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Commit a784efbf authored by James.Smart@Emulex.Com's avatar James.Smart@Emulex.Com Committed by James Bottomley
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[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: default avatarJames Smart <James.Smart@emulex.com>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
parent 68876920

drivers/scsi/lpfc/lpfc_scsi.c

+16 −7
Original line number Diff line number Diff line
@@ -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;

		}