From: Al Viro <viro@zeniv.linux.org.uk>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Jens Axboe <axboe@kernel.dk>, Jann Horn <jannh@google.com>,
linux-aio@kvack.org, linux-block@vger.kernel.org,
Linux API <linux-api@vger.kernel.org>,
hch@lst.de, jmoyer@redhat.com, avi@scylladb.com,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 13/18] io_uring: add file set registration
Date: Mon, 11 Feb 2019 17:35:21 +0000 [thread overview]
Message-ID: <20190211173521.GI2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190211085533.35190404@lwn.net>
On Mon, Feb 11, 2019 at 08:55:33AM -0700, Jonathan Corbet wrote:
> On Thu, 7 Feb 2019 11:45:40 -0700
> Jens Axboe <axboe@kernel.dk> wrote:
>
> > > OK, braindump time:
> >
> > [snip]
> >
> > This is great info, and I think it belongs in Documentation/ somewhere.
> > Not sure I've ever seen such a good and detailed dump of this before.
>
> I suspect I might be able to make something like that happen :) Stay
> tuned.
There are several typos I see in there (e.g. in
* struct file instances A and B being AF_UNIX sockets.
* A is a listener
* B is an established connection, with the other end
yet to be accepted on A
* the only references to A and B are in an SCM_RIGHTS
datagram sent over by A.
the last line should be "datagram sent over by B", of course - you can't
send anything over a listener socket, to start with).
Another thing is this:
* references cannot be extracted from SCM_RIGHTS datagrams
while the garbage collector is running (achieved by having
unix_notinflight() done before references out of SCM_RIGHTS)
* removal of SCM_RIGHTS associated with a socket can't
be done without a reference to that socket _outside_ of any
SCM_RIGHTS (automatically true).
That's worse than a typo - that's an actual bug (see the subthread
with Miklos). Correct version would be
* any references extracted from SCM_RIGHTS during the
garbage collector run will not be actually used until the end
of garbage collection. For normal recvmsg() it is guaranteed
by having unix_notinflight() called between the extraction of
scm_fp_list from the packet and doing anything else with the
references extracted. For MSG_PEEK recvmsg() it's actually
broken and lacks synchronization; Miklos has proposed to grab
and release unix_gc_lock in those, between scm_fp_dup() and
doing anything else with the references copied.
If you turn that thing into a coherent text, I'd appreciate a chance
to take a look at the result and see if anything else needs to be
corrected...
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@zeniv.linux.org.uk>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Jens Axboe <axboe@kernel.dk>, Jann Horn <jannh@google.com>,
linux-aio@kvack.org, linux-block@vger.kernel.org,
Linux API <linux-api@vger.kernel.org>,
hch@lst.de, jmoyer@redhat.com, avi@scylladb.com,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 13/18] io_uring: add file set registration
Date: Mon, 11 Feb 2019 17:35:21 +0000 [thread overview]
Message-ID: <20190211173521.GI2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190211085533.35190404@lwn.net>
On Mon, Feb 11, 2019 at 08:55:33AM -0700, Jonathan Corbet wrote:
> On Thu, 7 Feb 2019 11:45:40 -0700
> Jens Axboe <axboe@kernel.dk> wrote:
>
> > > OK, braindump time:
> >
> > [snip]
> >
> > This is great info, and I think it belongs in Documentation/ somewhere.
> > Not sure I've ever seen such a good and detailed dump of this before.
>
> I suspect I might be able to make something like that happen :) Stay
> tuned.
There are several typos I see in there (e.g. in
* struct file instances A and B being AF_UNIX sockets.
* A is a listener
* B is an established connection, with the other end
yet to be accepted on A
* the only references to A and B are in an SCM_RIGHTS
datagram sent over by A.
the last line should be "datagram sent over by B", of course - you can't
send anything over a listener socket, to start with).
Another thing is this:
* references cannot be extracted from SCM_RIGHTS datagrams
while the garbage collector is running (achieved by having
unix_notinflight() done before references out of SCM_RIGHTS)
* removal of SCM_RIGHTS associated with a socket can't
be done without a reference to that socket _outside_ of any
SCM_RIGHTS (automatically true).
That's worse than a typo - that's an actual bug (see the subthread
with Miklos). Correct version would be
* any references extracted from SCM_RIGHTS during the
garbage collector run will not be actually used until the end
of garbage collection. For normal recvmsg() it is guaranteed
by having unix_notinflight() called between the extraction of
scm_fp_list from the packet and doing anything else with the
references extracted. For MSG_PEEK recvmsg() it's actually
broken and lacks synchronization; Miklos has proposed to grab
and release unix_gc_lock in those, between scm_fp_dup() and
doing anything else with the references copied.
If you turn that thing into a coherent text, I'd appreciate a chance
to take a look at the result and see if anything else needs to be
corrected...
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next prev parent reply other threads:[~2019-02-11 17:35 UTC|newest]
Thread overview: 158+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 19:26 [PATCHSET v9] io_uring IO interface Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 01/18] fs: add an iopoll method to struct file_operations Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 02/18] block: wire up block device iopoll method Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 03/18] block: add bio_set_polled() helper Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 04/18] iomap: wire up the iopoll method Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 05/18] Add io_uring IO interface Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 06/18] io_uring: add fsync support Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 07/18] io_uring: support for IO polling Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 20:47 ` Jann Horn
2019-01-29 20:47 ` Jann Horn
2019-01-29 20:56 ` Jens Axboe
2019-01-29 20:56 ` Jens Axboe
2019-01-29 21:10 ` Jann Horn
2019-01-29 21:10 ` Jann Horn
2019-01-29 21:33 ` Jens Axboe
2019-01-29 21:33 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 08/18] fs: add fget_many() and fput_many() Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 09/18] io_uring: use fget/fput_many() for file references Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 23:31 ` Jann Horn
2019-01-29 23:31 ` Jann Horn
2019-01-29 23:44 ` Jens Axboe
2019-01-29 23:44 ` Jens Axboe
2019-01-30 15:33 ` Jens Axboe
2019-01-30 15:33 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 10/18] io_uring: batch io_kiocb allocation Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 11/18] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 12/18] io_uring: add support for pre-mapped user IO buffers Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 22:44 ` Jann Horn
2019-01-29 22:44 ` Jann Horn
2019-01-29 22:56 ` Jens Axboe
2019-01-29 22:56 ` Jens Axboe
2019-01-29 23:03 ` Jann Horn
2019-01-29 23:03 ` Jann Horn
2019-01-29 23:06 ` Jens Axboe
2019-01-29 23:06 ` Jens Axboe
2019-01-29 23:08 ` Jann Horn
2019-01-29 23:08 ` Jann Horn
2019-01-29 23:14 ` Jens Axboe
2019-01-29 23:14 ` Jens Axboe
2019-01-29 23:42 ` Jann Horn
2019-01-29 23:42 ` Jann Horn
2019-01-29 23:51 ` Jens Axboe
2019-01-29 23:51 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-30 1:29 ` Jann Horn
2019-01-30 1:29 ` Jann Horn
2019-01-30 15:35 ` Jens Axboe
2019-01-30 15:35 ` Jens Axboe
2019-02-04 2:56 ` Al Viro
2019-02-04 2:56 ` Al Viro
2019-02-05 2:19 ` Jens Axboe
2019-02-05 2:19 ` Jens Axboe
2019-02-05 17:57 ` Jens Axboe
2019-02-05 17:57 ` Jens Axboe
2019-02-05 19:08 ` Jens Axboe
2019-02-05 19:08 ` Jens Axboe
2019-02-06 0:27 ` Jens Axboe
2019-02-06 0:27 ` Jens Axboe
2019-02-06 1:01 ` Al Viro
2019-02-06 1:01 ` Al Viro
2019-02-06 17:56 ` Jens Axboe
2019-02-06 17:56 ` Jens Axboe
2019-02-07 4:05 ` Al Viro
2019-02-07 4:05 ` Al Viro
2019-02-07 16:14 ` Jens Axboe
2019-02-07 16:30 ` Al Viro
2019-02-07 16:30 ` Al Viro
2019-02-07 16:35 ` Jens Axboe
2019-02-07 16:35 ` Jens Axboe
2019-02-07 16:51 ` Al Viro
2019-02-07 16:51 ` Al Viro
2019-02-06 0:56 ` Al Viro
2019-02-06 0:56 ` Al Viro
2019-02-06 13:41 ` Jens Axboe
2019-02-06 13:41 ` Jens Axboe
2019-02-07 4:00 ` Al Viro
2019-02-07 4:00 ` Al Viro
2019-02-07 9:22 ` Miklos Szeredi
2019-02-07 9:22 ` Miklos Szeredi
2019-02-07 13:31 ` Al Viro
2019-02-07 13:31 ` Al Viro
2019-02-07 14:20 ` Miklos Szeredi
2019-02-07 14:20 ` Miklos Szeredi
2019-02-07 15:20 ` Al Viro
2019-02-07 15:20 ` Al Viro
2019-02-07 15:27 ` Miklos Szeredi
2019-02-07 15:27 ` Miklos Szeredi
2019-02-07 16:26 ` Al Viro
2019-02-07 16:26 ` Al Viro
2019-02-07 19:08 ` Miklos Szeredi
2019-02-07 19:08 ` Miklos Szeredi
2019-02-07 18:45 ` Jens Axboe
2019-02-07 18:45 ` Jens Axboe
2019-02-07 18:58 ` Jens Axboe
2019-02-07 18:58 ` Jens Axboe
2019-02-11 15:55 ` Jonathan Corbet
2019-02-11 15:55 ` Jonathan Corbet
2019-02-11 17:35 ` Al Viro [this message]
2019-02-11 17:35 ` Al Viro
2019-02-11 20:33 ` Jonathan Corbet
2019-02-11 20:33 ` Jonathan Corbet
2019-01-29 19:26 ` [PATCH 14/18] io_uring: add submission polling Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:26 ` [PATCH 15/18] io_uring: add io_kiocb ref count Jens Axboe
2019-01-29 19:26 ` Jens Axboe
2019-01-29 19:27 ` [PATCH 16/18] io_uring: add support for IORING_OP_POLL Jens Axboe
2019-01-29 19:27 ` Jens Axboe
2019-01-29 19:27 ` [PATCH 17/18] io_uring: allow workqueue item to handle multiple buffered requests Jens Axboe
2019-01-29 19:27 ` Jens Axboe
2019-01-29 19:27 ` [PATCH 18/18] io_uring: add io_uring_event cache hit information Jens Axboe
2019-01-29 19:27 ` Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2019-02-07 19:55 [PATCHSET v12] io_uring IO interface Jens Axboe
2019-02-07 19:55 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
2019-02-07 19:55 ` Jens Axboe
2019-02-08 12:17 ` Alan Jenkins
2019-02-08 12:17 ` Alan Jenkins
2019-02-08 12:57 ` Jens Axboe
2019-02-08 12:57 ` Jens Axboe
2019-02-08 14:02 ` Alan Jenkins
2019-02-08 14:02 ` Alan Jenkins
2019-02-08 15:13 ` Jens Axboe
2019-02-08 15:13 ` Jens Axboe
2019-02-12 12:29 ` Alan Jenkins
2019-02-12 12:29 ` Alan Jenkins
2019-02-12 15:17 ` Jens Axboe
2019-02-12 15:17 ` Jens Axboe
2019-02-12 17:21 ` Alan Jenkins
2019-02-12 17:21 ` Alan Jenkins
2019-02-12 17:33 ` Jens Axboe
2019-02-12 17:33 ` Jens Axboe
2019-02-12 20:23 ` Alan Jenkins
2019-02-12 20:23 ` Alan Jenkins
2019-02-12 21:10 ` Jens Axboe
2019-02-12 21:10 ` Jens Axboe
2019-02-01 15:23 [PATCHSET v11] io_uring IO interface Jens Axboe
2019-02-01 15:24 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
2019-02-01 15:24 ` Jens Axboe
2019-01-30 21:55 [PATCHSET v10] io_uring IO interface Jens Axboe
2019-01-30 21:55 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
2019-01-30 21:55 ` Jens Axboe
2019-01-28 21:35 [PATCHSET v8] io_uring IO interface Jens Axboe
2019-01-28 21:35 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
2019-01-28 21:35 ` Jens Axboe
2019-01-29 16:36 ` Jann Horn
2019-01-29 16:36 ` Jann Horn
2019-01-29 18:13 ` Jens Axboe
2019-01-29 18:13 ` Jens Axboe
2019-01-23 15:35 [PATCHSET v7] io_uring IO interface Jens Axboe
2019-01-23 15:35 ` [PATCH 13/18] io_uring: add file set registration Jens Axboe
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