[RFC PATCH 09/16] mm/memory: split non-tlb flushing part from zap_page_range_single()

[SeongJae Park <sj@kernel.org>]

Some of zap_page_range_single() callers such as [process_]madvise() with
MADV_DONEED[_LOCKED] cannot batch tlb flushes because
zap_page_range_single() does tlb flushing for each invocation.  Split
out core part of zap_page_range_single() except mmu_gather object
initialization and gathered tlb entries flushing part for such batched
tlb flushing usage.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/memory.c | 36 ++++++++++++++++++++++--------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index a838c8c44bfd..aadb2844c701 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2011,38 +2011,46 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
 	mmu_notifier_invalidate_range_end(&range);
 }
 
-/**
- * zap_page_range_single - remove user pages in a given range
- * @vma: vm_area_struct holding the applicable pages
- * @address: starting address of pages to zap
- * @size: number of bytes to zap
- * @details: details of shared cache invalidation
- *
- * The range must fit into one VMA.
- */
-void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
+static void unmap_vma_single(struct mmu_gather *tlb,
+		struct vm_area_struct *vma, unsigned long address,
 		unsigned long size, struct zap_details *details)
 {
 	const unsigned long end = address + size;
 	struct mmu_notifier_range range;
-	struct mmu_gather tlb;
 
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
 				address, end);
 	hugetlb_zap_begin(vma, &range.start, &range.end);
-	tlb_gather_mmu(&tlb, vma->vm_mm);
 	update_hiwater_rss(vma->vm_mm);
 	mmu_notifier_invalidate_range_start(&range);
 	/*
 	 * unmap 'address-end' not 'range.start-range.end' as range
 	 * could have been expanded for hugetlb pmd sharing.
 	 */
-	unmap_single_vma(&tlb, vma, address, end, details, false);
+	unmap_single_vma(tlb, vma, address, end, details, false);
 	mmu_notifier_invalidate_range_end(&range);
-	tlb_finish_mmu(&tlb);
 	hugetlb_zap_end(vma, details);
 }
 
+/**
+ * zap_page_range_single - remove user pages in a given range
+ * @vma: vm_area_struct holding the applicable pages
+ * @address: starting address of pages to zap
+ * @size: number of bytes to zap
+ * @details: details of shared cache invalidation
+ *
+ * The range must fit into one VMA.
+ */
+void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
+		unsigned long size, struct zap_details *details)
+{
+	struct mmu_gather tlb;
+
+	tlb_gather_mmu(&tlb, vma->vm_mm);
+	unmap_vma_single(&tlb, vma, address, size, details);
+	tlb_finish_mmu(&tlb);
+}
+
 /**
  * zap_vma_ptes - remove ptes mapping the vma
  * @vma: vm_area_struct holding ptes to be zapped
-- 
2.39.5