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Subject[PATCH 1/5 v2] blk-mq: Add prep/unprep support
Date
Allow users to hook into prep/unprep functions just before an IO is
dispatched to the device driver. This is necessary for request-based
logic to take place at upper layers.

Signed-off-by: Matias Bjørling <m@bjorling.me>
---
block/blk-mq.c | 28 ++++++++++++++++++++++++++--
include/linux/blk-mq.h | 1 +
2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 33c4285..f3dd028 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -338,6 +338,11 @@ EXPORT_SYMBOL(__blk_mq_end_request);

void blk_mq_end_request(struct request *rq, int error)
{
+ struct request_queue *q = rq->q;
+
+ if (q->unprep_rq_fn)
+ q->unprep_rq_fn(q, rq);
+
if (blk_update_request(rq, error, blk_rq_bytes(rq)))
BUG();
__blk_mq_end_request(rq, error);
@@ -753,6 +758,17 @@ static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
}
}

+static int blk_mq_prep_rq(struct request_queue *q, struct request *rq)
+{
+ if (!q->prep_rq_fn)
+ return 0;
+
+ if (rq->cmd_flags & REQ_DONTPREP)
+ return 0;
+
+ return q->prep_rq_fn(q, rq);
+}
+
/*
* Run this hardware queue, pulling any software queues mapped to it in.
* Note that this function currently has various problems around ordering
@@ -812,11 +828,15 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
bd.list = dptr;
bd.last = list_empty(&rq_list);

- ret = q->mq_ops->queue_rq(hctx, &bd);
+ ret = blk_mq_prep_rq(q, rq);
+ if (likely(!ret))
+ ret = q->mq_ops->queue_rq(hctx, &bd);
switch (ret) {
case BLK_MQ_RQ_QUEUE_OK:
queued++;
continue;
+ case BLK_MQ_RQ_QUEUE_DONE:
+ continue;
case BLK_MQ_RQ_QUEUE_BUSY:
list_add(&rq->queuelist, &rq_list);
__blk_mq_requeue_request(rq);
@@ -1270,10 +1290,14 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
* error (busy), just add it to our list as we previously
* would have done
*/
- ret = q->mq_ops->queue_rq(data.hctx, &bd);
+ ret = blk_mq_prep_rq(q, rq);
+ if (likely(!ret))
+ ret = q->mq_ops->queue_rq(data.hctx, &bd);
if (ret == BLK_MQ_RQ_QUEUE_OK)
goto done;
else {
+ if (ret == BLK_MQ_RQ_QUEUE_DONE)
+ goto done;
__blk_mq_requeue_request(rq);

if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 7aec861..d7b39af 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -140,6 +140,7 @@ enum {
BLK_MQ_RQ_QUEUE_OK = 0, /* queued fine */
BLK_MQ_RQ_QUEUE_BUSY = 1, /* requeue IO for later */
BLK_MQ_RQ_QUEUE_ERROR = 2, /* end IO with error */
+ BLK_MQ_RQ_QUEUE_DONE = 3, /* IO is already handled */

BLK_MQ_F_SHOULD_MERGE = 1 << 0,
BLK_MQ_F_TAG_SHARED = 1 << 1,
--
1.9.1


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