[patch 059/166] mm/sparse.c: introduce a new function clear_subsection_map()

Andrew Morton
2020-04-07T03:07:06Z

From: Baoquan He <bhe@redhat.com>
Subject: mm/sparse.c: introduce a new function clear_subsection_map()

Factor out the code which clear subsection map of one memory region from
section_deactivate() into clear_subsection_map().

And also add helper function is_subsection_map_empty() to check if the
current subsection map is empty or not.

Link: http://lkml.kernel.org/r/20200312124414.439-3-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/sparse.c | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)

--- a/mm/sparse.c~mm-sparsec-introduce-a-new-function-clear_subsection_map
+++ a/mm/sparse.c
@@ -705,15 +705,11 @@ static void free_map_bootmem(struct page
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

-static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
- struct vmem_altmap *altmap)
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
{
DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
DECLARE_BITMAP(tmp, SUBSECTIONS_PER_SECTION) = { 0 };
struct mem_section *ms = __pfn_to_section(pfn);
- bool section_is_early = early_section(ms);
- struct page *memmap = NULL;
- bool empty;
unsigned long *subsection_map = ms->usage
? &ms->usage->subsection_map[0] : NULL;

@@ -724,8 +720,28 @@ static void section_deactivate(unsigned
if (WARN(!subsection_map || !bitmap_equal(tmp, map, SUBSECTIONS_PER_SECTION),
"section already deactivated (%#lx + %ld)\n",
pfn, nr_pages))
- return;
+ return -EINVAL;
+
+ bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
+ return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+ return bitmap_empty(&ms->usage->subsection_map[0],
+ SUBSECTIONS_PER_SECTION);
+}

+static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
+ struct vmem_altmap *altmap)
+{
+ struct mem_section *ms = __pfn_to_section(pfn);
+ bool section_is_early = early_section(ms);
+ struct page *memmap = NULL;
+ bool empty;
+
+ if (clear_subsection_map(pfn, nr_pages))
+ return;
/*
* There are 3 cases to handle across two configurations
* (SPARSEMEM_VMEMMAP={y,n}):
@@ -743,8 +759,7 @@ static void section_deactivate(unsigned
*
* For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified
*/
- bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION);
- empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION);
+ empty = is_subsection_map_empty(ms);
if (empty) {
unsigned long section_nr = pfn_to_section_nr(pfn);

_