netdev - Re: [PATCH 1/3] io_uring: add support for async work inheriting files table

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Message-ID: <CAG48ez181=JoYudXee0KbU0vDZ=EbxmgB7q0mmjaA0gyp6MFBQ@mail.gmail.com>
Date:   Fri, 18 Oct 2019 16:34:24 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 1/3] io_uring: add support for async work inheriting files table

On Fri, Oct 18, 2019 at 4:01 PM Jens Axboe <axboe@...nel.dk> wrote:
> On 10/17/19 8:41 PM, Jann Horn wrote:
> > On Fri, Oct 18, 2019 at 4:01 AM Jens Axboe <axboe@...nel.dk> wrote:
> >> This is in preparation for adding opcodes that need to modify files
> >> in a process file table, either adding new ones or closing old ones.
[...]
> Updated patch1:
>
> http://git.kernel.dk/cgit/linux-block/commit/?h=for-5.5/io_uring-test&id=df6caac708dae8ee9a74c9016e479b02ad78d436

I don't understand what you're doing with old_files in there. In the
"s->files && !old_files" branch, "current->files = s->files" happens
without holding task_lock(), but current->files and s->files are also
the same already at that point anyway. And what's the intent behind
assigning stuff to old_files inside the loop? Isn't that going to
cause the workqueue to keep a modified current->files beyond the
runtime of the work?