scsi: target: core: Break up target_submit_cmd_map_sgls()

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.

Link: https://lore.kernel.org/r/20210227170006.5077-5-michael.christie@oracle.com
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>
Tested-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 8 insertions, 0 deletions

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 *);