From 153ad566724fe6f57b14f66e9726d295d22e576d Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Tue, 15 Jul 2025 12:56:16 -0700 Subject: [PATCH] mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show() After a recent change in clang to expose uninitialized warnings from const variables [1], there is a false positive warning from the if statement in advisor_mode_show(). mm/ksm.c:3687:11: error: variable 'output' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] 3687 | else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ mm/ksm.c:3690:33: note: uninitialized use occurs here 3690 | return sysfs_emit(buf, "%s\n", output); | ^~~~~~ Rewrite the if statement to implicitly make KSM_ADVISOR_NONE the else branch so that it is obvious to the compiler that ksm_advisor can only be KSM_ADVISOR_NONE or KSM_ADVISOR_SCAN_TIME due to the assignments in advisor_mode_store(). Link: https://lkml.kernel.org/r/20250715-ksm-fix-clang-21-uninit-warning-v1-1-f443feb4bfc4@kernel.org Fixes: 66790e9a735b ("mm/ksm: add sysfs knobs for advisor") Signed-off-by: Nathan Chancellor Closes: https://github.com/ClangBuiltLinux/linux/issues/2100 Link: https://github.com/llvm/llvm-project/commit/2464313eef01c5b1edf0eccf57a32cdee01472c7 [1] Acked-by: David Hildenbrand Cc: Chengming Zhou Cc: Stefan Roesch Cc: xu xin Cc: Signed-off-by: Andrew Morton --- mm/ksm.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 8583fb91ef136..a9d3e719e0899 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -3669,10 +3669,10 @@ static ssize_t advisor_mode_show(struct kobject *kobj, { const char *output; - if (ksm_advisor == KSM_ADVISOR_NONE) - output = "[none] scan-time"; - else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) + if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) output = "none [scan-time]"; + else + output = "[none] scan-time"; return sysfs_emit(buf, "%s\n", output); } -- 2.47.2