Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages()

[Ralph Campbell <rcampbell@xxxxxxxxxx>]

On 1/14/20 3:32 AM, Michal Hocko wrote:
> On Tue 14-01-20 11:23:52, Vlastimil Babka wrote:
> > On 1/14/20 10:10 AM, Michal Hocko wrote:
> > > [Cc Ralph]
> > > > The reason is dump_page() does not print page->flags universally
> > > > and only does so for KSM, Anon and File pages while excluding
> > > > reserved pages at boot. Wondering should not we make printing
> > > > page->flags universal ?
> > >
> > > We used to do that and this caught me as a surprise when looking again.
> > > This is a result of 76a1850e4572 ("mm/debug.c: __dump_page() prints an
> > > extra line") which is a cleanup patch and I suspect this result was not
> > > anticipated.
> > >
> > > The following will do the trick but I cannot really say I like the code
> > > duplication. pr_cont in this case sounds like a much cleaner solution to
> > > me.
> >
> > How about this then?
>
> Yes makes sense as well.
>
> > diff --git mm/debug.c mm/debug.c
> > index 0461df1207cb..6a52316af839 100644
> > --- mm/debug.c
> > +++ mm/debug.c
> > @@ -47,6 +47,7 @@ void __dump_page(struct page *page, const char *reason)
> >   	struct address_space *mapping;
> >   	bool page_poisoned = PagePoisoned(page);
> >   	int mapcount;
> > +	char *type = "";
> >   
> >   	/*
> >   	 * If struct page is poisoned don't access Page*() functions as that
> > @@ -78,9 +79,9 @@ void __dump_page(struct page *page, const char *reason)
> >   			page, page_ref_count(page), mapcount,
> >   			page->mapping, page_to_pgoff(page));
> >   	if (PageKsm(page))
> > -		pr_warn("ksm flags: %#lx(%pGp)\n", page->flags, &page->flags);
> > +		type = "ksm ";
> >   	else if (PageAnon(page))
> > -		pr_warn("anon flags: %#lx(%pGp)\n", page->flags, &page->flags);
> > +		type = "anon ";
> >   	else if (mapping) {
> >   		if (mapping->host && mapping->host->i_dentry.first) {
> >   			struct dentry *dentry;
> > @@ -88,10 +89,11 @@ void __dump_page(struct page *page, const char *reason)
> >   			pr_warn("%ps name:\"%pd\"\n", mapping->a_ops, dentry);
> >   		} else
> >   			pr_warn("%ps\n", mapping->a_ops);
> > -		pr_warn("flags: %#lx(%pGp)\n", page->flags, &page->flags);
> >   	}
> >   	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
> >   
> > +	pr_warn("%sflags: %#lx(%pGp)\n", type, page->flags, &page->flags);
> > +
> >   hex_only:
> >   	print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32,
> >   			sizeof(unsigned long), page,
Looks good to me. Thanks for the clean up.
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>