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-rw-r--r--mm/swapfile.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2b3a2d85e350..1155a6304119 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1232,6 +1232,11 @@ static unsigned char __swap_entry_free_locked(struct swap_info_struct *p,
* with get_swap_device() and put_swap_device(), unless the swap
* functions call get/put_swap_device() by themselves.
*
+ * Note that when only holding the PTL, swapoff might succeed immediately
+ * after freeing a swap entry. Therefore, immediately after
+ * __swap_entry_free(), the swap info might become stale and should not
+ * be touched without a prior get_swap_device().
+ *
* Check whether swap entry is valid in the swap device. If so,
* return pointer to swap_info_struct, and keep the swap entry valid
* via preventing the swap device from being swapoff, until
@@ -1609,13 +1614,19 @@ int free_swap_and_cache(swp_entry_t entry)
if (non_swap_entry(entry))
return 1;
- p = _swap_info_get(entry);
+ p = get_swap_device(entry);
if (p) {
+ if (WARN_ON(data_race(!p->swap_map[swp_offset(entry)]))) {
+ put_swap_device(p);
+ return 0;
+ }
+
count = __swap_entry_free(p, entry);
if (count == SWAP_HAS_CACHE &&
!swap_page_trans_huge_swapped(p, entry))
__try_to_reclaim_swap(p, swp_offset(entry),
TTRS_UNMAPPED | TTRS_FULL);
+ put_swap_device(p);
}
return p != NULL;
}