linux-kernel - Re: [PATCH 03/19] VFS: use d_alloc_parallel() in lookup_one_qstr

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Message-ID: <20250207200105.GF1977892@ZenIV>
Date: Fri, 7 Feb 2025 20:01:05 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: NeilBrown <neilb@...e.de>
Cc: Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jeff Layton <jlayton@...nel.org>,
	Dave Chinner <david@...morbit.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/19] VFS: use d_alloc_parallel() in
 lookup_one_qstr_excl() and rename it.

On Thu, Feb 06, 2025 at 04:42:40PM +1100, NeilBrown wrote:
> -	dentry = d_alloc(base, name);
> -	if (unlikely(!dentry))
> +	dentry = d_alloc_parallel(base, name);
> +	if (unlikely(IS_ERR_OR_NULL(dentry)))
>  		return ERR_PTR(-ENOMEM);

Huh?  When does d_alloc_parallel() return NULL and why do you
play with explicit ERR_PTR(-ENOMEM) here?

> +	if ((flags & LOOKUP_INTENT_FLAGS) == 0)

Yecchh...  Thank you (from all reviewers, I suspect) for the exciting
opportunity to verify what values are possible in lookup_flags in various
callers and which are guaranteed to intersect with your LOOKUP_INTENT_FLAGS
mask.

> +#define LOOKUP_INTENT_FLAGS	(LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_EXCL |	\
> +				 LOOKUP_RENAME_TARGET)
> +

... as well as figuring out WTF do LOOKUP_OPEN and LOOKUP_EXCL fit into
that.