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From:   SeongJae Park <sj@kernel.org>
To:     kernel test robot <lkp@intel.com>
Cc:     SeongJae Park <sj@kernel.org>, damon@lists.linux.dev,
        llvm@lists.linux.dev, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org
Subject: Re: [sj:damon/next 26/29] mm/damon/core.c:807:3: warning: variable 'err' is used uninitialized whenever 'if' condition is false
Date:   Wed, 21 Sep 2022 17:20:41 +0000
Message-Id: <20220921172041.51621-1-sj@kernel.org>
In-Reply-To: <202209220049.dcCdIisb-lkp@intel.com>
References: 
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Hi robot,


Thank you for the report, just fixed[1] and pushed!

[1] https://git.kernel.org/sj/c/5c2a0770beeab07243ac6632a2afcf637f343806


Thanks,
SJ

On Thu, 22 Sep 2022 00:06:55 +0800 kernel test robot <lkp@intel.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git damon/next
> head:   a5f85a5de8b74931ccd564bdb63194aedc99f2a9
> commit: 71af589c839d9564a9daa6bb0af2f7f4931ea19c [26/29] mm/damon/core: separate damos application logic
> config: hexagon-randconfig-r033-20220921 (https://download.01.org/0day-ci/archive/20220922/202209220049.dcCdIisb-lkp@intel.com/config)
> compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 791a7ae1ba3efd6bca96338e10ffde557ba83920)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git/commit/?id=71af589c839d9564a9daa6bb0af2f7f4931ea19c
>         git remote add sj https://git.kernel.org/pub/scm/linux/kernel/git/sj/linux.git
>         git fetch --no-tags sj damon/next
>         git checkout 71af589c839d9564a9daa6bb0af2f7f4931ea19c
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash mm/damon/
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> mm/damon/core.c:807:3: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>                    if (c->callback.before_scheme_apply)
>                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/linux/compiler.h:56:28: note: expanded from macro 'if'
>    #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
>                               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
>    #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
>                                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    mm/damon/core.c:809:8: note: uninitialized use occurs here
>                    if (!err)
>                         ^~~
>    include/linux/compiler.h:56:47: note: expanded from macro 'if'
>    #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
>                                                  ^~~~
>    include/linux/compiler.h:58:52: note: expanded from macro '__trace_if_var'
>    #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
>                                                       ^~~~
>    mm/damon/core.c:807:3: note: remove the 'if' if its condition is always true
>                    if (c->callback.before_scheme_apply)
>                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>    include/linux/compiler.h:56:23: note: expanded from macro 'if'
>    #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
>                          ^
>    mm/damon/core.c:787:9: note: initialize the variable 'err' to silence this warning
>            int err;
>                   ^
>                    = 0
>    1 warning generated.
> 
> 
> vim +807 mm/damon/core.c
> 
> b47f2bf827d3e3 SeongJae Park 2022-09-20  779  
> 71af589c839d95 SeongJae Park 2022-09-20  780  static void damos_apply_scheme(struct damon_ctx *c, struct damon_target *t,
> 71af589c839d95 SeongJae Park 2022-09-20  781  		struct damon_region *r, struct damos *s)
> b47f2bf827d3e3 SeongJae Park 2022-09-20  782  {
> b47f2bf827d3e3 SeongJae Park 2022-09-20  783  	struct damos_quota *quota = &s->quota;
> 71af589c839d95 SeongJae Park 2022-09-20  784  	unsigned long sz = r->ar.end - r->ar.start;
> b47f2bf827d3e3 SeongJae Park 2022-09-20  785  	struct timespec64 begin, end;
> b47f2bf827d3e3 SeongJae Park 2022-09-20  786  	unsigned long sz_applied = 0;
> 71af589c839d95 SeongJae Park 2022-09-20  787  	int err;
> b47f2bf827d3e3 SeongJae Park 2022-09-20  788  
> f7d911c39cbbb8 SeongJae Park 2022-03-22  789  	if (c->ops.apply_scheme) {
> 71af589c839d95 SeongJae Park 2022-09-20  790  		if (quota->esz && quota->charged_sz + sz > quota->esz) {
> 1cd2430300594a SeongJae Park 2021-11-05  791  			sz = ALIGN_DOWN(quota->esz - quota->charged_sz,
> 2b8a248d587334 SeongJae Park 2021-11-05  792  					DAMON_MIN_REGION);
> 2b8a248d587334 SeongJae Park 2021-11-05  793  			if (!sz)
> 2b8a248d587334 SeongJae Park 2021-11-05  794  				goto update_stat;
> 2886230666fa8b SeongJae Park 2022-08-14  795  			if (sz >= r->ar.end - r->ar.start) {
> 2886230666fa8b SeongJae Park 2022-08-14  796  				pr_err("sz: %lu, region: %lu-%lu (%lu), quota: %lu, charged: %lu\n",
> 2886230666fa8b SeongJae Park 2022-08-14  797  						sz, r->ar.start,
> 2886230666fa8b SeongJae Park 2022-08-14  798  						r->ar.end, r->ar.end -
> 2886230666fa8b SeongJae Park 2022-08-14  799  						r->ar.start,
> 2886230666fa8b SeongJae Park 2022-08-14  800  						quota->esz,
> 2886230666fa8b SeongJae Park 2022-08-14  801  						quota->charged_sz);
> 2886230666fa8b SeongJae Park 2022-08-14  802  				BUG();
> 2886230666fa8b SeongJae Park 2022-08-14  803  			}
> 4ed9824346c071 Kaixu Xia     2022-08-13  804  			damon_split_region_at(t, r, sz);
> 2b8a248d587334 SeongJae Park 2021-11-05  805  		}
> 1cd2430300594a SeongJae Park 2021-11-05  806  		ktime_get_coarse_ts64(&begin);
> 5cb21aeba065d6 SeongJae Park 2022-09-20 @807  		if (c->callback.before_scheme_apply)
> 71af589c839d95 SeongJae Park 2022-09-20  808  			err = c->callback.before_scheme_apply(c, t, r, s);
> 5cb21aeba065d6 SeongJae Park 2022-09-20  809  		if (!err)
> f7d911c39cbbb8 SeongJae Park 2022-03-22  810  			sz_applied = c->ops.apply_scheme(c, t, r, s);
> 1cd2430300594a SeongJae Park 2021-11-05  811  		ktime_get_coarse_ts64(&end);
> 1cd2430300594a SeongJae Park 2021-11-05  812  		quota->total_charged_ns += timespec64_to_ns(&end) -
> 1cd2430300594a SeongJae Park 2021-11-05  813  			timespec64_to_ns(&begin);
> 2b8a248d587334 SeongJae Park 2021-11-05  814  		quota->charged_sz += sz;
> 1cd2430300594a SeongJae Park 2021-11-05  815  		if (quota->esz && quota->charged_sz >= quota->esz) {
> 50585192bc2ef9 SeongJae Park 2021-11-05  816  			quota->charge_target_from = t;
> 50585192bc2ef9 SeongJae Park 2021-11-05  817  			quota->charge_addr_from = r->ar.end + 1;
> 50585192bc2ef9 SeongJae Park 2021-11-05  818  		}
> 2b8a248d587334 SeongJae Park 2021-11-05  819  	}
> 2f0b548c9f03a7 SeongJae Park 2021-11-05  820  	if (s->action != DAMOS_STAT)
> 1f366e421c8f69 SeongJae Park 2021-11-05  821  		r->age = 0;
> 2b8a248d587334 SeongJae Park 2021-11-05  822  
> 2b8a248d587334 SeongJae Park 2021-11-05  823  update_stat:
> 0e92c2ee9f4595 SeongJae Park 2022-01-14  824  	s->stat.nr_tried++;
> 0e92c2ee9f4595 SeongJae Park 2022-01-14  825  	s->stat.sz_tried += sz;
> 0e92c2ee9f4595 SeongJae Park 2022-01-14  826  	if (sz_applied)
> 0e92c2ee9f4595 SeongJae Park 2022-01-14  827  		s->stat.nr_applied++;
> 0e92c2ee9f4595 SeongJae Park 2022-01-14  828  	s->stat.sz_applied += sz_applied;
> 1f366e421c8f69 SeongJae Park 2021-11-05  829  }
> 71af589c839d95 SeongJae Park 2022-09-20  830  
> 
> :::::: The code at line 807 was first introduced by commit
> :::::: 5cb21aeba065d632fa56295d75151d6b70a2bd1b mm/damon/core: add a DAMON callback for scheme target regions check
> 
> :::::: TO: SeongJae Park <sj@kernel.org>
> :::::: CC: SeongJae Park <sj@kernel.org>
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp