From: Jinpu Wang <jinpu.wang@cloud.ionos.com>
To: Bart Van Assche <bvanassche@acm.org>, rpenyaev@suse.de
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>
Subject: Re: [PATCH v6 17/25] rnbd: client: main functionality
Date: Fri, 10 Jan 2020 15:45:39 +0100 [thread overview]
Message-ID: <CAMGffEm3tp_hjQT2kw9yKbuoXrkF5g6f-3prvx6buHoT+Mpb1Q@mail.gmail.com> (raw)
In-Reply-To: <aa7eeeda-b3d7-4a26-9043-53ce8c80eef1@acm.org>
> > +{
> > + DEFINE_WAIT_FUNC(wait, autoremove_wake_function);
> > +
> > + prepare_to_wait(&sess->rtrs_waitq, &wait, TASK_UNINTERRUPTIBLE);
> > + if (IS_ERR_OR_NULL(sess->rtrs)) {
> > + finish_wait(&sess->rtrs_waitq, &wait);
> > + return;
> > + }
> > + mutex_unlock(&sess_lock);
> > + /* After unlock session can be freed, so careful */
> > + schedule();
> > + mutex_lock(&sess_lock);
> > +}
>
> How can a function that calls schedule() and that is not surrounded by a
> loop be correct? What if e.g. schedule() finishes due to a spurious wakeup?
I checked in git history, this no clean explanation why we have to
call the mutex_unlock/schedul/mutex_lock magic
It's allowed to call schedule inside mutex, seems we can remove the
code snip, @Roman Penyaev do you remember why it was introduced?
>
> > +static struct rnbd_clt_session *__find_and_get_sess(const char *sessname)
> > +__releases(&sess_lock)
> > +__acquires(&sess_lock)
> > +{
> > + struct rnbd_clt_session *sess;
> > + int err;
> > +
> > +again:
> > + list_for_each_entry(sess, &sess_list, list) {
> > + if (strcmp(sessname, sess->sessname))
> > + continue;
> > +
> > + if (unlikely(sess->rtrs_ready && IS_ERR_OR_NULL(sess->rtrs)))
> > + /*
> > + * No RTRS connection, session is dying.
> > + */
> > + continue;
> > +
> > + if (likely(rnbd_clt_get_sess(sess))) {
> > + /*
> > + * Alive session is found, wait for RTRS connection.
> > + */
> > + mutex_unlock(&sess_lock);
> > + err = wait_for_rtrs_connection(sess);
> > + if (unlikely(err))
> > + rnbd_clt_put_sess(sess);
> > + mutex_lock(&sess_lock);
> > +
> > + if (unlikely(err))
> > + /* Session is dying, repeat the loop */
> > + goto again;
> > +
> > + return sess;
> > + }
> > + /*
> > + * Ref is 0, session is dying, wait for RTRS disconnect
> > + * in order to avoid session names clashes.
> > + */
> > + wait_for_rtrs_disconnection(sess);
> > + /*
> > + * RTRS is disconnected and soon session will be freed,
> > + * so repeat a loop.
> > + */
> > + goto again;
> > + }
> > +
> > + return NULL;
> > +}
>
> Since wait_for_rtrs_disconnection() unlocks sess_lock, can the
> list_for_each_entry() above trigger a use-after-free of sess->next?
>
> > +static size_t rnbd_clt_get_sg_size(struct scatterlist *sglist, u32 len)
> > +{
> > + struct scatterlist *sg;
> > + size_t tsize = 0;
> > + int i;
> > +
> > + for_each_sg(sglist, sg, len, i)
> > + tsize += sg->length;
> > + return tsize;
> > +}
>
> Please follow the example of other block drivers and use blk_rq_bytes()
> instead of iterating over the sg-list.
The amount of data that belongs to an I/O and the amount of data that
should be read or written to the disk (bi_size) can differ.
E.g. When WRITE_SAME is used, only a small amount of data is
transfered that is then written repeatedly over a lot of sectors.
this is why we get the size of data to be transfered via RTRS by
summing up the size
of the scather-gather list entries.
Will add a comment.
Thanks
next prev parent reply other threads:[~2020-01-10 14:45 UTC|newest]
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
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 [this message]
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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