mm: check nr_initialised with PAGES_PER_SECTION directly in defer_init()

When DEFERRED_STRUCT_PAGE_INIT is configured, only the first section of
each node's highest zone is initialized before defer stage.

static_init_pgcnt is used to store the number of pages like this:

    pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
                                              pgdat->node_spanned_pages);

because we don't want to overflow zone's range.

But this is not necessary, since defer_init() is called like this:

  memmap_init_zone()
    for pfn in [start_pfn, end_pfn)
      defer_init(pfn, end_pfn)

In case (pgdat->node_spanned_pages < PAGES_PER_SECTION), the loop would
stop before calling defer_init().

BTW, comparing PAGES_PER_SECTION with node_spanned_pages is not correct,
since nr_initialised is zone based instead of node based.  Even
node_spanned_pages is bigger than PAGES_PER_SECTION, its highest zone
would have pages less than PAGES_PER_SECTION.

Link: http://lkml.kernel.org/r/20181122094807.6985-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e0c3bc2..a6e3007 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -692,8 +692,6 @@ typedef struct pglist_data {
         * is the first PFN that needs to be initialised.
         */
        unsigned long first_deferred_pfn;
-       /* Number of non-deferred pages */
-       unsigned long static_init_pgcnt;
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a48db99..a1e5f0d 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -326,8 +326,13 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
        /* Always populate low zones for address-constrained allocations */
        if (end_pfn < pgdat_end_pfn(NODE_DATA(nid)))
                return false;
+
+       /*
+        * We start only with one section of pages, more pages are added as
+        * needed until the rest of deferred pages are initialized.
+        */
        nr_initialised++;
-       if ((nr_initialised > NODE_DATA(nid)->static_init_pgcnt) &&
+       if ((nr_initialised > PAGES_PER_SECTION) &&
            (pfn & (PAGES_PER_SECTION - 1)) == 0) {
                NODE_DATA(nid)->first_deferred_pfn = pfn;
                return true;
@@ -6585,12 +6590,6 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat) { }
 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
 static inline void pgdat_set_deferred_range(pg_data_t *pgdat)
 {
-       /*
-        * We start only with one section of pages, more pages are added as
-        * needed until the rest of deferred pages are initialized.
-        */
-       pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
-                                               pgdat->node_spanned_pages);
        pgdat->first_deferred_pfn = ULONG_MAX;
 }
 #else