[PATCH RFC 03/39] mmc: block: Introduce queue semantics

Adrian Hunter
2017-02-10T13:24:16Z

Change from viewing the requests in progress as 'current' and 'previous',
to viewing them as a queue. The current request is allocated to the first
free slot. The presence of incomplete requests is determined from the
count (mq->qcnt) of entries in the queue. Non-read-write requests (i.e.
discards and flushes) are not added to the queue at all and require no
special handling. Also no special handling is needed for the
MMC_BLK_NEW_REQUEST case.

As well as allowing an arbitrarily sized queue, the queue thread function
is significantly simpler.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
drivers/mmc/core/block.c | 42 ++++++++++++++++-----------
drivers/mmc/core/queue.c | 74 ++++++++++++++++++++++++++++++------------------
drivers/mmc/core/queue.h | 10 +++++--
3 files changed, 79 insertions(+), 47 deletions(-)

diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index b6d1497c395f..7568e576bba3 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -134,6 +134,13 @@ 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;
@@ -1631,14 +1638,23 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
struct mmc_blk_request *brq;
int disable_multi = 0, retry = 0, type, retune_retry_done = 0;
enum mmc_blk_status status;
- struct mmc_queue_req *mqrq_cur = mq->mqrq_cur;
+ struct mmc_queue_req *mqrq_cur = NULL;
struct mmc_queue_req *mq_rq;
struct request *old_req;
struct mmc_async_req *new_areq;
struct mmc_async_req *old_areq;
bool req_pending = true;

- if (!new_req && !mq->mqrq_prev->req)
+ 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;
+ }
+ }
+
+ if (!mq->qcnt)
return;

do {
@@ -1667,8 +1683,6 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
* and there is nothing more to do until it is
* complete.
*/
- if (status == MMC_BLK_NEW_REQUEST)
- mq->new_request = true;
return;
}

@@ -1785,6 +1799,8 @@ static void mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *new_req)
mq_rq->brq.retune_retry_done = retune_retry_done;
}
} while (req_pending);
+
+ mmc_queue_req_free(mq, mq_rq);
}

void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
@@ -1792,9 +1808,8 @@ void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
int ret;
struct mmc_blk_data *md = mq->blkdata;
struct mmc_card *card = md->queue.card;
- bool req_is_special = mmc_req_is_special(req);

- if (req && !mq->mqrq_prev->req)
+ if (req && !mq->qcnt)
/* claim host only for the first request */
mmc_get_card(card);

@@ -1806,20 +1821,19 @@ void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
goto out;
}

- mq->new_request = false;
if (req && req_op(req) == REQ_OP_DISCARD) {
/* complete ongoing async transfer before issuing discard */
- if (card->host->areq)
+ if (mq->qcnt)
mmc_blk_issue_rw_rq(mq, NULL);
mmc_blk_issue_discard_rq(mq, req);
} else if (req && req_op(req) == REQ_OP_SECURE_ERASE) {
/* complete ongoing async transfer before issuing secure erase*/
- if (card->host->areq)
+ if (mq->qcnt)
mmc_blk_issue_rw_rq(mq, NULL);
mmc_blk_issue_secdiscard_rq(mq, req);
} else if (req && req_op(req) == REQ_OP_FLUSH) {
/* complete ongoing async transfer before issuing flush */
- if (card->host->areq)
+ if (mq->qcnt)
mmc_blk_issue_rw_rq(mq, NULL);
mmc_blk_issue_flush(mq, req);
} else {
@@ -1827,13 +1841,7 @@ void mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
}

out:
- if ((!req && !mq->new_request) || req_is_special)
- /*
- * 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'.
- */
+ if (!mq->qcnt)
mmc_put_card(card);
}

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 031553c9be04..479638bfb092 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -49,6 +49,35 @@ 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;
@@ -59,7 +88,7 @@ static int mmc_queue_thread(void *d)

down(&mq->thread_sem);
do {
- struct request *req = NULL;
+ struct request *req;

spin_lock_irq(q->queue_lock);
set_current_state(TASK_INTERRUPTIBLE);
@@ -72,38 +101,17 @@ static int mmc_queue_thread(void *d)
* Dispatch queue is empty so set flags for
* mmc_request_fn() to wake us up.
*/
- if (mq->mqrq_prev->req)
+ if (mq->qcnt)
cntx->is_waiting_last_req = true;
else
mq->asleep = true;
}
- mq->mqrq_cur->req = req;
spin_unlock_irq(q->queue_lock);

- if (req || mq->mqrq_prev->req) {
- bool req_is_special = mmc_req_is_special(req);
-
+ if (req || mq->qcnt) {
set_current_state(TASK_RUNNING);
mmc_blk_issue_rq(mq, req);
cond_resched();
- if (mq->new_request) {
- mq->new_request = false;
- continue; /* fetch again */
- }
-
- /*
- * Current request becomes previous request
- * and vice versa.
- * In case of special requests, current request
- * has been finished. Do not assign it to previous
- * request.
- */
- if (req_is_special)
- mq->mqrq_cur->req = NULL;
-
- mq->mqrq_prev->brq.mrq.data = NULL;
- mq->mqrq_prev->req = NULL;
- swap(mq->mqrq_prev, mq->mqrq_cur);
} else {
if (kthread_should_stop()) {
set_current_state(TASK_RUNNING);
@@ -208,6 +216,20 @@ static void mmc_queue_free_mqrqs(struct mmc_queue_req *mqrq, int 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;
+}
+
#ifdef CONFIG_MMC_BLOCK_BOUNCE
static int mmc_queue_alloc_bounce_bufs(struct mmc_queue_req *mqrq, int qdepth,
unsigned int bouncesz)
@@ -307,7 +329,7 @@ static int __mmc_queue_alloc_shared_queue(struct mmc_card *card, int qdepth)
if (card->mqrq)
return -EINVAL;

- mqrq = kcalloc(qdepth, sizeof(*mqrq), GFP_KERNEL);
+ mqrq = mmc_queue_alloc_mqrqs(qdepth);
if (!mqrq)
return -ENOMEM;

@@ -368,8 +390,6 @@ int mmc_init_queue(struct mmc_queue *mq, struct mmc_card *card,

mq->mqrq = card->mqrq;
mq->qdepth = card->qdepth;
- mq->mqrq_cur = &mq->mqrq[0];
- mq->mqrq_prev = &mq->mqrq[1];
mq->queue->queuedata = mq;

blk_queue_prep_rq(mq->queue, mmc_prep_request);
diff --git a/drivers/mmc/core/queue.h b/drivers/mmc/core/queue.h
index 298ead2b4245..871796c3f406 100644
--- a/drivers/mmc/core/queue.h
+++ b/drivers/mmc/core/queue.h
@@ -34,21 +34,21 @@ struct mmc_queue_req {
struct scatterlist *bounce_sg;
unsigned int bounce_sg_len;
struct mmc_async_req areq;
+ int task_id;
};

struct mmc_queue {
struct mmc_card *card;
struct task_struct *thread;
struct semaphore thread_sem;
- bool new_request;
bool suspended;
bool asleep;
struct mmc_blk_data *blkdata;
struct request_queue *queue;
struct mmc_queue_req *mqrq;
- struct mmc_queue_req *mqrq_cur;
- struct mmc_queue_req *mqrq_prev;
int qdepth;
+ int qcnt;
+ unsigned long qslots;
};

extern int mmc_queue_alloc_shared_queue(struct mmc_card *card);
@@ -66,4 +66,8 @@ extern unsigned int mmc_queue_map_sg(struct mmc_queue *,

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
--
1.9.1