From:   Yang Shi <shy828301@gmail.com>
To:     mgorman@techsingularity.net, agk@redhat.com, snitzer@kernel.org,
        dm-devel@redhat.com, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [v2 PATCH 1/5] mm: page_alloc: add API for bulk allocator with callback
Date:   Tue, 14 Feb 2023 11:02:17 -0800
Message-Id: <20230214190221.1156876-2-shy828301@gmail.com>
In-Reply-To: <20230214190221.1156876-1-shy828301@gmail.com>
References: <20230214190221.1156876-1-shy828301@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Currently the bulk allocator support to pass pages via list or array,
but neither is suitable for some usecases, for example, dm-crypt, which
doesn't need a list, but array may be too big to fit on stack.  So
adding a new bulk allocator API, which passes in a callback function
that deal with the allocated pages.

The API defined in this patch will be used by the following patches.

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
 include/linux/gfp.h | 21 +++++++++++++++++----
 mm/mempolicy.c      | 12 +++++++-----
 mm/page_alloc.c     | 21 +++++++++++++++------
 3 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 65a78773dcca..265c19b4822f 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -182,7 +182,9 @@ struct folio *__folio_alloc(gfp_t gfp, unsigned int order, int preferred_nid,
 unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 				nodemask_t *nodemask, int nr_pages,
 				struct list_head *page_list,
-				struct page **page_array);
+				struct page **page_array,
+				void (*cb)(struct page *, void *),
+				void *data);
 
 unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
 				unsigned long nr_pages,
@@ -192,13 +194,15 @@ unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
 static inline unsigned long
 alloc_pages_bulk_list(gfp_t gfp, unsigned long nr_pages, struct list_head *list)
 {
-	return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, list, NULL);
+	return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, list, NULL,
+				  NULL, NULL);
 }
 
 static inline unsigned long
 alloc_pages_bulk_array(gfp_t gfp, unsigned long nr_pages, struct page **page_array)
 {
-	return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, NULL, page_array);
+	return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, NULL, page_array,
+				  NULL, NULL);
 }
 
 static inline unsigned long
@@ -207,7 +211,16 @@ alloc_pages_bulk_array_node(gfp_t gfp, int nid, unsigned long nr_pages, struct p
 	if (nid == NUMA_NO_NODE)
 		nid = numa_mem_id();
 
-	return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array);
+	return __alloc_pages_bulk(gfp, nid, NULL, nr_pages, NULL, page_array,
+				  NULL, NULL);
+}
+
+static inline unsigned long
+alloc_pages_bulk_cb(gfp_t gfp, unsigned long nr_pages,
+		    void (*cb)(struct page *page, void *data), void *data)
+{
+	return __alloc_pages_bulk(gfp, numa_mem_id(), NULL, nr_pages, NULL, NULL,
+				  cb, data);
 }
 
 static inline void warn_if_node_offline(int this_node, gfp_t gfp_mask)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 0919c7a719d4..00b2d5341790 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2318,12 +2318,13 @@ static unsigned long alloc_pages_bulk_array_interleave(gfp_t gfp,
 			nr_allocated = __alloc_pages_bulk(gfp,
 					interleave_nodes(pol), NULL,
 					nr_pages_per_node + 1, NULL,
-					page_array);
+					page_array, NULL, NULL);
 			delta--;
 		} else {
 			nr_allocated = __alloc_pages_bulk(gfp,
 					interleave_nodes(pol), NULL,
-					nr_pages_per_node, NULL, page_array);
+					nr_pages_per_node, NULL, page_array,
+					NULL, NULL);
 		}
 
 		page_array += nr_allocated;
@@ -2344,12 +2345,13 @@ 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(preferred_gfp, nid, &pol->nodes,
-					   nr_pages, NULL, page_array);
+					   nr_pages, NULL, page_array,
+					   NULL, NULL);
 
 	if (nr_allocated < nr_pages)
 		nr_allocated += __alloc_pages_bulk(gfp, numa_node_id(), NULL,
 				nr_pages - nr_allocated, NULL,
-				page_array + nr_allocated);
+				page_array + nr_allocated, NULL, NULL);
 	return nr_allocated;
 }
 
@@ -2377,7 +2379,7 @@ unsigned long alloc_pages_bulk_array_mempolicy(gfp_t gfp,
 
 	return __alloc_pages_bulk(gfp, policy_node(gfp, pol, numa_node_id()),
 				  policy_nodemask(gfp, pol), nr_pages, NULL,
-				  page_array);
+				  page_array, NULL, NULL);
 }
 
 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 1113483fa6c5..d23b8e49a8cd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5402,22 +5402,27 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
  * @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
+ * @cb: Optional callback to handle the page
+ * @data: The parameter passed in by the callback
  *
  * 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.
+ * is not NULL, or it is assumed if the page_array is valid, or it is
+ * passed to a callback if cb is valid.
  *
- * For lists, nr_pages is the number of pages that should be allocated.
+ * For lists and cb, 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 on the list or array.
+ * Returns the number of pages on the list or array or consumed by cb.
  */
 unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 			nodemask_t *nodemask, int nr_pages,
 			struct list_head *page_list,
-			struct page **page_array)
+			struct page **page_array,
+			void (*cb)(struct page *, void *),
+			void *data)
 {
 	struct page *page;
 	unsigned long __maybe_unused UP_flags;
@@ -5532,8 +5537,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 		prep_new_page(page, 0, gfp, 0);
 		if (page_list)
 			list_add(&page->lru, page_list);
-		else
+		else if (page_array)
 			page_array[nr_populated] = page;
+		else
+			cb(page, data);
 		nr_populated++;
 	}
 
@@ -5554,8 +5561,10 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
 	if (page) {
 		if (page_list)
 			list_add(&page->lru, page_list);
-		else
+		else if (page_array)
 			page_array[nr_populated] = page;
+		else
+			cb(page, data);
 		nr_populated++;
 	}
 
-- 
2.39.0