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

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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: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Mike Christie 2021-02-06 22:46:04 -06:00 committed by Martin K. Petersen
parent c435f0a9ec
commit b4046922b3
2 changed files with 56 additions and 32 deletions
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86
drivers/scsi/libiscsi.c
View File

@ -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);
scsi_cmds = iscsi_host_get_max_scsi_cmds(shost, cmds_max);
if (scsi_cmds < 0)
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)
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;

2
include/scsi/libiscsi.h
View File

@ -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