[PATCH v2 1/2] mm: alloc_pages_bulk_noprof: drop page_list argument

[Luiz Capitulino]

The commit 387ba26fb1cb ("mm/page_alloc: add a bulk page allocator") added
__alloc_pages_bulk() along with the page_list argument. The next
commit 0f87d9d30f21 ("mm/page_alloc: add an array-based interface to the
bulk page allocator") added the array-based argument. As it turns out, the
page_list argument has no users in the current tree (if it ever had any).
Dropping it allows for a slight simplification and eliminates some
unnecessary checks, now that page_array is required.

Also, note that the removal of the page_list argument was proposed before
in the thread below, where Matthew Wilcox mentions that:

  """
  Iterating a linked list is _expensive_.  It is about 10x quicker to
  iterate an array than a linked list.
  """
  (https://lore.kernel.org/linux-mm/20231025093254.xvomlctwhcuerzky@xxxxxxxxxxxxxxxxxxx)

Signed-off-by: Luiz Capitulino <luizcap@xxxxxxxxxx>
---
 include/linux/gfp.h |  8 ++------
 mm/mempolicy.c      | 14 +++++++-------
 mm/page_alloc.c     | 39 ++++++++++++---------------------------
 3 files changed, 21 insertions(+), 40 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index b0fe9f62d15b6..eebed36443b35 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -212,7 +212,6 @@ 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__))
 
@@ -223,11 +222,8 @@ unsigned long alloc_pages_bulk_array_mempolicy_noprof(gfp_t gfp,
 	alloc_hooks(alloc_pages_bulk_array_mempolicy_noprof(__VA_ARGS__))
 
 /* Bulk allocate order-0 pages */
-#define alloc_pages_bulk_list(_gfp, _nr_pages, _list)			\
-	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _list, NULL)
-
 #define alloc_pages_bulk_array(_gfp, _nr_pages, _page_array)		\
-	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, NULL, _page_array)
+	__alloc_pages_bulk(_gfp, numa_mem_id(), NULL, _nr_pages, _page_array)
 
 static inline unsigned long
 alloc_pages_bulk_array_node_noprof(gfp_t gfp, int nid, unsigned long nr_pages,
@@ -236,7 +232,7 @@ alloc_pages_bulk_array_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, NULL, page_array);
+	return alloc_pages_bulk_noprof(gfp, nid, NULL, nr_pages, page_array);
 }
 
 #define alloc_pages_bulk_array_node(...)				\
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 04f35659717ae..42a7b07ccc15a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2375,13 +2375,13 @@ static unsigned long alloc_pages_bulk_array_interleave(gfp_t gfp,
 		if (delta) {
 			nr_allocated = alloc_pages_bulk_noprof(gfp,
 					interleave_nodes(pol), NULL,
-					nr_pages_per_node + 1, NULL,
+					nr_pages_per_node + 1,
 					page_array);
 			delta--;
 		} else {
 			nr_allocated = alloc_pages_bulk_noprof(gfp,
 					interleave_nodes(pol), NULL,
-					nr_pages_per_node, NULL, page_array);
+					nr_pages_per_node, page_array);
 		}
 
 		page_array += nr_allocated;
@@ -2430,7 +2430,7 @@ static unsigned long alloc_pages_bulk_array_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,
-						  NULL, page_array);
+						  page_array);
 		page_array += nr_allocated;
 		total_allocated += nr_allocated;
 		/* if that's all the pages, no need to interleave */
@@ -2493,7 +2493,7 @@ static unsigned long alloc_pages_bulk_array_weighted_interleave(gfp_t gfp,
 		if (!node_pages)
 			break;
 		nr_allocated = __alloc_pages_bulk(gfp, node, NULL, node_pages,
-						  NULL, page_array);
+						  page_array);
 		page_array += nr_allocated;
 		total_allocated += nr_allocated;
 		if (total_allocated == nr_pages)
@@ -2517,11 +2517,11 @@ static unsigned long alloc_pages_bulk_array_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, NULL, page_array);
+					   nr_pages, page_array);
 
 	if (nr_allocated < nr_pages)
 		nr_allocated += alloc_pages_bulk_noprof(gfp, numa_node_id(), NULL,
-				nr_pages - nr_allocated, NULL,
+				nr_pages - nr_allocated,
 				page_array + nr_allocated);
 	return nr_allocated;
 }
@@ -2557,7 +2557,7 @@ unsigned long alloc_pages_bulk_array_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, NULL, page_array);
+				       nr_pages, 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 cae7b93864c23..4ce77a0e8d9a7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4531,28 +4531,23 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
 }
 
 /*
- * __alloc_pages_bulk - Allocate a number of order-0 pages to a list or array
+ * __alloc_pages_bulk - Allocate a number of order-0 pages to an 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 on the list or array
- * @page_list: Optional list to store the allocated pages
- * @page_array: Optional array to store the pages
+ * @nr_pages: The number of pages desired in the array
+ * @page_array: 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 page_list if page_list
- * is not NULL, otherwise it is assumed that the page_array is valid.
+ * allocate nr_pages quickly. Pages are added to the page_array.
  *
- * 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
+ * Note that 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 on the list or array.
+ * Returns the number of pages in the 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;
@@ -4570,7 +4565,7 @@ 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 (page_array && nr_populated < nr_pages && page_array[nr_populated])
+	while (nr_populated < nr_pages && page_array[nr_populated])
 		nr_populated++;
 
 	/* No pages requested? */
@@ -4578,7 +4573,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 		goto out;
 
 	/* Already populated array? */
-	if (unlikely(page_array && nr_pages - nr_populated == 0))
+	if (unlikely(nr_pages - nr_populated == 0))
 		goto out;
 
 	/* Bulk allocator does not support memcg accounting. */
@@ -4660,7 +4655,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 	while (nr_populated < nr_pages) {
 
 		/* Skip existing pages */
-		if (page_array && page_array[nr_populated]) {
+		if (page_array[nr_populated]) {
 			nr_populated++;
 			continue;
 		}
@@ -4678,11 +4673,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 		nr_account++;
 
 		prep_new_page(page, 0, gfp, 0);
-		if (page_list)
-			list_add(&page->lru, page_list);
-		else
-			page_array[nr_populated] = page;
-		nr_populated++;
+		page_array[nr_populated++] = page;
 	}
 
 	pcp_spin_unlock(pcp);
@@ -4699,14 +4690,8 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 
 failed:
 	page = __alloc_pages_noprof(gfp, 0, preferred_nid, nodemask);
-	if (page) {
-		if (page_list)
-			list_add(&page->lru, page_list);
-		else
-			page_array[nr_populated] = page;
-		nr_populated++;
-	}
-
+	if (page)
+		page_array[nr_populated++] = page;
 	goto out;
 }
 EXPORT_SYMBOL_GPL(alloc_pages_bulk_noprof);
-- 
2.47.1