block: Introduce request_queue.initialize_rq_fn()

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.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 21f6f10203038ee0f5446f3a261c7d34f803c151..09989028616ffd5a790a6aaf47d2b6c81dc58e3f 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1372,12 +1372,21 @@ 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)
 {
-       if (q->mq_ops)
-               return blk_mq_alloc_request(q, op,
+       struct request *req;
+
+       if (q->mq_ops) {
+               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);
+               if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn)
+                       q->mq_ops->initialize_rq_fn(req);
+       } else {
+               req = blk_old_get_request(q, op, gfp_mask);
+               if (!IS_ERR(req) && q->initialize_rq_fn)
+                       q->initialize_rq_fn(req);
+       }
+
+       return req;
 }
 EXPORT_SYMBOL(blk_get_request);
 

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 3077714250ce7b19516aa69584555cc4cfb3d0a6..366b83cee9550e1b490317ba758938b13ebf520e 100644 (file)
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -144,6 +144,8 @@ 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 e21dd893ee86cca629f9c16c3c1fd2e392e18f6a..9a36164487d086901dae9d773890eccbe421dfcc 100644 (file)
--- 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;