[linux-next:master 9762/11953] mm/page_vma_mapped.c:246 page_vma_mapped_walk() warn: always true condition '(pvmw->nr_pages >= (1 << ( - (12)))) => (0-u64max >= 0)'

kernel test robot
2022-03-13T03:01:54Z

tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head: 71941773e143369a73c9c4a3b62fbb60736a1182
commit: b786e44a4dbfe64476e7120ec7990b89a37be37d [9762/11953] mm: Convert page_vma_mapped_walk to work on PFNs
config: riscv-randconfig-m031-20220312 (https://download.01.org/0day-ci/archive/20220313/202203131056.WINF40Gt-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 11.2.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

smatch warnings:
mm/page_vma_mapped.c:246 page_vma_mapped_walk() warn: always true condition '(pvmw->nr_pages >= (1 << ( - (12)))) => (0-u64max >= 0)'

vim +246 mm/page_vma_mapped.c

126
127 /**
128 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
129 * @pvmw->address
130 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
131 * must be set. pmd, pte and ptl must be NULL.
132 *
133 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
134 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
135 * adjusted if needed (for PTE-mapped THPs).
136 *
137 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
138 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
139 * a loop to find all PTEs that map the THP.
140 *
141 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
142 * regardless of which page table level the page is mapped at. @pvmw->pmd is
143 * NULL.
144 *
145 * Returns false if there are no more page table entries for the page in
146 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
147 *
148 * If you need to stop the walk before page_vma_mapped_walk() returned false,
149 * use page_vma_mapped_walk_done(). It will do the housekeeping.
150 */
151 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
152 {
153 struct vm_area_struct *vma = pvmw->vma;
154 struct mm_struct *mm = vma->vm_mm;
155 unsigned long end;
156 pgd_t *pgd;
157 p4d_t *p4d;
158 pud_t *pud;
159 pmd_t pmde;
160
161 /* The only possible pmd mapping has been handled on last iteration */
162 if (pvmw->pmd && !pvmw->pte)
163 return not_found(pvmw);
164
165 if (unlikely(is_vm_hugetlb_page(vma))) {
166 unsigned long size = pvmw->nr_pages * PAGE_SIZE;
167 /* The only possible mapping was handled on last iteration */
168 if (pvmw->pte)
169 return not_found(pvmw);
170
171 /* when pud is not present, pte will be NULL */
172 pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
173 if (!pvmw->pte)
174 return false;
175
176 pvmw->ptl = huge_pte_lockptr(size_to_hstate(size), mm,
177 pvmw->pte);
178 spin_lock(pvmw->ptl);
179 if (!check_pte(pvmw))
180 return not_found(pvmw);
181 return true;
182 }
183
184 end = vma_address_end(pvmw);
185 if (pvmw->pte)
186 goto next_pte;
187 restart:
188 do {
189 pgd = pgd_offset(mm, pvmw->address);
190 if (!pgd_present(*pgd)) {
191 step_forward(pvmw, PGDIR_SIZE);
192 continue;
193 }
194 p4d = p4d_offset(pgd, pvmw->address);
195 if (!p4d_present(*p4d)) {
196 step_forward(pvmw, P4D_SIZE);
197 continue;
198 }
199 pud = pud_offset(p4d, pvmw->address);
200 if (!pud_present(*pud)) {
201 step_forward(pvmw, PUD_SIZE);
202 continue;
203 }
204
205 pvmw->pmd = pmd_offset(pud, pvmw->address);
206 /*
207 * Make sure the pmd value isn't cached in a register by the
208 * compiler and used as a stale value after we've observed a
209 * subsequent update.
210 */
211 pmde = READ_ONCE(*pvmw->pmd);
212
213 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
214 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
215 pmde = *pvmw->pmd;
216 if (likely(pmd_trans_huge(pmde))) {
217 if (pvmw->flags & PVMW_MIGRATION)
218 return not_found(pvmw);
219 if (!check_pmd(pmd_pfn(pmde), pvmw))
220 return not_found(pvmw);
221 return true;
222 }
223 if (!pmd_present(pmde)) {
224 swp_entry_t entry;
225
226 if (!thp_migration_supported() ||
227 !(pvmw->flags & PVMW_MIGRATION))
228 return not_found(pvmw);
229 entry = pmd_to_swp_entry(pmde);
230 if (!is_migration_entry(entry) ||
231 !check_pmd(swp_offset(entry), pvmw))
232 return not_found(pvmw);
233 return true;
234 }
235 /* THP pmd was split under us: handle on pte level */
236 spin_unlock(pvmw->ptl);
237 pvmw->ptl = NULL;
238 } else if (!pmd_present(pmde)) {
239 /*
240 * If PVMW_SYNC, take and drop THP pmd lock so that we
241 * cannot return prematurely, while zap_huge_pmd() has
242 * cleared *pmd but not decremented compound_mapcount().
243 */
244 if ((pvmw->flags & PVMW_SYNC) &&
245 transparent_hugepage_active(vma) &&
> 246 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
247 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
248
249 spin_unlock(ptl);
250 }
251 step_forward(pvmw, PMD_SIZE);
252 continue;
253 }
254 if (!map_pte(pvmw))
255 goto next_pte;
256 this_pte:
257 if (check_pte(pvmw))
258 return true;
259 next_pte:
260 do {
261 pvmw->address += PAGE_SIZE;
262 if (pvmw->address >= end)
263 return not_found(pvmw);
264 /* Did we cross page table boundary? */
265 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
266 if (pvmw->ptl) {
267 spin_unlock(pvmw->ptl);
268 pvmw->ptl = NULL;
269 }
270 pte_unmap(pvmw->pte);
271 pvmw->pte = NULL;
272 goto restart;
273 }
274 pvmw->pte++;
275 if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
276 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
277 spin_lock(pvmw->ptl);
278 }
279 } while (pte_none(*pvmw->pte));
280
281 if (!pvmw->ptl) {
282 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
283 spin_lock(pvmw->ptl);
284 }
285 goto this_pte;
286 } while (pvmw->address < end);
287
288 return false;
289 }
290

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