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Message-ID: <20250512123051.GA45370@system.software.com> Date: Mon, 12 May 2025 21:30:51 +0900 From: Byungchul Park <byungchul@...com> To: Mina Almasry <almasrymina@...gle.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, 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 02/19] netmem: introduce netmem alloc/put API to wrap page alloc/put API On Fri, May 09, 2025 at 07:08:23AM -0700, Mina Almasry wrote: > j > > On Fri, May 9, 2025 at 6:39 AM Mina Almasry <almasrymina@...gle.com> wrote: > > > > On Fri, May 9, 2025 at 4:51 AM Byungchul Park <byungchul@...com> wrote: > > > > > > To eliminate the use of struct page in page pool, the page pool code > > > should use netmem descriptor and API instead. > > > > > > As part of the work, introduce netmem alloc/put API allowing the code to > > > use them rather than struct page things. > > > > > > Signed-off-by: Byungchul Park <byungchul@...com> > > > --- > > > include/net/netmem.h | 18 ++++++++++++++++++ > > > 1 file changed, 18 insertions(+) > > > > > > diff --git a/include/net/netmem.h b/include/net/netmem.h > > > index 45c209d6cc689..c87a604e980b9 100644 > > > --- a/include/net/netmem.h > > > +++ b/include/net/netmem.h > > > @@ -138,6 +138,24 @@ static inline netmem_ref page_to_netmem(struct page *page) > > > return (__force netmem_ref)page; > > > } > > > > > > +static inline netmem_ref alloc_netmems_node(int nid, gfp_t gfp_mask, > > > + unsigned int order) > > > +{ > > > + return page_to_netmem(alloc_pages_node(nid, gfp_mask, order)); > > > +} > > > + > > > +static inline unsigned long alloc_netmems_bulk_node(gfp_t gfp, int nid, > > > + unsigned long nr_netmems, netmem_ref *netmem_array) > > > +{ > > > + return alloc_pages_bulk_node(gfp, nid, nr_netmems, > > > + (struct page **)netmem_array); > > > +} > > > + > > > +static inline void put_netmem(netmem_ref netmem) > > > +{ > > > + put_page(netmem_to_page(netmem)); > > > +} > > > > We can't really do this. netmem_ref is an abstraction that can be a > > struct page or struct net_iov underneath. We can't be sure when > > put_netmem is called that it is safe to convert to a page via > > netmem_to_page(). This will crash if put_netmem is called on a > > netmem_ref that is a net_iov underneath. > > > > On a closer look, it looks like this put_netmem is only called from > code paths where you are sure the netmem_ref is a page underneath, so > this is likely fine for now. There is a net_next series that is adding > proper put_netmem support [1]. It's probably best to rebase your work > on top of that, but this should be fine in the meantime. Indeed. Hm.. It'd be the best to work on the top of yours. If it takes too long, I keep working on as it is for now and will adjust this patch later once your work gets merged. Byungchul > [1] https://lore.kernel.org/netdev/20250508004830.4100853-1-almasrymina@google.com/ > > -- > Thanks, > Mina
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