1 files changed, 32 insertions, 23 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 5020b280a771..088358c8006b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -257,9 +257,11 @@ static int filemap_check_errors(struct address_space *mapping)
 {
         int ret = 0;
         /* Check for outstanding write errors */
-        if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
+        if (test_bit(AS_ENOSPC, &mapping->flags) &&
+            test_and_clear_bit(AS_ENOSPC, &mapping->flags))
                 ret = -ENOSPC;
-        if (test_and_clear_bit(AS_EIO, &mapping->flags))
+        if (test_bit(AS_EIO, &mapping->flags) &&
+            test_and_clear_bit(AS_EIO, &mapping->flags))
                 ret = -EIO;
         return ret;
 }
@@ -906,8 +908,8 @@ 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 +930,9 @@ 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 +985,8 @@ 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 +1101,8 @@ 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 +1130,9 @@ 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 +1200,9 @@ 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 +1267,9 @@ 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 +1343,17 @@ 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))