thp+memcg-numa: fix BUG at include/linux/mm.h:370!

THP's collapse_huge_page() has an understandable but ugly difference
in when its huge page is allocated: inside if NUMA but outside if not.
It's hardly surprising that the memcg failure path forgot that, freeing
the page in the non-NUMA case, then hitting a VM_BUG_ON in get_page()
(or even worse, using the freed page).

Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index dbe99a5f2073..113e35c47502 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1762,6 +1762,10 @@ static void collapse_huge_page(struct mm_struct *mm,
 #ifndef CONFIG_NUMA
         VM_BUG_ON(!*hpage);
         new_page = *hpage;
+        if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
+                up_read(&mm->mmap_sem);
+                return;
+        }
 #else
         VM_BUG_ON(*hpage);
         /*
@@ -1781,12 +1785,12 @@ static void collapse_huge_page(struct mm_struct *mm,
                 *hpage = ERR_PTR(-ENOMEM);
                 return;
         }
-#endif
         if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
                 up_read(&mm->mmap_sem);
                 put_page(new_page);
                 return;
         }
+#endif
 
         /* after allocating the hugepage upgrade to mmap_sem write mode */
         up_read(&mm->mmap_sem);