linux-kernel - Re: [PATCH] scsi: bnx2fc: make bnx2fc_recv

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Date:   Tue, 25 Jan 2022 12:32:54 -0500
From:   John Meneghini <jmeneghi@...hat.com>
To:     skashyap@...vell.com, njavali@...vell.com, mlombard@...hat.com
Cc:     linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        GR-QLogic-Storage-Upstream@...vell.com,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH] scsi: bnx2fc: make bnx2fc_recv_frame mp safe

Can I please get a review and approval for this patch?

I'd like this to get into v5.17-rc2

Thanks,

/John


On 1/24/22 09:51, John Meneghini wrote:
>      Running tests with a debug kernel shows that bnx2fc_recv_frame is
>      modifying the per_cpu lport stats counters in a non-mpsafe way.
>      Just boot a debug kernel and run the bnx2fc driver with the hardware
>      enabled.
> 
>      [ 1391.699147] BUG: using smp_processor_id() in preemptible [00000000] code: bnx2fc_
>      [ 1391.699160] caller is bnx2fc_recv_frame+0xbf9/0x1760 [bnx2fc]
>      [ 1391.699174] CPU: 2 PID: 4355 Comm: bnx2fc_l2_threa Kdump: loaded Tainted: G    B
>      [ 1391.699180] Hardware name: HP ProLiant DL120 G7, BIOS J01 07/01/2013
>      [ 1391.699183] Call Trace:
>      [ 1391.699188]  dump_stack_lvl+0x57/0x7d
>      [ 1391.699198]  check_preemption_disabled+0xc8/0xd0
>      [ 1391.699205]  bnx2fc_recv_frame+0xbf9/0x1760 [bnx2fc]
>      [ 1391.699215]  ? do_raw_spin_trylock+0xb5/0x180
>      [ 1391.699221]  ? bnx2fc_npiv_create_vports.isra.0+0x4e0/0x4e0 [bnx2fc]
>      [ 1391.699229]  ? bnx2fc_l2_rcv_thread+0xb7/0x3a0 [bnx2fc]
>      [ 1391.699240]  bnx2fc_l2_rcv_thread+0x1af/0x3a0 [bnx2fc]
>      [ 1391.699250]  ? bnx2fc_ulp_init+0xc0/0xc0 [bnx2fc]
>      [ 1391.699258]  kthread+0x364/0x420
>      [ 1391.699263]  ? _raw_spin_unlock_irq+0x24/0x50
>      [ 1391.699268]  ? set_kthread_struct+0x100/0x100
>      [ 1391.699273]  ret_from_fork+0x22/0x30
> 
>      To fix the problem: restore the old get_cpu/put_cpu code with some
>      modifications to reduce the size of the critical section.
> 
> Fixes: d576a5e80cd0 ("bnx2fc: Improve stats update mechanism")
> Tested-by: Guangwu Zhang <guazhang@...hat.com>
> Signed-off-by: John Meneghini <jmeneghi@...hat.com>
> ---
>   drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
> index 71fa62bd3083..e41a94dc2d1f 100644
> --- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
> +++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
> @@ -508,7 +508,8 @@ static int bnx2fc_l2_rcv_thread(void *arg)
>   
>   static void bnx2fc_recv_frame(struct sk_buff *skb)
>   {
> -	u32 fr_len;
> +	u64 crc_err;
> +	u32 fr_len, fr_crc;
>   	struct fc_lport *lport;
>   	struct fcoe_rcv_info *fr;
>   	struct fc_stats *stats;
> @@ -542,6 +543,11 @@ static void bnx2fc_recv_frame(struct sk_buff *skb)
>   	skb_pull(skb, sizeof(struct fcoe_hdr));
>   	fr_len = skb->len - sizeof(struct fcoe_crc_eof);
>   
> +	stats = per_cpu_ptr(lport->stats, get_cpu());
> +	stats->RxFrames++;
> +	stats->RxWords += fr_len / FCOE_WORD_TO_BYTE;
> +	put_cpu();
> +
>   	fp = (struct fc_frame *)skb;
>   	fc_frame_init(fp);
>   	fr_dev(fp) = lport;
> @@ -624,16 +630,15 @@ static void bnx2fc_recv_frame(struct sk_buff *skb)
>   		return;
>   	}
>   
> -	stats = per_cpu_ptr(lport->stats, smp_processor_id());
> -	stats->RxFrames++;
> -	stats->RxWords += fr_len / FCOE_WORD_TO_BYTE;
> +	fr_crc = le32_to_cpu(fr_crc(fp));
>   
> -	if (le32_to_cpu(fr_crc(fp)) !=
> -			~crc32(~0, skb->data, fr_len)) {
> -		if (stats->InvalidCRCCount < 5)
> +	if (unlikely(fr_crc != ~crc32(~0, skb->data, fr_len))) {
> +		stats = per_cpu_ptr(lport->stats, get_cpu());
> +		crc_err = (stats->InvalidCRCCount++);
> +		put_cpu();
> +		if (crc_err < 5)
>   			printk(KERN_WARNING PFX "dropping frame with "
>   			       "CRC error\n");
> -		stats->InvalidCRCCount++;
>   		kfree_skb(skb);
>   		return;
>   	}