[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 <lkp@intel.com>]

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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