mm: introduce __vm_flags_mod and use it in untrack_pfn

There are scenarios when vm_flags can be modified without exclusive
mmap_lock, such as:
- after VMA was isolated and mmap_lock was downgraded or dropped
- in exit_mmap when there are no other mm users and locking is unnecessary
Introduce __vm_flags_mod to avoid assertions when the caller takes
responsibility for the required locking.
Pass a hint to untrack_pfn to conditionally use __vm_flags_mod for
flags modification to avoid assertion.

Link: https://lkml.kernel.org/r/20230126193752.297968-7-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@google.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Peter Oskolkov <posk@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Punit Agrawal <punit.agrawal@bytedance.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 7 insertions, 6 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 4354b7987f36..ce1d84d022d3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1613,7 +1613,7 @@ void unmap_page_range(struct mmu_gather *tlb,
 static void unmap_single_vma(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long start_addr,
 		unsigned long end_addr,
-		struct zap_details *details)
+		struct zap_details *details, bool mm_wr_locked)
 {
 	unsigned long start = max(vma->vm_start, start_addr);
 	unsigned long end;
@@ -1628,7 +1628,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
 		uprobe_munmap(vma, start, end);
 
 	if (unlikely(vma->vm_flags & VM_PFNMAP))
-		untrack_pfn(vma, 0, 0);
+		untrack_pfn(vma, 0, 0, mm_wr_locked);
 
 	if (start != end) {
 		if (unlikely(is_vm_hugetlb_page(vma))) {
@@ -1675,7 +1675,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
  */
 void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
 		struct vm_area_struct *vma, unsigned long start_addr,
-		unsigned long end_addr)
+		unsigned long end_addr, bool mm_wr_locked)
 {
 	struct mmu_notifier_range range;
 	struct zap_details details = {
@@ -1689,7 +1689,8 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
 				start_addr, end_addr);
 	mmu_notifier_invalidate_range_start(&range);
 	do {
-		unmap_single_vma(tlb, vma, start_addr, end_addr, &details);
+		unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
+				 mm_wr_locked);
 	} while ((vma = mas_find(&mas, end_addr - 1)) != NULL);
 	mmu_notifier_invalidate_range_end(&range);
 }
@@ -1723,7 +1724,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
 	 * unmap 'address-end' not 'range.start-range.end' as range
 	 * could have been expanded for hugetlb pmd sharing.
 	 */
-	unmap_single_vma(&tlb, vma, address, end, details);
+	unmap_single_vma(&tlb, vma, address, end, details, false);
 	mmu_notifier_invalidate_range_end(&range);
 	tlb_finish_mmu(&tlb);
 }
@@ -2492,7 +2493,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
 
 	err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
 	if (err)
-		untrack_pfn(vma, pfn, PAGE_ALIGN(size));
+		untrack_pfn(vma, pfn, PAGE_ALIGN(size), true);
 	return err;
 }
 EXPORT_SYMBOL(remap_pfn_range);