linux-kernel - Re: [PATCH v4 10/17] vfs: make vfs_create break delegations on parent directory

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Message-ID: <68c1c557d9499e63ffca00c8880ca6b63d9c1304.camel@kernel.org>
Date: Tue, 04 Nov 2025 13:10:26 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Simon Horman <horms@...nel.org>
Cc: Miklos Szeredi <miklos@...redi.hu>, Alexander Viro
 <viro@...iv.linux.org.uk>,  Christian Brauner	 <brauner@...nel.org>, Jan
 Kara <jack@...e.cz>, Chuck Lever	 <chuck.lever@...cle.com>, Alexander Aring
 <alex.aring@...il.com>, Trond Myklebust <trondmy@...nel.org>, Anna
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 Shyam Prasad N	 <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
 Bharath SM	 <bharathsm@...rosoft.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>,  "Rafael J. Wysocki"	 <rafael@...nel.org>,
 Danilo Krummrich <dakr@...nel.org>, David Howells	 <dhowells@...hat.com>,
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 <senozhatsky@...omium.org>, Carlos Maiolino <cem@...nel.org>, Kuniyuki
 Iwashima	 <kuniyu@...gle.com>, "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, 
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 linux-unionfs@...r.kernel.org, 	linux-xfs@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH v4 10/17] vfs: make vfs_create break delegations on
 parent directory

On Tue, 2025-11-04 at 17:38 +0000, Simon Horman wrote:
> On Mon, Nov 03, 2025 at 07:52:38AM -0500, Jeff Layton wrote:
> > In order to add directory delegation support, we need to break
> > delegations on the parent whenever there is going to be a change in the
> > directory.
> > 
> > Add a delegated_inode parameter to struct createdata. Most callers just
> > leave that as a NULL pointer, but do_mknodat() is changed to wait for a
> > delegation break if there is one.
> > 
> > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > ---
> >  fs/namei.c         | 26 +++++++++++++++++---------
> >  include/linux/fs.h |  2 +-
> >  2 files changed, 18 insertions(+), 10 deletions(-)
> > 
> > diff --git a/fs/namei.c b/fs/namei.c
> 
> ...
> 
> > @@ -4359,6 +4362,8 @@ static int may_mknod(umode_t mode)
> >  static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  		unsigned int dev)
> >  {
> > +	struct delegated_inode delegated_inode = { };
> > +	struct createdata cargs = { };
> >  	struct mnt_idmap *idmap;
> >  	struct dentry *dentry;
> >  	struct path path;
> > @@ -4383,18 +4388,16 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> >  	switch (mode & S_IFMT) {
> >  		case 0:
> >  		case S_IFREG:
> > -		{
> > -			struct createdata args = { .idmap = idmap,
> > -						   .dir = path.dentry->d_inode,
> > -						   .dentry = dentry,
> > -						   .mode = mode,
> > -						   .excl = true };
> > -
> > -			error = vfs_create(&args);
> > +			cargs.idmap = idmap,
> > +			cargs.dir = path.dentry->d_inode,
> > +			cargs.dentry = dentry,
> > +			cargs.delegated_inode = &delegated_inode;
> > +			cargs.mode = mode,
> > +			cargs.excl = true,
> 
> Hi Jeff,
> 
> I don't think it makes any difference to the generated code.
> But I think it would be more intuitive to use ';' rather than ','
> at the end of the lines immediately above.
> 

Definitely. Will fix.

> > +			error = vfs_create(&cargs);
> >  			if (!error)
> >  				security_path_post_mknod(idmap, dentry);
> >  			break;
> > -		}
> >  		case S_IFCHR: case S_IFBLK:
> >  			error = vfs_mknod(idmap, path.dentry->d_inode,
> >  					  dentry, mode, new_decode_dev(dev));
> 
> ...

Thanks!
-- 
Jeff Layton <jlayton@...nel.org>