VFS: rename lookup_one_len family to lookup_noperm and remove permission check

The lookup_one_len family of functions is (now) only used internally by
a filesystem on itself either
- in a context where permission checking is irrelevant such as by a
  virtual filesystem populating itself, or xfs accessing its ORPHANAGE
  or dquota accessing the quota file; or
- in a context where a permission check (MAY_EXEC on the parent) has just
  been performed such as a network filesystem finding in "silly-rename"
  file in the same directory.  This is also the context after the
  _parentat() functions where currently lookup_one_qstr_excl() is used.

So the permission check is pointless.

The name "one_len" is unhelpful in understanding the purpose of these
functions and should be changed.  Most of the callers pass the len as
"strlen()" so using a qstr and QSTR() can simplify the code.

This patch renames these functions (include lookup_positive_unlocked()
which is part of the family despite the name) to have a name based on
"lookup_noperm".  They are changed to receive a 'struct qstr' instead
of separate name and len.  In a few cases the use of QSTR() results in a
new call to strlen().

try_lookup_noperm() takes a pointer to a qstr instead of the whole
qstr.  This is consistent with d_hash_and_lookup() (which is nearly
identical) and useful for lookup_noperm_unlocked().

The new lookup_noperm_common() doesn't take a qstr yet.  That will be
tidied up in a subsequent patch.

Signed-off-by: NeilBrown <neil@brown.name>
Link: https://lore.kernel.org/r/20250319031545.2999807-5-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 75715d8877ee..30c4944e1862 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -346,7 +346,7 @@ struct dentry *debugfs_lookup(const char *name, struct dentry *parent)
 	if (!parent)
 		parent = debugfs_mount->mnt_root;
 
-	dentry = lookup_positive_unlocked(name, parent, strlen(name));
+	dentry = lookup_noperm_positive_unlocked(&QSTR(name), parent);
 	if (IS_ERR(dentry))
 		return NULL;
 	return dentry;
@@ -388,7 +388,7 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
 	if (unlikely(IS_DEADDIR(d_inode(parent))))
 		dentry = ERR_PTR(-ENOENT);
 	else
-		dentry = lookup_one_len(name, parent, strlen(name));
+		dentry = lookup_noperm(&QSTR(name), parent);
 	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
 		if (d_is_dir(dentry))
 			pr_err("Directory '%s' with parent '%s' already present!\n",
@@ -872,7 +872,7 @@ int __printf(2, 3) debugfs_change_name(struct dentry *dentry, const char *fmt, .
 	}
 	if (strcmp(old_name.name.name, new_name) == 0)
 		goto out;
-	target = lookup_one_len(new_name, parent, strlen(new_name));
+	target = lookup_noperm(&QSTR(new_name), parent);
 	if (IS_ERR(target)) {
 		error = PTR_ERR(target);
 		goto out;