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Message-ID: <6021e64ed25c3b3e7880f17accb0f7a7b89fac0e.camel@kernel.org>
Date: Mon, 03 Nov 2025 19:30:57 -0500
From: Jeff Layton <jlayton@...nel.org>
To: NeilBrown <neil@...wn.name>
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
Schumaker <anna@...nel.org>, Steve French <sfrench@...ba.org>, Paulo
Alcantara <pc@...guebit.org>, Ronnie Sahlberg <ronniesahlberg@...il.com>,
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>,
Tyler Hicks <code@...icks.com>, Olga Kornievskaia <okorniev@...hat.com>,
Dai Ngo <Dai.Ngo@...cle.com>, Amir Goldstein <amir73il@...il.com>, Namjae
Jeon <linkinjeon@...nel.org>, Steve French <smfrench@...il.com>, Sergey
Senozhatsky <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>, Simon Horman
<horms@...nel.org>, 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, 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 11:14 +1100, NeilBrown wrote:
> On Mon, 03 Nov 2025, 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
> > index fdf4e78cd041de8c564b7d1d89a46ba2aaf79d53..e8973000a312fb05ebb63a0d9bd83b9a5f8f805d 100644
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -3487,6 +3487,9 @@ int vfs_create(struct createdata *args)
> >
> > mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
> > error = security_inode_create(dir, dentry, mode);
> > + if (error)
> > + return error;
> > + error = try_break_deleg(dir, args->delegated_inode);
> > if (error)
> > return error;
> > error = dir->i_op->create(idmap, dir, dentry, mode, args->excl);
> > @@ -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 = { };
>
> If we must have 'createdata', can it have a 'struct delegated_inode'
> rather than a pointer to it?
>
If we do that, then we'd need some way to signal that the caller
doesn't want to wait on the delegation break. Currently that's
indicated by setting cargs.delegated_inode to NULL. I suppose we could
add a bool for this or something.
I confess that I too am lukewarm on struct createdata. I can live with
it, but it's not clearly a win to me either.
Christian, thoughts?
>
> > 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,
> > + 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));
> > @@ -4406,6 +4409,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
> > }
> > out2:
> > end_creating_path(&path, dentry);
> > + if (is_delegated(&delegated_inode)) {
> > + error = break_deleg_wait(&delegated_inode);
> > + if (!error)
> > + goto retry;
> > + }
> > if (retry_estale(error, lookup_flags)) {
> > lookup_flags |= LOOKUP_REVAL;
> > goto retry;
> > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > index b61873767b37591aecadd147623d7dfc866bef82..cfcb20a7c4ce4b6dcec98b3eccbdb5ec8bab6fa9 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2116,12 +2116,12 @@ struct createdata {
> > struct mnt_idmap *idmap; // idmap of the mount the inode was found from
> > struct inode *dir; // inode of parent directory
> > struct dentry *dentry; // dentry of the child file
> > + struct delegated_inode *delegated_inode; // returns parent inode, if delegated
> > umode_t mode; // mode of the child file
> > bool excl; // whether the file must not yet exist
> > };
> >
> > int vfs_create(struct createdata *);
> > -
> > struct dentry *vfs_mkdir(struct mnt_idmap *, struct inode *,
> > struct dentry *, umode_t, struct delegated_inode *);
> > int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> >
> > --
> > 2.51.1
> >
> >
--
Jeff Layton <jlayton@...nel.org>
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