mm, thp: allow fallback when pte_alloc_one() fails for huge pmd

The transparent hugepages feature is careful to not invoke the oom
killer when a hugepage cannot be allocated.

pte_alloc_one() failing in __do_huge_pmd_anonymous_page(), however,
currently results in VM_FAULT_OOM which invokes the pagefault oom killer
to kill a memory-hogging task.

This is unnecessary since it's possible to drop the reference to the
hugepage and fallback to allocating a small page.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8ab2d24faae5..d7d7165156ca 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -640,11 +640,8 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
 
         VM_BUG_ON(!PageCompound(page));
         pgtable = pte_alloc_one(mm, haddr);
-        if (unlikely(!pgtable)) {
-                mem_cgroup_uncharge_page(page);
-                put_page(page);
+        if (unlikely(!pgtable))
                 return VM_FAULT_OOM;
-        }
 
         clear_huge_page(page, haddr, HPAGE_PMD_NR);
         __SetPageUptodate(page);
@@ -723,8 +720,14 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         put_page(page);
                         goto out;
                 }
+                if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
+                                                          page))) {
+                        mem_cgroup_uncharge_page(page);
+                        put_page(page);
+                        goto out;
+                }
 
-                return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
+                return 0;
         }
 out:
         /*