Merge patch series "VFS: improve interface for lookup_one functions"

NeilBrown <neil@brown.name> says:

VFS has some functions with names containing "lookup_one_len" and others
without the "_len".  This difference has nothing to do with "len".  This
is an historical accident but can be confusing.

The functions without "_len" take a "mnt_idmap" pointer.  This is found
in the "vfsmount" and that is an important question when choosing which
to use: do you have a vfsmount, or are you "inside" the filesystem.  A
related question is "is permission checking relevant here?".

nfsd and cachefiles *do* have a vfsmount but *don't* use the non-_len
functions.  They pass nop_mnt_idmap and refuse to work on filesystems
which have any other idmap.

This series changes nfsd and cachefile to use the lookup_one family of
functions and to explictily pass &nop_mnt_idmap which is consistent with
all other vfs interfaces used where &nop_mnt_idmap is explicitly passed.

The remaining uses of the "_one" functions do not require permission
checks so these are renamed to be "_noperm" and the permission checking
is removed.

This series also changes these lookup function to take a qstr instead of
separate name and len.  In many cases this simplifies the call.

* patches from https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name:
  VFS: change lookup_one_common and lookup_noperm_common to take a qstr
  Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS
  VFS: rename lookup_one_len family to lookup_noperm and remove permission check
  cachefiles: Use lookup_one() rather than lookup_one_len()
  nfsd: Use lookup_one() rather than lookup_one_len()
  VFS: improve interface for lookup_one functions

Link: https://lore.kernel.org/r/20250319031545.2999807-2-neil@brown.name
Signed-off-by: Christian Brauner <brauner@kernel.org>

3 files changed, 7 insertions, 9 deletions

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 38c236e38cef..b62cd3e9a18e 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -71,7 +71,6 @@ struct cachefiles_object {
 	int				debug_id;
 	spinlock_t			lock;
 	refcount_t			ref;
-	u8				d_name_len;	/* Length of filename */
 	enum cachefiles_content		content_info:8;	/* Info about content presence */
 	unsigned long			flags;
 #define CACHEFILES_OBJECT_USING_TMPFILE	0		/* Have an unlinked tmpfile */
diff --git a/fs/cachefiles/key.c b/fs/cachefiles/key.c
index bf935e25bdbe..4927b533b9ae 100644
--- a/fs/cachefiles/key.c
+++ b/fs/cachefiles/key.c
@@ -132,7 +132,6 @@ bool cachefiles_cook_key(struct cachefiles_object *object)
 success:
 	name[len] = 0;
 	object->d_name = name;
-	object->d_name_len = len;
 	_leave(" = %s", object->d_name);
 	return true;
 }
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 14d0cc894000..aecfc5c37b49 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -98,7 +98,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
 retry:
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		subdir = lookup_one_len(dirname, dir, strlen(dirname));
+		subdir = lookup_one(&nop_mnt_idmap, &QSTR(dirname), dir);
 	else
 		subdir = ERR_PTR(ret);
 	trace_cachefiles_lookup(NULL, dir, subdir);
@@ -338,7 +338,7 @@ try_again:
 		return -EIO;
 	}
 
-	grave = lookup_one_len(nbuffer, cache->graveyard, strlen(nbuffer));
+	grave = lookup_one(&nop_mnt_idmap, &QSTR(nbuffer), cache->graveyard);
 	if (IS_ERR(grave)) {
 		unlock_rename(cache->graveyard, dir);
 		trace_cachefiles_vfs_error(object, d_inode(cache->graveyard),
@@ -630,8 +630,8 @@ bool cachefiles_look_up_object(struct cachefiles_object *object)
 	/* Look up path "cache/vol/fanout/file". */
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		dentry = lookup_positive_unlocked(object->d_name, fan,
-						  object->d_name_len);
+		dentry = lookup_one_positive_unlocked(&nop_mnt_idmap,
+						      &QSTR(object->d_name), fan);
 	else
 		dentry = ERR_PTR(ret);
 	trace_cachefiles_lookup(object, fan, dentry);
@@ -683,7 +683,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 	inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
 	ret = cachefiles_inject_read_error();
 	if (ret == 0)
-		dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
+		dentry = lookup_one(&nop_mnt_idmap, &QSTR(object->d_name), fan);
 	else
 		dentry = ERR_PTR(ret);
 	if (IS_ERR(dentry)) {
@@ -702,7 +702,7 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 		dput(dentry);
 		ret = cachefiles_inject_read_error();
 		if (ret == 0)
-			dentry = lookup_one_len(object->d_name, fan, object->d_name_len);
+			dentry = lookup_one(&nop_mnt_idmap, &QSTR(object->d_name), fan);
 		else
 			dentry = ERR_PTR(ret);
 		if (IS_ERR(dentry)) {
@@ -751,7 +751,7 @@ static struct dentry *cachefiles_lookup_for_cull(struct cachefiles_cache *cache,
 
 	inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
 
-	victim = lookup_one_len(filename, dir, strlen(filename));
+	victim = lookup_one(&nop_mnt_idmap, &QSTR(filename), dir);
 	if (IS_ERR(victim))
 		goto lookup_error;
 	if (d_is_negative(victim))