| Message ID | 20221208180209.50845-2-ryncsn@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Clean up and fixes for swap | expand |
Kairui Song <ryncsn@gmail.com> writes: > From: Kairui Song <kasong@tencent.com> > > 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@tencent.com> LGTM, Thanks! Reviewed-by: "Huang, Ying" <ying.huang@intel.com> > --- > 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; > }
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; }