答复: [PATCH v2 1/2] block: Call .limit_depth() after .hctx has been set

[牛志国 (Zhiguo Niu) <Zhiguo.Niu@xxxxxxxxxx>]

-----邮件原件-----
发件人: Bart Van Assche <bvanassche@xxxxxxx> 
发送时间: 2024年5月10日 1:02
收件人: Jens Axboe <axboe@xxxxxxxxx>
抄送: linux-block@xxxxxxxxxxxxxxx; Christoph Hellwig <hch@xxxxxx>; Bart Van Assche <bvanassche@xxxxxxx>; Damien Le Moal <dlemoal@xxxxxxxxxx>; 牛志国 (Zhiguo Niu) <Zhiguo.Niu@xxxxxxxxxx>
主题: [PATCH v2 1/2] block: Call .limit_depth() after .hctx has been set


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Call .limit_depth() after data->hctx has been set such that data->hctx can be used in .limit_depth() implementations.

Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
Fixes: 07757588e507 ("block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 block/blk-mq.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c index 9f677ea85a52..a6310a550b78 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -448,6 +448,10 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
        if (data->cmd_flags & REQ_NOWAIT)
                data->flags |= BLK_MQ_REQ_NOWAIT;

+retry:
+       data->ctx = blk_mq_get_ctx(q);
+       data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
+
Hi Bart,
I tested basic function about these serial patches and results is pass, and no warning report after setting async_depth value by sysfs, But there is a little question here, if do "retry", the following if case will be re-run also, so 
Is there something wrong with this or can it be improved?  Otherwise
Tested-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
Thanks!
        if (q->elevator) {
                /*
                 * All requests use scheduler tags when an I/O scheduler is @@ -469,13 +473,9 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
                        if (ops->limit_depth)
                                ops->limit_depth(data->cmd_flags, data);
                }
-       }
-
-retry:
-       data->ctx = blk_mq_get_ctx(q);
-       data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
-       if (!(data->rq_flags & RQF_SCHED_TAGS))
+       } else {
                blk_mq_tag_busy(data->hctx);
+       }

        if (data->flags & BLK_MQ_REQ_RESERVED)
                data->rq_flags |= RQF_RESV;