[PATCH 04/14] target: break up target_submit_cmd_map_sgls

Mike Christie
2021-02-11T12:35:51Z

This breaks up target_submit_cmd_map_sgls into 3 helpers:

- target_init_cmd: Do the basic general setup and get a refcount to
the session to make sure the caller can execute the cmd.

- target_submit_prep: Do the mapping, cdb processing and get a ref
to the lun.

- target_submit: Pass the cmd to LIO core for execution.

The above functions must be used by drivers that either:
1. rely on lio for session shutdown synchronization by calling
target_stop_session.
2. need to map sgls

When the next patches are applied then simple drivers that
do not need the extra functionality above can use
target_submit_cmd and not worry about failures being returned
and how to handle them, since many drivers were getting this
wrong and would have hit refcount bugs.

Also, by breaking target_submit_cmd_map_sgls up into these 3
helper functions, we can allow the later patches to do the init/prep
from interrupt context and then do the submission from a workqueue.

Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Nilesh Javali <njavali@marvell.com>
Cc: Michael Cyr <mikecyr@linux.ibm.com>
Cc: Chris Boot <bootc@bootc.net>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
drivers/target/target_core_transport.c | 200 +++++++++++++++++--------
include/target/target_core_fabric.h | 8 +
2 files changed, 147 insertions(+), 61 deletions(-)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 013f4a5e8972..a82b7da09872 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1571,46 +1571,31 @@ transport_generic_map_mem_to_cmd(struct se_cmd *cmd, struct scatterlist *sgl,
}

/**
- * target_submit_cmd_map_sgls - lookup unpacked lun and submit uninitialized
- * se_cmd + use pre-allocated SGL memory.
- *
- * @se_cmd: command descriptor to submit
+ * target_init_cmd - initialize se_cmd
+ * @se_cmd: command descriptor to init
* @se_sess: associated se_sess for endpoint
- * @cdb: pointer to SCSI CDB
* @sense: pointer to SCSI sense buffer
* @unpacked_lun: unpacked LUN to reference for struct se_lun
* @data_length: fabric expected data transfer length
* @task_attr: SAM task attribute
* @data_dir: DMA data direction
* @flags: flags for command submission from target_sc_flags_tables
- * @sgl: struct scatterlist memory for unidirectional mapping
- * @sgl_count: scatterlist count for unidirectional mapping
- * @sgl_bidi: struct scatterlist memory for bidirectional READ mapping
- * @sgl_bidi_count: scatterlist count for bidirectional READ mapping
- * @sgl_prot: struct scatterlist memory protection information
- * @sgl_prot_count: scatterlist count for protection information
*
* Task tags are supported if the caller has set @se_cmd->tag.
*
- * Returns non zero to signal active I/O shutdown failure. All other
- * setup exceptions will be returned as a SCSI CHECK_CONDITION response,
- * but still return zero here.
+ * Returns:
+ * - less than zero to signal active I/O shutdown failure.
+ * - zero on success.
*
- * This may only be called from process context, and also currently
- * assumes internal allocation of fabric payload buffer by target-core.
+ * If the fabric driver calls target_stop_session, then it must check the
+ * return code and handle failures. This will never fail for other drivers,
+ * and the return code can be ignored.
*/
-int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess,
- unsigned char *cdb, unsigned char *sense, u64 unpacked_lun,
- u32 data_length, int task_attr, int data_dir, int flags,
- struct scatterlist *sgl, u32 sgl_count,
- struct scatterlist *sgl_bidi, u32 sgl_bidi_count,
- struct scatterlist *sgl_prot, u32 sgl_prot_count)
+int target_init_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
+ unsigned char *sense, u64 unpacked_lun,
+ u32 data_length, int task_attr, int data_dir, int flags)
{
struct se_portal_group *se_tpg;
- sense_reason_t rc;
- int ret;
-
- might_sleep();

se_tpg = se_sess->se_tpg;
BUG_ON(!se_tpg);
@@ -1618,53 +1603,69 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess

if (flags & TARGET_SCF_USE_CPUID)
se_cmd->se_cmd_flags |= SCF_USE_CPUID;
+ /*
+ * Signal bidirectional data payloads to target-core
+ */
+ if (flags & TARGET_SCF_BIDI_OP)
+ se_cmd->se_cmd_flags |= SCF_BIDI;
+
+ if (flags & TARGET_SCF_UNKNOWN_SIZE)
+ se_cmd->unknown_data_length = 1;
/*
* Initialize se_cmd for target operation. From this point
* exceptions are handled by sending exception status via
* target_core_fabric_ops->queue_status() callback
*/
- __target_init_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess,
- data_length, data_dir, task_attr, sense,
- unpacked_lun);
+ __target_init_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, data_length,
+ data_dir, task_attr, sense, unpacked_lun);

- if (flags & TARGET_SCF_UNKNOWN_SIZE)
- se_cmd->unknown_data_length = 1;
/*
* Obtain struct se_cmd->cmd_kref reference. A second kref_get here is
* necessary for fabrics using TARGET_SCF_ACK_KREF that expect a second
* kref_put() to happen during fabric packet acknowledgement.
*/
- ret = target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
- if (ret)
- return ret;
- /*
- * Signal bidirectional data payloads to target-core
- */
- if (flags & TARGET_SCF_BIDI_OP)
- se_cmd->se_cmd_flags |= SCF_BIDI;
+ return target_get_sess_cmd(se_cmd, flags & TARGET_SCF_ACK_KREF);
+}
+EXPORT_SYMBOL_GPL(target_init_cmd);
+
+/**
+ * target_submit_prep - prepare cmd for submission
+ * @se_cmd: command descriptor to prep
+ * @cdb: pointer to SCSI CDB
+ * @sgl: struct scatterlist memory for unidirectional mapping
+ * @sgl_count: scatterlist count for unidirectional mapping
+ * @sgl_bidi: struct scatterlist memory for bidirectional READ mapping
+ * @sgl_bidi_count: scatterlist count for bidirectional READ mapping
+ * @sgl_prot: struct scatterlist memory protection information
+ * @sgl_prot_count: scatterlist count for protection information
+ *
+ * Returns:
+ * - less than zero to signal failure.
+ * - zero on success.
+ * If failure is returned, lio will the callers queue_status to complete
+ * the cmd.
+ */
+int target_submit_prep(struct se_cmd *se_cmd, unsigned char *cdb,
+ struct scatterlist *sgl, u32 sgl_count,
+ struct scatterlist *sgl_bidi, u32 sgl_bidi_count,
+ struct scatterlist *sgl_prot, u32 sgl_prot_count)
+{
+ sense_reason_t rc;

rc = target_cmd_init_cdb(se_cmd, cdb);
- if (rc) {
- transport_send_check_condition_and_sense(se_cmd, rc, 0);
- target_put_sess_cmd(se_cmd);
- return 0;
- }
+ if (rc)
+ goto send_cc_direct;

/*
* Locate se_lun pointer and attach it to struct se_cmd
*/
rc = transport_lookup_cmd_lun(se_cmd);
- if (rc) {
- transport_send_check_condition_and_sense(se_cmd, rc, 0);
- target_put_sess_cmd(se_cmd);
- return 0;
- }
+ if (rc)
+ goto send_cc_direct;

rc = target_cmd_parse_cdb(se_cmd);
- if (rc != 0) {
- transport_generic_request_failure(se_cmd, rc);
- return 0;
- }
+ if (rc != 0)
+ goto generic_fail;

/*
* Save pointers for SGLs containing protection information,
@@ -1684,6 +1685,41 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess
if (sgl_count != 0) {
BUG_ON(!sgl);

+ rc = transport_generic_map_mem_to_cmd(se_cmd, sgl, sgl_count,
+ sgl_bidi, sgl_bidi_count);
+ if (rc != 0)
+ goto generic_fail;
+ }
+
+ return 0;
+
+send_cc_direct:
+ transport_send_check_condition_and_sense(se_cmd, rc, 0);
+ target_put_sess_cmd(se_cmd);
+ return -EIO;
+
+generic_fail:
+ transport_generic_request_failure(se_cmd, rc);
+ return -EIO;
+}
+EXPORT_SYMBOL_GPL(target_submit_prep);
+
+/**
+ * target_submit - perform final initialization and submit cmd to LIO core
+ * @se_cmd: command descriptor to submit
+ *
+ * target_submit_prep must have been called on the cmd, and this must be
+ * called from process context.
+ */
+void target_submit(struct se_cmd *se_cmd)
+{
+ struct scatterlist *sgl = se_cmd->t_data_sg;
+ unsigned char *buf = NULL;
+
+ might_sleep();
+
+ if (se_cmd->t_data_nents != 0) {
+ BUG_ON(!sgl);
/*
* A work-around for tcm_loop as some userspace code via
* scsi-generic do not memset their associated read buffers,
@@ -1694,8 +1730,6 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess
*/
if (!(se_cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) &&
se_cmd->data_direction == DMA_FROM_DEVICE) {
- unsigned char *buf = NULL;
-
if (sgl)
buf = kmap(sg_page(sgl)) + sgl->offset;

@@ -1705,12 +1739,6 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess
}
}

- rc = transport_generic_map_mem_to_cmd(se_cmd, sgl, sgl_count,
- sgl_bidi, sgl_bidi_count);
- if (rc != 0) {
- transport_generic_request_failure(se_cmd, rc);
- return 0;
- }
}

/*
@@ -1720,6 +1748,56 @@ int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess
core_alua_check_nonop_delay(se_cmd);

transport_handle_cdb_direct(se_cmd);
+}
+EXPORT_SYMBOL_GPL(target_submit);
+
+/**
+ * target_submit_cmd_map_sgls - lookup unpacked lun and submit uninitialized
+ * se_cmd + use pre-allocated SGL memory.
+ *
+ * @se_cmd: command descriptor to submit
+ * @se_sess: associated se_sess for endpoint
+ * @cdb: pointer to SCSI CDB
+ * @sense: pointer to SCSI sense buffer
+ * @unpacked_lun: unpacked LUN to reference for struct se_lun
+ * @data_length: fabric expected data transfer length
+ * @task_attr: SAM task attribute
+ * @data_dir: DMA data direction
+ * @flags: flags for command submission from target_sc_flags_tables
+ * @sgl: struct scatterlist memory for unidirectional mapping
+ * @sgl_count: scatterlist count for unidirectional mapping
+ * @sgl_bidi: struct scatterlist memory for bidirectional READ mapping
+ * @sgl_bidi_count: scatterlist count for bidirectional READ mapping
+ * @sgl_prot: struct scatterlist memory protection information
+ * @sgl_prot_count: scatterlist count for protection information
+ *
+ * Task tags are supported if the caller has set @se_cmd->tag.
+ *
+ * Returns non zero to signal active I/O shutdown failure. All other
+ * setup exceptions will be returned as a SCSI CHECK_CONDITION response,
+ * but still return zero here.
+ *
+ * This may only be called from process context, and also currently
+ * assumes internal allocation of fabric payload buffer by target-core.
+ */
+int target_submit_cmd_map_sgls(struct se_cmd *se_cmd, struct se_session *se_sess,
+ unsigned char *cdb, unsigned char *sense, u64 unpacked_lun,
+ u32 data_length, int task_attr, int data_dir, int flags,
+ struct scatterlist *sgl, u32 sgl_count,
+ struct scatterlist *sgl_bidi, u32 sgl_bidi_count,
+ struct scatterlist *sgl_prot, u32 sgl_prot_count)
+{
+ int rc;
+
+ rc = target_init_cmd(se_cmd, se_sess, sense, unpacked_lun,
+ data_length, task_attr, data_dir, flags);
+ if (rc < 0)
+ return rc;
+
+
+ target_submit_prep(se_cmd, cdb, sgl, sgl_count, sgl_bidi,
+ sgl_bidi_count, sgl_prot, sgl_prot_count);
+ target_submit(se_cmd);
return 0;
}
EXPORT_SYMBOL(target_submit_cmd_map_sgls);
diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
index 4975c4d2a933..4b5f6687393a 100644
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -151,6 +151,14 @@ void transport_deregister_session(struct se_session *);
void __target_init_cmd(struct se_cmd *,
const struct target_core_fabric_ops *,
struct se_session *, u32, int, int, unsigned char *, u64);
+int target_init_cmd(struct se_cmd *se_cmd, struct se_session *se_sess,
+ unsigned char *sense, u64 unpacked_lun, u32 data_length,
+ int task_attr, int data_dir, int flags);
+int target_submit_prep(struct se_cmd *se_cmd, unsigned char *cdb,
+ struct scatterlist *sgl, u32 sgl_count,
+ struct scatterlist *sgl_bidi, u32 sgl_bidi_count,
+ struct scatterlist *sgl_prot, u32 sgl_prot_count);
+void target_submit(struct se_cmd *se_cmd);
sense_reason_t transport_lookup_cmd_lun(struct se_cmd *);
sense_reason_t target_cmd_init_cdb(struct se_cmd *, unsigned char *);
sense_reason_t target_cmd_parse_cdb(struct se_cmd *);
--
2.25.1