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-rw-r--r--mm/rmap.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 09b08888120e..66cb69c1c5dd 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1252,6 +1252,17 @@ void page_add_file_rmap(struct page *page, bool compound)
}
if (!atomic_inc_and_test(compound_mapcount_ptr(page)))
goto out;
+
+ /*
+ * It is racy to ClearPageDoubleMap in page_remove_file_rmap();
+ * but page lock is held by all page_add_file_rmap() compound
+ * callers, and SetPageDoubleMap below warns if !PageLocked:
+ * so here is a place that DoubleMap can be safely cleared.
+ */
+ VM_WARN_ON_ONCE(!PageLocked(page));
+ if (nr == nr_pages && PageDoubleMap(page))
+ ClearPageDoubleMap(page);
+
if (PageSwapBacked(page))
__mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED,
nr_pages);