linux-kernel - [PATCH] mm/page_alloc: skip THP-sized PCP list when allocating non-CMA THP-sized page

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Date: Tue,  4 Jun 2024 17:14:20 +0800
From: yangge1116@....com
To: akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	baolin.wang@...ux.alibaba.com,
	liuzixing@...on.cn,
	yangge <yangge1116@....com>
Subject: [PATCH] mm/page_alloc: skip THP-sized PCP list when allocating non-CMA THP-sized page

From: yangge <yangge1116@....com>

Since commit 5d0a661d808f ("mm/page_alloc: use only one PCP list for
THP-sized allocations") no longer differentiates the migration type
of pages in THP-sized PCP list, it's possible to get a CMA page from
the list, in some cases, it's not acceptable, for example, allocating
a non-CMA page with PF_MEMALLOC_PIN flag returns a CMA page.

The patch forbids allocating non-CMA THP-sized page from THP-sized
PCP list to avoid the issue above.

Fixes: 5d0a661d808f ("mm/page_alloc: use only one PCP list for THP-sized allocations")
Signed-off-by: yangge <yangge1116@....com>
---
 mm/page_alloc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2e22ce5..0bdf471 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2987,10 +2987,20 @@ struct page *rmqueue(struct zone *preferred_zone,
 	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
 
 	if (likely(pcp_allowed_order(order))) {
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+		if (!IS_ENABLED(CONFIG_CMA) || alloc_flags & ALLOC_CMA ||
+						order != HPAGE_PMD_ORDER) {
+			page = rmqueue_pcplist(preferred_zone, zone, order,
+						migratetype, alloc_flags);
+			if (likely(page))
+				goto out;
+		}
+#else
 		page = rmqueue_pcplist(preferred_zone, zone, order,
 				       migratetype, alloc_flags);
 		if (likely(page))
 			goto out;
+#endif
 	}
 
 	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
-- 
2.7.4