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([2409:8a55:301b:e120:28db:76a6:1c67:659f]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-72dab84b639sm3744765b3a.84.2025.01.18.05.36.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Jan 2025 05:37:01 -0800 (PST) Message-ID: <3795e5e1-8a6a-4ee3-9778-1828ac5b2748@gmail.com> Date: Sat, 18 Jan 2025 21:36:52 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v7 3/8] page_pool: fix IOMMU crash when driver has already unbound To: Jesper Dangaard Brouer , Yunsheng Lin , davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: zhangkun09@huawei.com, liuyonglong@huawei.com, fanghaiqing@huawei.com, Robin Murphy , Alexander Duyck , IOMMU , Andrew Morton , Eric Dumazet , Simon Horman , Ilias Apalodimas , linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kernel-team References: <20250110130703.3814407-1-linyunsheng@huawei.com> <20250110130703.3814407-4-linyunsheng@huawei.com> <921c827c-41b7-40af-8c01-c21adbe8f41f@kernel.org> <2b5a58f3-d67a-4bf7-921a-033326958ac6@huawei.com> <95f258b2-52f5-4a80-a670-b9a182caec7c@kernel.org> <92bb3a19-a619-4bf7-9ef5-b9eb12a57983@huawei.com> Content-Language: en-US From: Yunsheng Lin In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 1/18/2025 12:56 AM, Jesper Dangaard Brouer wrote: ... >> I am not really sure about that, as using the PAGE_SIZE block to hold the >> item seems like a implementation detail, which might change in the >> future, >> renaming other function to something like that doesn't seem right to >> me IMHO. >> >> Also the next patch will add page_pool_item_blk_add() to support >> unlimited >> inflight pages, it seems a better name is needed for that too, perheps >> rename >> page_pool_item_blk_add() to page_pool_dynamic_item_add()? >> > > Hmmm... not sure about this. > I think I prefer page_pool_item_blk_add() over > page_pool_dynamic_item_add(). > >> For __page_pool_item_init(), perhaps just inline it back to >> page_pool_item_init() >> as __page_pool_item_init() is only used by page_pool_item_init(), and >> both of them >> are not really large function. > > I like that you had a helper function. So, don't merge > __page_pool_item_init() into page_pool_item_init() just to avoid naming > it differently. Any particular reason for the above suggestion? After reusing the page_pool_item_uninit() to fix the similar use-after-freed problem，it seems reasonable to not expose the item_blcok as much as possible as item_blcok is really an implementation detail that should be hidden as much as possible IMHO. If it is able to reused for supporting the unlimited item case, then I am agreed that it might be better to refactor it out, but it is not really reusable. static int page_pool_item_init(struct page_pool *pool) { #define PAGE_POOL_MIN_INFLIGHT_ITEMS 512 struct page_pool_item_block *block; int item_cnt; INIT_LIST_HEAD(&pool->item_blocks); init_llist_head(&pool->hold_items); init_llist_head(&pool->release_items); item_cnt = pool->p.pool_size * 2 + PP_ALLOC_CACHE_SIZE + PAGE_POOL_MIN_INFLIGHT_ITEMS; for (; item_cnt > 0; item_cnt -= ITEMS_PER_PAGE) { struct page *page; unsigned int i; page = alloc_pages_node(pool->p.nid, GFP_KERNEL, 0); if (!page) { page_pool_item_uninit(pool); return -ENOMEM; } block = page_address(page); block->pp = pool; list_add(&block->list, &pool->item_blocks); for (i = 0; i < ITEMS_PER_PAGE; i++) { page_pool_item_init_state(&block->items[i]); __llist_add(&block->items[i].lentry, &pool->hold_items); } } return 0; } > > Let me be more explicit what I'm asking for: > > IMHO you should rename: >  - __page_pool_item_init() to __page_pool_item_block_init() > and rename: >  - page_pool_item_init() to page_pool_item_block_init() > > I hope this make it more clear what I'm saying. > > --Jesper >