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configfs: dentry refcount needs to be pinned only once

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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>
This commit is contained in:
Al Viro 2026-05-12 03:19:41 -04:00
parent abe91a2aa9
commit 1a29e25799
1 changed files with 5 additions and 5 deletions
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10
fs/configfs/dir.c
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@ -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;