mm/page_isolation: fix potential missing call to unset_migratetype_isolate()

In start_isolate_page_range() undo path, pfn_to_online_page() just
checks the first pfn in a pageblock while __first_valid_page() will
traverse the pageblock until the first online pfn is found.  So we may
miss the call to unset_migratetype_isolate() in undo path and pages will
remain isolated unexpectedly.

Fix this by calling undo_isolate_page_range() and this will also help to
simplify the code further.  Note we shouldn't ever trigger it because
MAX_ORDER-1 aligned pfn ranges shouldn't contain memory holes now.

Link: https://lkml.kernel.org/r/20210914114348.15569-1-linmiaohe@huawei.com
Fixes: 3831faf2d5fd ("mm: __first_valid_page skip over offline pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index a95c2c6562d0f0ea9519c46b1e95a9d3d7408ab4..f93cc63d8fa1d6057aee2bc88b4bfb6a775ab66c 100644 (file)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -183,7 +183,6 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
                             unsigned migratetype, int flags)
 {
        unsigned long pfn;
-       unsigned long undo_pfn;
        struct page *page;
 
        BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
@@ -193,25 +192,12 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
             pfn < end_pfn;
             pfn += pageblock_nr_pages) {
                page = __first_valid_page(pfn, pageblock_nr_pages);
-               if (page) {
-                       if (set_migratetype_isolate(page, migratetype, flags)) {
-                               undo_pfn = pfn;
-                               goto undo;
-                       }
+               if (page && set_migratetype_isolate(page, migratetype, flags)) {
+                       undo_isolate_page_range(start_pfn, pfn, migratetype);
+                       return -EBUSY;
                }
        }
        return 0;
-undo:
-       for (pfn = start_pfn;
-            pfn < undo_pfn;
-            pfn += pageblock_nr_pages) {
-               struct page *page = pfn_to_online_page(pfn);
-               if (!page)
-                       continue;
-               unset_migratetype_isolate(page, migratetype);
-       }
-
-       return -EBUSY;
 }
 
 /*