linux-kernel - [PATCH v1 1/2] powerpc/pseries/cmm: call balloon_devinfo_init() also without CONFIG_BALLOON

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Message-ID: <20251021100606.148294-2-david@redhat.com>
Date: Tue, 21 Oct 2025 12:06:05 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org,
	linuxppc-dev@...ts.ozlabs.org,
	David Hildenbrand <david@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	stable@...r.kernel.org
Subject: [PATCH v1 1/2] powerpc/pseries/cmm: call balloon_devinfo_init() also without CONFIG_BALLOON_COMPACTION

We always have to initialize the balloon_dev_info, even when compaction
is not configured in: otherwise the containing list and the lock are
left uninitialized.

Likely not many such configs exist in practice, but let's CC stable to
be sure.

This was found by code inspection.

Fixes: fe030c9b85e6 ("powerpc/pseries/cmm: Implement balloon compaction")
Cc: <stable@...r.kernel.org>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 arch/powerpc/platforms/pseries/cmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/cmm.c b/arch/powerpc/platforms/pseries/cmm.c
index 0823fa2da1516..688f5fa1c7245 100644
--- a/arch/powerpc/platforms/pseries/cmm.c
+++ b/arch/powerpc/platforms/pseries/cmm.c
@@ -550,7 +550,6 @@ static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
 
 static void cmm_balloon_compaction_init(void)
 {
-	balloon_devinfo_init(&b_dev_info);
 	b_dev_info.migratepage = cmm_migratepage;
 }
 #else /* CONFIG_BALLOON_COMPACTION */
@@ -572,6 +571,7 @@ static int cmm_init(void)
 	if (!firmware_has_feature(FW_FEATURE_CMO) && !simulate)
 		return -EOPNOTSUPP;
 
+	balloon_devinfo_init(&b_dev_info);
 	cmm_balloon_compaction_init();
 
 	rc = register_oom_notifier(&cmm_oom_nb);
-- 
2.51.0