mmc: core: Allocate per-request data using the block layer core

The mmc_queue_req is a per-request state container the MMC core uses
to carry bounce buffers, pointers to asynchronous requests and so on.
Currently allocated as a static array of objects, then as a request
comes in, a mmc_queue_req is assigned to it, and used during the
lifetime of the request.

This is backwards compared to how other block layer drivers work:
they usally let the block core provide a per-request struct that get
allocated right beind the struct request, and which can be obtained
using the blk_mq_rq_to_pdu() helper. (The _mq_ infix in this function
name is misleading: it is used by both the old and the MQ block
layer.)

The per-request struct gets allocated to the size stored in the queue
variable .cmd_size initialized using the .init_rq_fn() and
cleaned up using .exit_rq_fn().

The block layer code makes the MMC core rely on this mechanism to
allocate the per-request mmc_queue_req state container.

Doing this make a lot of complicated queue handling go away. We only
need to keep the .qnct that keeps count of how many request are
currently being processed by the MMC layer. The MQ block layer will
replace also this once we transition to it.

Doing this refactoring is necessary to move the ioctl() operations
into custom block layer requests tagged with REQ_OP_DRV_[IN|OUT]
instead of the custom code using the BigMMCHostLock that we have
today: those require that per-request data be obtainable easily from
a request after creating a custom request with e.g.:

struct request *rq = blk_get_request(q, REQ_OP_DRV_IN, __GFP_RECLAIM);
struct mmc_queue_req *mq_rq = req_to_mq_rq(rq);

And this is not possible with the current construction, as the request
is not immediately assigned the per-request state container, but
instead it gets assigned when the request finally enters the MMC
queue, which is way too late for custom requests.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
[Ulf: Folded in the fix to drop a call to blk_cleanup_queue()]
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Heiner Kallweit <hkallweit1@gmail.com>

1 files changed, 12 insertions, 10 deletions

diff --git a/drivers/mmc/core/queue.h b/drivers/mmc/core/queue.h
index 871796c3f406..dae31bc0c2d3 100644
--- a/drivers/mmc/core/queue.h
+++ b/drivers/mmc/core/queue.h
@@ -3,9 +3,15 @@
 
 #include <linux/types.h>
 #include <linux/blkdev.h>
+#include <linux/blk-mq.h>
 #include <linux/mmc/core.h>
 #include <linux/mmc/host.h>
 
+static inline struct mmc_queue_req *req_to_mmc_queue_req(struct request *rq)
+{
+	return blk_mq_rq_to_pdu(rq);
+}
+
 static inline bool mmc_req_is_special(struct request *req)
 {
 	return req &&
@@ -34,7 +40,6 @@ struct mmc_queue_req {
 	struct scatterlist	*bounce_sg;
 	unsigned int		bounce_sg_len;
 	struct mmc_async_req	areq;
-	int			task_id;
 };
 
 struct mmc_queue {
@@ -45,14 +50,15 @@ struct mmc_queue {
 	bool			asleep;
 	struct mmc_blk_data	*blkdata;
 	struct request_queue	*queue;
-	struct mmc_queue_req	*mqrq;
-	int			qdepth;
+	/*
+	 * FIXME: this counter is not a very reliable way of keeping
+	 * track of how many requests that are ongoing. Switch to just
+	 * letting the block core keep track of requests and per-request
+	 * associated mmc_queue_req data.
+	 */
 	int			qcnt;
-	unsigned long		qslots;
 };
 
-extern int mmc_queue_alloc_shared_queue(struct mmc_card *card);
-extern void mmc_queue_free_shared_queue(struct mmc_card *card);
 extern int mmc_init_queue(struct mmc_queue *, struct mmc_card *, spinlock_t *,
 			  const char *);
 extern void mmc_cleanup_queue(struct mmc_queue *);
@@ -66,8 +72,4 @@ extern void mmc_queue_bounce_post(struct mmc_queue_req *);
 
 extern int mmc_access_rpmb(struct mmc_queue *);
 
-extern struct mmc_queue_req *mmc_queue_req_find(struct mmc_queue *,
-						struct request *);
-extern void mmc_queue_req_free(struct mmc_queue *, struct mmc_queue_req *);
-
 #endif