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Message-id: <176221525113.1793333.253208063990645256@noble.neil.brown.name>
Date: Tue, 04 Nov 2025 11:14:11 +1100
From: NeilBrown <neilb@...mail.net>
To: "Jeff Layton" <jlayton@...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 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,
"Jeff Layton" <jlayton@...nel.org>
Subject: Re: [PATCH v4 10/17] vfs: make vfs_create break delegations on parent
directory
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?
NeilBrown
> 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
>
>
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