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>

2 files changed, 10 insertions, 11 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 8d1395f945bf..a324f82df562 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -57,7 +57,8 @@ struct qstr {
 };
 
 #define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
-#define QSTR(n) (struct qstr)QSTR_INIT(n, strlen(n))
+#define QSTR_LEN(n,l) (struct qstr)QSTR_INIT(n,l)
+#define QSTR(n) QSTR_LEN(n, strlen(n))
 
 extern const struct qstr empty_name;
 extern const struct qstr slash_name;
@@ -287,7 +288,6 @@ extern void d_exchange(struct dentry *, struct dentry *);
 extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 
 extern struct dentry *d_lookup(const struct dentry *, const struct qstr *);
-extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
 
 static inline unsigned d_count(const struct dentry *dentry)
 {
diff --git a/include/linux/namei.h b/include/linux/namei.h
index e3042176cdf4..cb6ce97782e0 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -69,17 +69,16 @@ int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
 int vfs_path_lookup(struct dentry *, struct vfsmount *, const char *,
 		    unsigned int, struct path *);
 
-extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
-extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
-extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
-extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
-struct dentry *lookup_one(struct mnt_idmap *, const char *, struct dentry *, int);
+extern struct dentry *try_lookup_noperm(struct qstr *, struct dentry *);
+extern struct dentry *lookup_noperm(struct qstr *, struct dentry *);
+extern struct dentry *lookup_noperm_unlocked(struct qstr *, struct dentry *);
+extern struct dentry *lookup_noperm_positive_unlocked(struct qstr *, struct dentry *);
+struct dentry *lookup_one(struct mnt_idmap *, struct qstr *, struct dentry *);
 struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
-				   const char *name, struct dentry *base,
-				   int len);
+				   struct qstr *name, struct dentry *base);
 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
-					    const char *name,
-					    struct dentry *base, int len);
+					    struct qstr *name,
+					    struct dentry *base);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *path, unsigned int flags);