Merge branch 'topic/user-access-begin' into next

Merge the user_access_begin() series from Christophe. This is based on
a commit from Linus that went into v5.5-rc7.

1 files changed, 8 insertions, 1 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
index b20ab7cdac86..3822ecbd8a1f 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -777,7 +777,14 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 	if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) {
 		unsigned long section_nr = pfn_to_section_nr(pfn);
 
-		if (!section_is_early) {
+		/*
+		 * When removing an early section, the usage map is kept (as the
+		 * usage maps of other sections fall into the same page). It
+		 * will be re-used when re-adding the section - which is then no
+		 * longer an early section. If the usage map is PageReserved, it
+		 * was allocated during boot.
+		 */
+		if (!PageReserved(virt_to_page(ms->usage))) {
 			kfree(ms->usage);
 			ms->usage = NULL;
 		}