From: Jakub Kicinski Date: Tue, 28 Apr 2026 02:53:20 +0000 (-0700) Subject: net: add net_iov_init() and use it to initialize ->page_type X-Git-Tag: v7.1-rc2~22^2~11 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=735a309b4bfb9e1e26636ff4a3e8a146f53c54f9;p=thirdparty%2Fkernel%2Flinux.git net: add net_iov_init() and use it to initialize ->page_type Commit db359fccf212 ("mm: introduce a new page type for page pool in page type") added a page_type field to struct net_iov at the same offset as struct page::page_type, so that page_pool_set_pp_info() can call __SetPageNetpp() uniformly on both pages and net_iovs. The page-type API requires the field to hold the UINT_MAX "no type" sentinel before a type can be set; for real struct page that invariant is established by the page allocator on free. struct net_iov is not allocated through the page allocator, so the field is left as zero (io_uring zcrx, which uses __GFP_ZERO) or as slab garbage (devmem, which uses kvmalloc_objs() without zeroing). When the page pool then calls page_pool_set_pp_info() on a freshly-bound niov, __SetPageNetpp()'s VM_BUG_ON_PAGE(page->page_type != UINT_MAX) fires and the kernel BUGs. Triggered in selftests by io_uring zcrx setup through the fbnic queue restart path: kernel BUG at ./include/linux/page-flags.h:1062! RIP: 0010:page_pool_set_pp_info (./include/linux/page-flags.h:1062 net/core/page_pool.c:716) Call Trace: net_mp_niov_set_page_pool (net/core/page_pool.c:1360) io_pp_zc_alloc_netmems (io_uring/zcrx.c:1089 io_uring/zcrx.c:1110) fbnic_fill_bdq (./include/net/page_pool/helpers.h:160 drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:906) __fbnic_nv_restart (drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2470 drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2874) fbnic_queue_start (drivers/net/ethernet/meta/fbnic/fbnic_txrx.c:2903) netdev_rx_queue_reconfig (net/core/netdev_rx_queue.c:137) __netif_mp_open_rxq (net/core/netdev_rx_queue.c:234) io_register_zcrx (io_uring/zcrx.c:818 io_uring/zcrx.c:903) __io_uring_register (io_uring/register.c:931) __do_sys_io_uring_register (io_uring/register.c:1029) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) The same path is reachable through devmem dmabuf binding via netdev_nl_bind_rx_doit() -> net_devmem_bind_dmabuf_to_queue(). Add a net_iov_init() helper that stamps ->owner, ->type and the ->page_type sentinel, and use it from both the devmem and io_uring zcrx niov init loops. Fixes: db359fccf212 ("mm: introduce a new page type for page pool in page type") Acked-by: Vlastimil Babka (SUSE) Acked-by: Byungchul Park Reviewed-by: Jens Axboe Acked-by: Pavel Begunkov Link: https://patch.msgid.link/20260428025320.853452-1-kuba@kernel.org Signed-off-by: Jakub Kicinski --- diff --git a/include/net/netmem.h b/include/net/netmem.h index 507b74c9f52d..78fe51e5756b 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -127,6 +127,21 @@ static inline unsigned int net_iov_idx(const struct net_iov *niov) return niov - net_iov_owner(niov)->niovs; } +/* Initialize a niov: stamp the owning area, the memory provider type, + * and the page_type "no type" sentinel expected by the page-type API + * (see PAGE_TYPE_OPS in ) so that + * page_pool_set_pp_info() can later call __SetPageNetpp() on a niov + * cast to struct page. + */ +static inline void net_iov_init(struct net_iov *niov, + struct net_iov_area *owner, + enum net_iov_type type) +{ + niov->owner = owner; + niov->type = type; + niov->page_type = UINT_MAX; +} + /* netmem */ /** diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c index 7b93c87b8371..19837e0b5e91 100644 --- a/io_uring/zcrx.c +++ b/io_uring/zcrx.c @@ -495,10 +495,9 @@ static int io_zcrx_create_area(struct io_zcrx_ifq *ifq, for (i = 0; i < nr_iovs; i++) { struct net_iov *niov = &area->nia.niovs[i]; - niov->owner = &area->nia; + net_iov_init(niov, &area->nia, NET_IOV_IOURING); area->freelist[i] = i; atomic_set(&area->user_refs[i], 0); - niov->type = NET_IOV_IOURING; } if (ifq->dev) { diff --git a/net/core/devmem.c b/net/core/devmem.c index cde4c89bc146..468344739db2 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -297,8 +297,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, for (i = 0; i < owner->area.num_niovs; i++) { niov = &owner->area.niovs[i]; - niov->type = NET_IOV_DMABUF; - niov->owner = &owner->area; + net_iov_init(niov, &owner->area, NET_IOV_DMABUF); page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov), net_devmem_get_dma_addr(niov)); if (direction == DMA_TO_DEVICE)