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

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Message-ID: <874ixnl9vi.fsf@toke.dk>
Date: Wed, 14 May 2025 13:17:21 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Byungchul Park <byungchul@...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

Byungchul Park <byungchul@...com> writes:

> 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
>
> Is this net-next you are mentioning?  I will rebase on this if so.
>
>    https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/

Yup :)

-Toke