Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull dentry d_flags updates from Al Viro:
 "The current exclusion rules for dentry->d_flags stores are rather
  unpleasant. The basic rules are simple:

   - stores to dentry->d_flags are OK under dentry->d_lock

   - stores to dentry->d_flags are OK in the dentry constructor, before
     becomes potentially visible to other threads

  Unfortunately, there's a couple of exceptions to that, and that's
  where the headache comes from.

  The main PITA comes from d_set_d_op(); that primitive sets ->d_op of
  dentry and adjusts the flags that correspond to presence of individual
  methods. It's very easy to misuse; existing uses _are_ safe, but proof
  of correctness is brittle.

  Use in __d_alloc() is safe (we are within a constructor), but we might
  as well precalculate the initial value of 'd_flags' when we set the
  default ->d_op for given superblock and set 'd_flags' directly instead
  of messing with that helper.

  The reasons why other uses are safe are bloody convoluted; I'm not
  going to reproduce it here. See [1] for gory details, if you care. The
  critical part is using d_set_d_op() only just prior to
  d_splice_alias(), which makes a combination of d_splice_alias() with
  setting ->d_op, etc a natural replacement primitive.

  Better yet, if we go that way, it's easy to take setting ->d_op and
  modifying 'd_flags' under ->d_lock, which eliminates the headache as
  far as 'd_flags' exclusion rules are concerned. Other exceptions are
  minor and easy to deal with.

  What this series does:

   - d_set_d_op() is no longer available; instead a new primitive
     (d_splice_alias_ops()) is provided, equivalent to combination of
     d_set_d_op() and d_splice_alias().

   - new field of struct super_block - 's_d_flags'. This sets the
     default value of 'd_flags' to be used when allocating dentries on
     this filesystem.

   - new primitive for setting 's_d_op': set_default_d_op(). This
     replaces stores to 's_d_op' at mount time.

     All in-tree filesystems converted; out-of-tree ones will get caught
     by the compiler ('s_d_op' is renamed, so stores to it will be
     caught). 's_d_flags' is set by the same primitive to match the
     's_d_op'.

   - a lot of filesystems had sb->s_d_op->d_delete equal to
     always_delete_dentry; that is equivalent to setting
     DCACHE_DONTCACHE in 'd_flags', so such filesystems can bloody well
     set that bit in 's_d_flags' and drop 'd_delete()' from
     dentry_operations.

     In quite a few cases that results in empty dentry_operations, which
     means that we can get rid of those.

   - kill simple_dentry_operations - not needed anymore

   - massage d_alloc_parallel() to get rid of the other exception wrt
     'd_flags' stores - we can set DCACHE_PAR_LOOKUP as soon as we
     allocate the new dentry; no need to delay that until we commit to
     using the sucker.

  As the result, 'd_flags' stores are all either under ->d_lock or done
  before the dentry becomes visible in any shared data structures"

Link: https://lore.kernel.org/all/20250224010624.GT1977892@ZenIV/ [1]

* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (21 commits)
  configfs: use DCACHE_DONTCACHE
  debugfs: use DCACHE_DONTCACHE
  efivarfs: use DCACHE_DONTCACHE instead of always_delete_dentry()
  9p: don't bother with always_delete_dentry
  ramfs, hugetlbfs, mqueue: set DCACHE_DONTCACHE
  kill simple_dentry_operations
  devpts, sunrpc, hostfs: don't bother with ->d_op
  shmem: no dentry retention past the refcount reaching zero
  d_alloc_parallel(): set DCACHE_PAR_LOOKUP earlier
  make d_set_d_op() static
  simple_lookup(): just set DCACHE_DONTCACHE
  tracefs: Add d_delete to remove negative dentries
  set_default_d_op(): calculate the matching value for ->d_flags
  correct the set of flags forbidden at d_set_d_op() time
  split d_flags calculation out of d_set_d_op()
  new helper: set_default_d_op()
  fuse: no need for special dentry_operations for root dentry
  switch procfs from d_set_d_op() to d_splice_alias_ops()
  new helper: d_splice_alias_ops()
  procfs: kill ->proc_dops
  ...

Documentation/filesystems/porting.rst

@@ -1258,3 +1258,21 @@ iterator needed.  Instead of a cloned mount tree, the new interface returns
 an array of struct path, one for each mount collect_mounts() would've
 created.  These struct path point to locations in the caller's namespace
 that would be roots of the cloned mounts.
+
+---
+
+**mandatory**
+
+If your filesystem sets the default dentry_operations, use set_default_d_op()
+rather than manually setting sb->s_d_op.
+
+---
+
+**mandatory**
+
+d_set_d_op() is no longer exported (or public, for that matter); _if_
+your filesystem really needed that, make use of d_splice_alias_ops()
+to have them set.  Better yet, think hard whether you need different
+->d_op for different dentries - if not, just use set_default_d_op()
+at mount time and be done with that.  Currently procfs is the only
+thing that really needs ->d_op varying between dentries.

fs/9p/vfs_dentry.c

@@ -127,7 +127,6 @@ const struct dentry_operations v9fs_cached_dentry_operations = {
 };
 
 const struct dentry_operations v9fs_dentry_operations = {
-	.d_delete = always_delete_dentry,
 	.d_release = v9fs_dentry_release,
 	.d_unalias_trylock = v9fs_dentry_unalias_trylock,
 	.d_unalias_unlock = v9fs_dentry_unalias_unlock,

fs/9p/vfs_super.c

@@ -134,10 +134,12 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
 	if (retval)
 		goto release_sb;
 
-	if (v9ses->cache & (CACHE_META|CACHE_LOOSE))
-		sb->s_d_op = &v9fs_cached_dentry_operations;
-	else
-		sb->s_d_op = &v9fs_dentry_operations;
+	if (v9ses->cache & (CACHE_META|CACHE_LOOSE)) {
+		set_default_d_op(sb, &v9fs_cached_dentry_operations);
+	} else {
+		set_default_d_op(sb, &v9fs_dentry_operations);
+		sb->s_d_flags |= DCACHE_DONTCACHE;
+	}
 
 	inode = v9fs_get_new_inode_from_fid(v9ses, fid, sb);
 	if (IS_ERR(inode)) {

fs/adfs/super.c

@@ -397,7 +397,7 @@ static int adfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (asb->s_ftsuffix)
 		asb->s_namelen += 4;
 
-	sb->s_d_op = &adfs_dentry_operations;
+	set_default_d_op(sb, &adfs_dentry_operations);
 	root = adfs_iget(sb, &root_obj);
 	sb->s_root = d_make_root(root);
 	if (!sb->s_root) {

fs/affs/super.c

@@ -500,9 +500,9 @@ got_root:
 		return PTR_ERR(root_inode);
 
 	if (affs_test_opt(AFFS_SB(sb)->s_flags, SF_INTL))
-		sb->s_d_op = &affs_intl_dentry_operations;
+		set_default_d_op(sb, &affs_intl_dentry_operations);
 	else
-		sb->s_d_op = &affs_dentry_operations;
+		set_default_d_op(sb, &affs_dentry_operations);
 
 	sb->s_root = d_make_root(root_inode);
 	if (!sb->s_root) {

fs/afs/super.c

@@ -483,9 +483,9 @@ static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
 		goto error;
 
 	if (as->dyn_root) {
-		sb->s_d_op = &afs_dynroot_dentry_operations;
+		set_default_d_op(sb, &afs_dynroot_dentry_operations);
 	} else {
-		sb->s_d_op = &afs_fs_dentry_operations;
+		set_default_d_op(sb, &afs_fs_dentry_operations);
 		rcu_assign_pointer(as->volume->sb, sb);
 	}
 

fs/autofs/inode.c

@@ -311,7 +311,7 @@ static int autofs_fill_super(struct super_block *s, struct fs_context *fc)
 	s->s_blocksize_bits = 10;
 	s->s_magic = AUTOFS_SUPER_MAGIC;
 	s->s_op = &autofs_sops;
-	s->s_d_op = &autofs_dentry_operations;
+	set_default_d_op(s, &autofs_dentry_operations);
 	s->s_time_gran = 1;
 
 	/*

fs/btrfs/super.c

@@ -959,7 +959,7 @@ static int btrfs_fill_super(struct super_block *sb,
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_magic = BTRFS_SUPER_MAGIC;
 	sb->s_op = &btrfs_super_ops;
-	sb->s_d_op = &btrfs_dentry_operations;
+	set_default_d_op(sb, &btrfs_dentry_operations);
 	sb->s_export_op = &btrfs_export_ops;
 #ifdef CONFIG_FS_VERITY
 	sb->s_vop = &btrfs_verityops;

fs/ceph/super.c

@@ -1219,7 +1219,7 @@ static int ceph_set_super(struct super_block *s, struct fs_context *fc)
 	fsc->max_file_size = 1ULL << 40; /* temp value until we get mdsmap */
 
 	s->s_op = &ceph_super_ops;
-	s->s_d_op = &ceph_dentry_ops;
+	set_default_d_op(s, &ceph_dentry_ops);
 	s->s_export_op = &ceph_export_ops;
 
 	s->s_time_gran = 1;

fs/coda/inode.c

@@ -230,7 +230,7 @@ static int coda_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_blocksize_bits = 12;
 	sb->s_magic = CODA_SUPER_MAGIC;
 	sb->s_op = &coda_super_operations;
-	sb->s_d_op = &coda_dentry_operations;
+	set_default_d_op(sb, &coda_dentry_operations);
 	sb->s_time_gran = 1;
 	sb->s_time_min = S64_MIN;
 	sb->s_time_max = S64_MAX;

fs/configfs/dir.c

@@ -67,7 +67,6 @@ static void configfs_d_iput(struct dentry * dentry,
 
 const struct dentry_operations configfs_dentry_ops = {
 	.d_iput		= configfs_d_iput,
-	.d_delete	= always_delete_dentry,
 };
 
 #ifdef CONFIG_LOCKDEP

fs/configfs/mount.c

@@ -92,7 +92,8 @@ static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	configfs_root_group.cg_item.ci_dentry = root;
 	root->d_fsdata = &configfs_root;
 	sb->s_root = root;
-	sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
+	set_default_d_op(sb, &configfs_dentry_ops); /* the rest get that */
+	sb->s_d_flags |= DCACHE_DONTCACHE;
 	return 0;
 }
 

fs/dcache.c

@@ -1436,7 +1436,7 @@ int d_set_mounted(struct dentry *dentry)
 {
 	struct dentry *p;
 	int ret = -ENOENT;
-	write_seqlock(&rename_lock);
+	read_seqlock_excl(&rename_lock);
 	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
 		/* Need exclusion wrt. d_invalidate() */
 		spin_lock(&p->d_lock);
@@ -1456,7 +1456,7 @@ int d_set_mounted(struct dentry *dentry)
 	}
  	spin_unlock(&dentry->d_lock);
 out:
-	write_sequnlock(&rename_lock);
+	read_sequnlock_excl(&rename_lock);
 	return ret;
 }
 
@@ -1731,14 +1731,14 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	dentry->d_inode = NULL;
 	dentry->d_parent = dentry;
 	dentry->d_sb = sb;
-	dentry->d_op = NULL;
+	dentry->d_op = sb->__s_d_op;
+	dentry->d_flags = sb->s_d_flags;
 	dentry->d_fsdata = NULL;
 	INIT_HLIST_BL_NODE(&dentry->d_hash);
 	INIT_LIST_HEAD(&dentry->d_lru);
 	INIT_HLIST_HEAD(&dentry->d_children);
 	INIT_HLIST_NODE(&dentry->d_u.d_alias);
 	INIT_HLIST_NODE(&dentry->d_sib);
-	d_set_d_op(dentry, dentry->d_sb->s_d_op);
 
 	if (dentry->d_op && dentry->d_op->d_init) {
 		err = dentry->d_op->d_init(dentry);
@@ -1821,8 +1821,9 @@ struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
 	struct dentry *dentry = __d_alloc(sb, name);
 	if (likely(dentry)) {
 		dentry->d_flags |= DCACHE_NORCU;
-		if (!sb->s_d_op)
-			d_set_d_op(dentry, &anon_ops);
+		/* d_op_flags(&anon_ops) is 0 */
+		if (!dentry->d_op)
+			dentry->d_op = &anon_ops;
 	}
 	return dentry;
 }
@@ -1837,35 +1838,50 @@ struct dentry *d_alloc_name(struct dentry *parent, const char *name)
 }
 EXPORT_SYMBOL(d_alloc_name);
 
-void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
-{
-	WARN_ON_ONCE(dentry->d_op);
-	WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH	|
-				DCACHE_OP_COMPARE	|
-				DCACHE_OP_REVALIDATE	|
-				DCACHE_OP_WEAK_REVALIDATE	|
-				DCACHE_OP_DELETE	|
-				DCACHE_OP_REAL));
-	dentry->d_op = op;
-	if (!op)
-		return;
-	if (op->d_hash)
-		dentry->d_flags |= DCACHE_OP_HASH;
-	if (op->d_compare)
-		dentry->d_flags |= DCACHE_OP_COMPARE;
-	if (op->d_revalidate)
-		dentry->d_flags |= DCACHE_OP_REVALIDATE;
-	if (op->d_weak_revalidate)
-		dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
-	if (op->d_delete)
-		dentry->d_flags |= DCACHE_OP_DELETE;
-	if (op->d_prune)
-		dentry->d_flags |= DCACHE_OP_PRUNE;
-	if (op->d_real)
-		dentry->d_flags |= DCACHE_OP_REAL;
+#define DCACHE_OP_FLAGS \
+	(DCACHE_OP_HASH | DCACHE_OP_COMPARE | DCACHE_OP_REVALIDATE | \
+	 DCACHE_OP_WEAK_REVALIDATE | DCACHE_OP_DELETE | DCACHE_OP_PRUNE | \
+	 DCACHE_OP_REAL)
 
+static unsigned int d_op_flags(const struct dentry_operations *op)
+{
+	unsigned int flags = 0;
+	if (op) {
+		if (op->d_hash)
+			flags |= DCACHE_OP_HASH;
+		if (op->d_compare)
+			flags |= DCACHE_OP_COMPARE;
+		if (op->d_revalidate)
+			flags |= DCACHE_OP_REVALIDATE;
+		if (op->d_weak_revalidate)
+			flags |= DCACHE_OP_WEAK_REVALIDATE;
+		if (op->d_delete)
+			flags |= DCACHE_OP_DELETE;
+		if (op->d_prune)
+			flags |= DCACHE_OP_PRUNE;
+		if (op->d_real)
+			flags |= DCACHE_OP_REAL;
+	}
+	return flags;
 }
-EXPORT_SYMBOL(d_set_d_op);
+
+static void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
+{
+	unsigned int flags = d_op_flags(op);
+	WARN_ON_ONCE(dentry->d_op);
+	WARN_ON_ONCE(dentry->d_flags & DCACHE_OP_FLAGS);
+	dentry->d_op = op;
+	if (flags)
+		dentry->d_flags |= flags;
+}
+
+void set_default_d_op(struct super_block *s, const struct dentry_operations *ops)
+{
+	unsigned int flags = d_op_flags(ops);
+	s->__s_d_op = ops;
+	s->s_d_flags = (s->s_d_flags & ~DCACHE_OP_FLAGS) | flags;
+}
+EXPORT_SYMBOL(set_default_d_op);
 
 static unsigned d_flags_for_inode(struct inode *inode)
 {
@@ -2530,13 +2546,19 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 	unsigned int hash = name->hash;
 	struct hlist_bl_head *b = in_lookup_hash(parent, hash);
 	struct hlist_bl_node *node;
-	struct dentry *new = d_alloc(parent, name);
+	struct dentry *new = __d_alloc(parent->d_sb, name);
 	struct dentry *dentry;
 	unsigned seq, r_seq, d_seq;
 
 	if (unlikely(!new))
 		return ERR_PTR(-ENOMEM);
 
+	new->d_flags |= DCACHE_PAR_LOOKUP;
+	spin_lock(&parent->d_lock);
+	new->d_parent = dget_dlock(parent);
+	hlist_add_head(&new->d_sib, &parent->d_children);
+	spin_unlock(&parent->d_lock);
+
 retry:
 	rcu_read_lock();
 	seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
@@ -2620,8 +2642,6 @@ retry:
 		return dentry;
 	}
 	rcu_read_unlock();
-	/* we can't take ->d_lock here; it's OK, though. */
-	new->d_flags |= DCACHE_PAR_LOOKUP;
 	new->d_wait = wq;
 	hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b);
 	hlist_bl_unlock(b);
@@ -2667,7 +2687,8 @@ EXPORT_SYMBOL(__d_lookup_unhash_wake);
 
 /* inode->i_lock held if inode is non-NULL */
 
-static inline void __d_add(struct dentry *dentry, struct inode *inode)
+static inline void __d_add(struct dentry *dentry, struct inode *inode,
+			   const struct dentry_operations *ops)
 {
 	wait_queue_head_t *d_wait;
 	struct inode *dir = NULL;
@@ -2678,6 +2699,8 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
 		n = start_dir_add(dir);
 		d_wait = __d_lookup_unhash(dentry);
 	}
+	if (unlikely(ops))
+		d_set_d_op(dentry, ops);
 	if (inode) {
 		unsigned add_flags = d_flags_for_inode(inode);
 		hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
@@ -2709,7 +2732,7 @@ void d_add(struct dentry *entry, struct inode *inode)
 		security_d_instantiate(entry, inode);
 		spin_lock(&inode->i_lock);
 	}
-	__d_add(entry, inode);
+	__d_add(entry, inode, NULL);
 }
 EXPORT_SYMBOL(d_add);
 
@@ -2961,30 +2984,8 @@ out_err:
 	return ret;
 }
 
-/**
- * d_splice_alias - splice a disconnected dentry into the tree if one exists
- * @inode:  the inode which may have a disconnected dentry
- * @dentry: a negative dentry which we want to point to the inode.
- *
- * If inode is a directory and has an IS_ROOT alias, then d_move that in
- * place of the given dentry and return it, else simply d_add the inode
- * to the dentry and return NULL.
- *
- * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
- * we should error out: directories can't have multiple aliases.
- *
- * This is needed in the lookup routine of any filesystem that is exportable
- * (via knfsd) so that we can build dcache paths to directories effectively.
- *
- * If a dentry was found and moved, then it is returned.  Otherwise NULL
- * is returned.  This matches the expected return value of ->lookup.
- *
- * Cluster filesystems may call this function with a negative, hashed dentry.
- * In that case, we know that the inode will be a regular file, and also this
- * will only occur during atomic_open. So we need to check for the dentry
- * being already hashed only in the final case.
- */
-struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
+struct dentry *d_splice_alias_ops(struct inode *inode, struct dentry *dentry,
+				  const struct dentry_operations *ops)
 {
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
@@ -3030,9 +3031,37 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 		}
 	}
 out:
-	__d_add(dentry, inode);
+	__d_add(dentry, inode, ops);
 	return NULL;
 }
+
+/**
+ * d_splice_alias - splice a disconnected dentry into the tree if one exists
+ * @inode:  the inode which may have a disconnected dentry
+ * @dentry: a negative dentry which we want to point to the inode.
+ *
+ * If inode is a directory and has an IS_ROOT alias, then d_move that in
+ * place of the given dentry and return it, else simply d_add the inode
+ * to the dentry and return NULL.
+ *
+ * If a non-IS_ROOT directory is found, the filesystem is corrupt, and
+ * we should error out: directories can't have multiple aliases.
+ *
+ * This is needed in the lookup routine of any filesystem that is exportable
+ * (via knfsd) so that we can build dcache paths to directories effectively.
+ *
+ * If a dentry was found and moved, then it is returned.  Otherwise NULL
+ * is returned.  This matches the expected return value of ->lookup.
+ *
+ * Cluster filesystems may call this function with a negative, hashed dentry.
+ * In that case, we know that the inode will be a regular file, and also this
+ * will only occur during atomic_open. So we need to check for the dentry
+ * being already hashed only in the final case.
+ */
+struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
+{
+	return d_splice_alias_ops(inode, dentry, NULL);
+}
 EXPORT_SYMBOL(d_splice_alias);
 
 /*

fs/debugfs/inode.c

@@ -258,7 +258,6 @@ static struct vfsmount *debugfs_automount(struct path *path)
 }
 
 static const struct dentry_operations debugfs_dops = {
-	.d_delete = always_delete_dentry,
 	.d_release = debugfs_release_dentry,
 	.d_automount = debugfs_automount,
 };
@@ -273,7 +272,8 @@ static int debugfs_fill_super(struct super_block *sb, struct fs_context *fc)
 		return err;
 
 	sb->s_op = &debugfs_super_operations;
-	sb->s_d_op = &debugfs_dops;
+	set_default_d_op(sb, &debugfs_dops);
+	sb->s_d_flags |= DCACHE_DONTCACHE;
 
 	debugfs_apply_options(sb);
 

fs/devpts/inode.c

@@ -381,7 +381,7 @@ static int devpts_fill_super(struct super_block *s, struct fs_context *fc)
 	s->s_blocksize_bits = 10;
 	s->s_magic = DEVPTS_SUPER_MAGIC;
 	s->s_op = &devpts_sops;
-	s->s_d_op = &simple_dentry_operations;
+	s->s_d_flags = DCACHE_DONTCACHE;
 	s->s_time_gran = 1;
 	fsi->sb = s;
 

fs/ecryptfs/main.c

@@ -471,7 +471,7 @@ static int ecryptfs_get_tree(struct fs_context *fc)
 	sbi = NULL;
 	s->s_op = &ecryptfs_sops;
 	s->s_xattr = ecryptfs_xattr_handlers;
-	s->s_d_op = &ecryptfs_dops;
+	set_default_d_op(s, &ecryptfs_dops);
 
 	err = "Reading sb failed";
 	rc = kern_path(fc->source, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);

fs/efivarfs/super.c

@@ -183,7 +183,6 @@ static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
 static const struct dentry_operations efivarfs_d_ops = {
 	.d_compare = efivarfs_d_compare,
 	.d_hash = efivarfs_d_hash,
-	.d_delete = always_delete_dentry,
 };
 
 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
@@ -350,7 +349,8 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_blocksize_bits    = PAGE_SHIFT;
 	sb->s_magic             = EFIVARFS_MAGIC;
 	sb->s_op                = &efivarfs_ops;
-	sb->s_d_op		= &efivarfs_d_ops;
+	set_default_d_op(sb, &efivarfs_d_ops);
+	sb->s_d_flags |= DCACHE_DONTCACHE;
 	sb->s_time_gran         = 1;
 
 	if (!efivar_supports_writes())

fs/exfat/super.c

@@ -667,9 +667,9 @@ static int exfat_fill_super(struct super_block *sb, struct fs_context *fc)
 	}
 
 	if (sbi->options.utf8)
-		sb->s_d_op = &exfat_utf8_dentry_ops;
+		set_default_d_op(sb, &exfat_utf8_dentry_ops);
 	else
-		sb->s_d_op = &exfat_dentry_ops;
+		set_default_d_op(sb, &exfat_dentry_ops);
 
 	root_inode = new_inode(sb);
 	if (!root_inode) {

fs/fat/namei_msdos.c

@@ -646,7 +646,7 @@ static const struct inode_operations msdos_dir_inode_operations = {
 static void setup(struct super_block *sb)
 {
 	MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
-	sb->s_d_op = &msdos_dentry_operations;
+	set_default_d_op(sb, &msdos_dentry_operations);
 	sb->s_flags |= SB_NOATIME;
 }
 

fs/fat/namei_vfat.c

@@ -1187,9 +1187,9 @@ static void setup(struct super_block *sb)
 {
 	MSDOS_SB(sb)->dir_ops = &vfat_dir_inode_operations;
 	if (MSDOS_SB(sb)->options.name_check != 's')
-		sb->s_d_op = &vfat_ci_dentry_ops;
+		set_default_d_op(sb, &vfat_ci_dentry_ops);
 	else
-		sb->s_d_op = &vfat_dentry_ops;
+		set_default_d_op(sb, &vfat_dentry_ops);
 }
 
 static int vfat_fill_super(struct super_block *sb, struct fs_context *fc)