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

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Date:   Fri, 28 Jan 2022 15:48:46 -0500
From:   John Meneghini <jmeneghi@...hat.com>
To:     "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     Nilesh Javali <njavali@...vell.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        GR-QLogic-Storage-Upstream <GR-QLogic-Storage-Upstream@...vell.com>,
        Saurav Kashyap <skashyap@...vell.com>,
        "mlombard@...hat.com" <mlombard@...hat.com>,
        "guazhang@...hat.com" <guazhang@...hat.com>
Subject: Re: [EXT] [PATCH] scsi: bnx2fc: make bnx2fc_recv_frame mp safe

Thanks.

Martin, is it too late to get this into staging for v5.17-rc2?

Please merge this patch.

/John

On 1/27/22 00:13, Saurav Kashyap wrote:
> Hi John,
> 
>> -----Original Message-----
>> From: John Meneghini <jmeneghi@...hat.com>
>> Sent: Monday, January 24, 2022 8:21 PM
>> To: Saurav Kashyap <skashyap@...vell.com>
>> Cc: Nilesh Javali <njavali@...vell.com>; linux-scsi@...r.kernel.org; linux-
>> kernel@...r.kernel.org; GR-QLogic-Storage-Upstream <GR-QLogic-Storage-
>> Upstream@...vell.com>; mlombard@...hat.com; guazhang@...hat.com
>> Subject: [EXT] [PATCH] scsi: bnx2fc: make bnx2fc_recv_frame mp safe
>>
>> External Email
>>
>> ----------------------------------------------------------------------
>>      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;
>>   	}
>> --
> 
> Thanks for the patch.
> 
> Acked-by: Saurav Kashyap <skashyap@...vell.com>
> 
>> 2.27.0
>