[PATCH v2 11/11] hugetlb: batch TLB flushes when restoring vmemmap

[Mike Kravetz]

Update the hugetlb_vmemmap_restore path to take a 'batch' parameter that
indicates restoration is happening on a batch of pages.  When set, use
the existing mechanism (VMEMMAP_NO_TLB_FLUSH) to delay TLB flushing.
The routine hugetlb_vmemmap_restore_folios is the only user of this new
batch parameter and it will perform a global flush after all vmemmap is
restored.

Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
 mm/hugetlb_vmemmap.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 8c85e2c38538..11fda9d061eb 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -458,17 +458,19 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
  * @end:	end address of the vmemmap virtual address range that we want to
  *		remap.
  * @reuse:	reuse address.
+ * @flags:	modify behavior for bulk operations
  *
  * Return: %0 on success, negative error code otherwise.
  */
 static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
-			       unsigned long reuse)
+			       unsigned long reuse, unsigned long flags)
 {
 	LIST_HEAD(vmemmap_pages);
 	struct vmemmap_remap_walk walk = {
 		.remap_pte	= vmemmap_restore_pte,
 		.reuse_addr	= reuse,
 		.vmemmap_pages	= &vmemmap_pages,
+		.flags		= flags,
 	};
 
 	/* See the comment in the vmemmap_remap_free(). */
@@ -490,17 +492,7 @@ EXPORT_SYMBOL(hugetlb_optimize_vmemmap_key);
 static bool vmemmap_optimize_enabled = IS_ENABLED(CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON);
 core_param(hugetlb_free_vmemmap, vmemmap_optimize_enabled, bool, 0);
 
-/**
- * hugetlb_vmemmap_restore - restore previously optimized (by
- *			     hugetlb_vmemmap_optimize()) vmemmap pages which
- *			     will be reallocated and remapped.
- * @h:		struct hstate.
- * @head:	the head page whose vmemmap pages will be restored.
- *
- * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
- * negative error code otherwise.
- */
-int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
+static int __hugetlb_vmemmap_restore(const struct hstate *h, struct page *head, unsigned long flags)
 {
 	int ret;
 	unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
@@ -521,7 +513,7 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
 	 * When a HugeTLB page is freed to the buddy allocator, previously
 	 * discarded vmemmap pages must be allocated and remapping.
 	 */
-	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse);
+	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse, flags);
 	if (!ret) {
 		ClearHPageVmemmapOptimized(head);
 		static_branch_dec(&hugetlb_optimize_vmemmap_key);
@@ -530,6 +522,21 @@ int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
 	return ret;
 }
 
+/**
+ * hugetlb_vmemmap_restore - restore previously optimized (by
+ *			     hugetlb_vmemmap_optimize()) vmemmap pages which
+ *			     will be reallocated and remapped.
+ * @h:		struct hstate.
+ * @head:	the head page whose vmemmap pages will be restored.
+ *
+ * Return: %0 if @head's vmemmap pages have been reallocated and remapped,
+ * negative error code otherwise.
+ */
+int hugetlb_vmemmap_restore(const struct hstate *h, struct page *head)
+{
+	return __hugetlb_vmemmap_restore(h, head, 0UL);
+}
+
 /*
  * This function will attempt to resore vmemmap for a list of folios.  There
  * is no guarantee that restoration will be successful for all or any folios.
@@ -540,7 +547,9 @@ void hugetlb_vmemmap_restore_folios(const struct hstate *h, struct list_head *fo
 	struct folio *folio;
 
 	list_for_each_entry(folio, folio_list, lru)
-		(void)hugetlb_vmemmap_restore(h, &folio->page);
+		(void)__hugetlb_vmemmap_restore(h, &folio->page, VMEMMAP_NO_TLB_FLUSH);
+
+	flush_tlb_all();
 }
 
 /* Return true iff a HugeTLB whose vmemmap should and can be optimized. */
-- 
2.41.0