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From: Christoph Hellwig <hch@lst.de>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
	Chao Leng <lengchao@huawei.com>,
	linux-nvme@lists.infradead.org,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>
Subject: Re: [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs
Date: Sat, 20 Mar 2021 07:11:23 +0100	[thread overview]
Message-ID: <20210320061123.GA20852@lst.de> (raw)
In-Reply-To: <ac05c7cc-3613-ec8c-a718-6f3e74710b42@grimberg.me>

On Fri, Mar 19, 2021 at 12:34:25PM -0700, Sagi Grimberg wrote:
>
>> diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
>> index a1d476e1ac020f..92adebfaf86fd1 100644
>> --- a/drivers/nvme/host/multipath.c
>> +++ b/drivers/nvme/host/multipath.c
>> @@ -309,6 +309,7 @@ blk_qc_t nvme_ns_head_submit_bio(struct bio *bio)
>>   	 */
>>   	blk_queue_split(&bio);
>>   +retry:
>>   	srcu_idx = srcu_read_lock(&head->srcu);
>>   	ns = nvme_find_path(head);
>>   	if (likely(ns)) {
>> @@ -316,7 +317,12 @@ blk_qc_t nvme_ns_head_submit_bio(struct bio *bio)
>>   		bio->bi_opf |= REQ_NVME_MPATH;
>>   		trace_block_bio_remap(bio, disk_devt(ns->head->disk),
>>   				      bio->bi_iter.bi_sector);
>> -		ret = submit_bio_noacct(bio);
>> +
>> +		if (!blk_mq_submit_bio_direct(bio, &ret)) {
>> +			nvme_mpath_clear_current_path(ns);
>> +			srcu_read_unlock(&head->srcu, srcu_idx);
>
> Its a bit unusual to see mutation of a data protected by srcu while
> under the srcu_read_lock, can that be problematic somehow?

Hmm.  I don't think head->srcu is intended to protect the current path.
We also call nvme_mpath_clear_current_path from nvme_complete_rq or
nvme_ns_remove, which has no locking at all.  The srcu protection is
for head->list, but leaks into the current path due to the __rcu
annotations.

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  reply	other threads:[~2021-03-20  6:11 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 22:27 [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs Sagi Grimberg
2021-03-15 22:27 ` [PATCH 1/3] nvme: introduce nvme_ctrl_is_mpath helper Sagi Grimberg
2021-03-15 22:27 ` [PATCH 2/3] nvme-tcp: fix possible hang when trying to set a live path during I/O Sagi Grimberg
2021-03-15 22:27 ` [PATCH 3/3] nvme-rdma: " Sagi Grimberg
2021-03-16  3:24 ` [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs Chao Leng
2021-03-16  5:04   ` Sagi Grimberg
2021-03-16  6:18     ` Chao Leng
2021-03-16  6:25       ` Sagi Grimberg
2021-03-16 20:07 ` Sagi Grimberg
2021-03-16 20:42   ` Keith Busch
2021-03-16 23:51     ` Sagi Grimberg
2021-03-17  2:55       ` Chao Leng
2021-03-17  6:59         ` Christoph Hellwig
2021-03-17  7:59           ` Chao Leng
2021-03-17 18:43             ` Sagi Grimberg
2021-03-18  1:51               ` Chao Leng
2021-03-18  4:45                 ` Christoph Hellwig
2021-03-18 18:46                 ` Sagi Grimberg
2021-03-18 19:16                   ` Keith Busch
2021-03-18 19:31                     ` Sagi Grimberg
2021-03-18 21:52                       ` Keith Busch
2021-03-18 22:45                         ` Sagi Grimberg
2021-03-19 14:05                         ` Christoph Hellwig
2021-03-19 17:28                           ` Christoph Hellwig
2021-03-19 19:07                             ` Keith Busch
2021-03-19 19:34                             ` Sagi Grimberg
2021-03-20  6:11                               ` Christoph Hellwig [this message]
2021-03-21  6:49                                 ` Sagi Grimberg
2021-03-22  6:34                                   ` Christoph Hellwig
2021-03-17  8:16           ` Sagi Grimberg

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