target: use a workqueue for I/O completions
Instead of abusing the target processing thread for offloading I/O
completion in the backends to user context add a new workqueue. This means
completions can be processed as fast as available CPU time allows it,
including in parallel with other completions and more importantly I/O
submission or QUEUE FULL retries. This should give much better performance
especially on loaded systems.
As a fallout we can merge all the completed states into a single
one.
On the downside this change complicates lun reset handling a bit by
requiring us to cancel a work item only for those states that have it
initialized. The alternative would be to either always initialize the work
item to a dummy handler, or always use the same handler and do a switch on
the state. The long term solution will be a flag that says that the command
has an initialized work item, but that's only going to be useful once we
have more users.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 07104bf..8e2c83d 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -86,9 +86,7 @@
TRANSPORT_WRITE_PENDING = 3,
TRANSPORT_PROCESS_WRITE = 4,
TRANSPORT_PROCESSING = 5,
- TRANSPORT_COMPLETE_OK = 6,
- TRANSPORT_COMPLETE_FAILURE = 7,
- TRANSPORT_COMPLETE_TIMEOUT = 8,
+ TRANSPORT_COMPLETE = 6,
TRANSPORT_PROCESS_TMR = 9,
TRANSPORT_ISTATE_PROCESSING = 11,
TRANSPORT_NEW_CMD_MAP = 16,
@@ -492,6 +490,8 @@
struct completion transport_lun_stop_comp;
struct scatterlist *t_tasks_sg_chained;
+ struct work_struct work;
+
/*
* Used for pre-registered fabric SGL passthrough WRITE and READ
* with the special SCF_PASSTHROUGH_CONTIG_TO_SG case for TCM_Loop
