[SCSI] do not manipulate device reference counts in scsi_get/put_command

Many callers won't need this and we can optimize them away.  In addition
the handling in the __-prefixed variants was inconsistant to start with.

Based on an earlier patch from Bart Van Assche.

[jejb: fix kerneldoc probelm picked up by Fengguang Wu]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 492071ca45d1..007e979fa437 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -95,6 +95,7 @@ static void scsi_unprep_request(struct request *req)
         req->special = NULL;
 
         scsi_put_command(cmd);
+        put_device(&cmd->device->sdev_gendev);
 }
 
 /**
@@ -529,6 +530,7 @@ void scsi_next_command(struct scsi_cmnd *cmd)
         get_device(&sdev->sdev_gendev);
 
         scsi_put_command(cmd);
+        put_device(&sdev->sdev_gendev);
         scsi_run_queue(q);
 
         /* ok to remove device now */
@@ -1123,6 +1125,7 @@ err_exit:
         scsi_release_buffers(cmd);
         cmd->request->special = NULL;
         scsi_put_command(cmd);
+        put_device(&cmd->device->sdev_gendev);
         return error;
 }
 EXPORT_SYMBOL(scsi_init_io);
@@ -1133,9 +1136,15 @@ static struct scsi_cmnd *scsi_get_cmd_from_req(struct scsi_device *sdev,
         struct scsi_cmnd *cmd;
 
         if (!req->special) {
+                /* Bail if we can't get a reference to the device */
+                if (!get_device(&sdev->sdev_gendev))
+                        return NULL;
+
                 cmd = scsi_get_command(sdev, GFP_ATOMIC);
-                if (unlikely(!cmd))
+                if (unlikely(!cmd)) {
+                        put_device(&sdev->sdev_gendev);
                         return NULL;
+                }
                 req->special = cmd;
         } else {
                 cmd = req->special;
@@ -1298,6 +1307,7 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
                         struct scsi_cmnd *cmd = req->special;
                         scsi_release_buffers(cmd);
                         scsi_put_command(cmd);
+                        put_device(&cmd->device->sdev_gendev);
                         req->special = NULL;
                 }
                 break;