[PATCH] mmc: queue: ensure error propagation for non-blk

[Christian Loehle <CLoehle@hyperstone.com>]

Requests to the mmc layer usually come through a block device.
The exceptions are the RPMB chardev and debugfs, which issue their
own blk_mq requests through blk_execute_rq and do not query
the BLK_STS error but the mmc-internal drv_op_result.
This patch ensures that drv_op_result is set as error whenever
a BLK_STS error is set.

The behavior leads to a bug where the request never sees the error,
e.g. by directly erroring out at mmc_blk_mq_issue_rq if
mmc_blk_part_switch fails. The ioctl caller of the rpmb chardev then
can never see the error and thus may assume that their call executed
successfully when it did not.

While always checking the blk_execute_rq return value would be
advised, let's eliminate the error completely by always setting
drv_op_result in case of a BLK_STS error.

Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
---
 drivers/mmc/core/queue.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index b396e3900717..8240962e28f3 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -334,6 +334,9 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 		WRITE_ONCE(mq->busy, false);
 	}
 
+	/* Ensure request error propagates to non-blk callers, too. */
+	if (!req_to_mmc_queue_req(req)->drv_op_result && ret)
+		req_to_mmc_queue_req(req)->drv_op_result = ret;
 	return ret;
 }
 
-- 
2.37.3


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