linux-kernel - [PATCH v2 1/2] loop: Report EOPNOTSUPP properly

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Date:   Thu,  7 Feb 2019 12:57:28 -0800
From:   Evan Green <evgreen@...omium.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Bart Van Assche <bvanassche@....org>,
        Gwendal Grignou <gwendal@...omium.org>,
        Martin K Petersen <martin.petersen@...cle.com>,
        Alexis Savery <asavery@...omium.org>,
        Ming Lei <ming.lei@...hat.com>,
        Evan Green <evgreen@...omium.org>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] 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@...omium.org>
Reviewed-by: Ming Lei <ming.lei@...hat.com>
---

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

Ming, I opted to keep your Reviewed-by since the change since v1 was trivial.
Hope that's okay.

---
 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 cf5538942834..b6c2d8f3202b 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;
 	}
@@ -1878,7 +1880,10 @@ 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);
 	}
 }
-- 
2.20.1