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, 2 deletions

diff --git a/fs/smb/client/cached_dir.c b/fs/smb/client/cached_dir.c
index fe738623cf1b..e6fc92667d41 100644
--- a/fs/smb/client/cached_dir.c
+++ b/fs/smb/client/cached_dir.c
@@ -109,7 +109,8 @@ path_to_dentry(struct cifs_sb_info *cifs_sb, const char *path)
 		while (*s && *s != sep)
 			s++;
 
-		child = lookup_positive_unlocked(p, dentry, s - p);
+		child = lookup_noperm_positive_unlocked(&QSTR_LEN(p, s - p),
+							dentry);
 		dput(dentry);
 		dentry = child;
 	} while (!IS_ERR(dentry));
@@ -207,7 +208,7 @@ replay_again:
 	spin_unlock(&cfids->cfid_list_lock);
 
 	/*
-	 * Skip any prefix paths in @path as lookup_positive_unlocked() ends up
+	 * Skip any prefix paths in @path as lookup_noperm_positive_unlocked() ends up
 	 * calling ->lookup() which already adds those through
 	 * build_path_from_dentry().  Also, do it earlier as we might reconnect
 	 * below when trying to send compounded request and then potentially