[PATCH next v2 2/2] mm/huge_memory: Use per-VMA hugepage flag hints for exec THP COW

[Zhang Qilong <zhangqilong3@huawei.com>]

Using the per-VMA hugepage flag to avoid system wide default
behavior. If 'vma->vm_flags' indicates a preference for huge pages,
then the exec THP COW can be attempted.

Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
---
v2:
- Use 'vma->vm_flags' as hint for exec THP COW suggested by David

---
 mm/memory.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index 691e3ca38cc6..eb2bb36e284c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6128,10 +6128,17 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
 		}
 	}
 
 	if (is_exec_mapping(vm_flags) &&
 	    is_cow_mapping(vm_flags)) {
+		/*
+		 * Reuse the per-VMA flag, only if VM_HUGEPAGE is
+		 * set, do exec THP COW.
+		 */
+		if (!(vm_flags & VM_HUGEPAGE))
+			goto split;
+
 		ret = do_huge_pmd_exec_cow(vmf);
 		if (!(ret & VM_FAULT_FALLBACK))
 			return ret;
 	}
 
-- 
2.43.0