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, 5 insertions, 6 deletions

diff --git a/fs/nfs/unlink.c b/fs/nfs/unlink.c
index bf77399696a7..b55467911648 100644
--- a/fs/nfs/unlink.c
+++ b/fs/nfs/unlink.c
@@ -464,18 +464,17 @@ nfs_sillyrename(struct inode *dir, struct dentry *dentry)
 
 	sdentry = NULL;
 	do {
-		int slen;
 		dput(sdentry);
 		sillycounter++;
-		slen = scnprintf(silly, sizeof(silly),
-				SILLYNAME_PREFIX "%0*llx%0*x",
-				SILLYNAME_FILEID_LEN, fileid,
-				SILLYNAME_COUNTER_LEN, sillycounter);
+		scnprintf(silly, sizeof(silly),
+			  SILLYNAME_PREFIX "%0*llx%0*x",
+			  SILLYNAME_FILEID_LEN, fileid,
+			  SILLYNAME_COUNTER_LEN, sillycounter);
 
 		dfprintk(VFS, "NFS: trying to rename %pd to %s\n",
 				dentry, silly);
 
-		sdentry = lookup_one_len(silly, dentry->d_parent, slen);
+		sdentry = lookup_noperm(&QSTR(silly), dentry->d_parent);
 		/*
 		 * N.B. Better to return EBUSY here ... it could be
 		 * dangerous to delete the file while it's in use.