target: Add transport_handle_cdb_direct optimization

This patch adds a transport_handle_cdb_direct() optimization for mapping
and queueing tasks directly from within fabric processing context by calling
the newly exported transport_generic_new_cmd().  This currently expects to
be called from process context only, and will fail if called within interrupt
context.

This patch also leaves transport_generic_handle_cdb() unmodified for the
moment to function as expected with existing tcm_fc and ib_srpt fabrics,
and will be removed once these have been converted and tested with v4.1
code using transport_handle_cdb_direct().

Based on Andy's original patch here:

[PATCH 39/42] target: Call transport_new_cmd instead of adding to cmd queue

Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index d42a98e..1ae6eb7 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1842,12 +1842,36 @@ int transport_generic_handle_cdb(
                printk(KERN_ERR "cmd->se_lun is NULL\n");
                return -EINVAL;
        }
+
        transport_add_cmd_to_queue(cmd, TRANSPORT_NEW_CMD);
        return 0;
 }
 EXPORT_SYMBOL(transport_generic_handle_cdb);
 
 /*
+ * Used by fabric module frontends to queue tasks directly.
+ * Many only be used from process context only
+ */
+int transport_handle_cdb_direct(
+       struct se_cmd *cmd)
+{
+       if (!cmd->se_lun) {
+               dump_stack();
+               printk(KERN_ERR "cmd->se_lun is NULL\n");
+               return -EINVAL;
+       }
+       if (in_interrupt()) {
+               dump_stack();
+               printk(KERN_ERR "transport_generic_handle_cdb cannot be called"
+                               " from interrupt context\n");
+               return -EINVAL;
+       }
+
+       return transport_generic_new_cmd(cmd);
+}
+EXPORT_SYMBOL(transport_handle_cdb_direct);
+
+/*
  * Used by fabric module frontends defining a TFO->new_cmd_map() caller
  * to  queue up a newly setup se_cmd w/ TRANSPORT_NEW_CMD_MAP in order to
  * complete setup in TCM process context w/ TFO->new_cmd_map().

diff --git a/include/target/target_core_transport.h b/include/target/target_core_transport.h
index 604e669..2aae764 100644 (file)
--- a/include/target/target_core_transport.h
+++ b/include/target/target_core_transport.h
@@ -166,6 +166,7 @@ extern void transport_init_se_cmd(struct se_cmd *,
 extern void transport_free_se_cmd(struct se_cmd *);
 extern int transport_generic_allocate_tasks(struct se_cmd *, unsigned char *);
 extern int transport_generic_handle_cdb(struct se_cmd *);
+extern int transport_handle_cdb_direct(struct se_cmd *);
 extern int transport_generic_handle_cdb_map(struct se_cmd *);
 extern int transport_generic_handle_data(struct se_cmd *);
 extern void transport_new_cmd_failure(struct se_cmd *);