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)