From: Jann Horn <jannh@google.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>,
Network Development <netdev@vger.kernel.org>
Subject: Re: [PATCH 1/3] io_uring: add support for async work inheriting files table
Date: Fri, 18 Oct 2019 20:50:12 +0200 [thread overview]
Message-ID: <CAG48ez1akvnVpK3dMH4H=C2CsNGDZkDaxZEF2stGAPCnUcaa+g@mail.gmail.com> (raw)
In-Reply-To: <0a3de9b2-3d3a-07b5-0e1c-515f610fbf75@kernel.dk>
On Fri, Oct 18, 2019 at 8:16 PM Jens Axboe <axboe@kernel.dk> wrote:
> On 10/18/19 12:06 PM, Jann Horn wrote:
> > But actually, by the way: Is this whole files_struct thing creating a
> > reference loop? The files_struct has a reference to the uring file,
> > and the uring file has ACCEPT work that has a reference to the
> > files_struct. If the task gets killed and the accept work blocks, the
> > entire files_struct will stay alive, right?
>
> Yes, for the lifetime of the request, it does create a loop. So if the
> application goes away, I think you're right, the files_struct will stay.
> And so will the io_uring, for that matter, as we depend on the closing
> of the files to do the final reap.
>
> Hmm, not sure how best to handle that, to be honest. We need some way to
> break the loop, if the request never finishes.
A wacky and dubious approach would be to, instead of taking a
reference to the files_struct, abuse f_op->flush() to synchronously
flush out pending requests with references to the files_struct... But
it's probably a bad idea, given that in f_op->flush(), you can't
easily tell which files_struct the close is coming from. I suppose you
could keep a list of (fdtable, fd) pairs through which ACCEPT requests
have come in and then let f_op->flush() probe whether the file
pointers are gone from them...
next prev parent reply other threads:[~2019-10-18 18:50 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-17 21:28 [PATCHSET] io_uring: add support for accept(4) Jens Axboe
2019-10-17 21:28 ` [PATCH 1/3] io_uring: add support for async work inheriting files table Jens Axboe
2019-10-18 2:41 ` Jann Horn
2019-10-18 14:01 ` Jens Axboe
2019-10-18 14:34 ` Jann Horn
2019-10-18 14:37 ` Jens Axboe
2019-10-18 14:40 ` Jann Horn
2019-10-18 14:43 ` Jens Axboe
2019-10-18 14:52 ` Jann Horn
2019-10-18 15:00 ` Jens Axboe
2019-10-18 15:54 ` Jens Axboe
2019-10-18 16:20 ` Jann Horn
2019-10-18 16:36 ` Jens Axboe
2019-10-18 17:05 ` Jens Axboe
2019-10-18 18:06 ` Jann Horn
2019-10-18 18:16 ` Jens Axboe
2019-10-18 18:50 ` Jann Horn [this message]
2019-10-24 19:41 ` Jens Axboe
2019-10-24 20:31 ` Jann Horn
2019-10-24 22:04 ` Jens Axboe
2019-10-24 22:09 ` Jens Axboe
2019-10-24 23:13 ` Jann Horn
2019-10-25 0:35 ` Jens Axboe
2019-10-25 0:52 ` Jens Axboe
2019-10-23 12:04 ` Wolfgang Bumiller
2019-10-23 14:11 ` Jens Axboe
2019-10-17 21:28 ` [PATCH 2/3] net: add __sys_accept4_file() helper Jens Axboe
2019-10-17 21:28 ` [PATCH 3/3] io_uring: add support for IORING_OP_ACCEPT Jens Axboe
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