linux-kernel - Re: [RFC 13/19] page_pool: expand scope of is_pp

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Message-ID: <20250512125506.GD45370@system.software.com>
Date: Mon, 12 May 2025 21:55:06 +0900
From: Byungchul Park <byungchul@...com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: willy@...radead.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kernel_team@...ynix.com, kuba@...nel.org, almasrymina@...gle.com,
	ilias.apalodimas@...aro.org, harry.yoo@...cle.com, hawk@...nel.org,
	akpm@...ux-foundation.org, ast@...nel.org, daniel@...earbox.net,
	davem@...emloft.net, john.fastabend@...il.com,
	andrew+netdev@...n.ch, edumazet@...gle.com, pabeni@...hat.com,
	vishal.moola@...il.com
Subject: Re: [RFC 13/19] page_pool: expand scope of is_pp_{netmem,page}() to
 global

On Mon, May 12, 2025 at 02:46:36PM +0200, Toke Høiland-Jørgensen wrote:
> Byungchul Park <byungchul@...com> writes:
> 
> > Other than skbuff.c might need to check if a page or netmem is for page
> > pool, for example, page_alloc.c needs to check the page state, whether
> > it comes from page pool or not for their own purpose.
> >
> > Expand the scope of is_pp_netmem() and introduce is_pp_page() newly, so
> > that those who want to check the source can achieve the checking without
> > accessing page pool member, page->pp_magic, directly.
> >
> > Signed-off-by: Byungchul Park <byungchul@...com>
> > ---
> >  include/net/page_pool/types.h |  2 ++
> >  net/core/page_pool.c          | 10 ++++++++++
> >  net/core/skbuff.c             |  5 -----
> >  3 files changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
> > index 36eb57d73abc6..d3e1a52f01e09 100644
> > --- a/include/net/page_pool/types.h
> > +++ b/include/net/page_pool/types.h
> > @@ -299,4 +299,6 @@ static inline bool is_page_pool_compiled_in(void)
> >  /* Caller must provide appropriate safe context, e.g. NAPI. */
> >  void page_pool_update_nid(struct page_pool *pool, int new_nid);
> >  
> > +bool is_pp_netmem(netmem_ref netmem);
> > +bool is_pp_page(struct page *page);
> >  #endif /* _NET_PAGE_POOL_H */
> > diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> > index b61c1038f4c68..9c553e5a1b555 100644
> > --- a/net/core/page_pool.c
> > +++ b/net/core/page_pool.c
> > @@ -1225,3 +1225,13 @@ void net_mp_niov_clear_page_pool(struct netmem_desc *niov)
> >  
> >  	page_pool_clear_pp_info(netmem);
> >  }
> > +
> > +bool is_pp_netmem(netmem_ref netmem)
> > +{
> > +	return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
> > +}
> > +
> > +bool is_pp_page(struct page *page)
> > +{
> > +	return is_pp_netmem(page_to_netmem(page));
> > +}
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 6cbf77bc61fce..11098c204fe3e 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -893,11 +893,6 @@ static void skb_clone_fraglist(struct sk_buff *skb)
> >  		skb_get(list);
> >  }
> >  
> > -static bool is_pp_netmem(netmem_ref netmem)
> > -{
> > -	return (netmem_get_pp_magic(netmem) & ~0x3UL) == PP_SIGNATURE;
> > -}
> > -
> 
> This has already been moved to mm.h (and the check changed) by commit:
> 
> cd3c93167da0 ("page_pool: Move pp_magic check into helper functions")
> 
> You should definitely rebase this series on top of that (and the
> subsequent ee62ce7a1d90 ("page_pool: Track DMA-mapped pages and unmap
> them when destroying the pool")), as these change the semantics of how
> page_pool interacts with struct page.
> 
> Both of these are in net-next, which Mina already asked you to rebase
> on, so I guess you'll pick it up there, put flagging it here just for
> completeness :)

I will not miss it.  Thanks.

	Byungchul
> 
> -Toke
>