Re: [v4 PATCH 2/2] mm: swap: add comment for swap_vma_readahead

[Yang Shi]

On 1/2/19 11:41 PM, Huang, Ying wrote:
> Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> writes:
>
> > swap_vma_readahead()'s comment is missed, just add it.
> >
> > Cc: Huang Ying <ying.huang@xxxxxxxxx>
> > Cc: Tim Chen <tim.c.chen@xxxxxxxxx>
> > Cc: Minchan Kim <minchan@xxxxxxxxxx>
> > Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
> > ---
> >   mm/swap_state.c | 17 +++++++++++++++++
> >   1 file changed, 17 insertions(+)
> >
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 78d500e..dd8f698 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -698,6 +698,23 @@ static void swap_ra_info(struct vm_fault *vmf,
> >   	pte_unmap(orig_pte);
> >   }
> >   
> > +/**
> > + * swap_vm_readahead - swap in pages in hope we need them soon
> s/swap_vm_readahead/swap_vma_readahead/
>
> > + * @entry: swap entry of this memory
> > + * @gfp_mask: memory allocation flags
> > + * @vmf: fault information
> > + *
> > + * Returns the struct page for entry and addr, after queueing swapin.
> > + *
> > + * Primitive swap readahead code. We simply read in a few pages whoes
> > + * virtual addresses are around the fault address in the same vma.
> > + *
> > + * This has been extended to use the NUMA policies from the mm triggering
> > + * the readahead.
> What is this?  I know you copy it from swap_cluster_readahead(), but we
> have only one mm for vma readahead.

Aha, I see. Actually I was confused by this too, so just copied from 
swap_cluster_readahead.

> > + * Caller must hold down_read on the vma->vm_mm if vmf->vma is not NULL.
> Better to make it explicit that your are talking about mmap_sem?

Sure.

Thanks,
Yang

> Best Regards,
> Huang, Ying
>
> > + *
> > + */
> >   static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
> >   				       struct vm_fault *vmf)
> >   {