[PATCH] mmc: fix host release issue after discard operation

[Ray Jui]

Under function mmc_blk_issue_rq, after an MMC discard operation,
the MMC request data structure may be freed in memory. Later in
the same function, the check of req->cmd_flags & MMC_REQ_SPECIAL_MASK
is dangerous and invalid. It causes the MMC host not being released
when it should

This patch fixes the issue by marking the special request down before
the discard/flush operation

Reported by: Harold (SoonYeal) Yang <haroldsy@xxxxxxxxxxxx>
Signed-off-by: Ray Jui <rjui@xxxxxxxxxxxx>
---
 drivers/mmc/card/block.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 1a3163f..9e8e970 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -1954,7 +1954,7 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
 
 static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 {
-	int ret;
+	int ret, req_is_special = 0;
 	struct mmc_blk_data *md = mq->data;
 	struct mmc_card *card = md->queue.card;
 	struct mmc_host *host = card->host;
@@ -1973,6 +1973,10 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 		goto out;
 	}
 
+	/* mark special request here since req may be freed later */
+	if (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK))
+		req_is_special = 1;
+
 	mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
 	if (req && req->cmd_flags & REQ_DISCARD) {
 		/* complete ongoing async transfer before issuing discard */
@@ -1999,7 +2003,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 
 out:
 	if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) ||
-	     (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK)))
+	     req_is_special)
 		/*
 		 * Release host when there are no more requests
 		 * and after special request(discard, flush) is done.
-- 
1.7.9.5

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