target/tcm_loop: Make TMF processing slightly faster

Target drivers must guarantee that struct se_cmd and struct se_tmr_req
exist as long as target_tmr_work() is in progress. This is why the
tcm_loop driver today passes 1 as second argument to
transport_generic_free_cmd() from inside the TMF code. Instead of
making the TMF code wait, make the TMF code obtain two references
(SCF_ACK_KREF) and drop one reference from inside the .check_stop_free()
callback.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: David Disseldorp <ddiss@suse.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/loopback/tcm_loop.c b/drivers/target/loopback/tcm_loop.c
index 8cf556b4c5ca724e37bed9bedfe954ad8305ae51..b6a913e38b30183fc3099641c0a5b922677eca0d 100644 (file)
--- a/drivers/target/loopback/tcm_loop.c
+++ b/drivers/target/loopback/tcm_loop.c
@@ -51,19 +51,7 @@ static int tcm_loop_queue_status(struct se_cmd *se_cmd);
  */
 static int tcm_loop_check_stop_free(struct se_cmd *se_cmd)
 {
-       /*
-        * Do not release struct se_cmd's containing a valid TMR
-        * pointer.  These will be released directly in tcm_loop_device_reset()
-        * with transport_generic_free_cmd().
-        */
-       if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
-               return 0;
-       /*
-        * Release the struct se_cmd, which will make a callback to release
-        * struct tcm_loop_cmd * in tcm_loop_deallocate_core_cmd()
-        */
-       transport_generic_free_cmd(se_cmd, 0);
-       return 1;
+       return transport_generic_free_cmd(se_cmd, 0);
 }
 
 static void tcm_loop_release_cmd(struct se_cmd *se_cmd)
@@ -244,18 +232,23 @@ static int tcm_loop_issue_tmr(struct tcm_loop_tpg *tl_tpg,
        se_sess = tl_tpg->tl_nexus->se_sess;
 
        rc = target_submit_tmr(se_cmd, se_sess, tl_cmd->tl_sense_buf, lun,
-                              NULL, tmr, GFP_KERNEL, task, 0 /*flags*/);
+                              NULL, tmr, GFP_KERNEL, task,
+                              TARGET_SCF_ACK_KREF);
        if (rc < 0)
                goto release;
        wait_for_completion(&tl_cmd->tmr_done);
        ret = se_cmd->se_tmr_req->response;
+       target_put_sess_cmd(se_cmd);
+
+out:
+       return ret;
 
 release:
        if (se_cmd)
-               transport_generic_free_cmd(se_cmd, 1);
+               transport_generic_free_cmd(se_cmd, 0);
        else
                kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
-       return ret;
+       goto out;
 }
 
 static int tcm_loop_abort_task(struct scsi_cmnd *sc)