| Message ID | 20210907142145.112096-2-Niklas.Cassel@wdc.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | don't call io scheduler callbacks for passthrough requests | expand |
On Tue, Sep 07, 2021 at 02:21:55PM +0000, Niklas Cassel wrote: > From: Niklas Cassel <niklas.cassel@wdc.com> > > Currently, __blk_mq_alloc_request() (via blk_mq_rq_ctx_init()) calls the > I/O scheduler callback e->type->ops.prepare_request(), which will set > RQF_ELVPRIV, even though passthrough (and flush) requests will later > bypass the I/O scheduler in blk_mq_submit_bio(). > > Later, blk_mq_free_request() checks if the RQF_ELVPRIV flag is set, > if it is, the e->type->ops.finish_request() I/O scheduler callback > will be called. > > i.e., the prepare_request and finish_request I/O scheduler callbacks > will be called for requests which were never inserted to the I/O > scheduler. > > Fix this by not calling e->type->ops.prepare_request(), nor setting > the RQF_ELVPRIV flag for passthrough requests. > Since the RQF_ELVPRIV flag will not get set for passthrough requests, > e->type->ops.prepare_request() will no longer get called for > passthrough requests which were never inserted to the I/O scheduler. > > Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com> > --- > block/blk-mq.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 65d3a63aecc6..0816af125059 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -328,7 +328,12 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data, > data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++; > refcount_set(&rq->ref, 1); > > - if (!op_is_flush(data->cmd_flags)) { > + /* > + * Flush/passthrough requests are special and go directly to the > + * dispatch list, bypassing the scheduler. > + */ > + if (!op_is_flush(data->cmd_flags) && > + !blk_op_is_passthrough(data->cmd_flags)) { Looks fine: Reviewed-by: Ming Lei <ming.lei@redhat.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c index 65d3a63aecc6..0816af125059 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -328,7 +328,12 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data, data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++; refcount_set(&rq->ref, 1); - if (!op_is_flush(data->cmd_flags)) { + /* + * Flush/passthrough requests are special and go directly to the + * dispatch list, bypassing the scheduler. + */ + if (!op_is_flush(data->cmd_flags) && + !blk_op_is_passthrough(data->cmd_flags)) { struct elevator_queue *e = data->q->elevator; rq->elv.icq = NULL;