openwrt/target/linux/generic/hack-5.4/550-loop-Report-EOPNOTSUPP-properly.patch

From 2e864386e62e702a343be2507062ee08d5dfc810 Mon Sep 17 00:00:00 2001
From: Evan Green <evgreen@chromium.org>
Date: Thu, 14 Nov 2019 15:50:07 -0800
Subject: loop: Report EOPNOTSUPP properly

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 <evgreen@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/block/loop.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -462,7 +462,7 @@ static void lo_complete_rq(struct reques
 	if (!cmd->use_aio || cmd->ret < 0 || cmd->ret == blk_rq_bytes(rq) ||
 	    req_op(rq) != REQ_OP_READ) {
 		if (cmd->ret < 0)
-			ret = BLK_STS_IOERR;
+			ret = errno_to_blk_status(cmd->ret);
 		goto end_io;
 	}
 
@@ -1973,7 +1973,10 @@ static void loop_handle_cmd(struct loop_
  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);
 	}
 }