filelock: add struct delegated_inode

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.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20251111-dir-deleg-ro-v6-3-52f3feebb2f2@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 34 insertions, 15 deletions

diff --git a/include/linux/filelock.h b/include/linux/filelock.h
index 47da6aa28d8d..208d108df2d7 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 c895146c1444..909a88e3979d 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 86b0d47984a1..64e9afe7d647 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);