Merge tag 'v5.0-rc4' into asoc-5.1

Linux 5.0-rc4

1 files changed, 24 insertions, 2 deletions

diff --git a/mm/memory.c b/mm/memory.c
index a52663c0612d..e11ca9dd823f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2994,6 +2994,28 @@ static vm_fault_t __do_fault(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret;
 
+	/*
+	 * Preallocate pte before we take page_lock because this might lead to
+	 * deadlocks for memcg reclaim which waits for pages under writeback:
+	 *				lock_page(A)
+	 *				SetPageWriteback(A)
+	 *				unlock_page(A)
+	 * lock_page(B)
+	 *				lock_page(B)
+	 * pte_alloc_pne
+	 *   shrink_page_list
+	 *     wait_on_page_writeback(A)
+	 *				SetPageWriteback(B)
+	 *				unlock_page(B)
+	 *				# flush A, B to clear the writeback
+	 */
+	if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) {
+		vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
+		if (!vmf->prealloc_pte)
+			return VM_FAULT_OOM;
+		smp_wmb(); /* See comment in __pte_alloc() */
+	}
+
 	ret = vma->vm_ops->fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
 			    VM_FAULT_DONE_COW)))
@@ -4077,8 +4099,8 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		goto out;
 
 	if (range) {
-		range->start = address & PAGE_MASK;
-		range->end = range->start + PAGE_SIZE;
+		mmu_notifier_range_init(range, mm, address & PAGE_MASK,
+				     (address & PAGE_MASK) + PAGE_SIZE);
 		mmu_notifier_invalidate_range_start(range);
 	}
 	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);