linux-kernel - [PATCH 3.2 036/110] mmc: card: Fixup request missing in mmc_blk_issue_rw

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Message-ID: <lsq.1439201551.675962400@decadent.org.uk>
Date:	Mon, 10 Aug 2015 12:12:31 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Ding Wang" <justin.wang@...eadtrum.com>,
	"Ulf Hansson" <ulf.hansson@...aro.org>
Subject: [PATCH 3.2 036/110] mmc: card: Fixup request missing in
 mmc_blk_issue_rw_rq

3.2.71-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ding Wang <justin.wang@...eadtrum.com>

commit 29535f7b797df35cc9b6b3bca635591cdd3dd2a8 upstream.

The current handler of MMC_BLK_CMD_ERR in mmc_blk_issue_rw_rq function
may cause new coming request permanent missing when the ongoing
request (previoulsy started) complete end.

The problem scenario is as follows:
(1) Request A is ongoing;
(2) Request B arrived, and finally mmc_blk_issue_rw_rq() is called;
(3) Request A encounters the MMC_BLK_CMD_ERR error;
(4) In the error handling of MMC_BLK_CMD_ERR, suppose mmc_blk_cmd_err()
    end request A completed and return zero. Continue the error handling,
    suppose mmc_blk_reset() reset device success;
(5) Continue the execution, while loop completed because variable ret
    is zero now;
(6) Finally, mmc_blk_issue_rw_rq() return without processing request B.

The process related to the missing request may wait that IO request
complete forever, possibly crashing the application or hanging the system.

Fix this issue by starting new request when reset success.

Signed-off-by: Ding Wang <justin.wang@...eadtrum.com>
Fixes: 67716327eec7 ("mmc: block: add eMMC hardware reset support")
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/mmc/card/block.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -1285,9 +1285,11 @@ static int mmc_blk_issue_rw_rq(struct mm
 			break;
 		case MMC_BLK_CMD_ERR:
 			ret = mmc_blk_cmd_err(md, card, brq, req, ret);
-			if (!mmc_blk_reset(md, card->host, type))
-				break;
-			goto cmd_abort;
+			if (mmc_blk_reset(md, card->host, type))
+				goto cmd_abort;
+			if (!ret)
+				goto start_new_req;
+			break;
 		case MMC_BLK_RETRY:
 			if (retry++ < 5)
 				break;

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