Properly plumb out EOPNOTSUPP from loop driver operations, which may
get returned when for instance a discard operation is attempted but not
supported by the underlying block device. Before this change, everything
was reported in the log as an I/O error, which is scary and not
helpful in debugging.

Signed-off-by: Evan Green <redacted>
Reviewed-by: Ming Lei <redacted>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Gwendal Grignou <redacted>
Reviewed-by: Chaitanya Kulkarni <redacted>
---

Changes in v6:
- Updated tags

Changes in v5: None
Changes in v4: None
Changes in v3:
- Updated tags

Changes in v2:
- Unnested error if statement (Bart)

 drivers/block/loop.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index f6f77eaa7217..d749156a3d88 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c

@@ -458,7 +458,9 @@ static void lo_complete_rq(struct request *rq)
 
 	if (!cmd->use_aio || cmd->ret < 0 || cmd->ret == blk_rq_bytes(rq) ||
 	    req_op(rq) != REQ_OP_READ) {
-		if (cmd->ret < 0)
+		if (cmd->ret == -EOPNOTSUPP)
+			ret = BLK_STS_NOTSUPP;
+		else if (cmd->ret < 0)
 			ret = BLK_STS_IOERR;
 		goto end_io;
 	}

@@ -1940,7 +1942,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
  failed:
 	/* complete non-aio request */
 	if (!cmd->use_aio || ret) {
-		cmd->ret = ret ? -EIO : 0;
+		if (ret == -EOPNOTSUPP)
+			cmd->ret = ret;
+		else
+			cmd->ret = ret ? -EIO : 0;
 		blk_mq_complete_request(rq);
 	}
 }

-- 
2.21.0