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Date:   Thu, 14 Sep 2023 13:47:59 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Mike Rapoport <rppt@kernel.org>
Cc:     Sourav Panda <souravpanda@google.com>, corbet@lwn.net,
        gregkh@linuxfoundation.org, rafael@kernel.org,
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Subject: Re: [PATCH v1 1/1] mm: report per-page metadata information
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References: <20230913173000.4016218-1-souravpanda@google.com>
 <20230913173000.4016218-2-souravpanda@google.com>
 <20230913205125.GA3303@kernel.org>
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On Wed, Sep 13, 2023 at 11:51:25PM +0300, Mike Rapoport wrote:
> > @@ -387,8 +390,12 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
> >  
> >  	while (nr_pages--) {
> >  		page = alloc_pages_node(nid, gfp_mask, 0);
> > -		if (!page)
> > +		if (!page) {
> >  			goto out;
> > +		} else {
> > +			__mod_node_page_state(NODE_DATA(page_to_nid(page)),
> > +					      NR_PAGE_METADATA, 1);
> 
> We can update this once for nr_pages outside the loop, cannot we?

Except that nr_pages is being used as the loop counter.
Probably best to turn this into a normal (i = 0; i < nr_pages; i++)
loop, and then we can do as you say.  But this isn't a particularly
interesting high-performance loop.