[PATCH 1/2] mm: call back alloc_pages_bulk_list since it is useful

["zhaoyang.huang" <zhaoyang.huang@unisoc.com>]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

commit c8b979530f27 ("mm: alloc_pages_bulk_noprof: drop page_list
argument") drops alloc_pages_bulk_list. This commit would like to call back
it since it is proved to be helpful to the drivers which allocate a bulk of
pages(see patch of 2 in this series ).
I do notice that Matthew's comment of the time cost of iterating a list.
However, I also observed in our test that the extra page_array's allocation
could be more expensive than cpu iteration when direct reclaiming happens
when ram is low[1]. IMHO, could we leave the API here to have the users
choose between the array or list according to their scenarios.

[1]
android.hardwar-728     [002] .....   334.573875: system_heap_do_allocate: Execution time: order 0 1 us
android.hardwar-728     [002] .....   334.573879: system_heap_do_allocate: Execution time: order 0 2 us
android.hardwar-728     [002] .....   334.574239: system_heap_do_allocate: Execution time: order 0 354 us
android.hardwar-728     [002] .....   334.574247: system_heap_do_allocate: Execution time: order 0 4 us
android.hardwar-728     [002] .....   334.574250: system_heap_do_allocate: Execution time: order 0 2 us

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 include/linux/gfp.h |  9 +++++++--
 mm/mempolicy.c      | 14 +++++++-------
 mm/page_alloc.c     | 39 +++++++++++++++++++++++++++------------
 3 files changed, 41 insertions(+), 21 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 5ebf26fcdcfa..f1540c9fcd87 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -231,6 +231,7 @@ struct folio *__folio_alloc_noprof(gfp_t gfp, unsigned int order, int preferred_
 
 unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 				nodemask_t *nodemask, int nr_pages,
+				struct list_head *page_list,
 				struct page **page_array);
 #define __alloc_pages_bulk(...)			alloc_hooks(alloc_pages_bulk_noprof(__VA_ARGS__))
 
@@ -242,7 +243,11 @@ unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
 
 /* Bulk allocate order-0 pages */
 #define alloc_pages_bulk(_gfp, _nr_pages, _page_array)		\
-	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)
+	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, NULL, _page_array)
+
+#define alloc_pages_bulk_list(_gfp, _nr_pages, _list)			\
+	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _list, NULL)
+
 
 static inline unsigned long
 alloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,
@@ -251,7 +256,7 @@ alloc_pages_bulk_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,
 	if (nid == NUMA_NO_NODE)
 		nid = numa_mem_id();
 
-	return alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);
+	return alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, NULL, page_array);
 }
 
 #define alloc_pages_bulk_node(...)				\
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index eb83cff7db8c..26274302ee01 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2537,13 +2537,13 @@ static unsigned long alloc_pages_bulk_interleave(gfp_t gfp,
 		if (delta) {
 			nr_allocated = alloc_pages_bulk_noprof(gfp,
 					interleave_nodes(pol), NULL,
-					nr_pages_per_node + 1,
+					nr_pages_per_node + 1, NULL,
 					page_array);
 			delta--;
 		} else {
 			nr_allocated = alloc_pages_bulk_noprof(gfp,
 					interleave_nodes(pol), NULL,
-					nr_pages_per_node, page_array);
+					nr_pages_per_node, NULL, page_array);
 		}
 
 		page_array += nr_allocated;
@@ -2593,7 +2593,7 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
 	if (weight && node_isset(node, nodes)) {
 		node_pages = min(rem_pages, weight);
 		nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
-						  page_array);
+						  NULL, page_array);
 		page_array += nr_allocated;
 		total_allocated += nr_allocated;
 		/* if that's all the pages, no need to interleave */
@@ -2658,7 +2658,7 @@ static unsigned long alloc_pages_bulk_weighted_interleave(gfp_t gfp,
 		if (!node_pages)
 			break;
 		nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
-						  page_array);
+						  NULL, page_array);
 		page_array += nr_allocated;
 		total_allocated += nr_allocated;
 		if (total_allocated == nr_pages)
@@ -2682,11 +2682,11 @@ static unsigned long alloc_pages_bulk_preferred_many(gfp_t gfp, int nid,
 	preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
 
 	nr_allocated  = alloc_pages_bulk_noprof(preferred_gfp, nid, &pol->nodes,
-					   nr_pages, page_array);
+					   nr_pages, NULL, page_array);
 
 	if (nr_allocated < nr_pages)
 		nr_allocated += alloc_pages_bulk_noprof(gfp, numa_node_id(), NULL,
-				nr_pages - nr_allocated,
+				nr_pages - nr_allocated, NULL,
 				page_array + nr_allocated);
 	return nr_allocated;
 }
@@ -2722,7 +2722,7 @@ unsigned long alloc_pages_bulk_mempolicy_noprof(gfp_t gfp,
 	nid = numa_node_id();
 	nodemask = policy_nodemask(gfp, pol, NO_INTERLEAVE_INDEX, &nid);
 	return alloc_pages_bulk_noprof(gfp, nid, nodemask,
-				       nr_pages, page_array);
+				       nr_pages, NULL, page_array);
 }
 
 int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d1d037f97c5f..a95bdd8cbf5b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4940,23 +4940,28 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
 }
 
 /*
- * __alloc_pages_bulk - Allocate a number of order-0 pages to an array
+ * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
  * @gfp: GFP flags for the allocation
  * @preferred_nid: The preferred NUMA node ID to allocate from
  * @nodemask: Set of nodes to allocate from, may be NULL
- * @nr_pages: The number of pages desired in the array
- * @page_array: Array to store the pages
+ * @nr_pages: The number of pages desired on the list or array
+ * @page_list: Optional list to store the allocated pages
+ * @page_array: Optional array to store the pages
  *
  * This is a batched version of the page allocator that attempts to
- * allocate nr_pages quickly. Pages are added to the page_array.
+ * allocate nr_pages quickly. Pages are added to page_list if page_list
+ * is not NULL, otherwise it is assumed that the page_array is valid.
  *
- * Note that only NULL elements are populated with pages and nr_pages
+ * For lists, nr_pages is the number of pages that should be allocated.
+ *
+ * For arrays, only NULL elements are populated with pages and nr_pages
  * is the maximum number of pages that will be stored in the array.
  *
- * Returns the number of pages in the array.
+ * Returns the number of pages on the list or array.
  */
 unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 			nodemask_t *nodemask, int nr_pages,
+			struct list_head *page_list,
 			struct page **page_array)
 {
 	struct page *page;
@@ -4974,7 +4979,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	 * Skip populated array elements to determine if any pages need
 	 * to be allocated before disabling IRQs.
 	 */
-	while (nr_populated < nr_pages && page_array[nr_populated])
+	while (page_array && nr_populated < nr_pages && page_array[nr_populated])
 		nr_populated++;
 
 	/* No pages requested? */
@@ -4982,7 +4987,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 		goto out;
 
 	/* Already populated array? */
-	if (unlikely(nr_pages - nr_populated == 0))
+	if (unlikely(page_array && nr_pages - nr_populated == 0))
 		goto out;
 
 	/* Bulk allocator does not support memcg accounting. */
@@ -5064,7 +5069,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	while (nr_populated < nr_pages) {
 
 		/* Skip existing pages */
-		if (page_array[nr_populated]) {
+		if (page_array && page_array[nr_populated]) {
 			nr_populated++;
 			continue;
 		}
@@ -5083,7 +5088,11 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 
 		prep_new_page(page, 0, gfp, 0);
 		set_page_refcounted(page);
-		page_array[nr_populated++] = page;
+		if (page_list)
+			list_add(&page->lru, page_list);
+		else
+			page_array[nr_populated] = page;
+		nr_populated++;
 	}
 
 	pcp_spin_unlock(pcp);
@@ -5100,8 +5109,14 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 
 failed:
 	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask);
-	if (page)
-		page_array[nr_populated++] = page;
+	if (page) {
+		if (page_list)
+			list_add(&page->lru, page_list);
+		else
+			page_array[nr_populated] = page;
+		nr_populated++;
+	}
+
 	goto out;
 }
 EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
-- 
2.25.1