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Date:   Thu, 2 Nov 2023 13:39:03 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     kernel test robot <lkp@intel.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        oe-kbuild-all@lists.linux.dev,
        Linux Memory Management List <linux-mm@kvack.org>,
        maple-tree@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/12] maple_tree: Separate ma_state node from status.
Message-ID: <20231102173903.f4uizdrh3shj4b27@revolver>
Mail-Followup-To: "Liam R. Howlett" <Liam.Howlett@Oracle.com>,
        kernel test robot <lkp@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        oe-kbuild-all@lists.linux.dev,
        Linux Memory Management List <linux-mm@kvack.org>,
        maple-tree@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20231101171629.3612299-9-Liam.Howlett@oracle.com>
 <202311021622.6KoUHJP7-lkp@intel.com>
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* kernel test robot <lkp@intel.com> [231102 04:43]:
> Hi Liam,
>=20
> kernel test robot noticed the following build warnings:
>=20
> [auto build test WARNING on akpm-mm/mm-everything]
> [also build test WARNING on linus/master v6.6 next-20231102]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>=20
> url:    https://github.com/intel-lab-lkp/linux/commits/Liam-R-Howlett/map=
le_tree-Remove-unnecessary-default-labels-from-switch-statements/20231102-0=
33618
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-ev=
erything
> patch link:    https://lore.kernel.org/r/20231101171629.3612299-9-Liam.Ho=
wlett%40oracle.com
> patch subject: [PATCH 08/12] maple_tree: Separate ma_state node from stat=
us.
> config: arc-randconfig-001-20231102 (https://download.01.org/0day-ci/arch=
ive/20231102/202311021622.6KoUHJP7-lkp@intel.com/config)
> compiler: arceb-elf-gcc (GCC) 13.2.0
> reproduce (this is a W=3D1 build): (https://download.01.org/0day-ci/archi=
ve/20231102/202311021622.6KoUHJP7-lkp@intel.com/reproduce)
>=20
> If you fix the issue in a separate patch/commit (i.e. not just a new vers=
ion 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/202311021622.6KoUHJP7-lkp=
@intel.com/
>=20
> All warnings (new ones prefixed by >>):
>=20
>    drivers/base/regmap/regcache-maple.c: In function 'regcache_maple_drop=
':
>    drivers/base/regmap/regcache-maple.c:113:23: warning: 'lower_index' is=
 used uninitialized [-Wuninitialized]
>      113 |         unsigned long lower_index, lower_last;
>          |                       ^~~~~~~~~~~
>    drivers/base/regmap/regcache-maple.c:113:36: warning: 'lower_last' is =
used uninitialized [-Wuninitialized]
>      113 |         unsigned long lower_index, lower_last;
>          |                                    ^~~~~~~~~~
> >> drivers/base/regmap/regcache-maple.c:114:23: warning: 'upper_index' is=
 used uninitialized [-Wuninitialized]
>      114 |         unsigned long upper_index, upper_last;
>          |                       ^~~~~~~~~~~
> >> drivers/base/regmap/regcache-maple.c:114:36: warning: 'upper_last' is =
used uninitialized [-Wuninitialized]
>      114 |         unsigned long upper_index, upper_last;
>          |                                    ^~~~~~~~~~
>=20

From the above git blame, I can see that I didn't write any of this.
How did the bot blame my commits?  It's interesting because it cannot be
randomly selecting the author of the data structure being used..

Also, I don't see how the bot is correct.  Did you upgrade your bots GCC
and this is a false positive?


>=20
> vim +/upper_index +114 drivers/base/regmap/regcache-maple.c
>=20
> f033c26de5a5734 Mark Brown    2023-03-30  106 =20
> f033c26de5a5734 Mark Brown    2023-03-30  107  static int regcache_maple_=
drop(struct regmap *map, unsigned int min,
> f033c26de5a5734 Mark Brown    2023-03-30  108  			       unsigned int max=
)
> f033c26de5a5734 Mark Brown    2023-03-30  109  {
> f033c26de5a5734 Mark Brown    2023-03-30  110  	struct maple_tree *mt =3D=
 map->cache;
> f033c26de5a5734 Mark Brown    2023-03-30  111  	MA_STATE(mas, mt, min, ma=
x);
> f033c26de5a5734 Mark Brown    2023-03-30  112  	unsigned long *entry, *lo=
wer, *upper;
> f033c26de5a5734 Mark Brown    2023-03-30  113  	unsigned long lower_index=
, lower_last;
> f033c26de5a5734 Mark Brown    2023-03-30 @114  	unsigned long upper_index=
, upper_last;
> f033c26de5a5734 Mark Brown    2023-03-30  115  	int ret;
> f033c26de5a5734 Mark Brown    2023-03-30  116 =20
> f033c26de5a5734 Mark Brown    2023-03-30  117  	lower =3D NULL;

lower is null..

> f033c26de5a5734 Mark Brown    2023-03-30  118  	upper =3D NULL;
> f033c26de5a5734 Mark Brown    2023-03-30  119 =20
> f033c26de5a5734 Mark Brown    2023-03-30  120  	mas_lock(&mas);
> f033c26de5a5734 Mark Brown    2023-03-30  121 =20
> f033c26de5a5734 Mark Brown    2023-03-30  122  	mas_for_each(&mas, entry,=
 max) {
> f033c26de5a5734 Mark Brown    2023-03-30  123  		/*
> f033c26de5a5734 Mark Brown    2023-03-30  124  		 * This is safe because =
the regmap lock means the
> f033c26de5a5734 Mark Brown    2023-03-30  125  		 * Maple lock is redunda=
nt, but we need to take it due
> f033c26de5a5734 Mark Brown    2023-03-30  126  		 * to lockdep asserts in=
 the maple tree code.
> f033c26de5a5734 Mark Brown    2023-03-30  127  		 */
> f033c26de5a5734 Mark Brown    2023-03-30  128  		mas_unlock(&mas);
> f033c26de5a5734 Mark Brown    2023-03-30  129 =20
> f033c26de5a5734 Mark Brown    2023-03-30  130  		/* Do we need to save an=
y of this entry? */
> f033c26de5a5734 Mark Brown    2023-03-30  131  		if (mas.index < min) {
> f033c26de5a5734 Mark Brown    2023-03-30  132  			lower_index =3D mas.ind=
ex;
> f033c26de5a5734 Mark Brown    2023-03-30  133  			lower_last =3D min -1;
> f033c26de5a5734 Mark Brown    2023-03-30  134 =20
> f033c26de5a5734 Mark Brown    2023-03-30  135  			lower =3D kmemdup(entry=
, ((min - mas.index) *
> f033c26de5a5734 Mark Brown    2023-03-30  136  						sizeof(unsigned long=
)),
> b0393e1fe40e962 Guenter Roeck 2023-07-20  137  					map->alloc_flags);

Lower is only ever set here.. but lower_index/lower_last are also set
here..

> f033c26de5a5734 Mark Brown    2023-03-30  138  			if (!lower) {
> f033c26de5a5734 Mark Brown    2023-03-30  139  				ret =3D -ENOMEM;
> 451941ac1ee2be1 Mark Brown    2023-04-03  140  				goto out_unlocked;
> f033c26de5a5734 Mark Brown    2023-03-30  141  			}
> f033c26de5a5734 Mark Brown    2023-03-30  142  		}
> f033c26de5a5734 Mark Brown    2023-03-30  143 =20
> f033c26de5a5734 Mark Brown    2023-03-30  144  		if (mas.last > max) {
> f033c26de5a5734 Mark Brown    2023-03-30  145  			upper_index =3D max + 1=
;
> f033c26de5a5734 Mark Brown    2023-03-30  146  			upper_last =3D mas.last=
;
> f033c26de5a5734 Mark Brown    2023-03-30  147 =20
> f033c26de5a5734 Mark Brown    2023-03-30  148  			upper =3D kmemdup(&entr=
y[max + 1],
> f033c26de5a5734 Mark Brown    2023-03-30  149  					((mas.last - max) *
> f033c26de5a5734 Mark Brown    2023-03-30  150  					 sizeof(unsigned long=
)),
> b0393e1fe40e962 Guenter Roeck 2023-07-20  151  					map->alloc_flags);
> f033c26de5a5734 Mark Brown    2023-03-30  152  			if (!upper) {
> f033c26de5a5734 Mark Brown    2023-03-30  153  				ret =3D -ENOMEM;
> 451941ac1ee2be1 Mark Brown    2023-04-03  154  				goto out_unlocked;
> f033c26de5a5734 Mark Brown    2023-03-30  155  			}
> f033c26de5a5734 Mark Brown    2023-03-30  156  		}
> f033c26de5a5734 Mark Brown    2023-03-30  157 =20
> f033c26de5a5734 Mark Brown    2023-03-30  158  		kfree(entry);
> f033c26de5a5734 Mark Brown    2023-03-30  159  		mas_lock(&mas);
> f033c26de5a5734 Mark Brown    2023-03-30  160  		mas_erase(&mas);
> f033c26de5a5734 Mark Brown    2023-03-30  161 =20
> f033c26de5a5734 Mark Brown    2023-03-30  162  		/* Insert new nodes with=
 the saved data */
> f033c26de5a5734 Mark Brown    2023-03-30  163  		if (lower) {

Only used if lower isn't NULL, so we know lower_index and lower_last are
set.

> f033c26de5a5734 Mark Brown    2023-03-30  164  			mas_set_range(&mas, low=
er_index, lower_last);
> b0393e1fe40e962 Guenter Roeck 2023-07-20  165  			ret =3D mas_store_gfp(&=
mas, lower, map->alloc_flags);
> f033c26de5a5734 Mark Brown    2023-03-30  166  			if (ret !=3D 0)
> f033c26de5a5734 Mark Brown    2023-03-30  167  				goto out;
> f033c26de5a5734 Mark Brown    2023-03-30  168  			lower =3D NULL;

lower is reset for the next loop.

> f033c26de5a5734 Mark Brown    2023-03-30  169  		}
> f033c26de5a5734 Mark Brown    2023-03-30  170 =20
> f033c26de5a5734 Mark Brown    2023-03-30  171  		if (upper) {
> f033c26de5a5734 Mark Brown    2023-03-30  172  			mas_set_range(&mas, upp=
er_index, upper_last);
> b0393e1fe40e962 Guenter Roeck 2023-07-20  173  			ret =3D mas_store_gfp(&=
mas, upper, map->alloc_flags);
> f033c26de5a5734 Mark Brown    2023-03-30  174  			if (ret !=3D 0)
> f033c26de5a5734 Mark Brown    2023-03-30  175  				goto out;
> f033c26de5a5734 Mark Brown    2023-03-30  176  			upper =3D NULL;
> f033c26de5a5734 Mark Brown    2023-03-30  177  		}
> f033c26de5a5734 Mark Brown    2023-03-30  178  	}
> f033c26de5a5734 Mark Brown    2023-03-30  179 =20
> f033c26de5a5734 Mark Brown    2023-03-30  180  out:
> f033c26de5a5734 Mark Brown    2023-03-30  181  	mas_unlock(&mas);
> 451941ac1ee2be1 Mark Brown    2023-04-03  182  out_unlocked:
> f033c26de5a5734 Mark Brown    2023-03-30  183  	kfree(lower);
> f033c26de5a5734 Mark Brown    2023-03-30  184  	kfree(upper);
> f033c26de5a5734 Mark Brown    2023-03-30  185 =20
> f033c26de5a5734 Mark Brown    2023-03-30  186  	return ret;
> f033c26de5a5734 Mark Brown    2023-03-30  187  }
> f033c26de5a5734 Mark Brown    2023-03-30  188 =20
>=20
> --=20
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki