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.

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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>
Link: http://lkml.kernel.org/r/20200312124414.439-3-bhe@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/sparse.c b/mm/sparse.c
index 51965d56cd3932acd9be928eb25d5c1c7aae6cd6..01204c3b4649fc4201a687e5be8871e7e74d5f00 100644 (file)
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -705,15 +705,11 @@ static void free_map_bootmem(struct page *memmap)
 }
 #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 long pfn, unsigned long nr_pages,
        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 long pfn, unsigned long nr_pages,
         *
         * 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);