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: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index b271d3accd2af58ccf32418e2dbe8306a8d5f280..f64e2077754cd0881fe96484f4a1d0fa6cc7432c 100644 (file)
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -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;

diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 44a9554aea6249328d4c35eeff8bee27e8071d05..02f966e9358f68e3841ca8fe03ebf6da113e9d01 100644 (file)
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -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