From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <keith.busch@intel.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
Ming Lei <ming.lei@redhat.com>, Christoph Hellwig <hch@lst.de>,
Bart Van Assche <bart.vanassche@wdc.com>
Subject: Re: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce
Date: Tue, 22 May 2018 18:17:04 +0200 [thread overview]
Message-ID: <20180522161704.GA20000@lst.de> (raw)
In-Reply-To: <20180521231131.6685-4-keith.busch@intel.com>
Hi Keith,
I like this series a lot. One comment that is probably close
to the big discussion in the thread:
> switch (ret) {
> case BLK_EH_HANDLED:
> /*
> + * If the request is still in flight, the driver is requesting
> + * blk-mq complete it.
> */
> + if (blk_mq_rq_state(req) == MQ_RQ_IN_FLIGHT)
> + __blk_mq_complete_request(req);
> + break;
The state check here really irked me, and from the thread it seems like
I'm not the only one. At least for the NVMe case I think it is perfectly
safe, although I agree I'd rather audit what other drivers do carefully.
That being said I think BLK_EH_HANDLED seems like a fundamentally broken
idea, and I'd actually prefer to get rid of it over adding things like
the MQ_RQ_IN_FLIGHT check above.
E.g. if we look at the cases where nvme-pci returns it:
- if we did call nvme_dev_disable, we already canceled all requests,
so we might as well just return BLK_EH_NOT_HANDLED
- the poll for completion case already completed the command,
so we should return BLK_EH_NOT_HANDLED
So I think we need to fix up nvme and if needed any other driver
to return the right value and then assert that the request is
still in in-flight status for the BLK_EH_HANDLED case.
> @@ -124,16 +119,7 @@ static inline int blk_mq_rq_state(struct request *rq)
> static inline void blk_mq_rq_update_state(struct request *rq,
> enum mq_rq_state state)
> {
> + WRITE_ONCE(rq->state, state);
> }
I think this helper can go away now. But we should have a comment
near the state field documenting the concurrency implications.
> + u64 state;
This should probably be a mq_rq_state instead. Which means it needs
to be moved to blkdev.h, but that should be ok.
WARNING: multiple messages have this Message-ID (diff)
From: hch@lst.de (Christoph Hellwig)
Subject: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce
Date: Tue, 22 May 2018 18:17:04 +0200 [thread overview]
Message-ID: <20180522161704.GA20000@lst.de> (raw)
In-Reply-To: <20180521231131.6685-4-keith.busch@intel.com>
Hi Keith,
I like this series a lot. One comment that is probably close
to the big discussion in the thread:
> switch (ret) {
> case BLK_EH_HANDLED:
> /*
> + * If the request is still in flight, the driver is requesting
> + * blk-mq complete it.
> */
> + if (blk_mq_rq_state(req) == MQ_RQ_IN_FLIGHT)
> + __blk_mq_complete_request(req);
> + break;
The state check here really irked me, and from the thread it seems like
I'm not the only one. At least for the NVMe case I think it is perfectly
safe, although I agree I'd rather audit what other drivers do carefully.
That being said I think BLK_EH_HANDLED seems like a fundamentally broken
idea, and I'd actually prefer to get rid of it over adding things like
the MQ_RQ_IN_FLIGHT check above.
E.g. if we look at the cases where nvme-pci returns it:
- if we did call nvme_dev_disable, we already canceled all requests,
so we might as well just return BLK_EH_NOT_HANDLED
- the poll for completion case already completed the command,
so we should return BLK_EH_NOT_HANDLED
So I think we need to fix up nvme and if needed any other driver
to return the right value and then assert that the request is
still in in-flight status for the BLK_EH_HANDLED case.
> @@ -124,16 +119,7 @@ static inline int blk_mq_rq_state(struct request *rq)
> static inline void blk_mq_rq_update_state(struct request *rq,
> enum mq_rq_state state)
> {
> + WRITE_ONCE(rq->state, state);
> }
I think this helper can go away now. But we should have a comment
near the state field documenting the concurrency implications.
> + u64 state;
This should probably be a mq_rq_state instead. Which means it needs
to be moved to blkdev.h, but that should be ok.
next prev parent reply other threads:[~2018-05-22 16:17 UTC|newest]
Thread overview: 128+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-21 23:11 [RFC PATCH 0/3] blk-mq: Timeout rework Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-21 23:11 ` [RFC PATCH 1/3] blk-mq: Reference count request usage Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-22 2:27 ` Ming Lei
2018-05-22 2:27 ` Ming Lei
2018-05-22 15:19 ` Christoph Hellwig
2018-05-22 15:19 ` Christoph Hellwig
2018-05-21 23:11 ` [RFC PATCH 2/3] blk-mq: Fix timeout and state order Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-22 2:28 ` Ming Lei
2018-05-22 2:28 ` Ming Lei
2018-05-22 15:24 ` Christoph Hellwig
2018-05-22 15:24 ` Christoph Hellwig
2018-05-22 16:27 ` Bart Van Assche
2018-05-22 16:27 ` Bart Van Assche
2018-05-21 23:11 ` [RFC PATCH 3/3] blk-mq: Remove generation seqeunce Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-21 23:29 ` Bart Van Assche
2018-05-21 23:29 ` Bart Van Assche
2018-05-22 14:15 ` Keith Busch
2018-05-22 14:15 ` Keith Busch
2018-05-22 16:29 ` Bart Van Assche
2018-05-22 16:29 ` Bart Van Assche
2018-05-22 16:34 ` Keith Busch
2018-05-22 16:34 ` Keith Busch
2018-05-22 16:48 ` Bart Van Assche
2018-05-22 16:48 ` Bart Van Assche
2018-05-22 2:49 ` Ming Lei
2018-05-22 2:49 ` Ming Lei
2018-05-22 3:16 ` Jens Axboe
2018-05-22 3:16 ` Jens Axboe
2018-05-22 3:47 ` Ming Lei
2018-05-22 3:47 ` Ming Lei
2018-05-22 3:51 ` Jens Axboe
2018-05-22 3:51 ` Jens Axboe
2018-05-22 8:51 ` Ming Lei
2018-05-22 8:51 ` Ming Lei
2018-05-22 14:35 ` Jens Axboe
2018-05-22 14:35 ` Jens Axboe
2018-05-22 14:20 ` Keith Busch
2018-05-22 14:20 ` Keith Busch
2018-05-22 14:37 ` Ming Lei
2018-05-22 14:37 ` Ming Lei
2018-05-22 14:46 ` Keith Busch
2018-05-22 14:46 ` Keith Busch
2018-05-22 14:57 ` Ming Lei
2018-05-22 14:57 ` Ming Lei
2018-05-22 15:01 ` Keith Busch
2018-05-22 15:01 ` Keith Busch
2018-05-22 15:07 ` Ming Lei
2018-05-22 15:07 ` Ming Lei
2018-05-22 15:17 ` Keith Busch
2018-05-22 15:17 ` Keith Busch
2018-05-22 15:23 ` Ming Lei
2018-05-22 15:23 ` Ming Lei
2018-05-22 16:17 ` Christoph Hellwig [this message]
2018-05-22 16:17 ` Christoph Hellwig
2018-05-23 0:34 ` Ming Lei
2018-05-23 0:34 ` Ming Lei
2018-05-23 14:35 ` Keith Busch
2018-05-23 14:35 ` Keith Busch
2018-05-24 1:52 ` Ming Lei
2018-05-24 1:52 ` Ming Lei
2018-05-23 5:48 ` Hannes Reinecke
2018-05-23 5:48 ` Hannes Reinecke
2018-07-12 18:16 ` Bart Van Assche
2018-07-12 18:16 ` Bart Van Assche
2018-07-12 19:24 ` Keith Busch
2018-07-12 19:24 ` Keith Busch
2018-07-12 22:24 ` Bart Van Assche
2018-07-12 22:24 ` Bart Van Assche
2018-07-13 1:12 ` jianchao.wang
2018-07-13 1:12 ` jianchao.wang
2018-07-13 2:40 ` jianchao.wang
2018-07-13 2:40 ` jianchao.wang
2018-07-13 15:43 ` Keith Busch
2018-07-13 15:43 ` Keith Busch
2018-07-13 15:52 ` Bart Van Assche
2018-07-13 15:52 ` Bart Van Assche
2018-07-13 18:47 ` Keith Busch
2018-07-13 18:47 ` Keith Busch
2018-07-13 23:03 ` Bart Van Assche
2018-07-13 23:03 ` Bart Van Assche
2018-07-13 23:58 ` Keith Busch
2018-07-13 23:58 ` Keith Busch
2018-07-18 19:56 ` hch
2018-07-18 19:56 ` hch
2018-07-18 20:39 ` hch
2018-07-18 20:39 ` hch
2018-07-18 21:05 ` Bart Van Assche
2018-07-18 21:05 ` Bart Van Assche
2018-07-18 22:53 ` Keith Busch
2018-07-18 22:53 ` Keith Busch
2018-07-18 20:53 ` Keith Busch
2018-07-18 20:53 ` Keith Busch
2018-07-18 20:58 ` Bart Van Assche
2018-07-18 20:58 ` Bart Van Assche
2018-07-18 21:17 ` Keith Busch
2018-07-18 21:17 ` Keith Busch
2018-07-18 21:30 ` Bart Van Assche
2018-07-18 21:30 ` Bart Van Assche
2018-07-18 21:33 ` Keith Busch
2018-07-18 21:33 ` Keith Busch
2018-07-19 13:19 ` hch
2018-07-19 13:19 ` hch
2018-07-19 14:59 ` Keith Busch
2018-07-19 14:59 ` Keith Busch
2018-07-19 15:56 ` Keith Busch
2018-07-19 15:56 ` Keith Busch
2018-07-19 16:04 ` Bart Van Assche
2018-07-19 16:04 ` Bart Van Assche
2018-07-19 16:22 ` Keith Busch
2018-07-19 16:22 ` Keith Busch
2018-07-19 16:29 ` hch
2018-07-19 16:29 ` hch
2018-07-19 20:18 ` Keith Busch
2018-07-19 20:18 ` Keith Busch
2018-07-19 13:22 ` hch
2018-07-19 13:22 ` hch
2018-05-21 23:29 ` [RFC PATCH 0/3] blk-mq: Timeout rework Bart Van Assche
2018-05-21 23:29 ` Bart Van Assche
2018-05-22 14:06 ` Keith Busch
2018-05-22 14:06 ` Keith Busch
2018-05-22 16:30 ` Bart Van Assche
2018-05-22 16:30 ` Bart Van Assche
2018-05-22 16:44 ` Keith Busch
2018-05-22 16:44 ` Keith Busch
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