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From: Bart Van Assche <bvanassche@acm.org>
To: Jinpu Wang <jinpu.wang@cloud.ionos.com>
Cc: Jack Wang <jinpuwang@gmail.com>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	Sagi Grimberg <sagi@grimberg.me>,
	Leon Romanovsky <leon@kernel.org>,
	Doug Ledford <dledford@redhat.com>,
	Danil Kipnis <danil.kipnis@cloud.ionos.com>,
	rpenyaev@suse.de
Subject: Re: [PATCH v6 03/25] rtrs: private headers with rtrs protocol structs and helpers
Date: Thu, 2 Jan 2020 09:00:53 -0800
Message-ID: <51f2aec2-db24-ce7b-b3e8-68f9561a584b@acm.org> (raw)
In-Reply-To: <CAMGffEmC3T9M+RmeOXX4ecE3E01azjD8fz2Lz8kHC9Ff-Xx-Aw@mail.gmail.com>

On 1/2/20 7:27 AM, Jinpu Wang wrote:
> On Mon, Dec 30, 2019 at 8:48 PM Bart Van Assche <bvanassche@acm.org> wrote:
>> On 2019-12-30 02:29, Jack Wang wrote:
>>> +enum {
>>> +     SERVICE_CON_QUEUE_DEPTH = 512,
>>
>> What is a service connection?
> s/SERVICE_CON_QUEUE_DEPTH/CON_QUEUE_DEPTH/g, do you think
> CON_QUEUE_DEPTH is better or just QUEUE_DEPTH?

The name of the constant is fine, but what I meant is the following: has 
it been documented anywhere what the role of a "service connection" is?

>>> +struct rtrs_ib_dev_pool {
>>> +     struct mutex            mutex;
>>> +     struct list_head        list;
>>> +     enum ib_pd_flags        pd_flags;
>>> +     const struct rtrs_ib_dev_pool_ops *ops;
>>> +};
>>
>> What is the purpose of an rtrs_ib_dev_pool and what does it contain?
> The idea was documented in the patchset here:
> https://www.spinics.net/lists/linux-rdma/msg64025.html
> "'
> This is an attempt to make a device pool API out of a common code,
> which caches pair of ib_device and ib_pd pointers. I found 4 places,
> where this common functionality can be replaced by some lib calls:
> nvme, nvmet, iser and isert. Total deduplication gain in loc is not
> quite significant, but eventually new ULP IB code can also require
> the same device/pd pair cache, e.g. in our IBTRS module the same
> code has to be repeated again, which was observed by Sagi and he
> suggested to make a common helper function instead of producing
> another copy.
> '''

The word "pool" suggest ownership. Since struct rtrs_ib_dev_pool owns 
protection domains instead of RDMA devices, how about renaming that data 
structure into rtrs_pd_per_rdma_dev, rtrs_rdma_dev_pd or something 
similar? How about adding a comment like the following above that data 
structure?

/*
  * Data structure used to associate one protection domain (PD) with each
  * RDMA device.
  */

>>> +/**
>>> + * struct rtrs_msg_conn_req - Client connection request to the server
>>> + * @magic:      RTRS magic
>>> + * @version:    RTRS protocol version
>>> + * @cid:        Current connection id
>>> + * @cid_num:    Number of connections per session
>>> + * @recon_cnt:          Reconnections counter
>>> + * @sess_uuid:          UUID of a session (path)
>>> + * @paths_uuid:         UUID of a group of sessions (paths)
>>> + *
>>> + * NOTE: max size 56 bytes, see man rdma_connect().
>>> + */
>>> +struct rtrs_msg_conn_req {
>>> +     u8              __cma_version; /* Is set to 0 by cma.c in case of
>>> +                                     * AF_IB, do not touch that.
>>> +                                     */
>>> +     u8              __ip_version;  /* On sender side that should be
>>> +                                     * set to 0, or cma_save_ip_info()
>>> +                                     * extract garbage and will fail.
>>> +                                     */
>>
>> The above two fields and the comments next to it look suspicious to me.
>> Does RTRS perhaps try to generate CMA-formatted messages without using
>> the CMA to format these messages?
> The problem is in cma_format_hdr over-writes the first byte for AF_IB
> https://www.spinics.net/lists/linux-rdma/msg22397.html
> 
> No one fixes the problem since then.

How about adding that URL to the comment block above struct 
rtrs_msg_conn_req?

>>
>>> +     *errno = -(int)((payload >> 19) & 0x1ff);
>>
>> Is the '(int)' cast useful in the above expression? Can it be left out?
> I think it's necessary, and make it more clear errno is a negative int
> value, isn't it?

According to the C standard operations on unsigned integers "wrap 
around" so removing the cast should be safe. Anyway, this is not 
something I consider important.

Thanks,

Bart.

  reply index

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-30 10:29 [PATCH v6 00/25] RTRS (former IBTRS) rdma transport library and RNBD (former IBNBD) rdma network block device Jack Wang
2019-12-30 10:29 ` [PATCH v6 01/25] sysfs: export sysfs_remove_file_self() Jack Wang
2019-12-30 10:29 ` [PATCH v6 02/25] rtrs: public interface header to establish RDMA connections Jack Wang
2019-12-30 19:25   ` Bart Van Assche
2020-01-02 13:35     ` Jinpu Wang
2020-01-02 16:36       ` Bart Van Assche
2020-01-02 16:47         ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 03/25] rtrs: private headers with rtrs protocol structs and helpers Jack Wang
2019-12-30 19:48   ` Bart Van Assche
2020-01-02 15:27     ` Jinpu Wang
2020-01-02 17:00       ` Bart Van Assche [this message]
2020-01-02 18:26         ` Jason Gunthorpe
2020-01-03 12:31           ` Jinpu Wang
2020-01-03 12:27         ` Jinpu Wang
2019-12-31  0:07   ` Bart Van Assche
2020-01-03 13:48     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 04/25] rtrs: core: lib functions shared between client and server modules Jack Wang
2019-12-30 22:25   ` Bart Van Assche
2020-01-07 12:22     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 05/25] rtrs: client: private header with client structs and functions Jack Wang
2019-12-30 22:51   ` Bart Van Assche
2020-01-07 12:39     ` Jinpu Wang
2019-12-30 23:03   ` Bart Van Assche
2020-01-07 12:39     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 06/25] rtrs: client: main functionality Jack Wang
2019-12-30 23:53   ` Bart Van Assche
2020-01-02 18:23     ` Jason Gunthorpe
2020-01-03 14:30     ` Jinpu Wang
2020-01-03 16:12       ` Bart Van Assche
2019-12-30 10:29 ` [PATCH v6 07/25] rtrs: client: statistics functions Jack Wang
2020-01-02 21:07   ` Bart Van Assche
2020-01-03 14:39     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 08/25] rtrs: client: sysfs interface functions Jack Wang
2020-01-02 21:14   ` Bart Van Assche
2020-01-03 14:59     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 09/25] rtrs: server: private header with server structs and functions Jack Wang
2020-01-02 21:24   ` Bart Van Assche
2020-01-08 16:33     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 10/25] rtrs: server: main functionality Jack Wang
2020-01-02 22:03   ` Bart Van Assche
2020-01-07 13:19     ` Jinpu Wang
2020-01-07 18:25       ` Jason Gunthorpe
2020-01-10 17:38         ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 11/25] rtrs: server: statistics functions Jack Wang
2020-01-02 22:02   ` Bart Van Assche
2020-01-08 12:55     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 12/25] rtrs: server: sysfs interface functions Jack Wang
2020-01-02 22:06   ` Bart Van Assche
2020-01-07 14:40     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 13/25] rtrs: include client and server modules into kernel compilation Jack Wang
2020-01-02 22:11   ` Bart Van Assche
2020-01-03 16:19     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 14/25] rtrs: a bit of documentation Jack Wang
2019-12-30 23:19   ` Bart Van Assche
2020-01-07 14:48     ` Jinpu Wang
2020-01-02 22:21   ` Bart Van Assche
2020-01-07 15:49     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 15/25] rnbd: private headers with rnbd protocol structs and helpers Jack Wang
2020-01-02 22:34   ` Bart Van Assche
2020-01-07 16:53     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 16/25] rnbd: client: private header with client structs and functions Jack Wang
2020-01-02 22:37   ` Bart Van Assche
2020-01-07 17:09     ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 17/25] rnbd: client: main functionality Jack Wang
2020-01-02 23:55   ` Bart Van Assche
2020-01-08 14:22     ` Jinpu Wang
2020-01-10 14:45     ` Jinpu Wang
2020-01-10 15:09       ` Roman Penyaev
2020-01-10 15:29         ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 18/25] rnbd: client: sysfs interface functions Jack Wang
2020-01-03  0:03   ` Bart Van Assche
2020-01-08 13:06     ` Jinpu Wang
2020-01-08 16:39       ` Bart Van Assche
2020-01-08 16:51         ` Jinpu Wang
2019-12-30 10:29 ` [PATCH v6 19/25] rnbd: server: private header with server structs and functions Jack Wang
2019-12-30 10:29 ` [PATCH v6 20/25] rnbd: server: main functionality Jack Wang
2019-12-30 10:29 ` [PATCH v6 21/25] rnbd: server: functionality for IO submission to file or block dev Jack Wang
2019-12-30 10:29 ` [PATCH v6 22/25] rnbd: server: sysfs interface functions Jack Wang
2019-12-30 10:29 ` [PATCH v6 23/25] rnbd: include client and server modules into kernel compilation Jack Wang
2019-12-30 10:29 ` [PATCH v6 24/25] rnbd: a bit of documentation Jack Wang
2019-12-30 10:29 ` [PATCH v6 25/25] MAINTAINERS: Add maintainers for RNBD/RTRS modules Jack Wang
2019-12-30 12:22   ` Gal Pressman
2020-01-02  8:41     ` Jinpu Wang
2019-12-31  0:11 ` [PATCH v6 00/25] RTRS (former IBTRS) rdma transport library and RNBD (former IBNBD) rdma network block device Bart Van Assche
2020-01-02  8:48   ` Jinpu Wang
2019-12-31  2:39 ` Bart Van Assche
2020-01-02  9:20   ` Jinpu Wang
2020-01-02 18:28   ` Jason Gunthorpe
2020-01-03 12:34     ` Jinpu Wang

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