linux-kernel - Re: [PATCH] qla2xxx: Protect access to qpair members with qpair->qp

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Date:   Thu, 22 Jun 2017 15:19:27 +0100
From:   John Garry <john.garry@...wei.com>
To:     Johannes Thumshirn <jthumshirn@...e.de>,
        "Martin K . Petersen" <martin.petersen@...cle.com>
CC:     Linux SCSI Mailinglist <linux-scsi@...r.kernel.org>,
        "Linux Kernel Mailinglist" <linux-kernel@...r.kernel.org>,
        <qla2xxx-upstream@...gic.com>,
        Himanshu Madhani <himanshu.madhani@...ium.com>
Subject: Re: [PATCH] qla2xxx: Protect access to qpair members with
 qpair->qp_lock

On 22/06/2017 14:43, Johannes Thumshirn wrote:
> In qla2xx_start_scsi_mq() and qla2xx_dif_start_scsi_mq() we grab the
> qpair->qp_lock but do access members of the qpair before having the lock.
> Re-order the locking sequence to have all read and write access to qpair
> members under the qpair->qp_lock.
>
> Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
> ---
>  drivers/scsi/qla2xxx/qla_iocb.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/scsi/qla2xxx/qla_iocb.c b/drivers/scsi/qla2xxx/qla_iocb.c
> index 8404f17f3c6c..425ca1646a9a 100644
> --- a/drivers/scsi/qla2xxx/qla_iocb.c
> +++ b/drivers/scsi/qla2xxx/qla_iocb.c
> @@ -1770,10 +1770,6 @@ qla2xxx_start_scsi_mq(srb_t *sp)
>  	struct qla_hw_data *ha = vha->hw;
>  	struct qla_qpair *qpair = sp->qpair;
>
> -	/* Setup qpair pointers */
> -	rsp = qpair->rsp;
> -	req = qpair->req;

Can you check the call to qla2x00_marker() before the spinlock grab, 
which takes rsp and req as parameters?

> -
>  	/* So we know we haven't pci_map'ed anything yet */
>  	tot_dsds = 0;
>
> @@ -1788,6 +1784,10 @@ qla2xxx_start_scsi_mq(srb_t *sp)
>  	/* Acquire qpair specific lock */
>  	spin_lock_irqsave(&qpair->qp_lock, flags);
>
> +	/* Setup qpair pointers */
> +	rsp = qpair->rsp;
> +	req = qpair->req;
> +
>  	/* Check for room in outstanding command list. */
>  	handle = req->current_outstanding_cmd;
>  	for (index = 1; index < req->num_outstanding_cmds; index++) {
> @@ -1924,24 +1924,33 @@ qla2xxx_dif_start_scsi_mq(srb_t *sp)
>
>  #define QDSS_GOT_Q_SPACE	BIT_0
>
> +	/* Acquire ring specific lock */
> +	spin_lock_irqsave(&qpair->qp_lock, flags);
> +
>  	/* Check for host side state */
>  	if (!qpair->online) {
>  		cmd->result = DID_NO_CONNECT << 16;
> +		spin_unlock_irqrestore(&qpair->qp_lock, flags);
>  		return QLA_INTERFACE_ERROR;
>  	}
>
>  	if (!qpair->difdix_supported &&
>  		scsi_get_prot_op(cmd) != SCSI_PROT_NORMAL) {
>  		cmd->result = DID_NO_CONNECT << 16;
> +		spin_unlock_irqrestore(&qpair->qp_lock, flags);
>  		return QLA_INTERFACE_ERROR;
>  	}
>
> +	spin_unlock_irqrestore(&qpair->qp_lock, flags);
> +
>  	/* Only process protection or >16 cdb in this routine */
>  	if (scsi_get_prot_op(cmd) == SCSI_PROT_NORMAL) {
>  		if (cmd->cmd_len <= 16)
>  			return qla2xxx_start_scsi_mq(sp);
>  	}
>
> +	spin_lock_irqsave(&qpair->qp_lock, flags);
> +
>  	/* Setup qpair pointers */
>  	rsp = qpair->rsp;
>  	req = qpair->req;
> @@ -1957,9 +1966,6 @@ qla2xxx_dif_start_scsi_mq(srb_t *sp)
>  		vha->marker_needed = 0;
>  	}
>
> -	/* Acquire ring specific lock */
> -	spin_lock_irqsave(&qpair->qp_lock, flags);
> -
>  	/* Check for room in outstanding command list. */
>  	handle = req->current_outstanding_cmd;
>  	for (index = 1; index < req->num_outstanding_cmds; index++) {
>