linux-kernel - Re: [PATCH 05/13] selinux: Use simple_start_creating() / simple_done

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Message-ID: <3d8aeaea14712ad2cd0199cba62bc1398f7cc4a0.camel@kernel.org>
Date: Thu, 05 Feb 2026 07:36:37 -0500
From: Jeff Layton <jlayton@...nel.org>
To: NeilBrown <neil@...wn.name>, Christian Brauner <brauner@...nel.org>, 
 Alexander Viro <viro@...iv.linux.org.uk>, David Howells
 <dhowells@...hat.com>, Jan Kara <jack@...e.cz>, Chuck Lever
 <chuck.lever@...cle.com>, Miklos Szeredi <miklos@...redi.hu>, Amir
 Goldstein	 <amir73il@...il.com>, John Johansen
 <john.johansen@...onical.com>, Paul Moore	 <paul@...l-moore.com>, James
 Morris <jmorris@...ei.org>, "Serge E. Hallyn"	 <serge@...lyn.com>, Stephen
 Smalley <stephen.smalley.work@...il.com>
Cc: linux-kernel@...r.kernel.org, netfs@...ts.linux.dev, 
	linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org, 
	linux-unionfs@...r.kernel.org, apparmor@...ts.ubuntu.com, 
	linux-security-module@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH 05/13] selinux: Use simple_start_creating() /
 simple_done_creating()

On Wed, 2026-02-04 at 15:57 +1100, NeilBrown wrote:
> From: NeilBrown <neil@...wn.name>
> 
> Instead of explicitly locking the parent and performing a lookup in
> selinux, use simple_start_creating(), and then use
> simple_done_creating() to unlock.
> 
> This extends the region that the directory is locked for, and also
> performs a lookup.
> The lock extension is of no real consequence.
> The lookup uses simple_lookup() and so always succeeds.  Thus when
> d_make_persistent() is called the dentry will already be hashed.
> d_make_persistent() handles this case.
> 
> Signed-off-by: NeilBrown <neil@...wn.name>
> ---
>  security/selinux/selinuxfs.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index 896acad1f5f7..97e02cd5a9dc 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -1930,15 +1930,16 @@ static const struct inode_operations swapover_dir_inode_operations = {
>  static struct dentry *sel_make_swapover_dir(struct super_block *sb,
>  						unsigned long *ino)
>  {
> -	struct dentry *dentry = d_alloc_name(sb->s_root, ".swapover");
> +	struct dentry *dentry;
>  	struct inode *inode;
>  
> -	if (!dentry)
> +	inode = sel_make_inode(sb, S_IFDIR);
> +	if (!inode)
>  		return ERR_PTR(-ENOMEM);
>  
> -	inode = sel_make_inode(sb, S_IFDIR);
> -	if (!inode) {
> -		dput(dentry);
> +	dentry = simple_start_creating(sb->s_root, ".swapover");
> +	if (!dentry) {
> +		iput(inode);
>  		return ERR_PTR(-ENOMEM);
>  	}
>  
> @@ -1946,11 +1947,9 @@ static struct dentry *sel_make_swapover_dir(struct super_block *sb,
>  	inode->i_ino = ++(*ino);
>  	/* directory inodes start off with i_nlink == 2 (for "." entry) */
>  	inc_nlink(inode);
> -	inode_lock(sb->s_root->d_inode);
>  	d_make_persistent(dentry, inode);
>  	inc_nlink(sb->s_root->d_inode);
> -	inode_unlock(sb->s_root->d_inode);
> -	dput(dentry);
> +	simple_done_creating(dentry);
>  	return dentry;	// borrowed
>  }
>  

Reviewed-by: Jeff Layton <jlayton@...nel.org>