Hello Domenico Cerasuolo,
The patch 7c967f267b1d: "selftests: cgroup: add test_zswap with no
kmem bypass test" from Jun 21, 2023 (linux-next), leads to the
following Smatch static checker warning:
tools/testing/selftests/cgroup/test_zswap.c:211 test_no_kmem_bypass()
warn: unsigned 'stored_pages' is never less than zero.
./tools/testing/selftests/cgroup/test_zswap.c
197 /* Try to wakeup kswapd and let it push child memory to zswap */
198 set_min_free_kb(min_free_kb_high);
199 for (int i = 0; i < 20; i++) {
200 size_t stored_pages;
201 char *trigger_allocation = malloc(trigger_allocation_size);
202
203 if (!trigger_allocation)
204 break;
205 for (int i = 0; i < trigger_allocation_size; i += 4095)
206 trigger_allocation[i] = 'b';
207 usleep(100000);
208 free(trigger_allocation);
209 if (get_zswap_stored_pages(&stored_pages))
210 break;
--> 211 if (stored_pages < 0)
size_t can't be negative. Is there any reason to check this even?
212 break;
213 /* If memory was pushed to zswap, verify it belongs to memcg */
214 if (stored_pages > stored_pages_threshold) {
215 int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped ");
216 int delta = stored_pages * 4096 - zswapped;
217 int result_ok = delta < stored_pages * 4096 / 4;
218
219 ret = result_ok ? KSFT_PASS : KSFT_FAIL;
220 break;
221 }
222 }
223
224 kill(child_pid, SIGTERM);
regards,
dan carpenter
