[RFC PATCH 11/16] mm/madvise: let madvise_free_single_vma() caller batches tlb flushes

[SeongJae Park <sj@kernel.org>]

Update madvise_free_single_vma() function so that the caller can pass an
mmu_gather object that should be initialized and will be finished
outside, for batched tlb flushes.  Also modify madvise_free_single_vma()
internal code to support such usage while keeping support of olde usage
that the mmu_gather object is not passed.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/madvise.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 22da6699613c..767c5d21ee75 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -794,12 +794,19 @@ static const struct mm_walk_ops madvise_free_walk_ops = {
 	.walk_lock		= PGWALK_RDLOCK,
 };
 
-static int madvise_free_single_vma(struct vm_area_struct *vma,
-			unsigned long start_addr, unsigned long end_addr)
+static int madvise_free_single_vma(
+		struct mmu_gather *caller_tlb, struct vm_area_struct *vma,
+		unsigned long start_addr, unsigned long end_addr)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct mmu_notifier_range range;
-	struct mmu_gather tlb;
+	struct mmu_gather self_tlb;
+	struct mmu_gather *tlb;
+
+	if (caller_tlb)
+		tlb = caller_tlb;
+	else
+		tlb = &self_tlb;
 
 	/* MADV_FREE works for only anon vma at the moment */
 	if (!vma_is_anonymous(vma))
@@ -815,16 +822,18 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
 				range.start, range.end);
 
 	lru_add_drain();
-	tlb_gather_mmu(&tlb, mm);
+	if (!caller_tlb)
+		tlb_gather_mmu(tlb, mm);
 	update_hiwater_rss(mm);
 
 	mmu_notifier_invalidate_range_start(&range);
-	tlb_start_vma(&tlb, vma);
+	tlb_start_vma(tlb, vma);
 	walk_page_range(vma->vm_mm, range.start, range.end,
-			&madvise_free_walk_ops, &tlb);
-	tlb_end_vma(&tlb, vma);
+			&madvise_free_walk_ops, tlb);
+	tlb_end_vma(tlb, vma);
 	mmu_notifier_invalidate_range_end(&range);
-	tlb_finish_mmu(&tlb);
+	if (!caller_tlb)
+		tlb_finish_mmu(tlb);
 
 	return 0;
 }
@@ -957,7 +966,7 @@ static long madvise_dontneed_free(struct vm_area_struct *vma,
 	if (behavior == MADV_DONTNEED || behavior == MADV_DONTNEED_LOCKED)
 		return madvise_dontneed_single_vma(NULL, vma, start, end);
 	else if (behavior == MADV_FREE)
-		return madvise_free_single_vma(vma, start, end);
+		return madvise_free_single_vma(NULL, vma, start, end);
 	else
 		return -EINVAL;
 }
-- 
2.39.5