linux-kernel - Re: [RFC PATCH] io_uring: add support for IORING_OP

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Message-ID: <20210124021722.j4v7xrn4licf2aif@alap3.anarazel.de>
Date:   Sat, 23 Jan 2021 18:17:22 -0800
From:   Andres Freund <andres@...razel.de>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Lennert Buytenhek <buytenh@...tstofly.org>,
        Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-btrfs@...r.kernel.org
Subject: Re: [RFC PATCH] io_uring: add support for IORING_OP_GETDENTS64

Hi,

On 2021-01-24 01:59:05 +0000, Al Viro wrote:
> On Sat, Jan 23, 2021 at 03:50:55PM -0800, Andres Freund wrote:
> 
> > As there's only a shared lock, seems like both would end up with the
> > same ctx->pos and end up updating f_pos to the same offset (assuming the
> > same count).
> > 
> > Am I missing something?
> 
> This:
>         f = fdget_pos(fd);
>         if (!f.file)
>                 return -EBADF;
> in the callers.

Ah. Thanks for the explainer, userspace guy here ;). I hadn't realized
that fdget_pos acquired a lock around the position...

Regards,

Andres