[PATCH v3 03/12] block: Introduce request_queue.initialize_rq_fn()

[Bart Van Assche]

Several block drivers need to initialize the driver-private request
data after having called blk_get_request() and before .prep_rq_fn()
is called, e.g. when submitting a REQ_OP_SCSI_* request. Avoid that
that initialization code has to be repeated after every
blk_get_request() call by adding new callback functions to struct
request_queue and to struct blk_mq_ops.

Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Hannes Reinecke <h...@suse.com>
Cc: Omar Sandoval <osan...@fb.com>
---
 block/blk-core.c       | 17 +++++++++++++++--
 include/linux/blk-mq.h |  2 ++
 include/linux/blkdev.h |  4 ++++
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 3bc431a77309..86fc08898fac 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1308,12 +1308,25 @@ static struct request *blk_old_get_request(struct 
request_queue *q,
 struct request *blk_get_request(struct request_queue *q, unsigned int op,
                                gfp_t gfp_mask)
 {
+       struct request *req;
+
        if (q->mq_ops)
-               return blk_mq_alloc_request(q, op,
+               req = blk_mq_alloc_request(q, op,
                        (gfp_mask & __GFP_DIRECT_RECLAIM) ?
                                0 : BLK_MQ_REQ_NOWAIT);
        else
-               return blk_old_get_request(q, op, gfp_mask);
+               req = blk_old_get_request(q, op, gfp_mask);
+
+       if (IS_ERR(req))
+               goto out;
+
+       if (q->mq_ops && q->mq_ops->initialize_rq_fn)
+               q->mq_ops->initialize_rq_fn(req);
+       else if (!q->mq_ops && q->initialize_rq_fn)
+               q->initialize_rq_fn(req);
+
+out:
+       return req;
 }
 EXPORT_SYMBOL(blk_get_request);
 
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index a4759fd34e7e..61125d200492 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -143,6 +143,8 @@ struct blk_mq_ops {
        init_request_fn         *init_request;
        exit_request_fn         *exit_request;
        reinit_request_fn       *reinit_request;
+       /* Called from inside blk_get_request() */
+       void (*initialize_rq_fn)(struct request *rq);
 
        map_queues_fn           *map_queues;
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 6c4235018b49..cbc0028290e4 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -410,8 +410,12 @@ struct request_queue {
        rq_timed_out_fn         *rq_timed_out_fn;
        dma_drain_needed_fn     *dma_drain_needed;
        lld_busy_fn             *lld_busy_fn;
+       /* Called just after a request is allocated */
        init_rq_fn              *init_rq_fn;
+       /* Called just before a request is freed */
        exit_rq_fn              *exit_rq_fn;
+       /* Called from inside blk_get_request() */
+       void (*initialize_rq_fn)(struct request *rq);
 
        const struct blk_mq_ops *mq_ops;
 
-- 
2.12.2