linux-kernel - Re: [PATCH] nvme-fc: fix sleep-in-atomic-context bug caused by nvme_fc_rcv_ls

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Message-ID: <305fbf18-6759-9b00-6fc0-93a4a2e40be2@gmail.com>
Date:   Sun, 2 Oct 2022 10:12:15 -0700
From:   James Smart <jsmart2021@...il.com>
To:     Duoming Zhou <duoming@....edu.cn>, linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, james.smart@...adcom.com,
        kbusch@...nel.org, axboe@...com, hch@....de, sagi@...mberg.me
Subject: Re: [PATCH] nvme-fc: fix sleep-in-atomic-context bug caused by
 nvme_fc_rcv_ls_req

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 <duoming@....edu.cn>
> ---
>   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.

-- james


-- james