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s=arc-20220608; d=hostedemail.com; t=1761618270; a=rsa-sha256; cv=none; b=kcge1aKM3hxmsNNwut4yxUXHVrS3lNfzVSjwlGSgtXW6tLKXMLgcGQvpogMiz63CSdmVZX HTTYYR8bx8VBihZHQ8+3ivi4lBCkFyNygGSN+j0yzbk3XtK3E9eWOWiI35f4oDUeicpO28 9icJ/NC4ixQOK10ZOyJuSZ5NnGRc2rw= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=none; spf=pass (imf08.hostedemail.com: domain of byungchul@sk.com designates 166.125.252.92 as permitted sender) smtp.mailfrom=byungchul@sk.com X-AuditID: a67dfc5b-c45ff70000001609-8a-6900295ba92a Date: Tue, 28 Oct 2025 11:24:21 +0900 From: Byungchul Park To: Mina Almasry Cc: linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, sfr@canb.auug.org.au, dw@davidwei.uk, ap420073@gmail.com, dtatulea@nvidia.com Subject: Re: [RFC mm v4 1/2] page_pool: check if nmdesc->pp is !NULL to confirm its usage as pp for net_iov Message-ID: <20251028022421.GA77904@system.software.com> References: <20251023074410.78650-1-byungchul@sk.com> <20251023074410.78650-2-byungchul@sk.com> MIME-Version: 1.0 Content-Type: text/plain; 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However, ->pp_magic will be removed and page > > type bit in struct page e.g. PGTY_netpp should be used for that purpose. > > > > As a preparation, the check for net_iov, that is not page-backed, should > > avoid using ->pp_magic since net_iov doens't have to do with page type. > > Instead, nmdesc->pp can be used if a net_iov or its nmdesc belongs to a > > page pool, by making sure nmdesc->pp is NULL otherwise. > > > > For page-backed netmem, just leave unchanged as is, while for net_iov, > > make sure nmdesc->pp is initialized to NULL and use nmdesc->pp for the > > check. > > > > Signed-off-by: Byungchul Park > > --- > > net/core/devmem.c | 1 + > > net/core/netmem_priv.h | 8 ++++++++ > > net/core/page_pool.c | 16 ++++++++++++++-- > > 3 files changed, 23 insertions(+), 2 deletions(-) > > > > diff --git a/net/core/devmem.c b/net/core/devmem.c > > index d9de31a6cc7f..f81b700f1fd1 100644 > > --- a/net/core/devmem.c > > +++ b/net/core/devmem.c > > @@ -291,6 +291,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, > > niov = &owner->area.niovs[i]; > > niov->type = NET_IOV_DMABUF; > > niov->owner = &owner->area; > > + niov->desc.pp = NULL; > > Don't you also need to = NULL the niov allocations in io_uring zcrx, > or is that already done? Maybe mention in commit message. Yes, that's been already done by kvmalloc_array(__GFP_ZERO). I want to leave a comment explaining that on io_uring side like: diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c index e5ff49f3425e..f771bb3e756d 100644 --- a/io_uring/zcrx.c +++ b/io_uring/zcrx.c @@ -444,6 +444,10 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq, area->freelist[i] = i; atomic_set(&area->user_refs[i], 0); niov->type = NET_IOV_IOURING; + + /* niov->pp is already initialized to NULL by + * kvmalloc_array(__GFP_ZERO). + */ } area->free_count = nr_iovs; However, I dropped it as Pavel requested: https://lore.kernel.org/lkml/8d833a3f-ae18-4ea6-9092-ddaa48290a63@gmail.com/ I will mention it in commit message then. > Other than that, looks correct, > > Reviewed-by: Mina Almasry Thanks. Byungchul