mm: do_swap_page(): fix up the error code

do_swap_page() returns error codes from the VM_FAULT* space.  try_charge()
might return -ENOMEM, though, and then do_swap_page() simply returns 0
which means a success.

We almost never return ENOMEM for GFP_KERNEL single page charge.  Except
for async OOM handling (oom_disabled v1).  So this needs translation to
VM_FAULT_OOM otherwise the the page fault path will not notify the
userspace and wait for an action.

Link: http://lkml.kernel.org/r/20200617090238.GL9499@dhcp22.suse.cz
Fixes: 4c6355b25e8b ("mm: memcontrol: charge swapin pages on instantiation")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory.c b/mm/memory.c
index dc7f354..1c632fa 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3140,8 +3140,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
                                err = mem_cgroup_charge(page, vma->vm_mm,
                                                        GFP_KERNEL);
                                ClearPageSwapCache(page);
-                               if (err)
+                               if (err) {
+                                       ret = VM_FAULT_OOM;
                                        goto out_page;
+                               }
 
                                lru_cache_add(page);
                                swap_readpage(page, true);