From: "jianchao.wang" <jianchao.w.wang@oracle.com>
To: Keith Busch <kbusch@kernel.org>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
jsmart2021@gmail.com, bvanassche@acm.org, josef@toxicpanda.com,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
keith.busch@intel.com, hare@suse.de, jthumshirn@suse.de,
hch@lst.de, sagi@grimberg.me
Subject: Re: [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter
Date: Tue, 26 Mar 2019 09:17:24 +0800 [thread overview]
Message-ID: <70e14e12-2ffc-37db-dd8f-229bc580546e@oracle.com> (raw)
In-Reply-To: <20190325134917.GA4328@localhost.localdomain>
Hi Keith
On 3/25/19 9:49 PM, Keith Busch wrote:
> On Mon, Mar 25, 2019 at 01:38:37PM +0800, Jianchao Wang wrote:
>> blk_mq_tagset_inflight_iter is not safe that it could get stale request
>> in tags->rqs[]. Use blk_mq_queue_tag_inflight_iter here. A new helper
>> interface nvme_iterate_inflight_rqs is introduced to iterate
>> all of the ns under a ctrl.
>
> Nak, NVMe only iterates tags when new requests can't enter, allocated
> requests can't dispatch, and dispatched commands can't complete. So
> it is perfectly safe to iterate if the driver takes reasonable steps
> beforehand.
nvme_dev_disable just quiesce and freeze the request_queue, but not drain the enters.
So there still could be someone escapes the queue freeze checking and tries to allocate
request.
> Further, for M tags and N namespaces, we complete teardown
> in O(M) time, but this makes in O(M*N) without gaining anything.
>
Yes, it is indeed inefficient.
Thanks
Jianchao
next prev parent reply other threads:[~2019-03-26 1:18 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 5:38 [PATCH V2 0/8]: blk-mq: use static_rqs to iterate busy tags Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 1/8] blk-mq: get rid of the synchronize_rcu in __blk_mq_update_nr_hw_queues Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 2/8] blk-mq: use static_rqs instead of rqs to iterate tags Jianchao Wang
2019-03-25 7:12 ` Dongli Zhang
2019-03-25 7:14 ` jianchao.wang
2019-03-25 5:38 ` [PATCH V2 3/8] blk-mq: use blk_mq_queue_tag_inflight_iter in debugfs Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 4/8] mtip32xx: use blk_mq_queue_tag_inflight_iter Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 5/8] nbd: " Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 6/8] skd: " Jianchao Wang
2019-03-25 5:38 ` [PATCH V2 7/8] nvme: " Jianchao Wang
2019-03-25 13:49 ` Keith Busch
2019-03-26 1:17 ` jianchao.wang [this message]
2019-03-26 2:41 ` Ming Lei
2019-03-26 3:05 ` jianchao.wang
2019-03-26 23:57 ` Keith Busch
2019-03-27 2:03 ` jianchao.wang
2019-03-27 2:15 ` Keith Busch
2019-03-27 2:27 ` jianchao.wang
2019-03-27 2:33 ` Keith Busch
2019-03-27 2:45 ` jianchao.wang
2019-03-27 6:51 ` Keith Busch
2019-03-27 7:18 ` jianchao.wang
2019-03-25 5:38 ` [PATCH V2 8/8] blk-mq: remove blk_mq_tagset_busy_iter Jianchao Wang
2019-03-25 7:18 ` Hannes Reinecke
2019-03-25 7:37 ` jianchao.wang
2019-03-25 8:25 ` Hannes Reinecke
2019-03-25 9:12 ` jianchao.wang
2019-03-26 14:17 ` Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2019-03-25 5:28 [PATCH V2 0/8]: blk-mq: use static_rqs to iterate busy tags Jianchao Wang
2019-03-25 5:28 ` [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter Jianchao Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=70e14e12-2ffc-37db-dd8f-229bc580546e@oracle.com \
--to=jianchao.w.wang@oracle.com \
--cc=axboe@kernel.dk \
--cc=bvanassche@acm.org \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=josef@toxicpanda.com \
--cc=jsmart2021@gmail.com \
--cc=jthumshirn@suse.de \
--cc=kbusch@kernel.org \
--cc=keith.busch@intel.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nvme@lists.infradead.org \
--cc=sagi@grimberg.me \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®