[PATCH] ideas

[Lorenzo Stoakes (ARM)]

---
 mm/huge_memory.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index abc65d608c23..5fa01364f089 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -111,6 +111,34 @@ static bool vma_is_special_huge(const struct vm_area_struct *vma)
 	return vma_test_any(vma, VMA_PFNMAP_BIT, VMA_MIXEDMAP_BIT);
 }

+static bool should_obey_thp_file_tunables(const struct vm_area_struct *vma,
+					  bool forced_collapse)
+{
+	if (forced_collapse)
+		return false;
+	VM_WARN_ON_ONCE(vma_is_anonymous(vma));
+	/* Huge PFN mappings allocate no folios so the policy doesn't apply. */
+	if (vma_test(vma, VMA_PFNMAP_BIT) && vma->vm_ops->huge_fault)
+		return false;
+	return true;
+}
+
+static bool can_thp_collapse_file(const struct vm_area_struct *vma,
+		vm_flags_t vm_flags, bool forced_collapse)
+{
+	/* Override THP tunables? */
+	if (!should_obey_thp_file_tunables(vma, forced_collapse))
+		return true;
+	/* THP=always? */
+	if (hugepage_global_always())
+		return true;
+	/* THP=madvise? */
+	if (!hugepage_global_enabled())
+		return false;
+	/* Has VMA had madvise(..., MADV_HUGEPAGE) applied to it? */
+	return vm_flags & VM_HUGEPAGE;
+}
+
 unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 					 vm_flags_t vm_flags,
 					 enum tva_type type,
@@ -188,9 +216,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 		 * Enforce THP collapse requirements as necessary. Anonymous vmas
 		 * were already handled in thp_vma_allowable_orders().
 		 */
-		if (!forced_collapse &&
-		    (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
-						    !hugepage_global_always())))
+		if (!can_thp_collapse_file(vma, vm_flags, forced_collapse))
 			return 0;

 		/*
--
2.55.0