[SCSI] lpfc: Adjust lpfc_scsi_buf allocation

Adjust lpfc_scsi_buf allocation to account for lun_queue_depth and
error handling

Under high load and high duress, the error handler could steal some
command resources from the normal i/o path. Rework to allocate
additional resources to avoid this scneario.

Signed-off-by: James Smart <James.Smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 16 insertions, 7 deletions

diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index c993069a6500..b903d3b7b730 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/drivers/scsi/lpfc/lpfc_scsi.c
@@ -1152,24 +1152,33 @@ lpfc_slave_alloc(struct scsi_device *sdev)
         /*
          * Populate the cmds_per_lun count scsi_bufs into this host's globally
          * available list of scsi buffers.  Don't allocate more than the
-         * HBA limit conveyed to the midlayer via the host structure.  Note
-         * that this list of scsi bufs exists for the lifetime of the driver.
+         * HBA limit conveyed to the midlayer via the host structure.  The
+         * formula accounts for the lun_queue_depth + error handlers + 1
+         * extra.  This list of scsi bufs exists for the lifetime of the driver.
          */
         total = phba->total_scsi_bufs;
-        num_to_alloc = LPFC_CMD_PER_LUN;
+        num_to_alloc = phba->cfg_lun_queue_depth + 2;
         if (total >= phba->cfg_hba_queue_depth) {
-                printk(KERN_WARNING "%s, At config limitation of "
-                       "%d allocated scsi_bufs\n", __FUNCTION__, total);
+                lpfc_printf_log(phba, KERN_WARNING, LOG_FCP,
+                                "%d:0704 At limitation of %d preallocated "
+                                "command buffers\n", phba->brd_no, total);
                 return 0;
         } else if (total + num_to_alloc > phba->cfg_hba_queue_depth) {
+                lpfc_printf_log(phba, KERN_WARNING, LOG_FCP,
+                                "%d:0705 Allocation request of %d command "
+                                "buffers will exceed max of %d.  Reducing "
+                                "allocation request to %d.\n", phba->brd_no,
+                                num_to_alloc, phba->cfg_hba_queue_depth,
+                                (phba->cfg_hba_queue_depth - total));
                 num_to_alloc = phba->cfg_hba_queue_depth - total;
         }
 
         for (i = 0; i < num_to_alloc; i++) {
                 scsi_buf = lpfc_get_scsi_buf(phba);
                 if (!scsi_buf) {
-                        printk(KERN_ERR "%s, failed to allocate "
-                               "scsi_buf\n", __FUNCTION__);
+                        lpfc_printf_log(phba, KERN_ERR, LOG_FCP,
+                                        "%d:0706 Failed to allocate command "
+                                        "buffer\n", phba->brd_no);
                         break;
                 }