mm: alloc_pages_bulk_noprof: drop page_list argument

Patch series "mm: alloc_pages_bulk: small API refactor", v2.

Today, alloc_pages_bulk_noprof() supports two arguments to return
allocated pages: a linked list and an array.  There are also higher level
APIs for both.

However, the linked list API has apparently never been used.  So, this
series removes it along with the list API and also refactors the remaining
API naming for consistency.


This patch (of 2):

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@techsingularity.net)

Link: https://lkml.kernel.org/r/cover.1734991165.git.luizcap@redhat.com
Link: https://lkml.kernel.org/r/f1c75db91d08cafd211eca6a3b199b629d4ffe16.1734991165.git.luizcap@redhat.com
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 12 insertions, 27 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index df5d617738e7..7cdf1ac3e32a 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 @@ retry_this_zone:
 	while (nr_populated < nr_pages) {
 
 		/* Skip existing pages */
-		if (page_array && page_array[nr_populated]) {
+		if (page_array[nr_populated]) {
 			nr_populated++;
 			continue;
 		}
@@ -4679,11 +4674,7 @@ retry_this_zone:
 
 		prep_new_page(page, 0, gfp, 0);
 		set_page_refcounted(page);
-		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);
@@ -4700,14 +4691,8 @@ failed_irq:
 
 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);