Hi Waiman, I love your patch! Perhaps something to improve: [auto build test WARNING on axboe-block/for-next] [also build test WARNING on linus/master next-20220601] [cannot apply to v5.18] [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] url: https://github.com/intel-lab-lkp/linux/commits/Waiman-Long/blk-cgroup-Optimize-blkcg_rstat_flush/20220602-052441 base: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next config: x86_64-randconfig-a012 (https://download.01.org/0day-ci/archive/20220602/202206021418.wpJNbe3g-lkp@xxxxxxxxx/config) compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project c825abd6b0198fb088d9752f556a70705bc99dfd) 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://github.com/intel-lab-lkp/linux/commit/3f979cef411e5d5512b725753034b02f3b7baf44 git remote add linux-review https://github.com/intel-lab-lkp/linux git fetch --no-tags linux-review Waiman-Long/blk-cgroup-Optimize-blkcg_rstat_flush/20220602-052441 git checkout 3f979cef411e5d5512b725753034b02f3b7baf44 # 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=x86_64 SHELL=/bin/bash If you fix the issue, kindly add following tag where applicable Reported-by: kernel test robot <lkp@xxxxxxxxx> All warnings (new ones prefixed by >>): >> block/blk-cgroup.c:1255:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] if (!blkcg->lhead) ^~~~~~~~~~~~~ block/blk-cgroup.c:1306:9: note: uninitialized use occurs here return ret; ^~~ block/blk-cgroup.c:1255:2: note: remove the 'if' if its condition is always false if (!blkcg->lhead) ^~~~~~~~~~~~~~~~~~ block/blk-cgroup.c:1239:33: note: initialize the variable 'ret' to silence this warning struct cgroup_subsys_state *ret; ^ = NULL 1 warning generated. vim +1255 block/blk-cgroup.c 1234 1235 static struct cgroup_subsys_state * 1236 blkcg_css_alloc(struct cgroup_subsys_state *parent_css) 1237 { 1238 struct blkcg *blkcg; 1239 struct cgroup_subsys_state *ret; 1240 int i; 1241 1242 mutex_lock(&blkcg_pol_mutex); 1243 1244 if (!parent_css) { 1245 blkcg = &blkcg_root; 1246 } else { 1247 blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL); 1248 if (!blkcg) { 1249 ret = ERR_PTR(-ENOMEM); 1250 goto unlock; 1251 } 1252 } 1253 1254 blkcg->lhead = alloc_percpu_gfp(struct llist_head, GFP_KERNEL); > 1255 if (!blkcg->lhead) 1256 goto free_blkcg; 1257 init_blkcg_llists(blkcg); 1258 1259 for (i = 0; i < BLKCG_MAX_POLS ; i++) { 1260 struct blkcg_policy *pol = blkcg_policy[i]; 1261 struct blkcg_policy_data *cpd; 1262 1263 /* 1264 * If the policy hasn't been attached yet, wait for it 1265 * to be attached before doing anything else. Otherwise, 1266 * check if the policy requires any specific per-cgroup 1267 * data: if it does, allocate and initialize it. 1268 */ 1269 if (!pol || !pol->cpd_alloc_fn) 1270 continue; 1271 1272 cpd = pol->cpd_alloc_fn(GFP_KERNEL); 1273 if (!cpd) { 1274 ret = ERR_PTR(-ENOMEM); 1275 goto free_pd_blkcg; 1276 } 1277 blkcg->cpd[i] = cpd; 1278 cpd->blkcg = blkcg; 1279 cpd->plid = i; 1280 if (pol->cpd_init_fn) 1281 pol->cpd_init_fn(cpd); 1282 } 1283 1284 spin_lock_init(&blkcg->lock); 1285 refcount_set(&blkcg->online_pin, 1); 1286 INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_NOWAIT | __GFP_NOWARN); 1287 INIT_HLIST_HEAD(&blkcg->blkg_list); 1288 #ifdef CONFIG_CGROUP_WRITEBACK 1289 INIT_LIST_HEAD(&blkcg->cgwb_list); 1290 #endif 1291 list_add_tail(&blkcg->all_blkcgs_node, &all_blkcgs); 1292 1293 mutex_unlock(&blkcg_pol_mutex); 1294 return &blkcg->css; 1295 1296 free_pd_blkcg: 1297 for (i--; i >= 0; i--) 1298 if (blkcg->cpd[i]) 1299 blkcg_policy[i]->cpd_free_fn(blkcg->cpd[i]); 1300 free_percpu(blkcg->lhead); 1301 free_blkcg: 1302 if (blkcg != &blkcg_root) 1303 kfree(blkcg); 1304 unlock: 1305 mutex_unlock(&blkcg_pol_mutex); 1306 return ret; 1307 } 1308 -- 0-DAY CI Kernel Test Service https://01.org/lkp
