[RFC PATCH 18/37] mm: enable speculative fault handling in do_numa_page()

[Michel Lespinasse <michel@xxxxxxxxxxxxxx>]

Change handle_pte_fault() to allow speculative fault execution to proceed
through do_numa_page().

do_swap_page() does not implement speculative execution yet, so it
needs to abort with VM_FAULT_RETRY in that case.

Signed-off-by: Michel Lespinasse <michel@xxxxxxxxxxxxxx>
---
 mm/memory.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 78cc36749754..eea72bd78d06 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3346,6 +3346,11 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	vm_fault_t ret = 0;
 	void *shadow = NULL;
 
+	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
+		pte_unmap(vmf->pte);
+		return VM_FAULT_RETRY;
+	}
+
 	if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
 		goto out;
 
@@ -4342,17 +4347,17 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
 			return do_fault(vmf);
 	}
 
-	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
-		pte_unmap(vmf->pte);
-		return VM_FAULT_RETRY;
-	}
-
 	if (!pte_present(vmf->orig_pte))
 		return do_swap_page(vmf);
 
 	if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
 		return do_numa_page(vmf);
 
+	if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
+		pte_unmap(vmf->pte);
+		return VM_FAULT_RETRY;
+	}
+
 	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
 	spin_lock(vmf->ptl);
 	entry = vmf->orig_pte;
-- 
2.20.1