mm/various: give up if pte_offset_map[_lock]() fails

Following the examples of nearby code, various functions can just give up
if pte_offset_map() or pte_offset_map_lock() fails.  And there's no need
for a preliminary pmd_trans_unstable() or other such check, since such
cases are now safely handled inside.

Link: https://lkml.kernel.org/r/7b9bd85d-1652-cbf2-159d-f503b45e5b@google.comSigned-off-by: Hugh Dickins <hughd@google.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/gup.c

@@ -545,10 +545,10 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
 	if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
 			 (FOLL_PIN | FOLL_GET)))
 		return ERR_PTR(-EINVAL);
-	if (unlikely(pmd_bad(*pmd)))
-		return no_page_table(vma, flags);
 
 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+	if (!ptep)
+		return no_page_table(vma, flags);
 	pte = *ptep;
 	if (!pte_present(pte))
 		goto no_page;
@@ -852,8 +852,9 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
 	pmd = pmd_offset(pud, address);
 	if (!pmd_present(*pmd))
 		return -EFAULT;
-	VM_BUG_ON(pmd_trans_huge(*pmd));
 	pte = pte_offset_map(pmd, address);
+	if (!pte)
+		return -EFAULT;
 	if (pte_none(*pte))
 		goto unmap;
 	*vma = get_gate_vma(mm);
@@ -2468,6 +2469,8 @@ static int gup_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
 	pte_t *ptep, *ptem;
 
 	ptem = ptep = pte_offset_map(&pmd, addr);
+	if (!ptep)
+		return 0;
 	do {
 		pte_t pte = ptep_get_lockless(ptep);
 		struct page *page;

mm/ksm.c

@@ -431,10 +431,9 @@ static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long nex
 	pte_t *pte;
 	int ret;
 
-	if (pmd_leaf(*pmd) || !pmd_present(*pmd))
-		return 0;
-
 	pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
+	if (!pte)
+		return 0;
 	if (pte_present(*pte)) {
 		page = vm_normal_page(walk->vma, addr, *pte);
 	} else if (!pte_none(*pte)) {
@@ -1203,6 +1202,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
 	mmu_notifier_invalidate_range_start(&range);
 
 	ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
+	if (!ptep)
+		goto out_mn;
 	if (!pte_same(*ptep, orig_pte)) {
 		pte_unmap_unlock(ptep, ptl);
 		goto out_mn;

mm/memcontrol.c

@@ -6021,9 +6021,9 @@ static int mem_cgroup_count_precharge_pte_range(pmd_t *pmd,
 		return 0;
 	}
 
-	if (pmd_trans_unstable(pmd))
-		return 0;
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+	if (!pte)
+		return 0;
 	for (; addr != end; pte++, addr += PAGE_SIZE)
 		if (get_mctgt_type(vma, addr, *pte, NULL))
 			mc.precharge++;	/* increment precharge temporarily */
@@ -6241,10 +6241,10 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 		return 0;
 	}
 
-	if (pmd_trans_unstable(pmd))
-		return 0;
 retry:
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+	if (!pte)
+		return 0;
 	for (; addr != end; addr += PAGE_SIZE) {
 		pte_t ptent = *(pte++);
 		bool device = false;

mm/memory-failure.c

@@ -405,6 +405,8 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
 	if (pmd_devmap(*pmd))
 		return PMD_SHIFT;
 	pte = pte_offset_map(pmd, address);
+	if (!pte)
+		return 0;
 	if (pte_present(*pte) && pte_devmap(*pte))
 		ret = PAGE_SHIFT;
 	pte_unmap(pte);
@@ -791,11 +793,11 @@ static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
 		goto out;
 	}
 
-	if (pmd_trans_unstable(pmdp))
-		goto out;
-
 	mapped_pte = ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp,
 						addr, &ptl);
+	if (!ptep)
+		goto out;
+
 	for (; addr != end; ptep++, addr += PAGE_SIZE) {
 		ret = check_hwpoisoned_entry(*ptep, addr, PAGE_SHIFT,
 					     hwp->pfn, &hwp->tk);

mm/migrate.c

@@ -305,6 +305,9 @@ void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 	swp_entry_t entry;
 
 	ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+	if (!ptep)
+		return;
+
 	pte = *ptep;
 	pte_unmap(ptep);