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Mon, 31 Aug 2026 11:35:31 -0700 (PDT) From: Stanislav Fomichev X-Google-Original-From: Stanislav Fomichev To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, sdf@fomichev.me, bobbyeshleman@meta.com, almasrymina@google.com, linux-kernel@vger.kernel.org Subject: [PATCH net-next 1/2] net: devmem: replace gen_pool with freelist Date: Mon, 31 Aug 2026 11:35:28 -0700 Message-ID: <20260831183529.2517322-2-sdf@fomichev.me> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260831183529.2517322-1-sdf@fomichev.me> References: <20260831183529.2517322-1-sdf@fomichev.me> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" devmem only needs fixed-size net_iov allocations for each dma-buf binding. The gen_pool tracks the same free set indirectly through DMA addresses, which makes devmem depend on the generic allocator even though the users are fixed-size net_iov chunks. Mirror the io_uring zcrx model more closely by keeping a binding-level freelist protected by spin_lock_bh(). Use a single net_iov_area owner for the binding, populate each net_iov's DMA address while walking the SG table, and check at teardown that all net_iovs have returned to the freelist. Drop the NET_DEVMEM select of GENERIC_ALLOCATOR now that devmem no longer calls gen_pool APIs. Signed-off-by: Stanislav Fomichev --- net/Kconfig | 1 - net/core/devmem.c | 172 +++++++++++++++++++++------------------------- net/core/devmem.h | 16 ++--- 3 files changed, 85 insertions(+), 104 deletions(-) diff --git a/net/Kconfig b/net/Kconfig index e38477393551..76ab44aa439a 100644 --- a/net/Kconfig +++ b/net/Kconfig @@ -68,7 +68,6 @@ config SKB_EXTENSIONS =20 config NET_DEVMEM def_bool y - select GENERIC_ALLOCATOR depends on DMA_SHARED_BUFFER depends on PAGE_POOL =20 diff --git a/net/core/devmem.c b/net/core/devmem.c index f4d60654ce7f..34b3157677e1 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -8,7 +8,6 @@ */ =20 #include -#include #include #include #include @@ -30,23 +29,13 @@ static DEFINE_XARRAY_FLAGS(net_devmem_dmabuf_bindings, = XA_FLAGS_ALLOC1); =20 static const struct memory_provider_ops dmabuf_devmem_ops; =20 -static void net_devmem_dmabuf_free_chunk_owner(struct gen_pool *genpool, - struct gen_pool_chunk *chunk, - void *not_used) +static void +net_devmem_dmabuf_free_chunk_owner(struct dmabuf_genpool_chunk_owner *owne= r) { - struct dmabuf_genpool_chunk_owner *owner =3D chunk->owner; - - kvfree(owner->area.niovs); - kfree(owner); -} - -static dma_addr_t net_devmem_get_dma_addr(const struct net_iov *niov) -{ - struct dmabuf_genpool_chunk_owner *owner; - - owner =3D net_devmem_iov_to_chunk_owner(niov); - return owner->base_dma_addr + - ((dma_addr_t)net_iov_idx(niov) << owner->binding->niov_shift); + if (owner) { + kvfree(owner->area.niovs); + kfree(owner); + } } =20 static void net_devmem_dmabuf_binding_release(struct percpu_ref *ref) @@ -62,24 +51,18 @@ void __net_devmem_dmabuf_binding_free(struct work_struc= t *wq) { struct net_devmem_dmabuf_binding *binding =3D container_of(wq, typeof(*bi= nding), unbind_w); =20 - size_t size, avail; - - gen_pool_for_each_chunk(binding->chunk_pool, - net_devmem_dmabuf_free_chunk_owner, NULL); - - size =3D gen_pool_size(binding->chunk_pool); - avail =3D gen_pool_avail(binding->chunk_pool); - - if (!WARN(size !=3D avail, "can't destroy genpool. size=3D%zu, avail=3D%z= u", - size, avail)) - gen_pool_destroy(binding->chunk_pool); + WARN(binding->free_count !=3D binding->total_niovs, + "can't destroy dmabuf binding. total=3D%zu, free=3D%zu", + binding->total_niovs, binding->free_count); =20 + net_devmem_dmabuf_free_chunk_owner(binding->chunk_owner); dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt, binding->direction); dma_buf_detach(binding->dmabuf, binding->attachment); dma_buf_put(binding->dmabuf); xa_destroy(&binding->bound_rxqs); percpu_ref_exit(&binding->ref); + kvfree(binding->freelist); kvfree(binding->tx_vec); kfree(binding); } @@ -87,21 +70,16 @@ void __net_devmem_dmabuf_binding_free(struct work_struc= t *wq) struct net_iov * net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding) { - struct dmabuf_genpool_chunk_owner *owner; - unsigned long dma_addr; struct net_iov *niov; - ssize_t offset; - ssize_t index; - - dma_addr =3D gen_pool_alloc_owner(binding->chunk_pool, - 1UL << binding->niov_shift, - (void **)&owner); - if (!dma_addr) + spin_lock_bh(&binding->freelist_lock); + if (unlikely(!binding->free_count)) { + spin_unlock_bh(&binding->freelist_lock); return NULL; + } =20 - offset =3D dma_addr - owner->base_dma_addr; - index =3D offset >> binding->niov_shift; - niov =3D &owner->area.niovs[index]; + niov =3D binding->freelist[--binding->free_count]; + binding->freelist[binding->free_count] =3D NULL; + spin_unlock_bh(&binding->freelist_lock); =20 niov->desc.pp_magic =3D 0; niov->desc.pp =3D NULL; @@ -113,14 +91,15 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_bindi= ng *binding) void net_devmem_free_dmabuf(struct net_iov *niov) { struct net_devmem_dmabuf_binding *binding =3D net_devmem_iov_binding(niov= ); - unsigned long dma_addr =3D net_devmem_get_dma_addr(niov); - size_t niov_size =3D 1UL << binding->niov_shift; =20 - if (WARN_ON(!gen_pool_has_addr(binding->chunk_pool, dma_addr, - niov_size))) + spin_lock_bh(&binding->freelist_lock); + if (WARN_ON_ONCE(binding->free_count >=3D binding->total_niovs)) { + spin_unlock_bh(&binding->freelist_lock); return; + } =20 - gen_pool_free(binding->chunk_pool, dma_addr, niov_size); + binding->freelist[binding->free_count++] =3D niov; + spin_unlock_bh(&binding->freelist_lock); } =20 void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding) @@ -198,8 +177,11 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *v= dev, static u32 id_alloc_next; struct scatterlist *sg; struct dma_buf *dmabuf; - unsigned int sg_idx, i; - unsigned long virtual; + struct dmabuf_genpool_chunk_owner *owner; + unsigned int sg_idx; + size_t total_niovs; + size_t niov_idx; + size_t i; int err; =20 if (!dma_dev) { @@ -230,6 +212,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vd= ev, goto err_free_binding; =20 mutex_init(&binding->lock); + spin_lock_init(&binding->freelist_lock); =20 binding->dmabuf =3D dmabuf; binding->direction =3D direction; @@ -262,20 +245,10 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *= vdev, goto err_unmap; } } - - binding->chunk_pool =3D gen_pool_create(niov_shift, - dev_to_node(&dev->dev)); - if (!binding->chunk_pool) { - err =3D -ENOMEM; - goto err_tx_vec; - } - - virtual =3D 0; + total_niovs =3D 0; for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx) { dma_addr_t dma_addr =3D sg_dma_address(sg); - struct dmabuf_genpool_chunk_owner *owner; size_t len =3D sg_dma_len(sg); - struct net_iov *niov; =20 if (!IS_ALIGNED(dma_addr, niov_size) || !IS_ALIGNED(len, niov_size)) { @@ -283,63 +256,74 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *= vdev, NL_SET_ERR_MSG_FMT(extack, "dmabuf sg entry (addr=3D%pad, len=3D%zu) not aligned to niov size= %zu", &dma_addr, len, niov_size); - goto err_free_chunks; + goto err_tx_vec; } =20 - owner =3D kzalloc_node(sizeof(*owner), GFP_KERNEL, - dev_to_node(&dev->dev)); - if (!owner) { - err =3D -ENOMEM; - goto err_free_chunks; - } + total_niovs +=3D len >> niov_shift; + } =20 - owner->area.base_virtual =3D virtual; - owner->base_dma_addr =3D dma_addr; - owner->area.num_niovs =3D len >> niov_shift; - owner->binding =3D binding; + binding->freelist =3D kvmalloc_array(total_niovs, + sizeof(binding->freelist[0]), + GFP_KERNEL); + if (!binding->freelist) { + err =3D -ENOMEM; + goto err_tx_vec; + } + binding->total_niovs =3D total_niovs; =20 - err =3D gen_pool_add_owner(binding->chunk_pool, dma_addr, - dma_addr, len, dev_to_node(&dev->dev), - owner); - if (err) { - kfree(owner); - err =3D -EINVAL; - goto err_free_chunks; - } + owner =3D kzalloc_node(sizeof(*owner), GFP_KERNEL, + dev_to_node(&dev->dev)); + if (!owner) { + err =3D -ENOMEM; + goto err_free_freelist; + } =20 - owner->area.niovs =3D kvmalloc_objs(*owner->area.niovs, - owner->area.num_niovs); - if (!owner->area.niovs) { - err =3D -ENOMEM; - goto err_free_chunks; - } + owner->area.num_niovs =3D total_niovs; + owner->binding =3D binding; + owner->area.niovs =3D kvmalloc_objs(*owner->area.niovs, + owner->area.num_niovs); + if (!owner->area.niovs) { + err =3D -ENOMEM; + goto err_free_owner; + } + binding->chunk_owner =3D owner; + + niov_idx =3D 0; + for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx) { + dma_addr_t dma_addr =3D sg_dma_address(sg); + size_t len =3D sg_dma_len(sg); + struct net_iov *niov; + size_t nr_niovs =3D len >> niov_shift; =20 - for (i =3D 0; i < owner->area.num_niovs; i++) { - niov =3D &owner->area.niovs[i]; + for (i =3D 0; i < nr_niovs; i++, niov_idx++) { + niov =3D &owner->area.niovs[niov_idx]; 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)); + dma_addr); if (direction =3D=3D DMA_TO_DEVICE) - binding->tx_vec[owner->area.base_virtual / PAGE_SIZE + i] =3D niov; + binding->tx_vec[niov_idx] =3D niov; + binding->freelist[binding->free_count++] =3D niov; + dma_addr +=3D niov_size; } - - virtual +=3D len; } =20 err =3D xa_alloc_cyclic(&net_devmem_dmabuf_bindings, &binding->id, binding, xa_limit_32b, &id_alloc_next, GFP_KERNEL); if (err < 0) - goto err_free_chunks; + goto err_free_chunk_owner; =20 list_add(&binding->list, &priv->bindings); =20 return binding; =20 -err_free_chunks: - gen_pool_for_each_chunk(binding->chunk_pool, - net_devmem_dmabuf_free_chunk_owner, NULL); - gen_pool_destroy(binding->chunk_pool); +err_free_chunk_owner: + net_devmem_dmabuf_free_chunk_owner(binding->chunk_owner); + goto err_free_freelist; +err_free_owner: + kfree(owner); +err_free_freelist: + kvfree(binding->freelist); err_tx_vec: kvfree(binding->tx_vec); err_unmap: diff --git a/net/core/devmem.h b/net/core/devmem.h index 4a293a7d1149..a5ee2d8d9169 100644 --- a/net/core/devmem.h +++ b/net/core/devmem.h @@ -14,6 +14,7 @@ #include =20 struct netlink_ext_ack; +struct dmabuf_genpool_chunk_owner; =20 struct net_devmem_dmabuf_binding { struct dma_buf *dmabuf; 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Mon, 31 Aug 2026 11:35:33 -0700 (PDT) Received: from localhost ([2a03:2880:2ff:6::]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-856a2ea7c76sm4324211b3a.39.2026.08.31.11.35.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2026 11:35:32 -0700 (PDT) From: Stanislav Fomichev X-Google-Original-From: Stanislav Fomichev To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, sdf@fomichev.me, bobbyeshleman@meta.com, almasrymina@google.com, linux-kernel@vger.kernel.org Subject: [PATCH net-next 2/2] net: devmem: embed net_iov_area in binding Date: Mon, 31 Aug 2026 11:35:29 -0700 Message-ID: <20260831183529.2517322-3-sdf@fomichev.me> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260831183529.2517322-1-sdf@fomichev.me> References: <20260831183529.2517322-1-sdf@fomichev.me> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" After replacing the gen_pool with a binding-level freelist, devmem no longer needs a separate chunk owner object. There is only one net_iov_area for the binding, so store it directly in struct net_devmem_dmabuf_binding. Derive the binding from net_iov_owner() with container_of(), matching the pattern used by io_uring zcrx. This removes the leftover dmabuf_genpool_chunk_owner wrapper and its allocation/free path. Signed-off-by: Stanislav Fomichev --- net/core/devmem.c | 42 ++++++++++-------------------------------- net/core/devmem.h | 26 +++++++------------------- 2 files changed, 17 insertions(+), 51 deletions(-) diff --git a/net/core/devmem.c b/net/core/devmem.c index 34b3157677e1..84d6c30516c8 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -29,15 +29,6 @@ static DEFINE_XARRAY_FLAGS(net_devmem_dmabuf_bindings, X= A_FLAGS_ALLOC1); =20 static const struct memory_provider_ops dmabuf_devmem_ops; =20 -static void -net_devmem_dmabuf_free_chunk_owner(struct dmabuf_genpool_chunk_owner *owne= r) -{ - if (owner) { - kvfree(owner->area.niovs); - kfree(owner); - } -} - static void net_devmem_dmabuf_binding_release(struct percpu_ref *ref) { struct net_devmem_dmabuf_binding *binding =3D @@ -55,7 +46,7 @@ void __net_devmem_dmabuf_binding_free(struct work_struct = *wq) "can't destroy dmabuf binding. total=3D%zu, free=3D%zu", binding->total_niovs, binding->free_count); =20 - net_devmem_dmabuf_free_chunk_owner(binding->chunk_owner); + kvfree(binding->area.niovs); dma_buf_unmap_attachment_unlocked(binding->attachment, binding->sgt, binding->direction); dma_buf_detach(binding->dmabuf, binding->attachment); @@ -177,7 +168,6 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vd= ev, static u32 id_alloc_next; struct scatterlist *sg; struct dma_buf *dmabuf; - struct dmabuf_genpool_chunk_owner *owner; unsigned int sg_idx; size_t total_niovs; size_t niov_idx; @@ -271,23 +261,14 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *= vdev, } binding->total_niovs =3D total_niovs; =20 - owner =3D kzalloc_node(sizeof(*owner), GFP_KERNEL, - dev_to_node(&dev->dev)); - if (!owner) { + binding->area.num_niovs =3D total_niovs; + binding->area.niovs =3D kvmalloc_objs(*binding->area.niovs, + binding->area.num_niovs); + if (!binding->area.niovs) { err =3D -ENOMEM; goto err_free_freelist; } =20 - owner->area.num_niovs =3D total_niovs; - owner->binding =3D binding; - owner->area.niovs =3D kvmalloc_objs(*owner->area.niovs, - owner->area.num_niovs); - if (!owner->area.niovs) { - err =3D -ENOMEM; - goto err_free_owner; - } - binding->chunk_owner =3D owner; - niov_idx =3D 0; for_each_sgtable_dma_sg(binding->sgt, sg, sg_idx) { dma_addr_t dma_addr =3D sg_dma_address(sg); @@ -296,8 +277,8 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vd= ev, size_t nr_niovs =3D len >> niov_shift; =20 for (i =3D 0; i < nr_niovs; i++, niov_idx++) { - niov =3D &owner->area.niovs[niov_idx]; - net_iov_init(niov, &owner->area, NET_IOV_DMABUF); + niov =3D &binding->area.niovs[niov_idx]; + net_iov_init(niov, &binding->area, NET_IOV_DMABUF); page_pool_set_dma_addr_netmem(net_iov_to_netmem(niov), dma_addr); if (direction =3D=3D DMA_TO_DEVICE) @@ -311,17 +292,14 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *= vdev, binding, xa_limit_32b, &id_alloc_next, GFP_KERNEL); if (err < 0) - goto err_free_chunk_owner; + goto err_free_niovs; =20 list_add(&binding->list, &priv->bindings); =20 return binding; =20 -err_free_chunk_owner: - net_devmem_dmabuf_free_chunk_owner(binding->chunk_owner); - goto err_free_freelist; -err_free_owner: - kfree(owner); +err_free_niovs: + kvfree(binding->area.niovs); err_free_freelist: kvfree(binding->freelist); err_tx_vec: diff --git a/net/core/devmem.h b/net/core/devmem.h index a5ee2d8d9169..20a3eb90ea7f 100644 --- a/net/core/devmem.h +++ b/net/core/devmem.h @@ -14,9 +14,9 @@ #include =20 struct netlink_ext_ack; -struct dmabuf_genpool_chunk_owner; =20 struct net_devmem_dmabuf_binding { + struct net_iov_area area; struct dma_buf *dmabuf; struct dma_buf_attachment *attachment; struct sg_table *sgt; @@ -27,7 +27,6 @@ struct net_devmem_dmabuf_binding { * dereferenced. */ void *vdev; - struct dmabuf_genpool_chunk_owner *chunk_owner; /* Protect dev */ struct mutex lock; =20 @@ -83,11 +82,6 @@ struct net_devmem_dmabuf_binding { }; =20 #if defined(CONFIG_NET_DEVMEM) -struct dmabuf_genpool_chunk_owner { - struct net_iov_area area; - struct net_devmem_dmabuf_binding *binding; -}; - void __net_devmem_dmabuf_binding_free(struct work_struct *wq); struct net_devmem_dmabuf_binding * net_devmem_bind_dmabuf(struct net_device *dev, void *vdev, @@ -102,18 +96,12 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device = *dev, u32 rxq_idx, struct net_devmem_dmabuf_binding *binding, struct netlink_ext_ack *extack); =20 -static inline struct dmabuf_genpool_chunk_owner * -net_devmem_iov_to_chunk_owner(const struct net_iov *niov) -{ - struct net_iov_area *owner =3D net_iov_owner(niov); - - return container_of(owner, struct dmabuf_genpool_chunk_owner, area); -} - static inline struct net_devmem_dmabuf_binding * net_devmem_iov_binding(const struct net_iov *niov) { - return net_devmem_iov_to_chunk_owner(niov)->binding; + struct net_iov_area *owner =3D net_iov_owner(niov); + + return container_of(owner, struct net_devmem_dmabuf_binding, area); } =20 static inline u32 net_devmem_iov_binding_id(const struct net_iov *niov) @@ -123,11 +111,11 @@ static inline u32 net_devmem_iov_binding_id(const str= uct net_iov *niov) =20 static inline unsigned long net_iov_virtual_addr(const struct net_iov *nio= v) { - struct dmabuf_genpool_chunk_owner *co =3D - net_devmem_iov_to_chunk_owner(niov); + struct net_devmem_dmabuf_binding *binding =3D + net_devmem_iov_binding(niov); =20 return net_iov_owner(niov)->base_virtual + - ((unsigned long)net_iov_idx(niov) << co->binding->niov_shift); + ((unsigned long)net_iov_idx(niov) << binding->niov_shift); } =20 static inline bool --=20 2.53.0-Meta