Re: [PATCH 1/2] mm,swap: extract swap single page readahead into its own function

[Hillf Danton <hdanton@sina.com>]

On Wed, 23 Sep 2020 07:32:43 +0100 Christoph Hellwig wrote:
> On Mon, Sep 21, 2020 at 10:01:47PM -0400, Rik van Riel wrote:
> > +static struct page *swap_cluster_read_one(swp_entry_t entry,
> > +		unsigned long offset, gfp_t gfp_mask,
> > +		struct vm_area_struct *vma, unsigned long addr, bool readahead)
> > +{
> > +	bool page_allocated;
> > +	struct page *page;
> > +
> > +	page =__read_swap_cache_async(swp_entry(swp_type(entry), offset),
> > +				      gfp_mask, vma, addr, &page_allocated);
> 
> Missing whitespace after the "=".
> 
> > +	if (!page)
> > +		return NULL;
> > +	if (page_allocated) {
> > +		swap_readpage(page, false);
> > +		if (readahead) {
> > +			SetPageReadahead(page);
> > +			count_vm_event(SWAP_RA);
> > +		}
> > +	}
> > +	put_page(page);
> > +	return page;
> > +}

Check if put_page() makes page a hot potato at the call site
on the v2 spin.
> 
> I think swap_vma_readahead can be switched to your new helper
> pretty trivially as well, as could many of the users of
> read_swap_cache_async.