diff options
Diffstat (limited to 'mm/rmap.c')
| -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 6aebd1747251..3e340ee380cb 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1570,7 +1570,30 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, /* MADV_FREE page check */ if (!PageSwapBacked(page)) { - if (!PageDirty(page)) { + int ref_count, map_count; + + /* + * Synchronize with gup_pte_range(): + * - clear PTE; barrier; read refcount + * - inc refcount; barrier; read PTE + */ + smp_mb(); + + ref_count = page_ref_count(page); + map_count = page_mapcount(page); + + /* + * 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 && + !PageDirty(page)) { /* Invalidate as we cleared the pte */ mmu_notifier_invalidate_range(mm, address, address + PAGE_SIZE); |