netdev - Re: [PATCH 2/4] io_uring: io_uring: add support for async work inheriting files

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Message-ID: <0ea19a52-a1cf-ae8a-82d7-f4ffb3c0286b@kernel.dk>
Date:   Fri, 25 Oct 2019 15:45:33 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        linux-block@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, jannh@...gle.com
Subject: Re: [PATCH 2/4] io_uring: io_uring: add support for async work
 inheriting files

On 10/25/19 3:31 PM, Pavel Begunkov wrote:
> On 25/10/2019 20:30, Jens Axboe wrote:
>> +static int io_grab_files(struct io_ring_ctx *ctx, struct io_kiocb *req)
>> +{
>> +	int ret = -EBADF;
>> +
>> +	rcu_read_lock();
>> +	spin_lock_irq(&ctx->inflight_lock);
>> +	/*
>> +	 * We use the f_ops->flush() handler to ensure that we can flush
>> +	 * out work accessing these files if the fd is closed. Check if
>> +	 * the fd has changed since we started down this path, and disallow
>> +	 * this operation if it has.
>> +	 */
>> +	if (fcheck(req->submit.ring_fd) == req->submit.ring_file) {
> Can we get here from io_submit_sqes()?
> ring_fd will be uninitialised in this case.

We can't, we disallow submission of any opcode (for now just accept)
from the sq thread that needs a file table.

-- 
Jens Axboe