Commit b4046922 authored by Mike Christie's avatar Mike Christie Committed by Martin K. Petersen
Browse files

scsi: libiscsi: Add helper to calculate max SCSI cmds per session 

This patch just breaks out the code that calculates the number of SCSI cmds
that will be used for a SCSI session. It also adds a check that we don't go
over the host's can_queue value.

Link: https://lore.kernel.org/r/20210207044608.27585-6-michael.christie@oracle.com


Reviewed-by: default avatarLee Duncan <lduncan@suse.com>
Signed-off-by: default avatarMike Christie <michael.christie@oracle.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent c435f0a9

drivers/scsi/libiscsi.c

+54 −32
Original line number Diff line number Diff line
@@ -2648,6 +2648,56 @@ void iscsi_pool_free(struct iscsi_pool *q) 
}

EXPORT_SYMBOL_GPL(iscsi_pool_free);



int iscsi_host_get_max_scsi_cmds(struct Scsi_Host *shost,

				 uint16_t requested_cmds_max)

{

	int scsi_cmds, total_cmds = requested_cmds_max;



check:

	if (!total_cmds)

		total_cmds = ISCSI_DEF_XMIT_CMDS_MAX;

	/*

	 * The iscsi layer needs some tasks for nop handling and tmfs,

	 * so the cmds_max must at least be greater than ISCSI_MGMT_CMDS_MAX

	 * + 1 command for scsi IO.

	 */

	if (total_cmds < ISCSI_TOTAL_CMDS_MIN) {

		printk(KERN_ERR "iscsi: invalid max cmds of %d. Must be a power of two that is at least %d.\n",

		       total_cmds, ISCSI_TOTAL_CMDS_MIN);

		return -EINVAL;

	}



	if (total_cmds > ISCSI_TOTAL_CMDS_MAX) {

		printk(KERN_INFO "iscsi: invalid max cmds of %d. Must be a power of 2 less than or equal to %d. Using %d.\n",

		       requested_cmds_max, ISCSI_TOTAL_CMDS_MAX,

		       ISCSI_TOTAL_CMDS_MAX);

		total_cmds = ISCSI_TOTAL_CMDS_MAX;

	}



	if (!is_power_of_2(total_cmds)) {

		total_cmds = rounddown_pow_of_two(total_cmds);

		if (total_cmds < ISCSI_TOTAL_CMDS_MIN) {

			printk(KERN_ERR "iscsi: invalid max cmds of %d. Must be a power of 2 greater than %d.\n", requested_cmds_max, ISCSI_TOTAL_CMDS_MIN);

			return -EINVAL;

		}



		printk(KERN_INFO "iscsi: invalid max cmds %d. Must be a power of 2. Rounding max cmds down to %d.\n",

		       requested_cmds_max, total_cmds);

	}



	scsi_cmds = total_cmds - ISCSI_MGMT_CMDS_MAX;

	if (shost->can_queue && scsi_cmds > shost->can_queue) {

		total_cmds = shost->can_queue;



		printk(KERN_INFO "iscsi: requested max cmds %u is higher than driver limit. Using driver limit %u\n",

		       requested_cmds_max, shost->can_queue);

		goto check;

	}



	return scsi_cmds;

}

EXPORT_SYMBOL_GPL(iscsi_host_get_max_scsi_cmds);



/**

 * iscsi_host_add - add host to system

 * @shost: scsi host
@@ -2801,7 +2851,7 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost, 
	struct iscsi_host *ihost = shost_priv(shost);

	struct iscsi_session *session;

	struct iscsi_cls_session *cls_session;

	int cmd_i, scsi_cmds, total_cmds = cmds_max;

	int cmd_i, scsi_cmds;

	unsigned long flags;



	spin_lock_irqsave(&ihost->lock, flags);
@@ -2812,37 +2862,9 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost, 
	ihost->num_sessions++;

	spin_unlock_irqrestore(&ihost->lock, flags);



	if (!total_cmds)

		total_cmds = ISCSI_DEF_XMIT_CMDS_MAX;

	/*

	 * The iscsi layer needs some tasks for nop handling and tmfs,

	 * so the cmds_max must at least be greater than ISCSI_MGMT_CMDS_MAX

	 * + 1 command for scsi IO.

	 */

	if (total_cmds < ISCSI_TOTAL_CMDS_MIN) {

		printk(KERN_ERR "iscsi: invalid can_queue of %d. can_queue "

		       "must be a power of two that is at least %d.\n",

		       total_cmds, ISCSI_TOTAL_CMDS_MIN);

		goto dec_session_count;

	}



	if (total_cmds > ISCSI_TOTAL_CMDS_MAX) {

		printk(KERN_ERR "iscsi: invalid can_queue of %d. can_queue "

		       "must be a power of 2 less than or equal to %d.\n",

		       cmds_max, ISCSI_TOTAL_CMDS_MAX);

		total_cmds = ISCSI_TOTAL_CMDS_MAX;

	}



	if (!is_power_of_2(total_cmds)) {

		printk(KERN_ERR "iscsi: invalid can_queue of %d. can_queue "

		       "must be a power of 2.\n", total_cmds);

		total_cmds = rounddown_pow_of_two(total_cmds);

		if (total_cmds < ISCSI_TOTAL_CMDS_MIN)

	scsi_cmds = iscsi_host_get_max_scsi_cmds(shost, cmds_max);

	if (scsi_cmds < 0)

		goto dec_session_count;

		printk(KERN_INFO "iscsi: Rounding can_queue to %d.\n",

		       total_cmds);

	}

	scsi_cmds = total_cmds - ISCSI_MGMT_CMDS_MAX;



	cls_session = iscsi_alloc_session(shost, iscsit,

					  sizeof(struct iscsi_session) +
@@ -2858,7 +2880,7 @@ iscsi_session_setup(struct iscsi_transport *iscsit, struct Scsi_Host *shost, 
	session->lu_reset_timeout = 15;

	session->abort_timeout = 10;

	session->scsi_cmds_max = scsi_cmds;

	session->cmds_max = total_cmds;

	session->cmds_max = scsi_cmds + ISCSI_MGMT_CMDS_MAX;

	session->queued_cmdsn = session->cmdsn = initial_cmdsn;

	session->exp_cmdsn = initial_cmdsn + 1;

	session->max_cmdsn = initial_cmdsn + 1;

include/scsi/libiscsi.h

+2 −0
Original line number Diff line number Diff line
@@ -395,6 +395,8 @@ extern struct Scsi_Host *iscsi_host_alloc(struct scsi_host_template *sht, 
extern void iscsi_host_remove(struct Scsi_Host *shost);

extern void iscsi_host_free(struct Scsi_Host *shost);

extern int iscsi_target_alloc(struct scsi_target *starget);

extern int iscsi_host_get_max_scsi_cmds(struct Scsi_Host *shost,

					uint16_t requested_cmds_max);



/*

 * session management