[PATCH v6 11/17] vfs: make vfs_mknod break delegations on parent directory

Jeff Layton
2025-11-11T14:13:41Z

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 new delegated_inode pointer to vfs_mknod() and have the
appropriate callers wait when there is an outstanding delegation. All
other callers just set the pointer to NULL.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
drivers/base/devtmpfs.c | 2 +-
fs/ecryptfs/inode.c | 2 +-
fs/init.c | 2 +-
fs/namei.c | 23 +++++++++++++++--------
fs/nfsd/vfs.c | 2 +-
fs/overlayfs/overlayfs.h | 2 +-
include/linux/fs.h | 4 ++--
net/unix/af_unix.c | 2 +-
8 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index 104025104ef75381984fd94dfbd50feeaa8cdd22..2f576ecf18324f767cd5ac6cbd28adbf9f46b958 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -231,7 +231,7 @@ static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
return PTR_ERR(dentry);

err = vfs_mknod(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode,
- dev->devt);
+ dev->devt, NULL);
if (!err) {
struct iattr newattrs;

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 3341f00dd08753c8feab184dd82b8bfa63d3724a..83f06452476dec4025cc8f50e082ae6ccbbc7914 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -564,7 +564,7 @@ ecryptfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
rc = lock_parent(dentry, &lower_dentry, &lower_dir);
if (!rc)
rc = vfs_mknod(&nop_mnt_idmap, lower_dir,
- lower_dentry, mode, dev);
+ lower_dentry, mode, dev, NULL);
if (rc || d_really_is_negative(lower_dentry))
goto out;
rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb);
diff --git a/fs/init.c b/fs/init.c
index 895f8a09a71acfd03e11164e3b441a7d4e2de146..4f02260dd65b0dfcbfbf5812d2ec6a33444a3b1f 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -157,7 +157,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
error = security_path_mknod(&path, dentry, mode, dev);
if (!error)
error = vfs_mknod(mnt_idmap(path.mnt), path.dentry->d_inode,
- dentry, mode, new_decode_dev(dev));
+ dentry, mode, new_decode_dev(dev), NULL);
end_creating_path(&path, dentry);
return error;
}
diff --git a/fs/namei.c b/fs/namei.c
index b20f053374a578d36fb764e0df80fb7db9230dbe..e9616134390fb7f0d09a759be69bf677f8800bc5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4295,13 +4295,15 @@ inline struct dentry *start_creating_user_path(
}
EXPORT_SYMBOL(start_creating_user_path);

+
/**
* vfs_mknod - create device node or file
- * @idmap: idmap of the mount the inode was found from
- * @dir: inode of the parent directory
- * @dentry: dentry of the child device node
- * @mode: mode of the child device node
- * @dev: device number of device to create
+ * @idmap: idmap of the mount the inode was found from
+ * @dir: inode of the parent directory
+ * @dentry: dentry of the child device node
+ * @mode: mode of the child device node
+ * @dev: device number of device to create
+ * @delegated_inode: returns parent inode, if the inode is delegated.
*
* Create a device node or file.
*
@@ -4312,7 +4314,8 @@ EXPORT_SYMBOL(start_creating_user_path);
* raw inode simply pass @nop_mnt_idmap.
*/
int vfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
- struct dentry *dentry, umode_t mode, dev_t dev)
+ struct dentry *dentry, umode_t mode, dev_t dev,
+ struct delegated_inode *delegated_inode)
{
bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
int error = may_create(idmap, dir, dentry);
@@ -4336,6 +4339,10 @@ int vfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
if (error)
return error;

+ error = try_break_deleg(dir, delegated_inode);
+ if (error)
+ return error;
+
error = dir->i_op->mknod(idmap, dir, dentry, mode, dev);
if (!error)
fsnotify_create(dir, dentry);
@@ -4393,11 +4400,11 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode,
break;
case S_IFCHR: case S_IFBLK:
error = vfs_mknod(idmap, path.dentry->d_inode,
- dentry, mode, new_decode_dev(dev));
+ dentry, mode, new_decode_dev(dev), &di);
break;
case S_IFIFO: case S_IFSOCK:
error = vfs_mknod(idmap, path.dentry->d_inode,
- dentry, mode, 0);
+ dentry, mode, 0, &di);
break;
}
out2:
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index de5f46f8c6d3ab24fabddeed9bd59adbe7a486df..6684935007b17ed40723ff0a744045fd187ace5e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1573,7 +1573,7 @@ nfsd_create_locked(struct svc_rqst *rqstp, struct svc_fh *fhp,
case S_IFIFO:
case S_IFSOCK:
host_err = vfs_mknod(&nop_mnt_idmap, dirp, dchild,
- iap->ia_mode, rdev);
+ iap->ia_mode, rdev, NULL);
break;
default:
printk(KERN_WARNING "nfsd: bad file type %o in nfsd_create\n",
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index e30441cc9c63ff8b6c055db80be7974501d0023b..afd95721f76ea761cfe7133c3902028550f3e359 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -257,7 +257,7 @@ static inline int ovl_do_mknod(struct ovl_fs *ofs,
struct inode *dir, struct dentry *dentry,
umode_t mode, dev_t dev)
{
- int err = vfs_mknod(ovl_upper_mnt_idmap(ofs), dir, dentry, mode, dev);
+ int err = vfs_mknod(ovl_upper_mnt_idmap(ofs), dir, dentry, mode, dev, NULL);

pr_debug("mknod(%pd2, 0%o, 0%o) = %i\n", dentry, mode, dev, err);
return err;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 83b05aec4e10c846d3168018fb62284e45ceb1a8..1a5d86cfafaa97fc89d15cd1a156968b8c3dd377 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2116,7 +2116,7 @@ int vfs_create(struct mnt_idmap *, struct dentry *, umode_t,
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 *,
- umode_t, dev_t);
+ umode_t, dev_t, struct delegated_inode *);
int vfs_symlink(struct mnt_idmap *, struct inode *,
struct dentry *, const char *);
int vfs_link(struct dentry *, struct mnt_idmap *, struct inode *,
@@ -2152,7 +2152,7 @@ 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 768098dec2310008632558ae928703b37c3cc8ef..db1fd8d6a84c2c7c0d45b43d9c5a936b3d491b7b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1399,7 +1399,7 @@ 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);

--
2.51.1