1. 13 Oct, 2008 1 commit
    • Mike Christie's avatar
      [SCSI] Add helper code so transport classes/driver can control queueing (v3) · f0c0a376
      Mike Christie authored
      SCSI-ml manages the queueing limits for the device and host, but
      does not do so at the target level. However something something similar
      can come in userful when a driver is transitioning a transport object to
      the the blocked state, becuase at that time we do not want to queue
      io and we do not want the queuecommand to be called again.
      
      The patch adds code similar to the exisiting SCSI_ML_*BUSY handlers.
      You can now return SCSI_MLQUEUE_TARGET_BUSY when we hit
      a transport level queueing issue like the hw cannot allocate some
      resource at the iscsi session/connection level, or the target has temporarily
      closed or shrunk the queueing window, or if we are transitioning
      to the blocked state.
      
      bnx2i, when they rework their firmware according to netdev
      developers requests, will also need to be able to limit queueing at this
      level. bnx2i will hook into libiscsi, but will allocate a scsi host per
      netdevice/hba, so unlike pure software iscsi/iser which is allocating
      a host per session, it cannot set the scsi_host->can_queue and return
      SCSI_MLQUEUE_HOST_BUSY to reflect queueing limits on the transport.
      
      The iscsi class/driver can also set a scsi_target->can_queue value which
      reflects the max commands the driver/class can support. For iscsi this
      reflects the number of commands we can support for each session due to
      session/connection hw limits, driver limits, and to also reflect the
      session/targets's queueing window.
      
      Changes:
      v1 - initial patch.
      v2 - Fix scsi_run_queue handling of multiple blocked targets.
      Previously we would break from the main loop if a device was added back on
      the starved list. We now run over the list and check if any target is
      blocked.
      v3 - Rediff for scsi-misc.
      Signed-off-by: default avatarMike Christie <michaelc@cs.wisc.edu>
      Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
      f0c0a376
  2. 12 Oct, 2008 39 commits