mmc: block: fix the host's claim-release in special request

For normal request mmc_blk_issue_rq is called twice with asynchronous
transfer(cur and prev). Host's claim and release can be done in each
mmc_blk_issue_rq. However, Special request is currently excluded in
asynchronous transfer. After special request is finished, if there is
no new request, mmc_release_host won't be called in mmc_blk_issue_rq.
The problem is founded during mmc_suspend.

[<c0541124>] (__schedule+0x0/0x78c) from [<c05419e8>] (schedule+0x38/0x78)
[<c05419b0>] (schedule+0x0/0x78) from [<c03a843c>] (__mmc_claim_host+0xac/0x1b4)
[<c03a8390>] (__mmc_claim_host+0x0/0x1b4) from [<c03ac98c>] (mmc_suspend+0x28/0x9c)
[<c03ac964>] (mmc_suspend+0x0/0x9c) from [<c03aad24>] (mmc_suspend_host+0xb4/0x194)
...

Reported-by: Johan Rudholm <jrudholm@gmail.com>
Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Tested-by: Johan Rudholm <johan.rudholm@stericsson.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/card/block.c

@@ -1932,8 +1932,14 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 	}
 
 out:
-	if (!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST))
-		/* release host only when there are no more requests */
+	if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) ||
+	     (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK)))
+		/*
+		 * Release host when there are no more requests
+		 * and after special request(discard, flush) is done.
+		 * In case sepecial request, there is no reentry to
+		 * the 'mmc_blk_issue_rq' with 'mqrq_prev->req'.
+		 */
 		mmc_release_host(card->host);
 	return ret;
 }

drivers/mmc/card/queue.c

@@ -22,9 +22,6 @@
 
 #define MMC_QUEUE_BOUNCESZ	65536
 
-
-#define MMC_REQ_SPECIAL_MASK	(REQ_DISCARD | REQ_FLUSH)
-
 /*
  * Prepare a MMC request. This just filters out odd stuff.
  */

drivers/mmc/card/queue.h

@@ -1,6 +1,8 @@
 #ifndef MMC_QUEUE_H
 #define MMC_QUEUE_H
 
+#define MMC_REQ_SPECIAL_MASK	(REQ_DISCARD | REQ_FLUSH)
+
 struct request;
 struct task_struct;