The patch titled Subject: mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Nathan Chancellor nathan@kernel.org Subject: mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show() Date: Tue, 15 Jul 2025 12:56:16 -0700

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-f443... Fixes: 66790e9a735b ("mm/ksm: add sysfs knobs for advisor") Signed-off-by: Nathan Chancellor nathan@kernel.org Closes: https://github.com/ClangBuiltLinux/linux/issues/2100 Link: https://github.com/llvm/llvm-project/commit/2464313eef01c5b1edf0eccf57a32cde... [1] Cc: Chengming Zhou chengming.zhou@linux.dev Cc: David Hildenbrand david@redhat.com Cc: Stefan Roesch shr@devkernel.io Cc: xu xin xu.xin16@zte.com.cn Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/ksm.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/ksm.c~mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show +++ a/mm/ksm.c @@ -3669,10 +3669,10 @@ static ssize_t advisor_mode_show(struct { 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); } _

Patches currently in -mm which might be from nathan@kernel.org are

mm-ksm-fix-wsometimes-uninitialized-from-clang-21-in-advisor_mode_show.patch panic-add-panic_sys_info-sysctl-to-take-human-readable-string-parameter-fix.patch