diff options
| -rw-r--r-- | mm/rmap.c | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index bfcc8e3d412f..5cb970d51f0a 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1588,7 +1588,30 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, /* MADV_FREE page check */ if (!folio_test_swapbacked(folio)) { - if (!folio_test_dirty(folio)) { + int ref_count, map_count; + + /* + * Synchronize with gup_pte_range(): + * - clear PTE; barrier; read refcount + * - inc refcount; barrier; read PTE + */ + smp_mb(); + + ref_count = folio_ref_count(folio); + map_count = folio_mapcount(folio); + + /* + * Order reads for page refcount and dirty flag + * (see comments in __remove_mapping()). + */ + smp_rmb(); + + /* + * The only page refs must be one from isolation + * plus the rmap(s) (dropped by discard:). + */ + if (ref_count == 1 + map_count && + !folio_test_dirty(folio)) { /* Invalidate as we cleared the pte */ mmu_notifier_invalidate_range(mm, address, address + PAGE_SIZE); |