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

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Message-Id: <20251103-dir-deleg-ro-v4-10-961b67adee89@kernel.org>
Date: Mon, 03 Nov 2025 07:52:38 -0500
From: Jeff Layton <jlayton@...nel.org>
To: 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>, 
 NeilBrown <neil@...wn.name>, 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>
Cc: 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: [PATCH v4 10/17] vfs: make vfs_create break delegations on parent
 directory

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 = { };
 	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