While we released the pte lock, somebody else might faulted in this pte.
So we should check whether it's swap pte first to guard against such race
or swp_type would be unexpected. And we can also avoid some unnecessary
readahead cpu cycles possibly.
Fixes: ec560175c0b6 ("mm, swap: VMA based swap readahead")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
mm/swap_state.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 709c260d644a..3bf0d0c297bc 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -724,10 +724,10 @@ static void swap_ra_info(struct vm_fault *vmf,
{
struct vm_area_struct *vma = vmf->vma;
unsigned long ra_val;
- swp_entry_t entry;
+ swp_entry_t swap_entry;
unsigned long faddr, pfn, fpfn;
unsigned long start, end;
- pte_t *pte, *orig_pte;
+ pte_t *pte, *orig_pte, entry;
unsigned int max_win, hits, prev_win, win, left;
#ifndef CONFIG_64BIT
pte_t *tpte;
@@ -742,8 +742,13 @@ static void swap_ra_info(struct vm_fault *vmf,
faddr = vmf->address;
orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
- entry = pte_to_swp_entry(*pte);
- if ((unlikely(non_swap_entry(entry)))) {
+ entry = *pte;
+ if (unlikely(!is_swap_pte(entry))) {
+ pte_unmap(orig_pte);
+ return;
+ }
+ swap_entry = pte_to_swp_entry(entry);
+ if ((unlikely(non_swap_entry(swap_entry)))) {
pte_unmap(orig_pte);
return;
}
--
2.19.1
