On 09/19/14 17:27, Ming Lei wrote:
> On Fri, Sep 19, 2014 at 11:21 PM, Bart Van Assche <bvanass...@acm.org> wrote:
>> On 09/19/14 16:28, Ming Lei wrote:
>>>
>>> On Fri, Sep 19, 2014 at 9:00 PM, Bart Van Assche <bvanass...@acm.org>
>>> 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
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