Messages in this thread | | | From | "NeilBrown" <> | Subject | Re: [PATCH 09/15] mm/swap: avoid calling swp_swap_info when try to check SWP_STABLE_WRITES | Date | Tue, 10 May 2022 10:28:04 +1000 |
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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@huawei.com> > --- > 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 > >
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