Re: [sj:damon/next 156/181] mm/damon/paddr.c:195:7: warning: variable 'matched' is used uninitialized whenever 'if' condition is false

Re: [sj:damon/next 156/181] mm/damon/paddr.c:195:7: warning: variable 'matched' is used uninitialized whenever 'if' condition is false

[SeongJae Park]

On Tue, 21 Apr 2026 03:16:29 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git damon/next
> head:   ecd4906478687820c088904becbcf3c80ded7d81
> commit: 8c863600a03e3066ce88bf8db48953176befa4c4 [156/181] mm/damon/paddr: do data_attr filtering
> config: loongarch-allmodconfig (https://download.01.org/0day-ci/archive/20260421/202604210331.wdB3yt0y-lkp@intel.com/config)
> compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260421/202604210331.wdB3yt0y-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202604210331.wdB3yt0y-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> mm/damon/paddr.c:195:7: warning: variable 'matched' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>      195 |                 if (f->type == DAMON_FILTER_TYPE_ANON) {
>          |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    mm/damon/paddr.c:203:7: note: uninitialized use occurs here
>      203 |                 if (matched)
>          |                     ^~~~~~~
>    mm/damon/paddr.c:195:3: note: remove the 'if' if its condition is always true
>      195 |                 if (f->type == DAMON_FILTER_TYPE_ANON) {
>          |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    mm/damon/paddr.c:193:15: note: initialize the variable 'matched' to silence this warning
>      193 |                 bool matched;
>          |                             ^
>          |                              = 0
>    1 warning generated.

Thank you for this report!  I just pushed below as a fix to damon/next.

'''
Author: SeongJae Park <sj@kernel.org>
Date:   Mon Apr 20 20:52:35 2026 -0700

    mm/damon/paddr: initialize 'matched' in damon_pa_tests_pass()

    Reported-by: kernel test robot <lkp@intel.com>
    Closes: https://lore.kernel.org/oe-kbuild-all/202604210331.wdB3yt0y-lkp@intel.com/
    Signed-off-by: SeongJae Park <sj@kernel.org>

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 4788abce08a50..8d49c3e944cfe 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -190,14 +190,12 @@ static bool damon_pa_tests_pass(phys_addr_t pa, struct damon_counter *c)
        bool default_pass = true;

        damon_for_each_test(t, c) {
-               bool matched;
+               bool matched = false;

                if (t->type == DAMON_TEST_TYPE_ANON) {
                        struct folio *folio = damon_get_folio(PHYS_PFN(pa));

-                       if (!folio)
-                               matched = false;
-                       else
+                       if (folio)
                                matched = folio_test_anon(folio);
                }
                if (matched)
'''


Thanks,
SJ

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