linux-kernel - Re: buggered I_CREATING implementation?

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Message-ID: <20250911160548.GV39973@ZenIV>
Date: Thu, 11 Sep 2025 17:05:48 +0100
From: Al Viro <viro@...iv.linux.org.uk>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: brauner@...nel.org, jack@...e.cz, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: buggered I_CREATING implementation?

On Thu, Sep 11, 2025 at 05:15:47PM +0200, Mateusz Guzik wrote:

> So as far as I understand the intent was to make it so that discarded
> inodes can be tested for with:
> 	(inode->i_state & (I_NEW | I_CREATING) == I_CREATING)

It is not the intent.  The problem is dealing with incoming fhandle that
has guessed the inumber of freshly created (and not yet linked) inode.

> This means another call for the same inode will find it and:
> 
>                 if (unlikely(old->i_state & I_CREATING)) {
>                         spin_unlock(&old->i_lock);
>                         spin_unlock(&inode_hash_lock);
>                         return -EBUSY;
>                 }
> 
> ... return with -EBUSY instead of waiting to check what will happen with it.

What's there to wait for?