mm/swap: fix race when skipping swapcache

[thirdparty/linux.git] / mm / swapfile.c

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 556ff7347d5f04402b61cc5bd9d0d123a36dc1d5..746aa9da530255035b4624fefff862d416af836d 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3365,6 +3365,19 @@ int swapcache_prepare(swp_entry_t entry)
        return __swap_duplicate(entry, SWAP_HAS_CACHE);
 }
 
+void swapcache_clear(struct swap_info_struct *si, swp_entry_t entry)
+{
+       struct swap_cluster_info *ci;
+       unsigned long offset = swp_offset(entry);
+       unsigned char usage;
+
+       ci = lock_cluster_or_swap_info(si, offset);
+       usage = __swap_entry_free_locked(si, offset, SWAP_HAS_CACHE);
+       unlock_cluster_or_swap_info(si, ci);
+       if (!usage)
+               free_swap_slot(entry);
+}
+
 struct swap_info_struct *swp_swap_info(swp_entry_t entry)
 {
        return swap_type_to_swap_info(swp_type(entry));