linux-kernel - Re: [PATCH] ovl: set I_CREATING on inode being created

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Message-ID: <CA+55aFzd53LwrBfvdtKx7e_bQPhzsKEvCME1rGbrrY4pG94d=Q@mail.gmail.com>
Date:   Wed, 22 Aug 2018 07:53:08 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Miklos Szeredi <miklos@...redi.hu>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-unionfs@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] ovl: set I_CREATING on inode being created

On Wed, Aug 22, 2018 at 1:55 AM Miklos Szeredi <miklos@...redi.hu> wrote:
>
> +       spin_lock(&inode->i_lock);
> +       inode->i_state |= I_CREATING;
> +       spin_unlock(&inode->i_lock);
> +

Why is that spinlock protection there?

Isn't this a new inode that cannot possibly be reached any other way yet?

NOTE! This is a question. Maybe there is something I missed, and there
*are* other ways to reach that inode. But if that's true, isn't it
already too late to set I_CREATING?

So I'd like some clarification on this point before applying it. It's
possible that the spinlock is required, I just want to understand why.

          Linus