[RFC PATCH 1/5] mm: Enable fault around for shared file page fault

[Yin Fengwei <fengwei.yin@intel.com>]

Allow the batched page table population added to fault
around handler and benefit both file read and shared
fault.

Signed-off-by: Yin Fengwei <fengwei.yin@intel.com>
---
 mm/memory.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index ec833a2e0601..61ccd2d7e6a6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4545,6 +4545,17 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	vm_fault_t ret, tmp;
 
+	/*
+	 * Let's call ->map_pages() first and use ->fault() as fallback
+	 * if page by the offset is not ready to be mapped (cold cache or
+	 * something).
+	 */
+	if (should_fault_around(vmf)) {
+		ret = do_fault_around(vmf);
+		if (ret)
+			return ret;
+	}
+
 	ret = __do_fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
 		return ret;
-- 
2.30.2