From: Kairui Song <kasong@xxxxxxxxxxx>
Convert a volatile variable to more readable READ_ONCE. And this
actually avoids the code from reading the variable twice redundantly
when it races.
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
mm/swapfile.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 72e481aacd5d..ff4f3cb85232 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1836,13 +1836,13 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
pte_t *pte;
struct swap_info_struct *si;
int ret = 0;
- volatile unsigned char *swap_map;
si = swap_info[type];
pte = pte_offset_map(pmd, addr);
do {
struct folio *folio;
unsigned long offset;
+ unsigned char swp_count;
if (!is_swap_pte(*pte))
continue;
@@ -1853,7 +1853,6 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
offset = swp_offset(entry);
pte_unmap(pte);
- swap_map = &si->swap_map[offset];
folio = swap_cache_get_folio(entry, vma, addr);
if (!folio) {
struct page *page;
@@ -1870,8 +1869,10 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
folio = page_folio(page);
}
if (!folio) {
- if (*swap_map == 0 || *swap_map == SWAP_MAP_BAD)
+ swp_count = READ_ONCE(si->swap_map[offset]);
+ if (swp_count == 0 || swp_count == SWAP_MAP_BAD)
goto try_next;
+
return -ENOMEM;
}
--
2.35.2
