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([2620:10d:c092:600::1:2418]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7196e954csm750929066b.171.2025.04.01.03.08.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Apr 2025 03:08:01 -0700 (PDT) Message-ID: <3e0eb1fa-b501-4573-be9f-3d8e52593f75@gmail.com> Date: Tue, 1 Apr 2025 11:09:20 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v6 2/2] page_pool: Track DMA-mapped pages and unmap them when destroying the pool To: =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , Saeed Mahameed , Leon Romanovsky , Tariq Toukan , Andrew Lunn , Eric Dumazet , Paolo Abeni , Ilias Apalodimas , Simon Horman , Andrew Morton , Mina Almasry , Yonglong Liu , Yunsheng Lin , Matthew Wilcox Cc: netdev@vger.kernel.org, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, linux-mm@kvack.org, Qiuling Ren , Yuying Ma References: <20250401-page-pool-track-dma-v6-0-8b83474870d4@redhat.com> <20250401-page-pool-track-dma-v6-2-8b83474870d4@redhat.com> Content-Language: en-US From: Pavel Begunkov In-Reply-To: <20250401-page-pool-track-dma-v6-2-8b83474870d4@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 4/1/25 10:27, Toke Høiland-Jørgensen wrote: ... > Reported-by: Yonglong Liu > Closes: https://lore.kernel.org/r/8743264a-9700-4227-a556-5f931c720211@huawei.com > Fixes: ff7d6b27f894 ("page_pool: refurbish version of page_pool code") > Suggested-by: Mina Almasry > Reviewed-by: Mina Almasry > Reviewed-by: Jesper Dangaard Brouer > Tested-by: Jesper Dangaard Brouer > Tested-by: Qiuling Ren > Tested-by: Yuying Ma > Tested-by: Yonglong Liu > Acked-by: Jesper Dangaard Brouer > Signed-off-by: Toke Høiland-Jørgensen I haven't looked into the bit carving, but the rest looks good to me. A few nits below, ... > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index 7745ad924ae2d801580a6760eba9393e1cf67b01..52b5ddab7ecb405066fd55b8d61abfd4186b9dcf 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -227,6 +227,8 @@ static int page_pool_init(struct page_pool *pool, > return -EINVAL; > > pool->dma_map = true; > + > + xa_init_flags(&pool->dma_mapped, XA_FLAGS_ALLOC1); nit: might be better to init/destroy unconditionally, it doesn't allocate any memory. > } > > if (pool->slow.flags & PP_FLAG_DMA_SYNC_DEV) { > @@ -276,9 +278,6 @@ static int page_pool_init(struct page_pool *pool, > /* Driver calling page_pool_create() also call page_pool_destroy() */ > refcount_set(&pool->user_cnt, 1); > > - if (pool->dma_map) > - get_device(pool->p.dev); > - > if (pool->slow.flags & PP_FLAG_ALLOW_UNREADABLE_NETMEM) { > netdev_assert_locked(pool->slow.netdev); > rxq = __netif_get_rx_queue(pool->slow.netdev, > @@ -322,7 +321,7 @@ static void page_pool_uninit(struct page_pool *pool) > ptr_ring_cleanup(&pool->ring, NULL); > > if (pool->dma_map) > - put_device(pool->p.dev); > + xa_destroy(&pool->dma_mapped); > > #ifdef CONFIG_PAGE_POOL_STATS > if (!pool->system) > @@ -463,13 +462,21 @@ page_pool_dma_sync_for_device(const struct page_pool *pool, > netmem_ref netmem, > u32 dma_sync_size) > { > - if (pool->dma_sync && dma_dev_need_sync(pool->p.dev)) > - __page_pool_dma_sync_for_device(pool, netmem, dma_sync_size); > + if (READ_ONCE(pool->dma_sync) && dma_dev_need_sync(pool->p.dev)) { > + rcu_read_lock(); > + /* re-check under rcu_read_lock() to sync with page_pool_scrub() */ > + if (READ_ONCE(pool->dma_sync)) > + __page_pool_dma_sync_for_device(pool, netmem, > + dma_sync_size); > + rcu_read_unlock(); > + } > } > > -static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem) > +static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem, gfp_t gfp) > { > dma_addr_t dma; > + int err; > + u32 id; > > /* Setup DMA mapping: use 'struct page' area for storing DMA-addr > * since dma_addr_t can be either 32 or 64 bits and does not always fit > @@ -483,15 +490,28 @@ static bool page_pool_dma_map(struct page_pool *pool, netmem_ref netmem) > if (dma_mapping_error(pool->p.dev, dma)) > return false; > > - if (page_pool_set_dma_addr_netmem(netmem, dma)) > + if (in_softirq()) > + err = xa_alloc(&pool->dma_mapped, &id, netmem_to_page(netmem), > + PP_DMA_INDEX_LIMIT, gfp); > + else > + err = xa_alloc_bh(&pool->dma_mapped, &id, netmem_to_page(netmem), > + PP_DMA_INDEX_LIMIT, gfp); Is it an optimisation? bh disable should be reentrable and could just be xa_alloc_bh(). KERN_{NOTICE,INFO} Maybe? > + if (err) { > + WARN_ONCE(1, "couldn't track DMA mapping, please report to netdev@"); That can happen with enough memory pressure, I don't think it should be a warning. Maybe some pr_info? > goto unmap_failed; > + } > > + if (page_pool_set_dma_addr_netmem(netmem, dma)) { > + WARN_ONCE(1, "unexpected DMA address, please report to netdev@"); > + goto unmap_failed; > + } > + > + netmem_set_dma_index(netmem, id); > page_pool_dma_sync_for_device(pool, netmem, pool->p.max_len); > > return true; -- Pavel Begunkov