Re: [PATCH 02/12] fs/namei.c: move create error && negative dentry case in lookup_open up

[David Laight]

On Sun, 14 Jun 2026 18:44:28 +0200
Jori Koolstra <jkoolstra@xxxxxxxxx> wrote:

> O_CREAT is stripped when create_error is set in lookup_open(), so when
> lookup does not return an inode, the case
> 
> 	if (!dentry->d_inode && (open_flag & O_CREAT))
> 
> is always skipped. We can get rid of this cognitive step by handling the
> error case first.

You've just added an extra test into a normal/fast path.
OTOH the test isn't ideal the compiler needs to reverse the order of
the arguments to the && in spite of the unlikely().

Perhaps:
	if (dentry->d_inode)
		return dentry;

	if (open_flag & O_CREAT) {
		...
	} else {
		if (unlikely(create_error)) {
			error = create_error();
			goto out_dput;
		}
	}
	return dentry;

-- David

> 
> Signed-off-by: Jori Koolstra <jkoolstra@xxxxxxxxx>
> ---
>  fs/namei.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 64b91ed9efb7..f169d1123b17 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -4499,6 +4499,11 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
>  		}
>  	}
>  
> +	if (unlikely(create_error) && !dentry->d_inode) {
> +		error = create_error;
> +		goto out_dput;
> +	}
> +
>  	/* Negative dentry, just create the file */
>  	if (!dentry->d_inode && (open_flag & O_CREAT)) {
>  		/* but break the directory lease first! */
> @@ -4518,10 +4523,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
>  		if (error)
>  			goto out_dput;
>  	}
> -	if (unlikely(create_error) && !dentry->d_inode) {
> -		error = create_error;
> -		goto out_dput;
> -	}
> +
>  	return dentry;
>  
>  out_dput: