1 files changed, 23 insertions, 1 deletions
diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index ae3c2a35d61b..11df03e71288 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -21,7 +21,29 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw)
 			if (!is_swap_pte(*pvmw->pte))
 				return false;
 		} else {
-			if (!pte_present(*pvmw->pte))
+			/*
+			 * We get here when we are trying to unmap a private
+			 * device page from the process address space. Such
+			 * page is not CPU accessible and thus is mapped as
+			 * a special swap entry, nonetheless it still does
+			 * count as a valid regular mapping for the page (and
+			 * is accounted as such in page maps count).
+			 *
+			 * So handle this special case as if it was a normal
+			 * page mapping ie lock CPU page table and returns
+			 * true.
+			 *
+			 * For more details on device private memory see HMM
+			 * (include/linux/hmm.h or mm/hmm.c).
+			 */
+			if (is_swap_pte(*pvmw->pte)) {
+				swp_entry_t entry;
+
+				/* Handle un-addressable ZONE_DEVICE memory */
+				entry = pte_to_swp_entry(*pvmw->pte);
+				if (!is_device_private_entry(entry))
+					return false;
+			} else if (!pte_present(*pvmw->pte))
 				return false;
 		}
 	}