[PATCH v8 mm-new 02/12] mm: thp: remove vm_flags parameter from khugepaged_enter_vma()

[Yafang Shao <laoar.shao@gmail.com>]

The khugepaged_enter_vma() function requires handling in two specific
scenarios:
1. New VMA creation
  When a new VMA is created, if vma->vm_mm is not present in
  khugepaged_mm_slot, it must be added. In this case,
  khugepaged_enter_vma() is called after vma->vm_flags have been set,
  allowing direct use of the VMA's flags.
2. VMA flag modification
  When vma->vm_flags are modified (particularly when VM_HUGEPAGE is set),
  the system must recheck whether to add vma->vm_mm to khugepaged_mm_slot.
  Currently, khugepaged_enter_vma() is called before the flag update, so
  the call must be relocated to occur after vma->vm_flags have been set.

Additionally, khugepaged_enter_vma() is invoked in other contexts, such as
during VMA merging. However, these calls are unnecessary because the
existing VMA already ensures that vma->vm_mm is registered in
khugepaged_mm_slot. While removing these redundant calls represents a
potential optimization, that change should be addressed separately.
Because VMA merging only occurs when the vm_flags of both VMAs are
identical (excluding special flags like VM_SOFTDIRTY), we can safely use
target->vm_flags instead.

After this change, we can further remove vm_flags parameter from
thp_vma_allowable_order(). That will be handled in a followup patch.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
---
 include/linux/khugepaged.h |  6 ++----
 mm/huge_memory.c           |  2 +-
 mm/khugepaged.c            | 11 ++---------
 mm/madvise.c               |  7 +++++++
 mm/vma.c                   |  6 +++---
 5 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index f14680cd9854..b30814d3d665 100644
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -13,8 +13,7 @@ extern void khugepaged_destroy(void);
 extern int start_stop_khugepaged(void);
 extern void __khugepaged_enter(struct mm_struct *mm);
 extern void __khugepaged_exit(struct mm_struct *mm);
-extern void khugepaged_enter_vma(struct vm_area_struct *vma,
-				 vm_flags_t vm_flags);
+extern void khugepaged_enter_vma(struct vm_area_struct *vma);
 extern void khugepaged_enter_mm(struct mm_struct *mm);
 extern void khugepaged_min_free_kbytes_update(void);
 extern bool current_is_khugepaged(void);
@@ -39,8 +38,7 @@ static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm
 static inline void khugepaged_exit(struct mm_struct *mm)
 {
 }
-static inline void khugepaged_enter_vma(struct vm_area_struct *vma,
-					vm_flags_t vm_flags)
+static inline void khugepaged_enter_vma(struct vm_area_struct *vma)
 {
 }
 static inline void khugepaged_enter_mm(struct mm_struct *mm)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1b81680b4225..ac6601f30e65 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1346,7 +1346,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
 	ret = vmf_anon_prepare(vmf);
 	if (ret)
 		return ret;
-	khugepaged_enter_vma(vma, vma->vm_flags);
+	khugepaged_enter_vma(vma);
 
 	if (!(vmf->flags & FAULT_FLAG_WRITE) &&
 			!mm_forbids_zeropage(vma->vm_mm) &&
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index f47ac8c19447..04121ae7d18d 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -353,12 +353,6 @@ int hugepage_madvise(struct vm_area_struct *vma,
 #endif
 		*vm_flags &= ~VM_NOHUGEPAGE;
 		*vm_flags |= VM_HUGEPAGE;
-		/*
-		 * If the vma become good for khugepaged to scan,
-		 * register it here without waiting a page fault that
-		 * may not happen any time soon.
-		 */
-		khugepaged_enter_vma(vma, *vm_flags);
 		break;
 	case MADV_NOHUGEPAGE:
 		*vm_flags &= ~VM_HUGEPAGE;
@@ -467,10 +461,9 @@ void khugepaged_enter_mm(struct mm_struct *mm)
 	__khugepaged_enter(mm);
 }
 
-void khugepaged_enter_vma(struct vm_area_struct *vma,
-			  vm_flags_t vm_flags)
+void khugepaged_enter_vma(struct vm_area_struct *vma)
 {
-	if (!thp_vma_allowable_order(vma, vm_flags, TVA_KHUGEPAGED, PMD_ORDER))
+	if (!thp_vma_allowable_order(vma, vma->vm_flags, TVA_KHUGEPAGED, PMD_ORDER))
 		return;
 
 	khugepaged_enter_mm(vma->vm_mm);
diff --git a/mm/madvise.c b/mm/madvise.c
index 35ed4ab0d7c5..ab8b5d47badb 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1425,6 +1425,13 @@ static int madvise_vma_behavior(struct madvise_behavior *madv_behavior)
 	VM_WARN_ON_ONCE(madv_behavior->lock_mode != MADVISE_MMAP_WRITE_LOCK);
 
 	error = madvise_update_vma(new_flags, madv_behavior);
+	/*
+	 * If the vma become good for khugepaged to scan,
+	 * register it here without waiting a page fault that
+	 * may not happen any time soon.
+	 */
+	if (!error && new_flags & VM_HUGEPAGE)
+		khugepaged_enter_mm(vma->vm_mm);
 out:
 	/*
 	 * madvise() returns EAGAIN if kernel resources, such as
diff --git a/mm/vma.c b/mm/vma.c
index a1ec405bda25..6a548b0d64cd 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -973,7 +973,7 @@ static __must_check struct vm_area_struct *vma_merge_existing_range(
 	if (err || commit_merge(vmg))
 		goto abort;
 
-	khugepaged_enter_vma(vmg->target, vmg->vm_flags);
+	khugepaged_enter_vma(vmg->target);
 	vmg->state = VMA_MERGE_SUCCESS;
 	return vmg->target;
 
@@ -1093,7 +1093,7 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
 	 * following VMA if we have VMAs on both sides.
 	 */
 	if (vmg->target && !vma_expand(vmg)) {
-		khugepaged_enter_vma(vmg->target, vmg->vm_flags);
+		khugepaged_enter_vma(vmg->target);
 		vmg->state = VMA_MERGE_SUCCESS;
 		return vmg->target;
 	}
@@ -2520,7 +2520,7 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
 	 * call covers the non-merge case.
 	 */
 	if (!vma_is_anonymous(vma))
-		khugepaged_enter_vma(vma, map->vm_flags);
+		khugepaged_enter_vma(vma);
 	*vmap = vma;
 	return 0;
 
-- 
2.47.3