Re: [PATCH v3 26/48] scsi: iscsi: Stop using the SCSI pointer

[Lee Duncan <lduncan@suse.com>]

On 2/11/22 14:32, Bart Van Assche wrote:
> Instead of storing the iSCSI task pointer and the session age in the SCSI
> pointer, use command-private variables. This patch prepares for removal of
> the SCSI pointer from struct scsi_cmnd.
> 
> The list of iSCSI drivers has been obtained as follows:
> $ git grep -lw iscsi_host_alloc
> drivers/infiniband/ulp/iser/iscsi_iser.c
> drivers/scsi/be2iscsi/be_main.c
> drivers/scsi/bnx2i/bnx2i_iscsi.c
> drivers/scsi/cxgbi/libcxgbi.c
> drivers/scsi/iscsi_tcp.c
> drivers/scsi/libiscsi.c
> drivers/scsi/qedi/qedi_main.c
> drivers/scsi/qla4xxx/ql4_os.c
> include/scsi/libiscsi.h
> 
> Note: it is not clear to me how the qla4xxx driver can work without this
> patch since it uses the scsi_cmnd::SCp.ptr member for two different
> purposes:
> - The qla4xxx driver uses this member to store a struct srb pointer.
> - libiscsi uses this member to store a struct iscsi_task pointer.
> 
> Cc: Lee Duncan <lduncan@suse.com>
> Cc: Chris Leech <cleech@redhat.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Hannes Reinecke <hare@suse.de>
> Cc: Himanshu Madhani <himanshu.madhani@oracle.com>
> Cc: Nilesh Javali <njavali@marvell.com>
> Cc: Manish Rangankar <mrangankar@marvell.com>
> Cc: Karen Xie <kxie@chelsio.com>
> Cc: Ketan Mukadam <ketan.mukadam@broadcom.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> 
> iscsi
> ---
>   drivers/infiniband/ulp/iser/iscsi_iser.c |  1 +
>   drivers/scsi/be2iscsi/be_main.c          |  3 ++-
>   drivers/scsi/bnx2i/bnx2i_iscsi.c         |  1 +
>   drivers/scsi/cxgbi/cxgb3i/cxgb3i.c       |  1 +
>   drivers/scsi/cxgbi/cxgb4i/cxgb4i.c       |  1 +
>   drivers/scsi/iscsi_tcp.c                 |  1 +
>   drivers/scsi/libiscsi.c                  | 20 ++++++++++----------
>   drivers/scsi/qedi/qedi_fw.c              |  4 ++--
>   drivers/scsi/qedi/qedi_iscsi.c           |  1 +
>   drivers/scsi/qla4xxx/ql4_def.h           | 16 +++++++++++++---
>   drivers/scsi/qla4xxx/ql4_os.c            | 13 +++++++------
>   include/scsi/libiscsi.h                  | 12 ++++++++++++
>   12 files changed, 52 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/infiniband/ulp/iser/iscsi_iser.c b/drivers/infiniband/ulp/iser/iscsi_iser.c
> index 07e47021a71f..f8d0bab4424c 100644
> --- a/drivers/infiniband/ulp/iser/iscsi_iser.c
> +++ b/drivers/infiniband/ulp/iser/iscsi_iser.c
> @@ -971,6 +971,7 @@ static struct scsi_host_template iscsi_iser_sht = {
>   	.proc_name              = "iscsi_iser",
>   	.this_id                = -1,
>   	.track_queue_depth	= 1,
> +	.cmd_size		= sizeof(struct iscsi_cmd),
>   };
>   
>   static struct iscsi_transport iscsi_iser_transport = {
> diff --git a/drivers/scsi/be2iscsi/be_main.c b/drivers/scsi/be2iscsi/be_main.c
> index ab55681145f8..3bb0adefbe06 100644
> --- a/drivers/scsi/be2iscsi/be_main.c
> +++ b/drivers/scsi/be2iscsi/be_main.c
> @@ -218,7 +218,7 @@ static char const *cqe_desc[] = {
>   
>   static int beiscsi_eh_abort(struct scsi_cmnd *sc)
>   {
> -	struct iscsi_task *abrt_task = (struct iscsi_task *)sc->SCp.ptr;
> +	struct iscsi_task *abrt_task = iscsi_cmd(sc)->task;
>   	struct iscsi_cls_session *cls_session;
>   	struct beiscsi_io_task *abrt_io_task;
>   	struct beiscsi_conn *beiscsi_conn;
> @@ -403,6 +403,7 @@ static struct scsi_host_template beiscsi_sht = {
>   	.cmd_per_lun = BEISCSI_CMD_PER_LUN,
>   	.vendor_id = SCSI_NL_VID_TYPE_PCI | BE_VENDOR_ID,
>   	.track_queue_depth = 1,
> +	.cmd_size = sizeof(struct iscsi_cmd),
>   };
>   
>   static struct scsi_transport_template *beiscsi_scsi_transport;
> diff --git a/drivers/scsi/bnx2i/bnx2i_iscsi.c b/drivers/scsi/bnx2i/bnx2i_iscsi.c
> index e21b053b4f3e..fe86fd61a995 100644
> --- a/drivers/scsi/bnx2i/bnx2i_iscsi.c
> +++ b/drivers/scsi/bnx2i/bnx2i_iscsi.c
> @@ -2268,6 +2268,7 @@ static struct scsi_host_template bnx2i_host_template = {
>   	.sg_tablesize		= ISCSI_MAX_BDS_PER_CMD,
>   	.shost_groups		= bnx2i_dev_groups,
>   	.track_queue_depth	= 1,
> +	.cmd_size		= sizeof(struct iscsi_cmd),
>   };
>   
>   struct iscsi_transport bnx2i_iscsi_transport = {
> diff --git a/drivers/scsi/cxgbi/cxgb3i/cxgb3i.c b/drivers/scsi/cxgbi/cxgb3i/cxgb3i.c
> index f949a4e00783..ff9d4287937a 100644
> --- a/drivers/scsi/cxgbi/cxgb3i/cxgb3i.c
> +++ b/drivers/scsi/cxgbi/cxgb3i/cxgb3i.c
> @@ -98,6 +98,7 @@ static struct scsi_host_template cxgb3i_host_template = {
>   	.dma_boundary	= PAGE_SIZE - 1,
>   	.this_id	= -1,
>   	.track_queue_depth = 1,
> +	.cmd_size	= sizeof(struct iscsi_cmd),
>   };
>   
>   static struct iscsi_transport cxgb3i_iscsi_transport = {
> diff --git a/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c b/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> index efb3e2b3398e..53d91bf9c12a 100644
> --- a/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> +++ b/drivers/scsi/cxgbi/cxgb4i/cxgb4i.c
> @@ -116,6 +116,7 @@ static struct scsi_host_template cxgb4i_host_template = {
>   	.dma_boundary	= PAGE_SIZE - 1,
>   	.this_id	= -1,
>   	.track_queue_depth = 1,
> +	.cmd_size	= sizeof(struct iscsi_cmd),
>   };
>   
>   static struct iscsi_transport cxgb4i_iscsi_transport = {
> diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
> index 1bc37593c88f..9fee70d6434a 100644
> --- a/drivers/scsi/iscsi_tcp.c
> +++ b/drivers/scsi/iscsi_tcp.c
> @@ -1007,6 +1007,7 @@ static struct scsi_host_template iscsi_sw_tcp_sht = {
>   	.proc_name		= "iscsi_tcp",
>   	.this_id		= -1,
>   	.track_queue_depth	= 1,
> +	.cmd_size		= sizeof(struct iscsi_cmd),
>   };
>   
>   static struct iscsi_transport iscsi_sw_tcp_transport = {
> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> index 059dae8909ee..d69203d19f2c 100644
> --- a/drivers/scsi/libiscsi.c
> +++ b/drivers/scsi/libiscsi.c
> @@ -462,7 +462,7 @@ static void iscsi_free_task(struct iscsi_task *task)
>   
>   	if (sc) {
>   		/* SCSI eh reuses commands to verify us */
> -		sc->SCp.ptr = NULL;
> +		iscsi_cmd(sc)->task = NULL;
>   		/*
>   		 * queue command may call this to free the task, so
>   		 * it will decide how to return sc to scsi-ml.
> @@ -1344,10 +1344,10 @@ struct iscsi_task *iscsi_itt_to_ctask(struct iscsi_conn *conn, itt_t itt)
>   	if (!task || !task->sc)
>   		return NULL;
>   
> -	if (task->sc->SCp.phase != conn->session->age) {
> +	if (iscsi_cmd(task->sc)->age != conn->session->age) {
>   		iscsi_session_printk(KERN_ERR, conn->session,
>   				  "task's session age %d, expected %d\n",
> -				  task->sc->SCp.phase, conn->session->age);
> +				  iscsi_cmd(task->sc)->age, conn->session->age);
>   		return NULL;
>   	}
>   
> @@ -1645,8 +1645,8 @@ static inline struct iscsi_task *iscsi_alloc_task(struct iscsi_conn *conn,
>   			 (void *) &task, sizeof(void *)))
>   		return NULL;
>   
> -	sc->SCp.phase = conn->session->age;
> -	sc->SCp.ptr = (char *) task;
> +	iscsi_cmd(sc)->age = conn->session->age;
> +	iscsi_cmd(sc)->task = task;
>   
>   	refcount_set(&task->refcount, 1);
>   	task->state = ISCSI_TASK_PENDING;
> @@ -1683,7 +1683,7 @@ int iscsi_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *sc)
>   	struct iscsi_task *task = NULL;
>   
>   	sc->result = 0;
> -	sc->SCp.ptr = NULL;
> +	iscsi_cmd(sc)->task = NULL;
>   
>   	ihost = shost_priv(host);
>   
> @@ -1997,7 +1997,7 @@ enum blk_eh_timer_return iscsi_eh_cmd_timed_out(struct scsi_cmnd *sc)
>   
>   	spin_lock_bh(&session->frwd_lock);
>   	spin_lock(&session->back_lock);
> -	task = (struct iscsi_task *)sc->SCp.ptr;
> +	task = iscsi_cmd(sc)->task;
>   	if (!task) {
>   		/*
>   		 * Raced with completion. Blk layer has taken ownership
> @@ -2260,7 +2260,7 @@ int iscsi_eh_abort(struct scsi_cmnd *sc)
>   	 * if session was ISCSI_STATE_IN_RECOVERY then we may not have
>   	 * got the command.
>   	 */
> -	if (!sc->SCp.ptr) {
> +	if (!iscsi_cmd(sc)->task) {
>   		ISCSI_DBG_EH(session, "sc never reached iscsi layer or "
>   				      "it completed.\n");
>   		spin_unlock_bh(&session->frwd_lock);
> @@ -2273,7 +2273,7 @@ int iscsi_eh_abort(struct scsi_cmnd *sc)
>   	 * then let the host reset code handle this
>   	 */
>   	if (!session->leadconn || session->state != ISCSI_STATE_LOGGED_IN ||
> -	    sc->SCp.phase != session->age) {
> +	    iscsi_cmd(sc)->age != session->age) {
>   		spin_unlock_bh(&session->frwd_lock);
>   		mutex_unlock(&session->eh_mutex);
>   		ISCSI_DBG_EH(session, "failing abort due to dropped "
> @@ -2282,7 +2282,7 @@ int iscsi_eh_abort(struct scsi_cmnd *sc)
>   	}
>   
>   	spin_lock(&session->back_lock);
> -	task = (struct iscsi_task *)sc->SCp.ptr;
> +	task = iscsi_cmd(sc)->task;
>   	if (!task || !task->sc) {
>   		/* task completed before time out */
>   		ISCSI_DBG_EH(session, "sc completed while abort in progress\n");
> diff --git a/drivers/scsi/qedi/qedi_fw.c b/drivers/scsi/qedi/qedi_fw.c
> index 5916ed7662d5..4e99508ff95d 100644
> --- a/drivers/scsi/qedi/qedi_fw.c
> +++ b/drivers/scsi/qedi/qedi_fw.c
> @@ -603,9 +603,9 @@ static void qedi_scsi_completion(struct qedi_ctx *qedi,
>   		goto error;
>   	}
>   
> -	if (!sc_cmd->SCp.ptr) {
> +	if (!iscsi_cmd(sc_cmd)->task) {
>   		QEDI_WARN(&qedi->dbg_ctx,
> -			  "SCp.ptr is NULL, returned in another context.\n");
> +			  "NULL task pointer, returned in another context.\n");
>   		goto error;
>   	}
>   
> diff --git a/drivers/scsi/qedi/qedi_iscsi.c b/drivers/scsi/qedi/qedi_iscsi.c
> index 282ecb4e39bb..8196f89f404e 100644
> --- a/drivers/scsi/qedi/qedi_iscsi.c
> +++ b/drivers/scsi/qedi/qedi_iscsi.c
> @@ -59,6 +59,7 @@ struct scsi_host_template qedi_host_template = {
>   	.dma_boundary = QEDI_HW_DMA_BOUNDARY,
>   	.cmd_per_lun = 128,
>   	.shost_groups = qedi_shost_groups,
> +	.cmd_size = sizeof(struct iscsi_cmd),
>   };
>   
>   static void qedi_conn_free_login_resources(struct qedi_ctx *qedi,
> diff --git a/drivers/scsi/qla4xxx/ql4_def.h b/drivers/scsi/qla4xxx/ql4_def.h
> index 69a590546bf9..5f82c8afd5e0 100644
> --- a/drivers/scsi/qla4xxx/ql4_def.h
> +++ b/drivers/scsi/qla4xxx/ql4_def.h
> @@ -216,11 +216,21 @@
>   #define IDC_COMP_TOV			5
>   #define LINK_UP_COMP_TOV		30
>   
> -#define CMD_SP(Cmnd)			((Cmnd)->SCp.ptr)
> +/*
> + * Note: the data structure below does not have a struct iscsi_cmd member since
> + * the qla4xxx driver does not use libiscsi for SCSI I/O.
> + */
> +struct qla4xxx_cmd_priv {
> +	struct srb *srb;
> +};
> +
> +static inline struct qla4xxx_cmd_priv *qla4xxx_cmd_priv(struct scsi_cmnd *cmd)
> +{
> +	return scsi_cmd_priv(cmd);
> +}
>   
>   /*
> - * SCSI Request Block structure	 (srb)	that is placed
> - * on cmd->SCp location of every I/O	 [We have 22 bytes available]
> + * SCSI Request Block structure (srb) that is associated with each scsi_cmnd.
>    */
>   struct srb {
>   	struct list_head list;	/* (8)	 */
> diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
> index 0ae936d839f1..d64eda961412 100644
> --- a/drivers/scsi/qla4xxx/ql4_os.c
> +++ b/drivers/scsi/qla4xxx/ql4_os.c
> @@ -226,6 +226,7 @@ static struct scsi_host_template qla4xxx_driver_template = {
>   	.name			= DRIVER_NAME,
>   	.proc_name		= DRIVER_NAME,
>   	.queuecommand		= qla4xxx_queuecommand,
> +	.cmd_size		= sizeof(struct qla4xxx_cmd_priv),
>   
>   	.eh_abort_handler	= qla4xxx_eh_abort,
>   	.eh_device_reset_handler = qla4xxx_eh_device_reset,
> @@ -4054,7 +4055,7 @@ static struct srb* qla4xxx_get_new_srb(struct scsi_qla_host *ha,
>   	srb->ddb = ddb_entry;
>   	srb->cmd = cmd;
>   	srb->flags = 0;
> -	CMD_SP(cmd) = (void *)srb;
> +	qla4xxx_cmd_priv(cmd)->srb = srb;
>   
>   	return srb;
>   }
> @@ -4067,7 +4068,7 @@ static void qla4xxx_srb_free_dma(struct scsi_qla_host *ha, struct srb *srb)
>   		scsi_dma_unmap(cmd);
>   		srb->flags &= ~SRB_DMA_VALID;
>   	}
> -	CMD_SP(cmd) = NULL;
> +	qla4xxx_cmd_priv(cmd)->srb = NULL;
>   }
>   
>   void qla4xxx_srb_compl(struct kref *ref)
> @@ -4640,7 +4641,7 @@ static int qla4xxx_cmd_wait(struct scsi_qla_host *ha)
>   			 * the scsi/block layer is going to prevent
>   			 * the tag from being released.
>   			 */
> -			if (cmd != NULL && CMD_SP(cmd))
> +			if (cmd != NULL && qla4xxx_cmd_priv(cmd)->srb)
>   				break;
>   		}
>   		spin_unlock_irqrestore(&ha->hardware_lock, flags);
> @@ -9079,7 +9080,7 @@ struct srb *qla4xxx_del_from_active_array(struct scsi_qla_host *ha,
>   	if (!cmd)
>   		return srb;
>   
> -	srb = (struct srb *)CMD_SP(cmd);
> +	srb = qla4xxx_cmd_priv(cmd)->srb;
>   	if (!srb)
>   		return srb;
>   
> @@ -9121,7 +9122,7 @@ static int qla4xxx_eh_wait_on_command(struct scsi_qla_host *ha,
>   
>   	do {
>   		/* Checking to see if its returned to OS */
> -		rp = (struct srb *) CMD_SP(cmd);
> +		rp = qla4xxx_cmd_priv(cmd)->srb;
>   		if (rp == NULL) {
>   			done++;
>   			break;
> @@ -9215,7 +9216,7 @@ static int qla4xxx_eh_abort(struct scsi_cmnd *cmd)
>   	}
>   
>   	spin_lock_irqsave(&ha->hardware_lock, flags);
> -	srb = (struct srb *) CMD_SP(cmd);
> +	srb = qla4xxx_cmd_priv(cmd)->srb;
>   	if (!srb) {
>   		spin_unlock_irqrestore(&ha->hardware_lock, flags);
>   		ql4_printk(KERN_INFO, ha, "scsi%ld:%d:%llu: Specified command has already completed.\n",
> diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
> index 4ee233e5a6ff..cb805ed9cbf1 100644
> --- a/include/scsi/libiscsi.h
> +++ b/include/scsi/libiscsi.h
> @@ -19,6 +19,7 @@
>   #include <linux/refcount.h>
>   #include <scsi/iscsi_proto.h>
>   #include <scsi/iscsi_if.h>
> +#include <scsi/scsi_cmnd.h>
>   #include <scsi/scsi_transport_iscsi.h>
>   
>   struct scsi_transport_template;
> @@ -152,6 +153,17 @@ static inline bool iscsi_task_is_completed(struct iscsi_task *task)
>   	       task->state == ISCSI_TASK_ABRT_SESS_RECOV;
>   }
>   
> +/* Private data associated with struct scsi_cmnd. */
> +struct iscsi_cmd {
> +	struct iscsi_task	*task;
> +	int			age;
> +};
> +
> +static inline struct iscsi_cmd *iscsi_cmd(struct scsi_cmnd *cmd)
> +{
> +	return scsi_cmd_priv(cmd);
> +}
> +
>   /* Connection's states */
>   enum {
>   	ISCSI_CONN_INITIAL_STAGE,
> 

Reviewed-by: Lee Duncan <lduncan@suse.com>