mm/memory_hotplug: simplify page offlining

We make sure that we cannot have any memory holes right at the beginning
of offline_pages().  We no longer need walk_system_ram_range() and can
call test_pages_isolated() and __offline_isolated_pages() directly.

offlined_pages always corresponds to nr_pages, so we can simplify that.

[akpm@linux-foundation.org: patch conflict resolution]

Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Charan Teja Reddy <charante@codeaurora.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20200819175957.28465-4-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 03a8825..c3977ce 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1384,28 +1384,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
        return ret;
 }
 
-/* Mark all sections offline and remove all free pages from the buddy. */
-static int
-offline_isolated_pages_cb(unsigned long start, unsigned long nr_pages,
-                       void *data)
-{
-       unsigned long *offlined_pages = (unsigned long *)data;
-
-       *offlined_pages += __offline_isolated_pages(start, start + nr_pages);
-       return 0;
-}
-
-/*
- * Check all pages in range, recorded as memory resource, are isolated.
- */
-static int
-check_pages_isolated_cb(unsigned long start_pfn, unsigned long nr_pages,
-                       void *data)
-{
-       return test_pages_isolated(start_pfn, start_pfn + nr_pages,
-                                  MEMORY_OFFLINE);
-}
-
 static int __init cmdline_parse_movable_node(char *p)
 {
        movable_node_enabled = true;
@@ -1492,7 +1470,7 @@ static int count_system_ram_pages_cb(unsigned long start_pfn,
 int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
 {
        const unsigned long end_pfn = start_pfn + nr_pages;
-       unsigned long pfn, system_ram_pages = 0, offlined_pages = 0;
+       unsigned long pfn, system_ram_pages = 0;
        int ret, node, nr_isolate_pageblock;
        unsigned long flags;
        struct zone *zone;
@@ -1590,9 +1568,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
                        reason = "failure to dissolve huge pages";
                        goto failed_removal_isolated;
                }
-               /* check again */
-               ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn,
-                                           NULL, check_pages_isolated_cb);
+
                /*
                 * per-cpu pages are drained in start_isolate_page_range, but if
                 * there are still pages that are not free, make sure that we
@@ -1605,15 +1581,15 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
                 * because has_unmovable_pages explicitly checks for
                 * PageBuddy on freed pages on other zones.
                 */
+               ret = test_pages_isolated(start_pfn, end_pfn, MEMORY_OFFLINE);
                if (ret)
                        drain_all_pages(zone);
        } while (ret);
 
-       /* Ok, all of our target is isolated.
-          We cannot do rollback at this point. */
-       walk_system_ram_range(start_pfn, end_pfn - start_pfn,
-                             &offlined_pages, offline_isolated_pages_cb);
-       pr_info("Offlined Pages %ld\n", offlined_pages);
+       /* Mark all sections offline and remove free pages from the buddy. */
+       __offline_isolated_pages(start_pfn, end_pfn);
+       pr_info("Offlined Pages %ld\n", nr_pages);
+
        /*
         * Onlining will reset pagetype flags and makes migrate type
         * MOVABLE, so just need to decrease the number of isolated
@@ -1624,11 +1600,11 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages)
        spin_unlock_irqrestore(&zone->lock, flags);
 
        /* removal success */
-       adjust_managed_page_count(pfn_to_page(start_pfn), -offlined_pages);
-       zone->present_pages -= offlined_pages;
+       adjust_managed_page_count(pfn_to_page(start_pfn), -nr_pages);
+       zone->present_pages -= nr_pages;
 
        pgdat_resize_lock(zone->zone_pgdat, &flags);
-       zone->zone_pgdat->node_present_pages -= offlined_pages;
+       zone->zone_pgdat->node_present_pages -= nr_pages;
        pgdat_resize_unlock(zone->zone_pgdat, &flags);
 
        init_per_zone_wmark_min();