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:228 test_no_kmem_bypass()
error: uninitialized symbol 'test_group'.
./tools/testing/selftests/cgroup/test_zswap.c
148 static int test_no_kmem_bypass(const char *root)
149 {
150 size_t min_free_kb_high, min_free_kb_low, min_free_kb_original;
151 struct no_kmem_bypass_child_args *values;
152 size_t trigger_allocation_size;
153 int wait_child_iteration = 0;
154 long stored_pages_threshold;
155 struct sysinfo sys_info;
156 int ret = KSFT_FAIL;
157 int child_status;
158 char *test_group;
159 pid_t child_pid;
160
161 /* Read sys info and compute test values accordingly */
162 if (sysinfo(&sys_info) != 0)
163 return KSFT_FAIL;
164 if (sys_info.totalram > 5000000000)
165 return KSFT_SKIP;
166 values = mmap(0, sizeof(struct no_kmem_bypass_child_args), PROT_READ |
167 PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
168 if (values == MAP_FAILED)
169 return KSFT_FAIL;
170 if (read_min_free_kb(&min_free_kb_original))
171 return KSFT_FAIL;
172 min_free_kb_high = sys_info.totalram / 2000;
173 min_free_kb_low = sys_info.totalram / 500000;
174 values->target_alloc_bytes = (sys_info.totalram - min_free_kb_high * 1000) +
175 sys_info.totalram * 5 / 100;
176 stored_pages_threshold = sys_info.totalram / 5 / 4096;
177 trigger_allocation_size = sys_info.totalram / 20;
178
179 /* Set up test memcg */
180 if (cg_write(root, "cgroup.subtree_control", "+memory"))
181 goto out;
test_group is not initialized here. Undoing stuff which hasn't been
done is the canonical bug with "goto out;" labels.
182 test_group = cg_name(root, "kmem_bypass_test");
183 if (!test_group)
184 goto out;
185
186 /* Spawn memcg child and wait for it to allocate */
187 set_min_free_kb(min_free_kb_low);
188 if (cg_create(test_group))
test_group is allocated but not created. Is it okay to call
destroy on this path?
189 goto out;
190 values->child_allocated = false;
191 child_pid = cg_run_nowait(test_group, no_kmem_bypass_child, values);
192 if (child_pid < 0)
193 goto out;
194 while (!values->child_allocated && wait_child_iteration++ < 10000)
195 usleep(1000);
196
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)
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);
225 waitpid(child_pid, &child_status, 0);
226 out:
227 set_min_free_kb(min_free_kb_original);
--> 228 cg_destroy(test_group);
229 free(test_group);
230 return ret;
231 }
regards,
dan carpenter
