the reduced number of transparent huge pages that could be used
-	  by the guest workload. Allowing the compaction & migration for memory
-	  pages enlisted as being part of memory balloon devices avoids the
-	  scenario aforementioned and helps improving memory defragmentation.
+	depends on MIGRATION && MEMORY_BALLOON
+	help
+	  Allow for migration of pages inflated in a memory balloon such that
+	  they can be allocated from memory areas only available for movable
+	  allocations (e.g., ZONE_MOVABLE, CMA) and such that they can be
+	  migrated for memory defragmentation purposes by memory compaction.
 
 #
 # support for memory compaction
-- 
2.52.0