-/**
- * scsi_done - Invoke completion on finished SCSI command.
- * @cmd: The SCSI Command for which a low-level device driver (LLDD) gives
- * ownership back to SCSI Core -- i.e. the LLDD has finished with it.
- *
- * Description: This function is the mid-level's (SCSI Core) interrupt routine,
- * which regains ownership of the SCSI command (de facto) from a LLDD, and
- * calls blk_complete_request() for further processing.
- *
- * This function is interrupt context safe.
- */
-static void scsi_done(struct scsi_cmnd *cmd)
-{
- trace_scsi_dispatch_cmd_done(cmd);
- blk_complete_request(cmd->request);
-}
-
-/*
- * Function: scsi_request_fn()
- *
- * Purpose: Main strategy routine for SCSI.
- *
- * Arguments: q - Pointer to actual queue.
- *
- * Returns: Nothing
- *
- * Lock status: request queue lock assumed to be held when called.
- *
- * Note: See sd_zbc.c sd_zbc_write_lock_zone() for write order
- * protection for ZBC disks.
- */
-static void scsi_request_fn(struct request_queue *q)
- __releases(q->queue_lock)
- __acquires(q->queue_lock)
-{
- struct scsi_device *sdev = q->queuedata;
- struct Scsi_Host *shost;
- struct scsi_cmnd *cmd;
- struct request *req;
-
- /*
- * To start with, we keep looping until the queue is empty, or until
- * the host is no longer able to accept any more requests.
- */
- shost = sdev->host;
- for (;;) {
- int rtn;
- /*
- * get next queueable request. We do this early to make sure
- * that the request is fully prepared even if we cannot
- * accept it.
- */
- req = blk_peek_request(q);
- if (!req)
- break;
-
- if (unlikely(!scsi_device_online(sdev))) {
- sdev_printk(KERN_ERR, sdev,
- "rejecting I/O to offline device\n");
- scsi_kill_request(req, q);
- continue;
- }
-
- if (!scsi_dev_queue_ready(q, sdev))
- break;
-
- /*
- * Remove the request from the request list.
- */
- if (!(blk_queue_tagged(q) && !blk_queue_start_tag(q, req)))
- blk_start_request(req);
-
- spin_unlock_irq(q->queue_lock);
- cmd = blk_mq_rq_to_pdu(req);
- if (cmd != req->special) {
- printk(KERN_CRIT "impossible request in %s.\n"
- "please mail a stack trace to "
- "linux-scsi@vger.kernel.org\n",
- __func__);
- blk_dump_rq_flags(req, "foo");
- BUG();
- }
-
- /*
- * We hit this when the driver is using a host wide
- * tag map. For device level tag maps the queue_depth check
- * in the device ready fn would prevent us from trying
- * to allocate a tag. Since the map is a shared host resource
- * we add the dev to the starved list so it eventually gets
- * a run when a tag is freed.
- */
- if (blk_queue_tagged(q) && !(req->rq_flags & RQF_QUEUED)) {
- spin_lock_irq(shost->host_lock);
- if (list_empty(&sdev->starved_entry))
- list_add_tail(&sdev->starved_entry,
- &shost->starved_list);
- spin_unlock_irq(shost->host_lock);
- goto not_ready;
- }
-
- if (!scsi_target_queue_ready(shost, sdev))
- goto not_ready;
-
- if (!scsi_host_queue_ready(q, shost, sdev))
- goto host_not_ready;
-
- if (sdev->simple_tags)
- cmd->flags |= SCMD_TAGGED;
- else
- cmd->flags &= ~SCMD_TAGGED;
-
- /*
- * Finally, initialize any error handling parameters, and set up
- * the timers for timeouts.
- */
- scsi_init_cmd_errh(cmd);
-
- /*
- * Dispatch the command to the low-level driver.
- */
- cmd->scsi_done = scsi_done;
- rtn = scsi_dispatch_cmd(cmd);
- if (rtn) {
- scsi_queue_insert(cmd, rtn);
- spin_lock_irq(q->queue_lock);
- goto out_delay;
- }
- spin_lock_irq(q->queue_lock);
- }
-
- return;
-
- host_not_ready:
- if (scsi_target(sdev)->can_queue > 0)
- atomic_dec(&scsi_target(sdev)->target_busy);
- not_ready:
- /*
- * lock q, handle tag, requeue req, and decrement device_busy. We
- * must return with queue_lock held.
- *
- * Decrementing device_busy without checking it is OK, as all such
- * cases (host limits or settings) should run the queue at some
- * later time.
- */
- spin_lock_irq(q->queue_lock);
- blk_requeue_request(q, req);
- atomic_dec(&sdev->device_busy);
-out_delay:
- if (!atomic_read(&sdev->device_busy) && !scsi_device_blocked(sdev))
- blk_delay_queue(q, SCSI_QUEUE_DELAY);
-}
-