[PATCH] scsi: core: set result when the command cannot be dispatched

[Jaesoo Lee <jalee@xxxxxxxxxxxxxxx>]

When SCSI blk-mq is enabled, there is a bug in handling errors in scsi_queue_rq.
Specifically, the bug is not setting result field of scsi_request correctly when
the dispatch of the command has been failed. Since the upper layer code
including the sg_io ioctl expects to receive any error status from result field
of scsi_request, the error is silently ignored and this could cause data
corruptions for some applications. This commit also fixes another bug that the
result field is not initialized when scsi_request is allocated.

Signed-off-by: Jaesoo Lee <jalee@xxxxxxxxxxxxxxx>
---
 block/scsi_ioctl.c      | 1 +
 drivers/scsi/scsi_lib.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 533f4ae..f2d7979 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -723,6 +723,7 @@ void scsi_req_init(struct scsi_request *req)
        req->cmd = req->__cmd;
        req->cmd_len = BLK_MAX_CDB;
        req->sense_len = 0;
+       req->result = 0;
 }
 EXPORT_SYMBOL(scsi_req_init);

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 2018967..af1488d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1699,6 +1699,7 @@ static blk_status_t scsi_queue_rq(struct
blk_mq_hw_ctx *hctx,
                        ret = BLK_STS_DEV_RESOURCE;
                break;
        default:
+               scsi_req(req)->result = DID_NO_CONNECT << 16;
                /*
                 * Make sure to release all allocated ressources when
                 * we hit an error, as we will never see this command
--
2.7.4