linux-kernel - Re: [PATCH RFC 08/24] vfs: make vfs_mknod break delegations on parent directory

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Message-ID: <20240320-jaguar-bildband-699e7ef5dc64@brauner>
Date: Wed, 20 Mar 2024 14:42:41 +0100
From: Christian Brauner <brauner@...nel.org>
To: Jeff Layton <jlayton@...nel.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
	Chuck Lever <chuck.lever@...cle.com>, Alexander Aring <alex.aring@...il.com>, 
	Trond Myklebust <trond.myklebust@...merspace.com>, Anna Schumaker <anna@...nel.org>, 
	Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@...guebit.com>, 
	Ronnie Sahlberg <ronniesahlberg@...il.com>, Shyam Prasad N <sprasad@...rosoft.com>, 
	Tom Talpey <tom@...pey.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, David Howells <dhowells@...hat.com>, 
	Tyler Hicks <code@...icks.com>, Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>, 
	Dai Ngo <Dai.Ngo@...cle.com>, Miklos Szeredi <miklos@...redi.hu>, 
	Amir Goldstein <amir73il@...il.com>, Namjae Jeon <linkinjeon@...nel.org>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org, 
	netfs@...ts.linux.dev, ecryptfs@...r.kernel.org, linux-unionfs@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH RFC 08/24] vfs: make vfs_mknod break delegations on
 parent directory

>  int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> -              umode_t, dev_t);
> +              umode_t, dev_t, struct inode **);

So we will have at least the following helpers with an additional
delegated inode argument.

vfs_unlink()
vfs_link()
notify_change()
vfs_create()
vfs_mknod()
vfs_mkdir()
vfs_rmdir()

>From looking at callers all these helpers will be called with non-NULL
delegated inode argument in vfs only. Unless it is generally conceivable
that other callers will want to pass a non-NULL inode argument over time
it might make more sense to add vfs_<operation>_delegated() or
__vfs_<operation>() and make vfs_mknod() and friends exported wrappers
around it.

I mean it's a matter of preference ultimately but this seems cleaner to
me. So at least for the new ones we should consider it. Would also make
the patch smaller.

>  int vfs_symlink(struct mnt_idmap *, struct inode *,
>  		struct dentry *, const char *);
>  int vfs_link(struct dentry *, struct mnt_idmap *, struct inode *,
> @@ -1879,7 +1879,7 @@ static inline int vfs_whiteout(struct mnt_idmap *idmap,
>  			       struct inode *dir, struct dentry *dentry)
>  {
>  	return vfs_mknod(idmap, dir, dentry, S_IFCHR | WHITEOUT_MODE,
> -			 WHITEOUT_DEV);
> +			 WHITEOUT_DEV, NULL);
>  }
>  
>  struct file *kernel_tmpfile_open(struct mnt_idmap *idmap,
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 0748e7ea5210..34fbcc90c984 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -1227,7 +1227,7 @@ static int unix_bind_bsd(struct sock *sk, struct sockaddr_un *sunaddr,
>  	idmap = mnt_idmap(parent.mnt);
>  	err = security_path_mknod(&parent, dentry, mode, 0);
>  	if (!err)
> -		err = vfs_mknod(idmap, d_inode(parent.dentry), dentry, mode, 0);
> +		err = vfs_mknod(idmap, d_inode(parent.dentry), dentry, mode, 0, NULL);
>  	if (err)
>  		goto out_path;
>  	err = mutex_lock_interruptible(&u->bindlock);
> 
> -- 
> 2.44.0
>