Subject: [PATCH 7/8] debugfs: switch to simplefs inode creation API

From: Emanuele Giuseppe Esposito <[email-masked]>
Date: Tue, 14 Apr 2020 14:43:01 +0200

The only difference, compared to the pre-existing code, is that symlink
creation now triggers fsnotify_create.  This was a bug in the debugfs
code, since for example vfs_symlink does call fsnotify_create.

Signed-off-by: Emanuele Giuseppe Esposito <[email-masked]>
---
 fs/debugfs/inode.c | 144 +++++----------------------------------------
 1 file changed, 15 insertions(+), 129 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 834b5872ca0d..7a2369373b85 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -294,68 +294,6 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
 }
 EXPORT_SYMBOL_GPL(debugfs_lookup);
 
-static struct dentry *start_creating(const char *name, struct dentry *parent)
-{
-	struct dentry *dentry;
-	int error;
-
-	pr_debug("creating file '%s'\n", name);
-
-	if (IS_ERR(parent))
-		return parent;
-
-	error = simple_pin_fs(&debugfs, &debug_fs_type);
-	if (error) {
-		pr_err("Unable to pin filesystem for file '%s'\n", name);
-		return ERR_PTR(error);
-	}
-
-	/* If the parent is not specified, we create it in the root.
-	 * We need the root dentry to do this, which is in the super
-	 * block. A pointer to that is in the struct vfsmount that we
-	 * have around.
-	 */
-	if (!parent)
-		parent = debugfs.mount->mnt_root;
-
-	inode_lock(d_inode(parent));
-	if (unlikely(IS_DEADDIR(d_inode(parent))))
-		dentry = ERR_PTR(-ENOENT);
-	else
-		dentry = lookup_one_len(name, parent, strlen(name));
-	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
-		if (d_is_dir(dentry))
-			pr_err("Directory '%s' with parent '%s' already present!\n",
-			       name, parent->d_name.name);
-		else
-			pr_err("File '%s' in directory '%s' already present!\n",
-			       name, parent->d_name.name);
-		dput(dentry);
-		dentry = ERR_PTR(-EEXIST);
-	}
-
-	if (IS_ERR(dentry)) {
-		inode_unlock(d_inode(parent));
-		simple_release_fs(&debugfs);
-	}
-
-	return dentry;
-}
-
-static struct dentry *failed_creating(struct dentry *dentry)
-{
-	inode_unlock(d_inode(dentry->d_parent));
-	dput(dentry);
-	simple_release_fs(&debugfs);
-	return ERR_PTR(-ENOMEM);
-}
-
-static struct dentry *end_creating(struct dentry *dentry)
-{
-	inode_unlock(d_inode(dentry->d_parent));
-	return dentry;
-}
-
 static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 				struct dentry *parent, void *data,
 				const struct file_operations *proxy_fops,
@@ -364,32 +302,17 @@ static struct dentry *__debugfs_create_file(const char *name, umode_t mode,
 	struct dentry *dentry;
 	struct inode *inode;
 
-	if (!(mode & S_IFMT))
-		mode |= S_IFREG;
-	BUG_ON(!S_ISREG(mode));
-	dentry = start_creating(name, parent);
-
+	dentry = simplefs_create_file(&debugfs, &debug_fs_type,
+				      name, mode, parent, data, &inode);
 	if (IS_ERR(dentry))
 		return dentry;
 
-	inode = simple_new_inode(dentry->d_sb);
-	if (unlikely(!inode)) {
-		pr_err("out of free dentries, can not create file '%s'\n",
-		       name);
-		return failed_creating(dentry);
-	}
-
-	inode->i_mode = mode;
-	inode->i_private = data;
-
 	inode->i_op = &debugfs_file_inode_operations;
 	inode->i_fop = proxy_fops;
 	dentry->d_fsdata = (void *)((unsigned long)real_fops |
 				DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
 
-	d_instantiate(dentry, inode);
-	fsnotify_create(d_inode(dentry->d_parent), dentry);
-	return end_creating(dentry);
+	return simplefs_finish_dentry(dentry, inode);
 }
 
 /**
@@ -522,29 +445,16 @@ EXPORT_SYMBOL_GPL(debugfs_create_file_size);
  */
 struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
 {
-	struct dentry *dentry = start_creating(name, parent);
+	struct dentry *dentry;
 	struct inode *inode;
 
+	dentry = simplefs_create_dir(&debugfs, &debug_fs_type,
+				     name, 0755, parent, &inode);
 	if (IS_ERR(dentry))
 		return dentry;
 
-	inode = simple_new_inode(dentry->d_sb);
-	if (unlikely(!inode)) {
-		pr_err("out of free dentries, can not create directory '%s'\n",
-		       name);
-		return failed_creating(dentry);
-	}
-
-	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
 	inode->i_op = &debugfs_dir_inode_operations;
-	inode->i_fop = &simple_dir_operations;
-
-	/* directory inodes start off with i_nlink == 2 (for "." entry) */
-	inc_nlink(inode);
-	d_instantiate(dentry, inode);
-	inc_nlink(d_inode(dentry->d_parent));
-	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
-	return end_creating(dentry);
+	return simplefs_finish_dentry(dentry, inode);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_dir);
 
@@ -564,29 +474,19 @@ struct dentry *debugfs_create_automount(const char *name,
 					debugfs_automount_t f,
 					void *data)
 {
-	struct dentry *dentry = start_creating(name, parent);
+	struct dentry *dentry;
 	struct inode *inode;
 
+	dentry = simplefs_create_dentry(&debugfs, &debug_fs_type, name, parent,
+					&inode);
 	if (IS_ERR(dentry))
 		return dentry;
 
-	inode = simple_new_inode(dentry->d_sb);
-	if (unlikely(!inode)) {
-		pr_err("out of free dentries, can not create automount '%s'\n",
-		       name);
-		return failed_creating(dentry);
-	}
-
 	make_empty_dir_inode(inode);
 	inode->i_flags |= S_AUTOMOUNT;
 	inode->i_private = data;
 	dentry->d_fsdata = (void *)f;
-	/* directory inodes start off with i_nlink == 2 (for "." entry) */
-	inc_nlink(inode);
-	d_instantiate(dentry, inode);
-	inc_nlink(d_inode(dentry->d_parent));
-	fsnotify_mkdir(d_inode(dentry->d_parent), dentry);
-	return end_creating(dentry);
+	return simplefs_finish_dentry(dentry, inode);
 }
 EXPORT_SYMBOL(debugfs_create_automount);
 
@@ -618,28 +518,14 @@ struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
 {
 	struct dentry *dentry;
 	struct inode *inode;
-	char *link = kstrdup(target, GFP_KERNEL);
-	if (!link)
-		return ERR_PTR(-ENOMEM);
 
-	dentry = start_creating(name, parent);
-	if (IS_ERR(dentry)) {
-		kfree(link);
+	dentry = simplefs_create_symlink(&debugfs, &debug_fs_type,
+					 name, parent, target, &inode);
+	if (IS_ERR(dentry))
 		return dentry;
-	}
 
-	inode = simple_new_inode(dentry->d_sb);
-	if (unlikely(!inode)) {
-		pr_err("out of free dentries, can not create symlink '%s'\n",
-		       name);
-		kfree(link);
-		return failed_creating(dentry);
-	}
-	inode->i_mode = S_IFLNK | S_IRWXUGO;
 	inode->i_op = &debugfs_symlink_inode_operations;
-	inode->i_link = link;
-	d_instantiate(dentry, inode);
-	return end_creating(dentry);
+	return simplefs_finish_dentry(dentry, inode);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
 
-- 
2.25.2