diff --git a/[refs] b/[refs]
index 44593da63bb9..db98175ffc4f 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 436814e61f5c526ed123853a9bf63fb2ff4ff94b
+refs/heads/master: e0897d75f0b22e8c3a7287a48548c5686ef73447
diff --git a/trunk/mm/memory.c b/trunk/mm/memory.c
index 1b7dc662bf9f..8762c4f915fc 100644
--- a/trunk/mm/memory.c
+++ b/trunk/mm/memory.c
@@ -1225,7 +1225,15 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
 		next = pmd_addr_end(addr, end);
 		if (pmd_trans_huge(*pmd)) {
 			if (next - addr != HPAGE_PMD_SIZE) {
-				VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
+#ifdef CONFIG_DEBUG_VM
+				if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
+					pr_err("%s: mmap_sem is unlocked! addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
+						__func__, addr, end,
+						vma->vm_start,
+						vma->vm_end);
+					BUG();
+				}
+#endif
 				split_huge_page_pmd(vma->vm_mm, pmd);
 			} else if (zap_huge_pmd(tlb, vma, pmd, addr))
 				goto next;