On Sun, 2017-05-21 at 08:34 +0200, Christoph Hellwig wrote: > On Fri, May 19, 2017 at 11:30:05AM -0700, Bart Van Assche wrote: > > Several block drivers need to initialize the driver-private 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 a new callback function to struct > > request_queue. > > > > Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com> > > Cc: Jens Axboe <ax...@fb.com> > > Cc: Christoph Hellwig <h...@lst.de> > > Cc: Omar Sandoval <osan...@fb.com> > > Cc: Hannes Reinecke <h...@suse.com> > > Cc: linux-block@vger.kernel.org > > --- > > block/blk-core.c | 3 +++ > > block/blk-mq.c | 3 +++ > > include/linux/blkdev.h | 4 ++++ > > 3 files changed, 10 insertions(+) > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > index a69d420b7ff0..f2540d164679 100644 > > --- a/block/blk-core.c > > +++ b/block/blk-core.c > > @@ -126,6 +126,9 @@ void blk_rq_init(struct request_queue *q, struct > > request *rq) > > rq->start_time = jiffies; > > set_start_time_ns(rq); > > rq->part = NULL; > > + > > + if (q->initialize_rq_fn) > > + q->initialize_rq_fn(rq); > > Can we keep this out of the fast path and only do it from the > blk_get_request / blk_mq_alloc_request path? And while were at it > I think those two should be merged as far as the public interface > goes, that is we should also expose the flags argument for the > legacy path.
Hello Christoph, For blk-mq I could move the .initialize_rq_fn() call from blk_mq_rq_ctx_init() into blk_mq_sched_get_request(). I can't move it higher up in the request allocation call chain because otherwise blk_mq_alloc_request_hctx() wouldn't call .initialize_rq_fn(). For blk-sq I'm not sure that the .initialize_rq_fn() call can be moved because I'd like all blk_rq_init() callers to call .initialize_rq_fn(), including ide_prep_sense(). Are you sure it would help to move the .initialize_rq_fn() calls? Thanks, Bart.
