[{"id":3674792,"web_url":"http://patchwork.ozlabs.org/comment/3674792/","msgid":"","list_archive_url":null,"date":"2026-04-08T14:09:18","subject":"Re: [Intel-wired-lan] [PATCH iwl-next v2 7/8] ixgbe: use GFP_KERNEL\n in ixgbe_fcoe_ddp_setup()","submitter":{"id":92459,"url":"http://patchwork.ozlabs.org/api/people/92459/","name":"Kohei Enju","email":"kohei@enjuk.jp"},"content":"On 04/08 15:12, Aleksandr Loktionov wrote:\n> ixgbe_fcoe_ddp_setup() is always called from process context (FCoE\n> offload setup paths) and never from an atomic context. Using GFP_ATOMIC\n\nAs I mentioned in v1, I don't think this path is non-atomic.\n\nfc_exch_seq_send()\n fc_exch_alloc() # acquires ep->ex_lock (spinlock) internally\n fc_fcp_ddp_setup()\n lport->tt.ddp_setup() == fcoe_ddp_setup()\n .ndo_fcoe_ddp_setup() == ixgbe_fcoe_ddp_get()\n ixgbe_fcoe_ddp_setup()\n ...\n spin_unlock_bh(&ep->ex_lock);\n\nSo even if this runs in process context, it still appears to be in\natomic context while ep->ex_lock is held and also bh is disabled.\nGFP_KERNEL still looks unsafe here for me.\n\nIf I'm misreading something, please let me know.\nThanks.","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=osuosl.org header.i=@osuosl.org header.a=rsa-sha256\n header.s=default header.b=pgGOGS4+;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=osuosl.org\n (client-ip=140.211.166.137; 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a=rsa-sha256; c=relaxed/relaxed; d=osuosl.org;\n\ts=default; t=1775657369;\n\tbh=bYzchrb2PJb1o1pVGTErHKK6Im21E7HDexP01h7Ldws=;\n\th=Date:From:To:Cc:References:In-Reply-To:Subject:List-Id:\n\t List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe:\n\t From;\n\tb=pgGOGS4+nlJCaOZ8cKZfrGVwFFB/hyRopCL5Hja0/nt8AcA/eDVe9hUH8R7r/7yz/\n\t ii2kk56+YHGCu9+RdcjpG2tK6MXQwaYBaIFuvsheAQfyhhiwjQyoNI4JFarH2HjpsE\n\t LH+i3HC7yCWuXS+OKVCYSNGKC7UHjZsPa6vWDuLJjLr3W9ScWArdJr7yx5dJBKAQ1J\n\t 01qfHObCCdrez9JKHvfoSMCQNX57OmY9b94BqFv3ETjUvSy6V7xX7MKh4Eehm9KcSB\n\t 4RHuXm2HrIazXAaa38MLK5zB76MC1RQwu6NbC8HuTx6dNaC8taT7+WQ5aV6H1wBpd3\n\t cObgCP1tPod8A==","Received-SPF":"Pass (mailfrom) identity=mailfrom; client-ip=49.212.198.91;\n helo=www2881.sakura.ne.jp; envelope-from=kohei@enjuk.jp; receiver=","DMARC-Filter":"OpenDMARC Filter v1.4.2 smtp2.osuosl.org 54A99400C8","Date":"Wed, 8 Apr 2026 23:09:18 +0900","From":"Kohei Enju ","To":"Aleksandr Loktionov ","Cc":"intel-wired-lan@lists.osuosl.org, anthony.l.nguyen@intel.com,\n netdev@vger.kernel.org","Message-ID":"","References":"<20260408131216.2662245-1-aleksandr.loktionov@intel.com>\n <20260408131216.2662245-8-aleksandr.loktionov@intel.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20260408131216.2662245-8-aleksandr.loktionov@intel.com>","X-Mailman-Original-DKIM-Signature":"a=rsa-sha256;\n bh=bYzchrb2PJb1o1pVGTErHKK6Im21E7HDexP01h7Ldws=;\n c=relaxed/relaxed; d=enjuk.jp;\n h=From:Message-ID:To:Subject:Date;\n s=rs20251215; t=1775657359; v=1;\n b=UvddOKBuf42IdroTWJsyDyQKYzZRTfDkYThL6stQ0Ibpp1q4Ti9T/39mTlbzGiNb\n E8q0Atfo1haypJpPBRofmN00JTS6tZx1Xh/xYhSb+JjnKkrRZ+L1kUB0iPa0v/NY\n 93LEx+F7LWre+wfz8oKiIr2qxcLOeDjI7Xn3PhqeYizDzz3RiHH+yGhZ7cFIomgb\n 3Eomxh4mnBr/OEpt7+KlDiRYD77cWAtMS5RMb9BkDgsg3NhxRUQVcy2VMkcOoOTd\n q1vm8CcEBSURWi7igzCyHM1fL/KYyII11oFtrsZAXj7GeZ621Ga6sPrtrvhHTbhz\n MEz1QjdnBIcK9jwqJ0dBoQ==","X-Mailman-Original-Authentication-Results":["smtp2.osuosl.org;\n dmarc=pass (p=none dis=none)\n header.from=enjuk.jp","smtp2.osuosl.org;\n dkim=pass (2048-bit key,\n unprotected) header.d=enjuk.jp header.i=@enjuk.jp header.a=rsa-sha256\n header.s=rs20251215 header.b=UvddOKBu"],"Subject":"Re: [Intel-wired-lan] [PATCH iwl-next v2 7/8] ixgbe: use GFP_KERNEL\n in ixgbe_fcoe_ddp_setup()","X-BeenThere":"intel-wired-lan@osuosl.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Intel Wired Ethernet Linux Kernel Driver Development\n ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"intel-wired-lan-bounces@osuosl.org","Sender":"\"Intel-wired-lan\" "}},{"id":3677204,"web_url":"http://patchwork.ozlabs.org/comment/3677204/","msgid":"<20260414132935.757593-1-horms@kernel.org>","list_archive_url":null,"date":"2026-04-14T13:29:35","subject":"Re: [Intel-wired-lan] [PATCH iwl-next v2 7/8] ixgbe: use GFP_KERNEL\n in ixgbe_fcoe_ddp_setup()","submitter":{"id":82748,"url":"http://patchwork.ozlabs.org/api/people/82748/","name":"Simon Horman","email":"horms@kernel.org"},"content":"This is an AI-generated review of your patch. The human sending this\nemail has considered the AI review valid, or at least plausible.\n\nFor local reproduction steps see https://netdev-ai.bots.linux.dev/ai-local.html\n---\nixgbe: use GFP_KERNEL in ixgbe_fcoe_ddp_setup()\n\nThis commit restructures ixgbe_fcoe_ddp_setup() to use GFP_KERNEL\ninstead of GFP_ATOMIC by splitting get_cpu()/put_cpu() usage into two\nnarrow critical sections, moving DMA mapping and pool allocation between\nthem where preemption is enabled.\n\n> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_fcoe.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_fcoe.c\n> index 011fda9c6193..e338ff0e6522 100644\n> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_fcoe.c\n> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_fcoe.c\n\n[ ... ]\n\n> @@ -179,29 +180,43 @@ static int ixgbe_fcoe_ddp_setup(struct net_device *netdev, u16 xid,\n> \t\treturn 0;\n> \t}\n>\n> +\t/* Pin to current CPU only to read the per-CPU pool pointer; drop\n> +\t * the pin before any allocations that may sleep under direct reclaim.\n> +\t */\n> \tddp_pool = per_cpu_ptr(fcoe->ddp_pool, get_cpu());\n> \tif (!ddp_pool->pool) {\n> \t\te_warn(drv, \"xid=0x%x no ddp pool for fcoe\\n\", xid);\n> -\t\tgoto out_noddp;\n> +\t\tput_cpu();\n> +\t\treturn 0;\n> \t}\n> +\tpool = ddp_pool->pool;\n> +\tput_cpu();\n>\n> \t/* setup dma from scsi command sgl */\n> \tdmacount = dma_map_sg(&adapter->pdev->dev, sgl, sgc, DMA_FROM_DEVICE);\n> \tif (dmacount == 0) {\n> \t\te_err(drv, \"xid 0x%x DMA map error\\n\", xid);\n> -\t\tgoto out_noddp;\n> +\t\treturn 0;\n> \t}\n>\n> -\t/* alloc the udl from per cpu ddp pool */\n> -\tddp->udl = dma_pool_alloc(ddp_pool->pool, GFP_ATOMIC, &ddp->udp);\n> +\t/* Allocate from per-CPU pool; GFP_KERNEL is safe: preemption is\n> +\t * re-enabled after the put_cpu() above. Per-CPU DMA pools are only\n> +\t * destroyed under RTNL during interface teardown, so the saved pool\n> +\t * pointer remains valid.\n> +\t */\n> +\tddp->udl = dma_pool_alloc(pool, GFP_KERNEL, &ddp->udp);\n\nIs this safe given the calling context?\n\nLooking at the call path from the FCoE stack:\n\nfc_exch_seq_send()\n fc_exch_alloc()\n fc_exch_em_alloc()\n spin_lock_bh(&pool->lock)\n # allocate exchange\n # set ep->ex_lock = held\n return with ep->ex_lock still held\n fc_fcp_ddp_setup()\n lport->tt.ddp_setup()\n .ndo_fcoe_ddp_setup() == ixgbe_fcoe_ddp_get()\n ixgbe_fcoe_ddp_setup() # <-- we are here\n # ... continues with ep->ex_lock held\n spin_unlock_bh(&ep->ex_lock)\n\nfc_exch_em_alloc() acquires ep->ex_lock (a spinlock) and returns with\nit held. The lock remains held through fc_fcp_ddp_setup() and into\nixgbe_fcoe_ddp_setup(). Additionally, spin_lock_bh() disables bottom\nhalves.\n\nCan GFP_KERNEL be used while holding ep->ex_lock with BH disabled, or\ndoes this require GFP_ATOMIC?","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","intel-wired-lan@lists.osuosl.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=osuosl.org header.i=@osuosl.org header.a=rsa-sha256\n header.s=default header.b=qx4unpy3;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=osuosl.org\n (client-ip=140.211.166.137; helo=smtp4.osuosl.org;\n envelope-from=intel-wired-lan-bounces@osuosl.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature ECDSA (secp384r1) server-digest SHA384)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fw4rZ0lT6z1xtJ\n\tfor ; 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