Re: [PATCH v5 03/17] filelock: add struct delegated_inode

From: Jan Kara
Date: Tue Nov 11 2025 - 06:10:54 EST

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On Wed 05-11-25 11:53:49, Jeff Layton wrote:
> The current API requires a pointer to an inode pointer. It's easy for
> callers to get this wrong. Add a new delegated_inode structure and use
> that to pass back any inode that needs to be waited on.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>

I didn't find anything particularly problematic with struct inode ** but I
agree this seems a tad bit cleaner and harder to get wrong. So feel free to
add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

Honza

> ---
> fs/attr.c | 2 +-
> fs/namei.c | 18 +++++++++---------
> fs/open.c | 8 ++++----
> fs/posix_acl.c | 8 ++++----
> fs/utimes.c | 4 ++--
> fs/xattr.c | 12 ++++++------
> include/linux/filelock.h | 36 +++++++++++++++++++++++++++---------
> include/linux/fs.h | 9 +++++----
> include/linux/xattr.h | 4 ++--
> 9 files changed, 60 insertions(+), 41 deletions(-)
>
> diff --git a/fs/attr.c b/fs/attr.c
> index 795f231d00e8eaaadf5b62f241655cb4b69cb507..b9ec6b47bab2fc2b561677b639633bd32994022f 100644
> --- a/fs/attr.c
> +++ b/fs/attr.c
> @@ -415,7 +415,7 @@ EXPORT_SYMBOL(may_setattr);
> * performed on the raw inode simply pass @nop_mnt_idmap.
> */
> int notify_change(struct mnt_idmap *idmap, struct dentry *dentry,
> - struct iattr *attr, struct inode **delegated_inode)
> + struct iattr *attr, struct delegated_inode *delegated_inode)
> {
> struct inode *inode = dentry->d_inode;
> umode_t mode = inode->i_mode;
> diff --git a/fs/namei.c b/fs/namei.c
> index 7377020a2cba02501483020e0fc93c279fb38d3e..bf42f146f847a5330fc581595c7256af28d9db90 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -4648,7 +4648,7 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
> * raw inode simply pass @nop_mnt_idmap.
> */
> int vfs_unlink(struct mnt_idmap *idmap, struct inode *dir,
> - struct dentry *dentry, struct inode **delegated_inode)
> + struct dentry *dentry, struct delegated_inode *delegated_inode)
> {
> struct inode *target = dentry->d_inode;
> int error = may_delete(idmap, dir, dentry, 0);
> @@ -4706,7 +4706,7 @@ int do_unlinkat(int dfd, struct filename *name)
> struct qstr last;
> int type;
> struct inode *inode = NULL;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> unsigned int lookup_flags = 0;
> retry:
> error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
> @@ -4743,7 +4743,7 @@ int do_unlinkat(int dfd, struct filename *name)
> if (inode)
> iput(inode); /* truncate the inode here */
> inode = NULL;
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> @@ -4892,7 +4892,7 @@ SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newn
> */
> int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap,
> struct inode *dir, struct dentry *new_dentry,
> - struct inode **delegated_inode)
> + struct delegated_inode *delegated_inode)
> {
> struct inode *inode = old_dentry->d_inode;
> unsigned max_links = dir->i_sb->s_max_links;
> @@ -4968,7 +4968,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
> struct mnt_idmap *idmap;
> struct dentry *new_dentry;
> struct path old_path, new_path;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> int how = 0;
> int error;
>
> @@ -5012,7 +5012,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
> new_dentry, &delegated_inode);
> out_dput:
> end_creating_path(&new_path, new_dentry);
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error) {
> path_put(&old_path);
> @@ -5098,7 +5098,7 @@ int vfs_rename(struct renamedata *rd)
> struct inode *new_dir = d_inode(rd->new_parent);
> struct dentry *old_dentry = rd->old_dentry;
> struct dentry *new_dentry = rd->new_dentry;
> - struct inode **delegated_inode = rd->delegated_inode;
> + struct delegated_inode *delegated_inode = rd->delegated_inode;
> unsigned int flags = rd->flags;
> bool is_dir = d_is_dir(old_dentry);
> struct inode *source = old_dentry->d_inode;
> @@ -5261,7 +5261,7 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
> struct path old_path, new_path;
> struct qstr old_last, new_last;
> int old_type, new_type;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> unsigned int lookup_flags = 0, target_flags =
> LOOKUP_RENAME_TARGET | LOOKUP_CREATE;
> bool should_retry = false;
> @@ -5369,7 +5369,7 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd,
> exit3:
> unlock_rename(new_path.dentry, old_path.dentry);
> exit_lock_rename:
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> diff --git a/fs/open.c b/fs/open.c
> index 3d64372ecc675e4795eb0a0deda10f8f67b95640..fdaa6f08f6f4cac5c2fefd3eafa5e430e51f3979 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -631,7 +631,7 @@ SYSCALL_DEFINE1(chroot, const char __user *, filename)
> int chmod_common(const struct path *path, umode_t mode)
> {
> struct inode *inode = path->dentry->d_inode;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> struct iattr newattrs;
> int error;
>
> @@ -651,7 +651,7 @@ int chmod_common(const struct path *path, umode_t mode)
> &newattrs, &delegated_inode);
> out_unlock:
> inode_unlock(inode);
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> @@ -756,7 +756,7 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
> struct mnt_idmap *idmap;
> struct user_namespace *fs_userns;
> struct inode *inode = path->dentry->d_inode;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> int error;
> struct iattr newattrs;
> kuid_t uid;
> @@ -791,7 +791,7 @@ int chown_common(const struct path *path, uid_t user, gid_t group)
> error = notify_change(idmap, path->dentry, &newattrs,
> &delegated_inode);
> inode_unlock(inode);
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> diff --git a/fs/posix_acl.c b/fs/posix_acl.c
> index 4050942ab52f95741da2df13d191ade5c5ca12a2..768f027c142811ea907fe8545155ba7abd016305 100644
> --- a/fs/posix_acl.c
> +++ b/fs/posix_acl.c
> @@ -1091,7 +1091,7 @@ int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> int acl_type;
> int error;
> struct inode *inode = d_inode(dentry);
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
>
> acl_type = posix_acl_type(acl_name);
> if (acl_type < 0)
> @@ -1141,7 +1141,7 @@ int vfs_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> out_inode_unlock:
> inode_unlock(inode);
>
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> @@ -1212,7 +1212,7 @@ int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> int acl_type;
> int error;
> struct inode *inode = d_inode(dentry);
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
>
> acl_type = posix_acl_type(acl_name);
> if (acl_type < 0)
> @@ -1249,7 +1249,7 @@ int vfs_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
> out_inode_unlock:
> inode_unlock(inode);
>
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> diff --git a/fs/utimes.c b/fs/utimes.c
> index c7c7958e57b22f91646ca9f76d18781b64d371a3..bf9f45bdef54947de7ac55c9f873ae9d0336dafa 100644
> --- a/fs/utimes.c
> +++ b/fs/utimes.c
> @@ -22,7 +22,7 @@ int vfs_utimes(const struct path *path, struct timespec64 *times)
> int error;
> struct iattr newattrs;
> struct inode *inode = path->dentry->d_inode;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
>
> if (times) {
> if (!nsec_valid(times[0].tv_nsec) ||
> @@ -66,7 +66,7 @@ int vfs_utimes(const struct path *path, struct timespec64 *times)
> error = notify_change(mnt_idmap(path->mnt), path->dentry, &newattrs,
> &delegated_inode);
> inode_unlock(inode);
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 8851a5ef34f5ab34383975dd4cef537de3f6391e..32d445fb60aaf2aaf4b16b62934dc99bad378067 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -274,7 +274,7 @@ int __vfs_setxattr_noperm(struct mnt_idmap *idmap,
> int
> __vfs_setxattr_locked(struct mnt_idmap *idmap, struct dentry *dentry,
> const char *name, const void *value, size_t size,
> - int flags, struct inode **delegated_inode)
> + int flags, struct delegated_inode *delegated_inode)
> {
> struct inode *inode = dentry->d_inode;
> int error;
> @@ -305,7 +305,7 @@ vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> const char *name, const void *value, size_t size, int flags)
> {
> struct inode *inode = dentry->d_inode;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> const void *orig_value = value;
> int error;
>
> @@ -322,7 +322,7 @@ vfs_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
> flags, &delegated_inode);
> inode_unlock(inode);
>
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> @@ -533,7 +533,7 @@ EXPORT_SYMBOL(__vfs_removexattr);
> int
> __vfs_removexattr_locked(struct mnt_idmap *idmap,
> struct dentry *dentry, const char *name,
> - struct inode **delegated_inode)
> + struct delegated_inode *delegated_inode)
> {
> struct inode *inode = dentry->d_inode;
> int error;
> @@ -567,7 +567,7 @@ vfs_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
> const char *name)
> {
> struct inode *inode = dentry->d_inode;
> - struct inode *delegated_inode = NULL;
> + struct delegated_inode delegated_inode = { };
> int error;
>
> retry_deleg:
> @@ -576,7 +576,7 @@ vfs_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
> name, &delegated_inode);
> inode_unlock(inode);
>
> - if (delegated_inode) {
> + if (is_delegated(&delegated_inode)) {
> error = break_deleg_wait(&delegated_inode);
> if (!error)
> goto retry_deleg;
> diff --git a/include/linux/filelock.h b/include/linux/filelock.h
> index 47da6aa28d8dc9122618d02c6608deda0f3c4d3e..208d108df2d73a9df65e5dc9968d074af385f881 100644
> --- a/include/linux/filelock.h
> +++ b/include/linux/filelock.h
> @@ -486,25 +486,35 @@ static inline int break_deleg(struct inode *inode, unsigned int flags)
> return 0;
> }
>
> -static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
> +struct delegated_inode {
> + struct inode *di_inode;
> +};
> +
> +static inline bool is_delegated(struct delegated_inode *di)
> +{
> + return di->di_inode;
> +}
> +
> +static inline int try_break_deleg(struct inode *inode,
> + struct delegated_inode *di)
> {
> int ret;
>
> ret = break_deleg(inode, LEASE_BREAK_NONBLOCK);
> - if (ret == -EWOULDBLOCK && delegated_inode) {
> - *delegated_inode = inode;
> + if (ret == -EWOULDBLOCK && di) {
> + di->di_inode = inode;
> ihold(inode);
> }
> return ret;
> }
>
> -static inline int break_deleg_wait(struct inode **delegated_inode)
> +static inline int break_deleg_wait(struct delegated_inode *di)
> {
> int ret;
>
> - ret = break_deleg(*delegated_inode, 0);
> - iput(*delegated_inode);
> - *delegated_inode = NULL;
> + ret = break_deleg(di->di_inode, 0);
> + iput(di->di_inode);
> + di->di_inode = NULL;
> return ret;
> }
>
> @@ -523,6 +533,13 @@ static inline int break_layout(struct inode *inode, bool wait)
> }
>
> #else /* !CONFIG_FILE_LOCKING */
> +struct delegated_inode { };
> +
> +static inline bool is_delegated(struct delegated_inode *di)
> +{
> + return false;
> +}
> +
> static inline int break_lease(struct inode *inode, bool wait)
> {
> return 0;
> @@ -533,12 +550,13 @@ static inline int break_deleg(struct inode *inode, unsigned int flags)
> return 0;
> }
>
> -static inline int try_break_deleg(struct inode *inode, struct inode **delegated_inode)
> +static inline int try_break_deleg(struct inode *inode,
> + struct delegated_inode *delegated_inode)
> {
> return 0;
> }
>
> -static inline int break_deleg_wait(struct inode **delegated_inode)
> +static inline int break_deleg_wait(struct delegated_inode *delegated_inode)
> {
> BUG();
> return 0;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index c895146c1444be36e0a779df55622cc38c9419ff..909a88e3979d4f1ba3104f3d05145e1096ed44d5 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -80,6 +80,7 @@ struct fs_context;
> struct fs_parameter_spec;
> struct file_kattr;
> struct iomap_ops;
> +struct delegated_inode;
>
> extern void __init inode_init(void);
> extern void __init inode_init_early(void);
> @@ -2119,10 +2120,10 @@ int vfs_mknod(struct mnt_idmap *, struct inode *, struct dentry *,
> int vfs_symlink(struct mnt_idmap *, struct inode *,
> struct dentry *, const char *);
> int vfs_link(struct dentry *, struct mnt_idmap *, struct inode *,
> - struct dentry *, struct inode **);
> + struct dentry *, struct delegated_inode *);
> int vfs_rmdir(struct mnt_idmap *, struct inode *, struct dentry *);
> int vfs_unlink(struct mnt_idmap *, struct inode *, struct dentry *,
> - struct inode **);
> + struct delegated_inode *);
>
> /**
> * struct renamedata - contains all information required for renaming
> @@ -2140,7 +2141,7 @@ struct renamedata {
> struct dentry *old_dentry;
> struct dentry *new_parent;
> struct dentry *new_dentry;
> - struct inode **delegated_inode;
> + struct delegated_inode *delegated_inode;
> unsigned int flags;
> } __randomize_layout;
>
> @@ -3071,7 +3072,7 @@ static inline int bmap(struct inode *inode, sector_t *block)
> #endif
>
> int notify_change(struct mnt_idmap *, struct dentry *,
> - struct iattr *, struct inode **);
> + struct iattr *, struct delegated_inode *);
> int inode_permission(struct mnt_idmap *, struct inode *, int);
> int generic_permission(struct mnt_idmap *, struct inode *, int);
> static inline int file_permission(struct file *file, int mask)
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index 86b0d47984a16d935dd1c45ca80a3b8bb5b7295b..64e9afe7d647dc38f686a4b5c6f765e061cde54c 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -85,12 +85,12 @@ int __vfs_setxattr_noperm(struct mnt_idmap *, struct dentry *,
> const char *, const void *, size_t, int);
> int __vfs_setxattr_locked(struct mnt_idmap *, struct dentry *,
> const char *, const void *, size_t, int,
> - struct inode **);
> + struct delegated_inode *);
> int vfs_setxattr(struct mnt_idmap *, struct dentry *, const char *,
> const void *, size_t, int);
> int __vfs_removexattr(struct mnt_idmap *, struct dentry *, const char *);
> int __vfs_removexattr_locked(struct mnt_idmap *, struct dentry *,
> - const char *, struct inode **);
> + const char *, struct delegated_inode *);
> int vfs_removexattr(struct mnt_idmap *, struct dentry *, const char *);
>
> ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
>
> --
> 2.51.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR

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