On Tue, Aug 12, 2025 at 02:55:55AM +0800, kernel test robot wrote:
Hi Dominique,
kernel test robot noticed the following build warnings:
[auto build test WARNING on 8f5ae30d69d7543eee0d70083daf4de8fe15d585]
url: https://github.com/intel-lab-lkp/linux/commits/Dominique-Martinet-via-B4-Rel... base: 8f5ae30d69d7543eee0d70083daf4de8fe15d585 patch link: https://lore.kernel.org/r/20250811-iot_iter_folio-v1-1-d9c223adf93c%40codewr... patch subject: [PATCH 1/2] iov_iter: iterate_folioq: fix handling of offset >= folio size config: i386-buildonly-randconfig-002-20250811 (https://download.01.org/0day-ci/archive/20250812/202508120250.Eooq2ydr-lkp@i...) compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250812/202508120250.Eooq2ydr-lkp@i...)
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/202508120250.Eooq2ydr-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from lib/iov_iter.c:14:
include/linux/iov_iter.h:171:7: warning: variable 'remain' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
171 | if (skip >= fsize) | ^~~~~~~~~~~~~include/linux/iov_iter.h:190:7: note: uninitialized use occurs here 190 | if (remain) | ^~~~~~ include/linux/iov_iter.h:171:3: note: remove the 'if' if its condition is always false 171 | if (skip >= fsize) | ^~~~~~~~~~~~~~~~~~ 172 | goto next; | ~~~~~~~~~ include/linux/iov_iter.h:163:22: note: initialize the variable 'remain' to silence this warning 163 | size_t part, remain, consumed; | ^ | = 0 1 warning generated.
I see this in -next now, should remain be zero initialized or is there some other fix that is needed?
vim +171 include/linux/iov_iter.h
143 144 /* 145 * Handle ITER_FOLIOQ. 146 */ 147 static __always_inline 148 size_t iterate_folioq(struct iov_iter *iter, size_t len, void *priv, void *priv2, 149 iov_step_f step) 150 { 151 const struct folio_queue *folioq = iter->folioq; 152 unsigned int slot = iter->folioq_slot; 153 size_t progress = 0, skip = iter->iov_offset; 154 155 if (slot == folioq_nr_slots(folioq)) { 156 /* The iterator may have been extended. */ 157 folioq = folioq->next; 158 slot = 0; 159 } 160 161 do { 162 struct folio *folio = folioq_folio(folioq, slot); 163 size_t part, remain, consumed; 164 size_t fsize; 165 void *base; 166 167 if (!folio) 168 break; 169 170 fsize = folioq_folio_size(folioq, slot);
171 if (skip >= fsize)
172 goto next; 173 base = kmap_local_folio(folio, skip); 174 part = umin(len, PAGE_SIZE - skip % PAGE_SIZE); 175 remain = step(base, progress, part, priv, priv2); 176 kunmap_local(base); 177 consumed = part - remain; 178 len -= consumed; 179 progress += consumed; 180 skip += consumed; 181 if (skip >= fsize) { 182 next: 183 skip = 0; 184 slot++; 185 if (slot == folioq_nr_slots(folioq) && folioq->next) { 186 folioq = folioq->next; 187 slot = 0; 188 } 189 } 190 if (remain) 191 break; 192 } while (len); 193 194 iter->folioq_slot = slot; 195 iter->folioq = folioq; 196 iter->iov_offset = skip; 197 iter->count -= progress; 198 return progress; 199 } 200
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