linux-kernel - [PATCH V2] mm/hugetlb: Ensure adequate CMA areas available for hugetlb

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Message-Id: <20240215043405.2379295-1-anshuman.khandual@arm.com>
Date: Thu, 15 Feb 2024 10:04:05 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-mm@...ck.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Muchun Song <muchun.song@...ux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH V2] mm/hugetlb: Ensure adequate CMA areas available for hugetlb_cma[]

HugeTLB CMA area array is being created for possible MAX_NUMNODES without
ensuring corresponding MAX_CMA_AREAS support in CMA. This fails the build
for such scenarios indicating need for CONFIG_CMA_AREAS adjustment.

Cc: Muchun Song <muchun.song@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
This patch applies on v6.8-rc4

Changes in V2:

- Replaced VM_WARN_ON() with BUILD_BUG_ON() per Andrew

Changes in V1:

https://lore.kernel.org/all/20240209065036.1412670-1-anshuman.khandual@arm.com/

 mm/hugetlb.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ed1581b670d4..30dc02e19616 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7743,6 +7743,13 @@ void __init hugetlb_cma_reserve(int order)
 	}
 
 	reserved = 0;
+
+	/*
+	 * There needs to be enough MAX_CMA_AREAS to accommodate
+	 * MAX_NUMNODES heap areas being created here. Otherwise
+	 * adjust CONFIG_CMA_AREAS as required.
+	 */
+	BUILD_BUG_ON(MAX_CMA_AREAS < MAX_NUMNODES);
 	for_each_online_node(nid) {
 		int res;
 		char name[CMA_MAX_NAME];
-- 
2.25.1