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mm/ksm: fix -Wsometimes-uninitialized from clang-21 in advisor_mode_show()

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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: 66790e9a73 ("mm/ksm: add sysfs knobs for advisor")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2100
Link: 2464313eef [1]
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
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>
This commit is contained in:
Nathan Chancellor 2025-07-15 12:56:16 -07:00 committed by Andrew Morton
parent d367a177e2
commit 153ad56672
1 changed files with 3 additions and 3 deletions
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6
mm/ksm.c
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@ -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);
}