From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH 8/8] IB/srp: Add multichannel support Date: Fri, 19 Sep 2014 17:35:11 +0200 Message-ID: <541C4D2F.9060907@acm.org> References: <541C27BF.6070609@acm.org> <541C28E0.7010705@acm.org> <541C49EC.6030404@acm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org To: Ming Lei Cc: "linux-scsi@vger.kernel.org" , linux-rdma , Christoph Hellwig , Jens Axboe , Robert Elliott List-Id: linux-rdma@vger.kernel.org On 09/19/14 17:27, Ming Lei wrote: > On Fri, Sep 19, 2014 at 11:21 PM, Bart Van Assche wrote: >> On 09/19/14 16:28, Ming Lei wrote: >>> >>> On Fri, Sep 19, 2014 at 9:00 PM, Bart Van Assche >>> wrote: >>>> >>>> @@ -2643,7 +2754,8 @@ static struct scsi_host_template srp_template = { >>>> .proc_name = DRV_NAME, >>>> .slave_configure = srp_slave_configure, >>>> .info = srp_target_info, >>>> - .queuecommand = srp_queuecommand, >>>> + .queuecommand = srp_sq_queuecommand, >>>> + .mq_queuecommand = srp_mq_queuecommand, >>> >>> >>> Another choice is to obtain hctx from request directly, then mq can >>> reuse the .queuecommand interface too. >> >> >> Hello Ming, >> >> Is the hctx information already available in the request data structure ? I >> have found a mq_ctx member but no hctx member. Did I perhaps overlook >> something ? > > You are right, but the mq_ctx can be mapped to hctx like below way: > > ctx = rq->mq_ctx; > hctx = q->mq_ops->map_queue(q, ctx->cpu); Hello Ming, Had you already noticed that the blk_mq_ctx data structure is a private data structure (declared in block/blk-mq.h) and hence not available to SCSI LLDs ? However, what might be possible is to cache the hctx pointer in the request structure, e.g. like in the (completely untested) patch below. [PATCH] blk-mq: Cache hardware context pointer in struct request Cache the hardware context pointer in struct request such that block drivers can determine which hardware queue has been selected by reading rq->mq_hctx->queue_num. This information is needed to select the appropriate hardware queue in e.g. SCSI LLDs. --- block/blk-flush.c | 6 +----- block/blk-mq.c | 16 +++++++++------- include/linux/blkdev.h | 1 + 3 files changed, 11 insertions(+), 12 deletions(-) diff --git a/block/blk-flush.c b/block/blk-flush.c index 3cb5e9e..698812d 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -327,13 +327,9 @@ static void flush_data_end_io(struct request *rq, int error) static void mq_flush_data_end_io(struct request *rq, int error) { struct request_queue *q = rq->q; - struct blk_mq_hw_ctx *hctx; - struct blk_mq_ctx *ctx; + struct blk_mq_hw_ctx *hctx = rq->mq_hctx; unsigned long flags; - ctx = rq->mq_ctx; - hctx = q->mq_ops->map_queue(q, ctx->cpu); - /* * After populating an empty queue, kick it to avoid stall. Read * the comment in flush_end_io(). diff --git a/block/blk-mq.c b/block/blk-mq.c index 383ea0c..8e428fe 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -210,6 +210,7 @@ __blk_mq_alloc_request(struct blk_mq_alloc_data *data, int rw) } rq->tag = tag; + rq->mq_hctx = data->hctx; blk_mq_rq_ctx_init(data->q, data->ctx, rq, rw); return rq; } @@ -267,12 +268,10 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx, void blk_mq_free_request(struct request *rq) { struct blk_mq_ctx *ctx = rq->mq_ctx; - struct blk_mq_hw_ctx *hctx; - struct request_queue *q = rq->q; + struct blk_mq_hw_ctx *hctx = rq->mq_hctx; ctx->rq_completed[rq_is_sync(rq)]++; - hctx = q->mq_ops->map_queue(q, ctx->cpu); __blk_mq_free_request(hctx, ctx, rq); } @@ -287,10 +286,10 @@ void blk_mq_free_request(struct request *rq) void blk_mq_clone_flush_request(struct request *flush_rq, struct request *orig_rq) { - struct blk_mq_hw_ctx *hctx = - orig_rq->q->mq_ops->map_queue(orig_rq->q, orig_rq->mq_ctx->cpu); + struct blk_mq_hw_ctx *hctx = orig_rq->mq_hctx; flush_rq->mq_ctx = orig_rq->mq_ctx; + flush_rq->mq_hctx = hctx; flush_rq->tag = orig_rq->tag; memcpy(blk_mq_rq_to_pdu(flush_rq), blk_mq_rq_to_pdu(orig_rq), hctx->cmd_size); @@ -956,6 +955,7 @@ void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue, rq->mq_ctx = ctx = current_ctx; hctx = q->mq_ops->map_queue(q, ctx->cpu); + rq->mq_hctx = hctx; if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA) && !(rq->cmd_flags & (REQ_FLUSH_SEQ))) { @@ -1001,6 +1001,7 @@ static void blk_mq_insert_requests(struct request_queue *q, rq = list_first_entry(list, struct request, queuelist); list_del_init(&rq->queuelist); rq->mq_ctx = ctx; + rq->mq_hctx = hctx; __blk_mq_insert_request(hctx, rq, false); } spin_unlock(&ctx->lock); @@ -1475,6 +1476,8 @@ static int blk_mq_hctx_cpu_offline(struct blk_mq_hw_ctx *hctx, int cpu) return NOTIFY_OK; ctx = blk_mq_get_ctx(q); + hctx = q->mq_ops->map_queue(q, ctx->cpu); + spin_lock(&ctx->lock); while (!list_empty(&tmp)) { @@ -1482,10 +1485,9 @@ static int blk_mq_hctx_cpu_offline(struct blk_mq_hw_ctx *hctx, int cpu) rq = list_first_entry(&tmp, struct request, queuelist); rq->mq_ctx = ctx; + rq->mq_hctx = hctx; list_move_tail(&rq->queuelist, &ctx->rq_list); } - - hctx = q->mq_ops->map_queue(q, ctx->cpu); blk_mq_hctx_mark_pending(hctx, ctx); spin_unlock(&ctx->lock); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 518b465..e3a14a2 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -105,6 +105,7 @@ struct request { struct request_queue *q; struct blk_mq_ctx *mq_ctx; + struct blk_mq_hw_ctx *mq_hctx; u64 cmd_flags; enum rq_cmd_type_bits cmd_type; -- 1.8.4.5