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[98.164.255.77]) by smtp.gmail.com with ESMTPSA id cq15-20020a05622a424f00b0035cdd7a42d0sm8342371qtb.22.2022.10.02.19.56.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 02 Oct 2022 19:56:12 -0700 (PDT) Message-ID: <2f36fa52-2dc3-21f3-b53c-d0a9186c3ceb@gmail.com> Date: Sun, 2 Oct 2022 19:56:10 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH] nvme-fc: fix sleep-in-atomic-context bug caused by nvme_fc_rcv_ls_req Content-Language: en-US To: duoming@zju.edu.cn Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, james.smart@broadcom.com, kbusch@kernel.org, axboe@fb.com, hch@lst.de, sagi@grimberg.me References: <20221002001909.20070-1-duoming@zju.edu.cn> <305fbf18-6759-9b00-6fc0-93a4a2e40be2@gmail.com> <7bd9e071.1063f1.1839b89cefa.Coremail.duoming@zju.edu.cn> From: James Smart In-Reply-To: <7bd9e071.1063f1.1839b89cefa.Coremail.duoming@zju.edu.cn> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/2/2022 6:50 PM, duoming@zju.edu.cn wrote: > Hello, > > On Sun, 2 Oct 2022 10:12:15 -0700 James Smart wrote: > >> On 10/1/2022 5:19 PM, Duoming Zhou wrote: >>> The function lpfc_poll_timeout() is a timer handler that runs in an >>> atomic context, but it calls "kzalloc(.., GFP_KERNEL)" that may sleep. >>> As a result, the sleep-in-atomic-context bug will happen. The processes >>> is shown below: >>> >>> lpfc_poll_timeout() >>> lpfc_sli_handle_fast_ring_event() >>> lpfc_sli_process_unsol_iocb() >>> lpfc_complete_unsol_iocb() >>> lpfc_nvme_unsol_ls_handler() >>> lpfc_nvme_handle_lsreq() >>> nvme_fc_rcv_ls_req() >>> kzalloc(sizeof(.., GFP_KERNEL) //may sleep >>> >>> This patch changes the gfp_t parameter of kzalloc() from GFP_KERNEL to >>> GFP_ATOMIC in order to mitigate the bug. >>> >>> Fixes: 14fd1e98afaf ("nvme-fc: Add Disconnect Association Rcv support") >>> Signed-off-by: Duoming Zhou >>> --- >>> drivers/nvme/host/fc.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c >>> index 127abaf9ba5..36698dfc8b3 100644 >>> --- a/drivers/nvme/host/fc.c >>> +++ b/drivers/nvme/host/fc.c >>> @@ -1754,7 +1754,7 @@ nvme_fc_rcv_ls_req(struct nvme_fc_remote_port *portptr, >>> lsop = kzalloc(sizeof(*lsop) + >>> sizeof(union nvmefc_ls_requests) + >>> sizeof(union nvmefc_ls_responses), >>> - GFP_KERNEL); >>> + GFP_ATOMIC); >>> if (!lsop) { >>> dev_info(lport->dev, >>> "RCV %s LS failed: No memory\n", >> >> I would prefer this was fixed within lpfc rather than introducing atomic >> allocations (1st in either host or target transport). It was introduced >> by lpfc change in irq handling style. > > Thank your for your reply and suggestions! > > Do you think change the lpfc_poll_timeout() to a delayed_work is better? > > Best regards, > Duoming Zhou as a minimum: the lpfc_complete_unsol_iocb handler should be passing off the iocb to a work queue routine - so that the context changes so that either nvme host or nvmet ls callback routines can be called. If possible, it should do the axchg alloc - to avoid a GFP_ATOMIC there as well... It's usually best for these nvme LS's and ELS's to be done in a slow path thread/work queue element. That may mean segmenting a little earlier in the path. -- james