target: Make ABORT and LUN RESET handling synchronous

Instead of invoking target driver callback functions from the
context that handles an abort or LUN RESET task management function,
only set the abort flag from that context and perform the actual
abort handling from the context of the regular command processing
flow. This approach has the following advantages:
- The task management function code becomes much easier to read and
  to verify since the number of potential race conditions against
  the command processing flow is strongly reduced.
- It is no longer needed to store the command state into the command
  itself since that information is no longer needed from the context
  where a task management function is processed.

Notes:
- With this patch applied the CMD_T_ABORTED flag is checked at two points
  by the target core: just before local execution of a command starts
  (see also target_execute_cmd()) and also just before the response is
  sent (see also target_complete_cmd()).
- A new reference count is introduced that tracks the number of
  references held by the target driver, namely se_cmd.tgt_ref.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andy Grover <agrover@redhat.com>
Cc: David Disseldorp <ddiss@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index c84e5eecb94d..e5e0fd852ff5 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -444,6 +444,7 @@ struct se_cmd {
 	unsigned		cmd_wait_set:1;
 	unsigned		unknown_data_length:1;
 	bool			state_active:1;
+	bool			send_abort_response:1;
 	u64			tag; /* SAM command identifier aka task tag */
 	/* Delay for ALUA Active/NonOptimized state access in milliseconds */
 	int			alua_nonop_delay;