[3.16.y-ckt stable] Patch "mmc: card: Fixup request missing in mmc_blk_issue_rw_rq" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    mmc: card: Fixup request missing in mmc_blk_issue_rw_rq

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 6eb33049f62d6ca5e8eb6efba3430db6ae23689f Mon Sep 17 00:00:00 2001
From: Ding Wang <justin.wang at spreadtrum.com>
Date: Mon, 18 May 2015 20:14:15 +0800
Subject: mmc: card: Fixup request missing in mmc_blk_issue_rw_rq

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 at spreadtrum.com>
Fixes: 67716327eec7 ("mmc: block: add eMMC hardware reset support")
Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/mmc/card/block.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e32206ecfa04..7ec3c79852e5 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -1910,9 +1910,11 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
 			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;