linux-kernel - Re: [PATCH v6 3/7] Reimplement RLIMIT

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Message-ID: <20210222101141.uve6hnftsakf4u7n@example.org>
Date:   Mon, 22 Feb 2021 11:11:41 +0100
From:   Alexey Gladkov <gladkov.alexey@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     LKML <linux-kernel@...r.kernel.org>, io-uring@...r.kernel.org,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux Containers <containers@...ts.linux-foundation.org>,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH v6 3/7] Reimplement RLIMIT_NPROC on top of ucounts

On Sun, Feb 21, 2021 at 04:38:10PM -0700, Jens Axboe wrote:
> On 2/15/21 5:41 AM, Alexey Gladkov wrote:
> > diff --git a/fs/io-wq.c b/fs/io-wq.c
> > index a564f36e260c..5b6940c90c61 100644
> > --- a/fs/io-wq.c
> > +++ b/fs/io-wq.c
> > @@ -1090,10 +1091,7 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
> >  		wqe->node = alloc_node;
> >  		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
> >  		atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
> > -		if (wq->user) {
> > -			wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
> > -					task_rlimit(current, RLIMIT_NPROC);
> > -		}
> > +		wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers = task_rlimit(current, RLIMIT_NPROC);
> 
> This doesn't look like an equivalent transformation. But that may be
> moot if we merge the io_uring-worker.v3 series, as then you would not
> have to touch io-wq at all.

In the current code the wq->user is always set to current_user():

io_uring_create [1]
`- io_sq_offload_create
   `- io_init_wq_offload [2]
      `-io_wq_create [3]

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/io_uring.c#n9752
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/io_uring.c#n8107
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/io-wq.c#n1070

So, specifying max_workers always happens.

-- 
Rgrds, legion