From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 12 May 2026 07:19:41 +0000 (-0400)
Subject: configfs: dentry refcount needs to be pinned only once
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1a29e25799bcd7c3b2285f46e2c630b62d969b25;p=thirdparty%2Fkernel%2Flinux.git

configfs: dentry refcount needs to be pinned only once

currently we have a weird situation where
	* symlinks and roots of subtrees created by mkdir are pinned once
	* subdirectories of subtrees created by mkdir are pinned twice
	* roots of subtrees created by register_{group,subsystem} are pinned
twice.

It makes things harder to follow for no good reason.  The goal is to
encapsulate the unbalanced dget/dput into d_{make,discard}_persisitent()
and, preferably, allow a use of simple_recursive_removal() or analogue
thereof.  So let's regularize that and pin things only once.

create_default_group() and configfs_register_subsystem() don't need to
keep their reference around on success - configfs_create_dir() has pinned
the sucker already.  So we can drop the reference passed to
configfs_create_dir() (via configfs_attach_group(), etc.) both on success
and on failure.  On the removal side we no longer have the double references,
so we need an explicit dget() to compensate.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
index 87a0847d88b9d..4836ffb3b70f7 100644
--- a/fs/configfs/dir.c
+++ b/fs/configfs/dir.c
@@ -657,7 +657,7 @@ static void detach_groups(struct dentry *dentry)
 		if (!(sd->s_type & CONFIGFS_USET_DEFAULT))
 			continue;
 
-		child = sd->s_dentry;
+		child = dget(sd->s_dentry);
 		spin_unlock(&configfs_dirent_lock);
 
 		inode_lock(d_inode(child));
@@ -708,8 +708,8 @@ static int create_default_group(struct config_group *parent_group,
 		} else {
 			BUG_ON(d_inode(child));
 			d_drop(child);
-			dput(child);
 		}
+		dput(child);
 	}
 
 	return ret;
@@ -1781,7 +1781,7 @@ EXPORT_SYMBOL(configfs_register_group);
 void configfs_unregister_group(struct config_group *group)
 {
 	struct configfs_subsystem *subsys = group->cg_subsys;
-	struct dentry *dentry = group->cg_item.ci_dentry;
+	struct dentry *dentry = dget(group->cg_item.ci_dentry);
 	struct dentry *parent = group->cg_item.ci_parent->ci_dentry;
 	struct configfs_dirent *sd = dentry->d_fsdata;
 	struct configfs_fragment *frag = sd->s_frag;
@@ -1896,12 +1896,12 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 		if (err) {
 			BUG_ON(d_inode(dentry));
 			d_drop(dentry);
-			dput(dentry);
 		} else {
 			spin_lock(&configfs_dirent_lock);
 			configfs_dir_set_ready(dentry->d_fsdata);
 			spin_unlock(&configfs_dirent_lock);
 		}
+		dput(dentry);
 	}
 
 	inode_unlock(d_inode(root));
@@ -1920,7 +1920,7 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
 void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
 {
 	struct config_group *group = &subsys->su_group;
-	struct dentry *dentry = group->cg_item.ci_dentry;
+	struct dentry *dentry = dget(group->cg_item.ci_dentry);
 	struct dentry *root = dentry->d_sb->s_root;
 	struct configfs_dirent *sd = dentry->d_fsdata;
 	struct configfs_fragment *frag = sd->s_frag;