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

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Message-ID: <DM6PR18MB3034D4C12A94CF3121F8B565D2219@DM6PR18MB3034.namprd18.prod.outlook.com>
Date:   Thu, 27 Jan 2022 05:13:29 +0000
From:   Saurav Kashyap <skashyap@...vell.com>
To:     John Meneghini <jmeneghi@...hat.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>,
        "mlombard@...hat.com" <mlombard@...hat.com>,
        "guazhang@...hat.com" <guazhang@...hat.com>
Subject: RE: [EXT] [PATCH] scsi: bnx2fc: make bnx2fc_recv_frame mp safe

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