scsi: target: Allow userspace to request direct submissions

This allows userspace to request the fabric drivers do direct submissions
if they support it. With the new device file, submit_type, users can
write 0 - 2 to control how commands are submitted to the backend:

 0 - TARGET_FABRIC_DEFAULT_SUBMIT - LIO will use the fabric's default
     submission type. This is the default for compat.

 1 - TARGET_DIRECT_SUBMIT - LIO will submit the cmd to the backend from the
     calling context if the fabric the cmd was received on supports it,
     else it will use the fabric's default type.

 2 - TARGET_QUEUE_SUBMIT - LIO will queue the cmd to the LIO submission
     workqueue which will pass it to the backend.

When using an NVMe drive and vhost-scsi with direct submission we see
around a 20% improvement in 4K I/Os:

fio jobs        1       2       4       8       10
--------------------------------------------------
defer           94K     190K    394K    770K    890K
direct          128K    252K    488K    950K    -

And when using the queueing mode, we now no longer see issues like where
the iSCSI tx thread is blocked in the block layer waiting on a tag so it
can't respond to a nop or perform I/Os for other LUs.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-6-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/target/loopback/tcm_loop.c b/drivers/target/loopback/tcm_loop.c
index fbacccdd2ff68500578d758581bd2f01ba52e7ab..8e4035ff367485a17de0e2e609cc9ad4ff2457e3 100644 (file)
--- a/drivers/target/loopback/tcm_loop.c
+++ b/drivers/target/loopback/tcm_loop.c
@@ -154,7 +154,7 @@ static void tcm_loop_target_queue_cmd(struct tcm_loop_cmd *tl_cmd)
                               GFP_ATOMIC))
                return;
 
-       target_queue_submission(se_cmd);
+       target_submit(se_cmd);
        return;
 
 out_done:

diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c
index 936e5ff1b209ecb9df704766d214326eee5e811d..f7eaf17e9050be8499772af13972ea4d6cc225bd 100644 (file)
--- a/drivers/target/target_core_configfs.c
+++ b/drivers/target/target_core_configfs.c
@@ -577,6 +577,7 @@ DEF_CONFIGFS_ATTRIB_SHOW(unmap_granularity_alignment);
 DEF_CONFIGFS_ATTRIB_SHOW(unmap_zeroes_data);
 DEF_CONFIGFS_ATTRIB_SHOW(max_write_same_len);
 DEF_CONFIGFS_ATTRIB_SHOW(emulate_rsoc);
+DEF_CONFIGFS_ATTRIB_SHOW(submit_type);
 
 #define DEF_CONFIGFS_ATTRIB_STORE_U32(_name)                           \
 static ssize_t _name##_store(struct config_item *item, const char *page,\
@@ -1231,6 +1232,24 @@ static ssize_t emulate_rsoc_store(struct config_item *item,
        return count;
 }
 
+static ssize_t submit_type_store(struct config_item *item, const char *page,
+                                size_t count)
+{
+       struct se_dev_attrib *da = to_attrib(item);
+       int ret;
+       u8 val;
+
+       ret = kstrtou8(page, 0, &val);
+       if (ret < 0)
+               return ret;
+
+       if (val > TARGET_QUEUE_SUBMIT)
+               return -EINVAL;
+
+       da->submit_type = val;
+       return count;
+}
+
 CONFIGFS_ATTR(, emulate_model_alias);
 CONFIGFS_ATTR(, emulate_dpo);
 CONFIGFS_ATTR(, emulate_fua_write);
@@ -1266,6 +1285,7 @@ CONFIGFS_ATTR(, unmap_zeroes_data);
 CONFIGFS_ATTR(, max_write_same_len);
 CONFIGFS_ATTR(, alua_support);
 CONFIGFS_ATTR(, pgr_support);
+CONFIGFS_ATTR(, submit_type);
 
 /*
  * dev_attrib attributes for devices using the target core SBC/SPC
@@ -1308,6 +1328,7 @@ struct configfs_attribute *sbc_attrib_attrs[] = {
        &attr_alua_support,
        &attr_pgr_support,
        &attr_emulate_rsoc,
+       &attr_submit_type,
        NULL,
 };
 EXPORT_SYMBOL(sbc_attrib_attrs);
@@ -1325,6 +1346,7 @@ struct configfs_attribute *passthrough_attrib_attrs[] = {
        &attr_emulate_pr,
        &attr_alua_support,
        &attr_pgr_support,
+       &attr_submit_type,
        NULL,
 };
 EXPORT_SYMBOL(passthrough_attrib_attrs);

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index b7ac60f4a21945b1545e7d7112f09efe2e906a69..0f3fd775fe6dd27ab29a4e27c19db5ce34f12429 100644 (file)
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -779,6 +779,7 @@ struct se_device *target_alloc_device(struct se_hba *hba, const char *name)
        dev->dev_attrib.unmap_zeroes_data =
                                DA_UNMAP_ZEROES_DATA_DEFAULT;
        dev->dev_attrib.max_write_same_len = DA_MAX_WRITE_SAME_LEN;
+       dev->dev_attrib.submit_type = TARGET_FABRIC_DEFAULT_SUBMIT;
 
        xcopy_lun = &dev->xcopy_lun;
        rcu_assign_pointer(xcopy_lun->lun_se_dev, dev);

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 6c8f6055fc1e68535dafbdc39de7140a29a0bf36..f1fab7e0ea3d36fbdf2f19947f20e4140e088a76 100644 (file)
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1575,14 +1575,7 @@ target_cmd_parse_cdb(struct se_cmd *cmd)
 }
 EXPORT_SYMBOL(target_cmd_parse_cdb);
 
-/**
- * target_submit - perform final initialization and submit cmd to LIO core
- * @cmd: command descriptor to submit
- *
- * target_submit_prep or something similar must have been called on the cmd,
- * and this must be called from process context.
- */
-int target_submit(struct se_cmd *cmd)
+static int __target_submit(struct se_cmd *cmd)
 {
        sense_reason_t ret;
 
@@ -1642,7 +1635,6 @@ int target_submit(struct se_cmd *cmd)
                transport_generic_request_failure(cmd, ret);
        return 0;
 }
-EXPORT_SYMBOL_GPL(target_submit);
 
 sense_reason_t
 transport_generic_map_mem_to_cmd(struct se_cmd *cmd, struct scatterlist *sgl,
@@ -1904,7 +1896,7 @@ void target_queued_submit_work(struct work_struct *work)
                        se_plug = target_plug_device(se_dev);
                }
 
-               target_submit(se_cmd);
+               __target_submit(se_cmd);
        }
 
        if (se_plug)
@@ -1927,6 +1919,35 @@ void target_queue_submission(struct se_cmd *se_cmd)
 }
 EXPORT_SYMBOL_GPL(target_queue_submission);
 
+/**
+ * target_submit - perform final initialization and submit cmd to LIO core
+ * @cmd: command descriptor to submit
+ *
+ * target_submit_prep or something similar must have been called on the cmd,
+ * and this must be called from process context.
+ */
+int target_submit(struct se_cmd *se_cmd)
+{
+       const struct target_core_fabric_ops *tfo = se_cmd->se_sess->se_tpg->se_tpg_tfo;
+       struct se_dev_attrib *da = &se_cmd->se_dev->dev_attrib;
+       u8 submit_type;
+
+       if (da->submit_type == TARGET_FABRIC_DEFAULT_SUBMIT)
+               submit_type = tfo->default_submit_type;
+       else if (da->submit_type == TARGET_DIRECT_SUBMIT &&
+                tfo->direct_submit_supp)
+               submit_type = TARGET_DIRECT_SUBMIT;
+       else
+               submit_type = TARGET_QUEUE_SUBMIT;
+
+       if (submit_type == TARGET_DIRECT_SUBMIT)
+               return __target_submit(se_cmd);
+
+       target_queue_submission(se_cmd);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(target_submit);
+
 static void target_complete_tmr_failure(struct work_struct *work)
 {
        struct se_cmd *se_cmd = container_of(work, struct se_cmd, work);

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index dc274463bdf0273b8cb239004033a1aefd46e28e..4e3b2c25c7213e16083c2b43cd5e947686d292ea 100644 (file)
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -909,7 +909,7 @@ static void vhost_scsi_target_queue_cmd(struct vhost_scsi_cmd *cmd)
                               cmd->tvc_prot_sgl_count, GFP_KERNEL))
                return;
 
-       target_queue_submission(se_cmd);
+       target_submit(se_cmd);
 }
 
 static void

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 401abdf8a9ef5b1828d1433ccc8f6e55085ecf4d..97099a5e3f6c800f94f011b93ef7bf97c28a905b 100644 (file)
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -726,6 +726,7 @@ struct se_dev_attrib {
        u32             unmap_granularity;
        u32             unmap_granularity_alignment;
        u32             max_write_same_len;
+       u8              submit_type;
        struct se_device *da_dev;
        struct config_group da_group;
 };