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authorMike Christie <michaelc@cs.wisc.edu>2008-08-18 00:24:38 +0400
committerJames Bottomley <James.Bottomley@HansenPartnership.com>2008-10-13 17:28:46 +0400
commitf0c0a376d0fcd4c5579ecf5e95f88387cba85211 (patch)
tree16b97ab71a22106cb1e5c1a177ab6c8103fe5a48 /include/scsi/scsi_device.h
parent4480f15b3306f43bbb0310d461142b4e897ca45b (diff)
downloadlinux-f0c0a376d0fcd4c5579ecf5e95f88387cba85211.tar.xz
[SCSI] Add helper code so transport classes/driver can control queueing (v3)
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: Mike Christie <michaelc@cs.wisc.edu> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Diffstat (limited to 'include/scsi/scsi_device.h')
-rw-r--r--include/scsi/scsi_device.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index b49e725be039..a37a8148a310 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -238,6 +238,16 @@ struct scsi_target {
* for the device at a time. */
unsigned int pdt_1f_for_no_lun; /* PDT = 0x1f */
/* means no lun present */
+ /* commands actually active on LLD. protected by host lock. */
+ unsigned int target_busy;
+ /*
+ * LLDs should set this in the slave_alloc host template callout.
+ * If set to zero then there is not limit.
+ */
+ unsigned int can_queue;
+ unsigned int target_blocked;
+ unsigned int max_target_blocked;
+#define SCSI_DEFAULT_TARGET_BLOCKED 3
char scsi_level;
struct execute_work ew;