mm/slab.c: fix an infinite loop in leaks_show()

[mirror_ubuntu-bionic-kernel.git] / mm / page_vma_mapped.c

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index ae3c2a35d61b7cae4fbecea4421bbd0450b81c53..11df03e71288c3fe0b78e164eca835ac4332e5ca 100644 (file)
--- 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;
                }
        }