scsi: lpfc: Correct upcalling nvmet_fc transport during io done downcall

When the transport calls into the lpfc target to release an IO job
structure, which corresponds to an exchange, and if the driver was waiting
for an exchange in order to post a previously received command to the
transport, the driver immediately takes the IO job and reuses the context
for the prior command and calls nvmet_fc_rcv_fcp_req() to tell the
transport about a newly received command.

Problem is, the execution of the IO job release may be in the context of
the back end driver and its bio completion handlers, thus it may be in a
irq context and protection code kicks in in the bio and request layers that
are subsequently called.

Rework lpfc so that instead of immediately upcalling, queue it to a
deferred work thread and have the thread make the upcall.

Took advantage of this change to remove duplicated code with the normal
command receive path that preps the IO job and upcalls nvmet_fc. Created a
common routine both paths use.

Also corrected some errors that were found during review of the context
freeing and reuse - basically unlocked operations and a somewhat disjoint
set of calls to release associated job elements. Cleaned up this path and
added locks for coherency.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc.h

@@ -144,6 +144,7 @@ struct lpfc_nvmet_ctxbuf {
 	struct lpfc_nvmet_rcv_ctx *context;
 	struct lpfc_iocbq *iocbq;
 	struct lpfc_sglq *sglq;
+	struct work_struct defer_work;
 };
 
 struct lpfc_dma_pool {

drivers/scsi/lpfc/lpfc_nvmet.h

@@ -137,6 +137,7 @@ struct lpfc_nvmet_rcv_ctx {
 #define LPFC_NVMET_XBUSY		0x4  /* XB bit set on IO cmpl */
 #define LPFC_NVMET_CTX_RLS		0x8  /* ctx free requested */
 #define LPFC_NVMET_ABTS_RCV		0x10  /* ABTS received on exchange */
+#define LPFC_NVMET_CTX_REUSE_WQ		0x20  /* ctx reused via WQ */
 #define LPFC_NVMET_DEFER_WQFULL		0x40  /* Waiting on a free WQE */
 	struct rqb_dmabuf *rqb_buffer;
 	struct lpfc_nvmet_ctxbuf *ctxbuf;