From be6d3cc0858b8e5ee011ed24cb59c6046bdd9c82 Mon Sep 17 00:00:00 2001
From: Kalesh Singh <kaleshsingh@google.com>
Date: Tue, 27 May 2025 21:08:21 -0700
Subject: [PATCH] Revert "UPSTREAM: mm: page_alloc: fix highatomic typing in
 multi-block buddies"

This reverts commit b9e2be445ad4b2df6192388c19c3304b148b0364.

Change-Id: Iffcd9077371ecf2705acd742a2b86d25efa94dd7
Bug: 420771453
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
---
 mm/page_alloc.c | 50 ++++++++++++++++---------------------------------
 1 file changed, 16 insertions(+), 34 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 162c6e24e526..5b8e6118a57c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2174,12 +2174,10 @@ int find_suitable_fallback(struct free_area *area, unsigned int order,
 }
 
 /*
- * Reserve the pageblock(s) surrounding an allocation request for
- * exclusive use of high-order atomic allocations if there are no
- * empty page blocks that contain a page with a suitable order
+ * Reserve a pageblock for exclusive use of high-order atomic allocations if
+ * there are no empty page blocks that contain a page with a suitable order
  */
-static void reserve_highatomic_pageblock(struct page *page, int order,
-					 struct zone *zone)
+static void reserve_highatomic_pageblock(struct page *page, struct zone *zone)
 {
 	int mt;
 	unsigned long max_managed, flags;
@@ -2209,17 +2207,10 @@ static void reserve_highatomic_pageblock(struct page *page, int order,
 	/* Yoink! */
 	mt = get_pageblock_migratetype(page);
 	/* Only reserve normal pageblocks (i.e., they can merge with others) */
-	if (!migratetype_is_mergeable(mt))
-		goto out_unlock;
-
-	if (order < pageblock_order) {
-		if (move_freepages_block(zone, page, mt, MIGRATE_HIGHATOMIC) == -1)
-			goto out_unlock;
-		zone->nr_reserved_highatomic += pageblock_nr_pages;
-	} else {
-		change_pageblock_range(page, order, MIGRATE_HIGHATOMIC);
-		zone->nr_reserved_highatomic += 1 << order;
-	}
+	if (migratetype_is_mergeable(mt))
+		if (move_freepages_block(zone, page, mt,
+					 MIGRATE_HIGHATOMIC) != -1)
+			zone->nr_reserved_highatomic += pageblock_nr_pages;
 
 out_unlock:
 	spin_unlock_irqrestore(&zone->lock, flags);
@@ -2231,7 +2222,7 @@ out_unlock:
  * intense memory pressure but failed atomic allocations should be easier
  * to recover from than an OOM.
  *
- * If @force is true, try to unreserve pageblocks even though highatomic
+ * If @force is true, try to unreserve a pageblock even though highatomic
  * pageblock is exhausted.
  */
 static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
@@ -2279,7 +2270,6 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
 			 * adjust the count once.
 			 */
 			if (is_migrate_highatomic(mt)) {
-				unsigned long size;
 				/*
 				 * It should never happen but changes to
 				 * locking could inadvertently allow a per-cpu
@@ -2287,9 +2277,9 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
 				 * while unreserving so be safe and watch for
 				 * underflows.
 				 */
-				size = max(pageblock_nr_pages, 1UL << order);
-				size = min(size, zone->nr_reserved_highatomic);
-				zone->nr_reserved_highatomic -= size;
+				zone->nr_reserved_highatomic -= min(
+						pageblock_nr_pages,
+						zone->nr_reserved_highatomic);
 			}
 
 			/*
@@ -2301,19 +2291,11 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac,
 			 * of pageblocks that cannot be completely freed
 			 * may increase.
 			 */
-			if (order < pageblock_order)
-				ret = move_freepages_block(zone, page, mt,
-							   ac->migratetype);
-			else {
-				move_to_free_list(page, zone, order, mt,
-						  ac->migratetype);
-				change_pageblock_range(page, order,
-						       ac->migratetype);
-				ret = 1;
-			}
+			ret = move_freepages_block(zone, page, mt,
+						   ac->migratetype);
 			/*
-			 * Reserving the block(s) already succeeded,
-			 * so this should not fail on zone boundaries.
+			 * Reserving this block already succeeded, so this should
+			 * not fail on zone boundaries.
 			 */
 			WARN_ON_ONCE(ret == -1);
 			if (ret > 0) {
@@ -3605,7 +3587,7 @@ try_this_zone:
 			 * if the pageblock should be reserved for the future
 			 */
 			if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
-				reserve_highatomic_pageblock(page, order, zone);
+				reserve_highatomic_pageblock(page, zone);
 
 			return page;
 		} else {