On Mon, 09 May 2022, Miaohe Lin wrote:
> Use flags of si directly to check SWP_STABLE_WRITES to avoid possible
> READ_ONCE and thus save some cpu cycles.
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 9c3e7e6ac202..89dd15504f3d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3892,7 +3892,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> */
> exclusive = true;
> } else if (exclusive && PageWriteback(page) &&
> - (swp_swap_info(entry)->flags & SWP_STABLE_WRITES)) {
> + (si->flags & SWP_STABLE_WRITES)) {
Should this have a data_race() annotation. Other bit-tests of si->flags
do because scan_swap_map_slots can update it asynchronously, but we know
that won't matter in practice.
Thanks,
NeilBrown
> /*
> * This is tricky: not all swap backends support
> * concurrent page modifications while under writeback.
> --
> 2.23.0
>
>
