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>

drivers/mmc/core/block.c

@@ -129,13 +129,6 @@ static inline int mmc_blk_part_switch(struct mmc_card *card,
 				      struct mmc_blk_data *md);
 static int get_card_status(struct mmc_card *card, u32 *status, int retries);
 
-static void mmc_blk_requeue(struct request_queue *q, struct request *req)
-{
-	spin_lock_irq(q->queue_lock);
-	blk_requeue_request(q, req);
-	spin_unlock_irq(q->queue_lock);
-}
-
 static struct mmc_blk_data *mmc_blk_get(struct gendisk *disk)
 {
 	struct mmc_blk_data *md;
@@ -1642,7 +1635,7 @@ static void mmc_blk_rw_cmd_abort(struct mmc_queue *mq, struct mmc_card *card,
 	if (mmc_card_removed(card))
 		req->rq_flags |= RQF_QUIET;
 	while (blk_end_request(req, -EIO, blk_rq_cur_bytes(req)));
-	mmc_queue_req_free(mq, mqrq);
+	mq->qcnt--;
 }
 
 /**
@@ -1662,7 +1655,7 @@ static void mmc_blk_rw_try_restart(struct mmc_queue *mq, struct request *req,
 	if (mmc_card_removed(mq->card)) {
 		req->rq_flags |= RQF_QUIET;
 		blk_end_request_all(req, -EIO);
-		mmc_queue_req_free(mq, mqrq);
+		mq->qcnt--; /* FIXME: just set to 0? */
 		return;
 	}
 	/* Else proceed and try to restart the current async request */
@@ -1685,12 +1678,8 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
 	bool req_pending = true;
 
 	if (new_req) {
-		mqrq_cur = mmc_queue_req_find(mq, new_req);
-		if (!mqrq_cur) {
-			WARN_ON(1);
-			mmc_blk_requeue(mq->queue, new_req);
-			new_req = NULL;
-		}
+		mqrq_cur = req_to_mmc_queue_req(new_req);
+		mq->qcnt++;
 	}
 
 	if (!mq->qcnt)
@@ -1764,12 +1753,12 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
 				if (req_pending)
 					mmc_blk_rw_cmd_abort(mq, card, old_req, mq_rq);
 				else
-					mmc_queue_req_free(mq, mq_rq);
+					mq->qcnt--;
 				mmc_blk_rw_try_restart(mq, new_req, mqrq_cur);
 				return;
 			}
 			if (!req_pending) {
-				mmc_queue_req_free(mq, mq_rq);
+				mq->qcnt--;
 				mmc_blk_rw_try_restart(mq, new_req, mqrq_cur);
 				return;
 			}
@@ -1814,7 +1803,7 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
 			req_pending = blk_end_request(old_req, -EIO,
 						      brq->data.blksz);
 			if (!req_pending) {
-				mmc_queue_req_free(mq, mq_rq);
+				mq->qcnt--;
 				mmc_blk_rw_try_restart(mq, new_req, mqrq_cur);
 				return;
 			}
@@ -1844,7 +1833,7 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
 		}
 	} while (req_pending);
 
-	mmc_queue_req_free(mq, mq_rq);
+	mq->qcnt--;
 }
 
 void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
@@ -2166,7 +2155,6 @@ static int mmc_blk_probe(struct mmc_card *card)
 {
 	struct mmc_blk_data *md, *part_md;
 	char cap_str[10];
-	int ret;
 
 	/*
 	 * Check that the card supports the command class(es) we need.
@@ -2176,15 +2164,9 @@ static int mmc_blk_probe(struct mmc_card *card)
 
 	mmc_fixup_device(card, mmc_blk_fixups);
 
-	ret = mmc_queue_alloc_shared_queue(card);
-	if (ret)
-		return ret;
-
 	md = mmc_blk_alloc(card);
-	if (IS_ERR(md)) {
-		mmc_queue_free_shared_queue(card);
+	if (IS_ERR(md))
 		return PTR_ERR(md);
-	}
 
 	string_get_size((u64)get_capacity(md->disk), 512, STRING_UNITS_2,
 			cap_str, sizeof(cap_str));
@@ -2222,7 +2204,6 @@ static int mmc_blk_probe(struct mmc_card *card)
  out:
 	mmc_blk_remove_parts(card, md);
 	mmc_blk_remove_req(md);
-	mmc_queue_free_shared_queue(card);
 	return 0;
 }
 
@@ -2240,7 +2221,6 @@ static void mmc_blk_remove(struct mmc_card *card)
 	pm_runtime_put_noidle(&card->dev);
 	mmc_blk_remove_req(md);
 	dev_set_drvdata(&card->dev, NULL);
-	mmc_queue_free_shared_queue(card);
 }
 
 static int _mmc_blk_suspend(struct mmc_card *card)

drivers/mmc/core/queue.c

@@ -40,35 +40,6 @@ static int mmc_prep_request(struct request_queue *q, struct request *req)
 	return BLKPREP_OK;
 }
 
-struct mmc_queue_req *mmc_queue_req_find(struct mmc_queue *mq,
-					 struct request *req)
-{
-	struct mmc_queue_req *mqrq;
-	int i = ffz(mq->qslots);
-
-	if (i >= mq->qdepth)
-		return NULL;
-
-	mqrq = &mq->mqrq[i];
-	WARN_ON(mqrq->req || mq->qcnt >= mq->qdepth ||
-		test_bit(mqrq->task_id, &mq->qslots));
-	mqrq->req = req;
-	mq->qcnt += 1;
-	__set_bit(mqrq->task_id, &mq->qslots);
-
-	return mqrq;
-}
-
-void mmc_queue_req_free(struct mmc_queue *mq,
-			struct mmc_queue_req *mqrq)
-{
-	WARN_ON(!mqrq->req || mq->qcnt < 1 ||
-		!test_bit(mqrq->task_id, &mq->qslots));
-	mqrq->req = NULL;
-	mq->qcnt -= 1;
-	__clear_bit(mqrq->task_id, &mq->qslots);
-}
-
 static int mmc_queue_thread(void *d)
 {
 	struct mmc_queue *mq = d;
@@ -149,11 +120,11 @@ static void mmc_request_fn(struct request_queue *q)
 		wake_up_process(mq->thread);
 }
 
-static struct scatterlist *mmc_alloc_sg(int sg_len)
+static struct scatterlist *mmc_alloc_sg(int sg_len, gfp_t gfp)
 {
 	struct scatterlist *sg;
 
-	sg = kmalloc_array(sg_len, sizeof(*sg), GFP_KERNEL);
+	sg = kmalloc_array(sg_len, sizeof(*sg), gfp);
 	if (sg)
 		sg_init_table(sg, sg_len);
 
@@ -179,80 +150,6 @@ static void mmc_queue_setup_discard(struct request_queue *q,
 		queue_flag_set_unlocked(QUEUE_FLAG_SECERASE, q);
 }
 
-static void mmc_queue_req_free_bufs(struct mmc_queue_req *mqrq)
-{
-	kfree(mqrq->bounce_sg);
-	mqrq->bounce_sg = NULL;
-
-	kfree(mqrq->sg);
-	mqrq->sg = NULL;
-
-	kfree(mqrq->bounce_buf);
-	mqrq->bounce_buf = NULL;
-}
-
-static void mmc_queue_reqs_free_bufs(struct mmc_queue_req *mqrq, int qdepth)
-{
-	int i;
-
-	for (i = 0; i < qdepth; i++)
-		mmc_queue_req_free_bufs(&mqrq[i]);
-}
-
-static void mmc_queue_free_mqrqs(struct mmc_queue_req *mqrq, int qdepth)
-{
-	mmc_queue_reqs_free_bufs(mqrq, qdepth);
-	kfree(mqrq);
-}
-
-static struct mmc_queue_req *mmc_queue_alloc_mqrqs(int qdepth)
-{
-	struct mmc_queue_req *mqrq;
-	int i;
-
-	mqrq = kcalloc(qdepth, sizeof(*mqrq), GFP_KERNEL);
-	if (mqrq) {
-		for (i = 0; i < qdepth; i++)
-			mqrq[i].task_id = i;
-	}
-
-	return mqrq;
-}
-
-static int mmc_queue_alloc_bounce_bufs(struct mmc_queue_req *mqrq, int qdepth,
-				       unsigned int bouncesz)
-{
-	int i;
-
-	for (i = 0; i < qdepth; i++) {
-		mqrq[i].bounce_buf = kmalloc(bouncesz, GFP_KERNEL);
-		if (!mqrq[i].bounce_buf)
-			return -ENOMEM;
-
-		mqrq[i].sg = mmc_alloc_sg(1);
-		if (!mqrq[i].sg)
-			return -ENOMEM;
-
-		mqrq[i].bounce_sg = mmc_alloc_sg(bouncesz / 512);
-		if (!mqrq[i].bounce_sg)
-			return -ENOMEM;
-	}
-
-	return 0;
-}
-
-static bool mmc_queue_alloc_bounce(struct mmc_queue_req *mqrq, int qdepth,
-				   unsigned int bouncesz)
-{
-	int ret;
-
-	ret = mmc_queue_alloc_bounce_bufs(mqrq, qdepth, bouncesz);
-	if (ret)
-		mmc_queue_reqs_free_bufs(mqrq, qdepth);
-
-	return !ret;
-}
-
 static unsigned int mmc_queue_calc_bouncesz(struct mmc_host *host)
 {
 	unsigned int bouncesz = MMC_QUEUE_BOUNCESZ;
@@ -273,71 +170,61 @@ static unsigned int mmc_queue_calc_bouncesz(struct mmc_host *host)
 	return bouncesz;
 }
 
-static int mmc_queue_alloc_sgs(struct mmc_queue_req *mqrq, int qdepth,
-			       int max_segs)
+/**
+ * mmc_init_request() - initialize the MMC-specific per-request data
+ * @q: the request queue
+ * @req: the request
+ * @gfp: memory allocation policy
+ */
+static int mmc_init_request(struct request_queue *q, struct request *req,
+			    gfp_t gfp)
 {
-	int i;
+	struct mmc_queue_req *mq_rq = req_to_mmc_queue_req(req);
+	struct mmc_queue *mq = q->queuedata;
+	struct mmc_card *card = mq->card;
+	struct mmc_host *host = card->host;
 
-	for (i = 0; i < qdepth; i++) {
-		mqrq[i].sg = mmc_alloc_sg(max_segs);
-		if (!mqrq[i].sg)
+	mq_rq->req = req;
+
+	if (card->bouncesz) {
+		mq_rq->bounce_buf = kmalloc(card->bouncesz, gfp);
+		if (!mq_rq->bounce_buf)
+			return -ENOMEM;
+		if (card->bouncesz > 512) {
+			mq_rq->sg = mmc_alloc_sg(1, gfp);
+			if (!mq_rq->sg)
+				return -ENOMEM;
+			mq_rq->bounce_sg = mmc_alloc_sg(card->bouncesz / 512,
+							gfp);
+			if (!mq_rq->bounce_sg)
+				return -ENOMEM;
+		}
+	} else {
+		mq_rq->bounce_buf = NULL;
+		mq_rq->bounce_sg = NULL;
+		mq_rq->sg = mmc_alloc_sg(host->max_segs, gfp);
+		if (!mq_rq->sg)
 			return -ENOMEM;
 	}
 
 	return 0;
 }
 
-void mmc_queue_free_shared_queue(struct mmc_card *card)
-{
-	if (card->mqrq) {
-		mmc_queue_free_mqrqs(card->mqrq, card->qdepth);
-		card->mqrq = NULL;
-	}
-}
-
-static int __mmc_queue_alloc_shared_queue(struct mmc_card *card, int qdepth)
+static void mmc_exit_request(struct request_queue *q, struct request *req)
 {
-	struct mmc_host *host = card->host;
-	struct mmc_queue_req *mqrq;
-	unsigned int bouncesz;
-	int ret = 0;
-
-	if (card->mqrq)
-		return -EINVAL;
+	struct mmc_queue_req *mq_rq = req_to_mmc_queue_req(req);
 
-	mqrq = mmc_queue_alloc_mqrqs(qdepth);
-	if (!mqrq)
-		return -ENOMEM;
-
-	card->mqrq = mqrq;
-	card->qdepth = qdepth;
+	/* It is OK to kfree(NULL) so this will be smooth */
+	kfree(mq_rq->bounce_sg);
+	mq_rq->bounce_sg = NULL;
 
-	bouncesz = mmc_queue_calc_bouncesz(host);
+	kfree(mq_rq->bounce_buf);
+	mq_rq->bounce_buf = NULL;
 
-	if (bouncesz && !mmc_queue_alloc_bounce(mqrq, qdepth, bouncesz)) {
-		bouncesz = 0;
-		pr_warn("%s: unable to allocate bounce buffers\n",
-			mmc_card_name(card));
-	}
+	kfree(mq_rq->sg);
+	mq_rq->sg = NULL;
 
-	card->bouncesz = bouncesz;
-
-	if (!bouncesz) {
-		ret = mmc_queue_alloc_sgs(mqrq, qdepth, host->max_segs);
-		if (ret)
-			goto out_err;
-	}
-
-	return ret;
-
-out_err:
-	mmc_queue_free_shared_queue(card);
-	return ret;
-}
-
-int mmc_queue_alloc_shared_queue(struct mmc_card *card)
-{
-	return __mmc_queue_alloc_shared_queue(card, 2);
+	mq_rq->req = NULL;
 }
 
 /**
@@ -360,13 +247,21 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
 		limit = (u64)dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
 
 	mq->card = card;
-	mq->queue = blk_init_queue(mmc_request_fn, lock);
+	mq->queue = blk_alloc_queue(GFP_KERNEL);
 	if (!mq->queue)
 		return -ENOMEM;
-
-	mq->mqrq = card->mqrq;
-	mq->qdepth = card->qdepth;
+	mq->queue->queue_lock = lock;
+	mq->queue->request_fn = mmc_request_fn;
+	mq->queue->init_rq_fn = mmc_init_request;
+	mq->queue->exit_rq_fn = mmc_exit_request;
+	mq->queue->cmd_size = sizeof(struct mmc_queue_req);
 	mq->queue->queuedata = mq;
+	mq->qcnt = 0;
+	ret = blk_init_allocated_queue(mq->queue);
+	if (ret) {
+		blk_cleanup_queue(mq->queue);
+		return ret;
+	}
 
 	blk_queue_prep_rq(mq->queue, mmc_prep_request);
 	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, mq->queue);
@@ -374,6 +269,7 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
 	if (mmc_can_erase(card))
 		mmc_queue_setup_discard(mq->queue, card);
 
+	card->bouncesz = mmc_queue_calc_bouncesz(host);
 	if (card->bouncesz) {
 		blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_ANY);
 		blk_queue_max_hw_sectors(mq->queue, card->bouncesz / 512);
@@ -400,7 +296,6 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,
 	return 0;
 
 cleanup_queue:
-	mq->mqrq = NULL;
 	blk_cleanup_queue(mq->queue);
 	return ret;
 }
@@ -422,7 +317,6 @@ void mmc_cleanup_queue(struct mmc_queue *mq)
 	blk_start_queue(q);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 
-	mq->mqrq = NULL;
 	mq->card = NULL;
 }
 EXPORT_SYMBOL(mmc_cleanup_queue);

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

include/linux/mmc/card.h

@@ -305,9 +305,7 @@ struct mmc_card {
 	struct mmc_part	part[MMC_NUM_PHY_PARTITION]; /* physical partitions */
 	unsigned int    nr_parts;
 
-	struct mmc_queue_req	*mqrq;		/* Shared queue structure */
 	unsigned int		bouncesz;	/* Bounce buffer size */
-	int			qdepth;		/* Shared queue depth */
 };
 
 static inline bool mmc_large_sector(struct mmc_card *card)