3 files changed, 40 insertions, 37 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 5020b280a771..000a220e2a41 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -906,8 +906,8 @@ EXPORT_SYMBOL(page_cache_prev_hole);
  * Looks up the page cache slot at @mapping & @offset.  If there is a
  * page cache page, it is returned with an increased refcount.
  *
- * If the slot holds a shadow entry of a previously evicted page, it
- * is returned.
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
  *
  * Otherwise, %NULL is returned.
  */
@@ -928,9 +928,9 @@ repeat:
                         if (radix_tree_deref_retry(page))
                                 goto repeat;
                         /*
-                         * Otherwise, shmem/tmpfs must be storing a swap entry
-                         * here as an exceptional entry: so return it without
-                         * attempting to raise page count.
+                         * A shadow entry of a recently evicted page,
+                         * or a swap entry from shmem/tmpfs.  Return
+                         * it without attempting to raise page count.
                          */
                         goto out;
                 }
@@ -983,8 +983,8 @@ EXPORT_SYMBOL(find_get_page);
  * page cache page, it is returned locked and with an increased
  * refcount.
  *
- * If the slot holds a shadow entry of a previously evicted page, it
- * is returned.
+ * If the slot holds a shadow entry of a previously evicted page, or a
+ * swap entry from shmem/tmpfs, it is returned.
  *
  * Otherwise, %NULL is returned.
  *
@@ -1099,8 +1099,8 @@ EXPORT_SYMBOL(find_or_create_page);
  * with ascending indexes.  There may be holes in the indices due to
  * not-present pages.
  *
- * Any shadow entries of evicted pages are included in the returned
- * array.
+ * Any shadow entries of evicted pages, or swap entries from
+ * shmem/tmpfs, are included in the returned array.
  *
  * find_get_entries() returns the number of pages and shadow entries
  * which were found.
@@ -1128,9 +1128,9 @@ repeat:
                         if (radix_tree_deref_retry(page))
                                 goto restart;
                         /*
-                         * Otherwise, we must be storing a swap entry
-                         * here as an exceptional entry: so return it
-                         * without attempting to raise page count.
+                         * A shadow entry of a recently evicted page,
+                         * or a swap entry from shmem/tmpfs.  Return
+                         * it without attempting to raise page count.
                          */
                         goto export;
                 }
@@ -1198,9 +1198,9 @@ repeat:
                                 goto restart;
                         }
                         /*
-                         * Otherwise, shmem/tmpfs must be storing a swap entry
-                         * here as an exceptional entry: so skip over it -
-                         * we only reach this from invalidate_mapping_pages().
+                         * A shadow entry of a recently evicted page,
+                         * or a swap entry from shmem/tmpfs.  Skip
+                         * over it.
                          */
                         continue;
                 }
@@ -1265,9 +1265,9 @@ repeat:
                                 goto restart;
                         }
                         /*
-                         * Otherwise, shmem/tmpfs must be storing a swap entry
-                         * here as an exceptional entry: so stop looking for
-                         * contiguous pages.
+                         * A shadow entry of a recently evicted page,
+                         * or a swap entry from shmem/tmpfs.  Stop
+                         * looking for contiguous pages.
                          */
                         break;
                 }
@@ -1341,10 +1341,17 @@ repeat:
                                 goto restart;
                         }
                         /*
-                         * This function is never used on a shmem/tmpfs
-                         * mapping, so a swap entry won't be found here.
+                         * A shadow entry of a recently evicted page.
+                         *
+                         * Those entries should never be tagged, but
+                         * this tree walk is lockless and the tags are
+                         * looked up in bulk, one radix tree node at a
+                         * time, so there is a sizable window for page
+                         * reclaim to evict a page we saw tagged.
+                         *
+                         * Skip over it.
                          */
-                        BUG();
+                        continue;
                 }
 
                 if (!page_cache_get_speculative(page))
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 29501f040568..c47dffdcb246 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6686,16 +6686,20 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
                 pgoff = pte_to_pgoff(ptent);
 
         /* page is moved even if it's not RSS of this task(page-faulted). */
-        page = find_get_page(mapping, pgoff);
-
 #ifdef CONFIG_SWAP
         /* shmem/tmpfs may report page out on swap: account for that too. */
-        if (radix_tree_exceptional_entry(page)) {
-                swp_entry_t swap = radix_to_swp_entry(page);
-                if (do_swap_account)
-                        *entry = swap;
-                page = find_get_page(swap_address_space(swap), swap.val);
-        }
+        if (shmem_mapping(mapping)) {
+                page = find_get_entry(mapping, pgoff);
+                if (radix_tree_exceptional_entry(page)) {
+                        swp_entry_t swp = radix_to_swp_entry(page);
+                        if (do_swap_account)
+                                *entry = swp;
+                        page = find_get_page(swap_address_space(swp), swp.val);
+                }
+        } else
+                page = find_get_page(mapping, pgoff);
+#else
+        page = find_get_page(mapping, pgoff);
 #endif
         return page;
 }
diff --git a/mm/truncate.c b/mm/truncate.c
index e5cc39ab0751..6a78c814bebf 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -484,14 +484,6 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
         unsigned long count = 0;
         int i;
 
-        /*
-         * Note: this function may get called on a shmem/tmpfs mapping:
-         * pagevec_lookup() might then return 0 prematurely (because it
-         * got a gangful of swap entries); but it's hardly worth worrying
-         * about - it can rarely have anything to free from such a mapping
-         * (most pages are dirty), and already skips over any difficulties.
-         */
-
         pagevec_init(&pvec, 0);
         while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
                         min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,