Re: [PATCH 4/4] nvme: wire up async polling for io passthrough commands

From: Kanchan Joshi <joshi.k@samsung.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: hch@lst.de, io-uring@vger.kernel.org,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	ming.lei@redhat.com, joshiiitr@gmail.com, gost.dev@samsung.com,
	Anuj Gupta <anuj20.g@samsung.com>
Subject: Re: [PATCH 4/4] nvme: wire up async polling for io passthrough commands
Date: Fri, 5 Aug 2022 22:37:07 +0530	[thread overview]
Message-ID: <20220805170707.GC17011@test-zns> (raw)
In-Reply-To: <769524f5-c725-85f7-e7ac-ca3b2b2d884e@kernel.dk>

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On Fri, Aug 05, 2022 at 11:03:55AM -0600, Jens Axboe wrote:
>On 8/5/22 9:42 AM, Kanchan Joshi wrote:
>> @@ -685,6 +721,29 @@ int nvme_ns_head_chr_uring_cmd(struct io_uring_cmd *ioucmd,
>>  	srcu_read_unlock(&head->srcu, srcu_idx);
>>  	return ret;
>>  }
>> +
>> +int nvme_ns_head_chr_uring_cmd_iopoll(struct io_uring_cmd *ioucmd)
>> +{
>> +	struct cdev *cdev = file_inode(ioucmd->file)->i_cdev;
>> +	struct nvme_ns_head *head = container_of(cdev, struct nvme_ns_head, cdev);
>> +	int srcu_idx = srcu_read_lock(&head->srcu);
>> +	struct nvme_ns *ns = nvme_find_path(head);
>> +	struct bio *bio;
>> +	int ret = 0;
>> +	struct request_queue *q;
>> +
>> +	if (ns) {
>> +		rcu_read_lock();
>> +		bio = READ_ONCE(ioucmd->private);
>> +		q = ns->queue;
>> +		if (test_bit(QUEUE_FLAG_POLL, &q->queue_flags) && bio
>> +				&& bio->bi_bdev)
>> +			ret = bio_poll(bio, 0, 0);
>> +		rcu_read_unlock();
>> +	}
>> +	srcu_read_unlock(&head->srcu, srcu_idx);
>> +	return ret;
>> +}
>>  #endif /* CONFIG_NVME_MULTIPATH */
>
>Looks like that READ_ONCE() should be:
>
>	bio = READ_ONCE(ioucmd->cookie);
>
>?
Damn, indeed. Would have caught if I had compiled this with
NVME_MULTIPATH config enabled. Thanks for the catch.

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