Re: [PATCH] mmc: block: fix read single on recovery logic

["Christian Löhle" <CLoehle@hyperstone.com>]

So could anyone take a long at this so far?



From: Christian Löhle
Sent: Wednesday, January 5, 2022 5:43 PM
To: ulf.hansson@linaro.org; Christian Löhle; linux-mmc@vger.kernel.org; linux-kernel@vger.kernel.org
Cc: Avri Altman
Subject: [PATCH] mmc: block: fix read single on recovery logic
    
On reads with MMC_READ_MULTIPLE_BLOCK that fail,
the recovery handler will use MMC_READ_SINGLE_BLOCK for
each of the blocks, up to MMC_READ_SINGLE_RETRIES times each.
The logic for this is fixed to never report unsuccessful reads
as success to the block layer.

On command error with retries remaining, blk_update_request was
called with whatever value error was set last to.
In case it was last set to BLK_STS_OK (default), the read will be
reported as success, even though there was no data read from the device.
This could happen on a CRC mismatch for the response,
a card rejecting the command (e.g. again due to a CRC mismatch).
In case it was last set to BLK_STS_IOERR, the error is reported correctly,
but no retries will be attempted.

The patch now will count both command and data errors as retries and
send BLK_STS_IOERR if there are no retries remaining,
or BLK_STS_OK if the single read was successful in the meantime.

Signed-off-by: Christian Loehle <cloehle@hyperstone.com>
---
 drivers/mmc/core/block.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 90e1bcd03b46..d7d880ce0f8a 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -1682,31 +1682,31 @@ static void mmc_blk_read_single(struct mmc_queue *mq, struct request *req)
         struct mmc_card *card = mq->card;
         struct mmc_host *host = card->host;
         blk_status_t error = BLK_STS_OK;
-       int retries = 0;
 
         do {
                 u32 status;
                 int err;
+               int retries = 0;
 
-               mmc_blk_rw_rq_prep(mqrq, card, 1, mq);
+               while (retries++ < MMC_READ_SINGLE_RETRIES) {
+                       mmc_blk_rw_rq_prep(mqrq, card, 1, mq);
 
-               mmc_wait_for_req(host, mrq);
+                       mmc_wait_for_req(host, mrq);
 
-               err = mmc_send_status(card, &status);
-               if (err)
-                       goto error_exit;
-
-               if (!mmc_host_is_spi(host) &&
-                   !mmc_ready_for_data(status)) {
-                       err = mmc_blk_fix_state(card, req);
+                       err = mmc_send_status(card, &status);
                         if (err)
                                 goto error_exit;
-               }
 
-               if (mrq->cmd->error && retries++ < MMC_READ_SINGLE_RETRIES)
-                       continue;
+                       if (!mmc_host_is_spi(host) &&
+                           !mmc_ready_for_data(status)) {
+                               err = mmc_blk_fix_state(card, req);
+                               if (err)
+                                       goto error_exit;
+                       }
 
-               retries = 0;
+                       if (!mrq->cmd->error && !mrq->data->error)
+                               break;
+               }
 
                 if (mrq->cmd->error ||
                     mrq->data->error ||
-- 
2.34.1
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