nfs: change mkdir inode_operation to return alternate dentry if needed.

mkdir now allows a different dentry to be returned which is sometimes
relevant for nfs.

This patch changes the nfs_rpc_ops mkdir op to return a dentry, and
passes that back to the caller.

The mkdir nfs_rpc_op will return NULL if the original dentry should be
used.  This matches the mkdir inode_operation.

nfs4_do_create() is duplicated to nfs4_do_mkdir() which is changed to
handle the specifics of directories.  Consequently the current special
handling for directories is removed from nfs4_do_create()

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-6-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/nfs/dir.c

@@ -2426,7 +2426,7 @@ struct dentry *nfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 			 struct dentry *dentry, umode_t mode)
 {
 	struct iattr attr;
-	int error;
+	struct dentry *ret;
 
 	dfprintk(VFS, "NFS: mkdir(%s/%lu), %pd\n",
 			dir->i_sb->s_id, dir->i_ino, dentry);
@@ -2435,14 +2435,9 @@ struct dentry *nfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	attr.ia_mode = mode | S_IFDIR;
 
 	trace_nfs_mkdir_enter(dir, dentry);
-	error = NFS_PROTO(dir)->mkdir(dir, dentry, &attr);
-	trace_nfs_mkdir_exit(dir, dentry, error);
-	if (error != 0)
-		goto out_err;
-	return NULL;
-out_err:
-	d_drop(dentry);
-	return ERR_PTR(error);
+	ret = NFS_PROTO(dir)->mkdir(dir, dentry, &attr);
+	trace_nfs_mkdir_exit(dir, dentry, PTR_ERR_OR_ZERO(ret));
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nfs_mkdir);
 

fs/nfs/nfs3proc.c

@@ -578,13 +578,13 @@ nfs3_proc_symlink(struct inode *dir, struct dentry *dentry, struct folio *folio,
 	return status;
 }
 
-static int
+static struct dentry *
 nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 {
 	struct posix_acl *default_acl, *acl;
 	struct nfs3_createdata *data;
-	struct dentry *d_alias;
-	int status = -ENOMEM;
+	struct dentry *ret = ERR_PTR(-ENOMEM);
+	int status;
 
 	dprintk("NFS call  mkdir %pd\n", dentry);
 
@@ -592,8 +592,9 @@ nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 	if (data == NULL)
 		goto out;
 
-	status = posix_acl_create(dir, &sattr->ia_mode, &default_acl, &acl);
-	if (status)
+	ret = ERR_PTR(posix_acl_create(dir, &sattr->ia_mode,
+				       &default_acl, &acl));
+	if (IS_ERR(ret))
 		goto out;
 
 	data->msg.rpc_proc = &nfs3_procedures[NFS3PROC_MKDIR];
@@ -602,25 +603,27 @@ nfs3_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 	data->arg.mkdir.len = dentry->d_name.len;
 	data->arg.mkdir.sattr = sattr;
 
-	d_alias = nfs3_do_create(dir, dentry, data);
-	status = PTR_ERR_OR_ZERO(d_alias);
+	ret = nfs3_do_create(dir, dentry, data);
 
-	if (status != 0)
+	if (IS_ERR(ret))
 		goto out_release_acls;
 
-	if (d_alias)
-		dentry = d_alias;
+	if (ret)
+		dentry = ret;
 
 	status = nfs3_proc_setacls(d_inode(dentry), acl, default_acl);
+	if (status) {
+		dput(ret);
+		ret = ERR_PTR(status);
+	}
 
-	dput(d_alias);
 out_release_acls:
 	posix_acl_release(acl);
 	posix_acl_release(default_acl);
 out:
 	nfs3_free_createdata(data);
-	dprintk("NFS reply mkdir: %d\n", status);
-	return status;
+	dprintk("NFS reply mkdir: %d\n", PTR_ERR_OR_ZERO(ret));
+	return ret;
 }
 
 static int

fs/nfs/nfs4proc.c

@@ -5133,9 +5133,6 @@ static int nfs4_do_create(struct inode *dir, struct dentry *dentry, struct nfs4_
 				    &data->arg.seq_args, &data->res.seq_res, 1);
 	if (status == 0) {
 		spin_lock(&dir->i_lock);
-		/* Creating a directory bumps nlink in the parent */
-		if (data->arg.ftype == NF4DIR)
-			nfs4_inc_nlink_locked(dir);
 		nfs4_update_changeattr_locked(dir, &data->res.dir_cinfo,
 					      data->res.fattr->time_start,
 					      NFS_INO_INVALID_DATA);
@@ -5145,6 +5142,25 @@ static int nfs4_do_create(struct inode *dir, struct dentry *dentry, struct nfs4_
 	return status;
 }
 
+static struct dentry *nfs4_do_mkdir(struct inode *dir, struct dentry *dentry,
+				    struct nfs4_createdata *data)
+{
+	int status = nfs4_call_sync(NFS_SERVER(dir)->client, NFS_SERVER(dir), &data->msg,
+				    &data->arg.seq_args, &data->res.seq_res, 1);
+
+	if (status)
+		return ERR_PTR(status);
+
+	spin_lock(&dir->i_lock);
+	/* Creating a directory bumps nlink in the parent */
+	nfs4_inc_nlink_locked(dir);
+	nfs4_update_changeattr_locked(dir, &data->res.dir_cinfo,
+				      data->res.fattr->time_start,
+				      NFS_INO_INVALID_DATA);
+	spin_unlock(&dir->i_lock);
+	return nfs_add_or_obtain(dentry, data->res.fh, data->res.fattr);
+}
+
 static void nfs4_free_createdata(struct nfs4_createdata *data)
 {
 	nfs4_label_free(data->fattr.label);
@@ -5201,25 +5217,26 @@ static int nfs4_proc_symlink(struct inode *dir, struct dentry *dentry,
 	return err;
 }
 
-static int _nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
-		struct iattr *sattr, struct nfs4_label *label)
+static struct dentry *_nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
+				       struct iattr *sattr,
+				       struct nfs4_label *label)
 {
 	struct nfs4_createdata *data;
-	int status = -ENOMEM;
+	struct dentry *ret = ERR_PTR(-ENOMEM);
 
 	data = nfs4_alloc_createdata(dir, &dentry->d_name, sattr, NF4DIR);
 	if (data == NULL)
 		goto out;
 
 	data->arg.label = label;
-	status = nfs4_do_create(dir, dentry, data);
+	ret = nfs4_do_mkdir(dir, dentry, data);
 
 	nfs4_free_createdata(data);
 out:
-	return status;
+	return ret;
 }
 
-static int nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
+static struct dentry *nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
 				      struct iattr *sattr)
 {
 	struct nfs_server *server = NFS_SERVER(dir);
@@ -5227,6 +5244,7 @@ static int nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
 		.interruptible = true,
 	};
 	struct nfs4_label l, *label;
+	struct dentry *alias;
 	int err;
 
 	label = nfs4_label_init_security(dir, dentry, sattr, &l);
@@ -5234,14 +5252,15 @@ static int nfs4_proc_mkdir(struct inode *dir, struct dentry *dentry,
 	if (!(server->attr_bitmask[2] & FATTR4_WORD2_MODE_UMASK))
 		sattr->ia_mode &= ~current_umask();
 	do {
-		err = _nfs4_proc_mkdir(dir, dentry, sattr, label);
+		alias = _nfs4_proc_mkdir(dir, dentry, sattr, label);
+		err = PTR_ERR_OR_ZERO(alias);
 		trace_nfs4_mkdir(dir, &dentry->d_name, err);
 		err = nfs4_handle_exception(NFS_SERVER(dir), err,
 				&exception);
 	} while (exception.retry);
 	nfs4_label_release_security(label);
 
-	return err;
+	return alias;
 }
 
 static int _nfs4_proc_readdir(struct nfs_readdir_arg *nr_arg,

fs/nfs/proc.c

@@ -446,13 +446,14 @@ nfs_proc_symlink(struct inode *dir, struct dentry *dentry, struct folio *folio,
 	return status;
 }
 
-static int
+static struct dentry *
 nfs_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 {
 	struct nfs_createdata *data;
 	struct rpc_message msg = {
 		.rpc_proc	= &nfs_procedures[NFSPROC_MKDIR],
 	};
+	struct dentry *alias = NULL;
 	int status = -ENOMEM;
 
 	dprintk("NFS call  mkdir %pd\n", dentry);
@@ -464,12 +465,15 @@ nfs_proc_mkdir(struct inode *dir, struct dentry *dentry, struct iattr *sattr)
 
 	status = rpc_call_sync(NFS_CLIENT(dir), &msg, 0);
 	nfs_mark_for_revalidate(dir);
-	if (status == 0)
-		status = nfs_instantiate(dentry, data->res.fh, data->res.fattr);
+	if (status == 0) {
+		alias = nfs_add_or_obtain(dentry, data->res.fh, data->res.fattr);
+		status = PTR_ERR_OR_ZERO(alias);
+	} else
+		alias = ERR_PTR(status);
 	nfs_free_createdata(data);
 out:
 	dprintk("NFS reply mkdir: %d\n", status);
-	return status;
+	return alias;
 }
 
 static int

include/linux/nfs_xdr.h

@@ -1802,7 +1802,7 @@ struct nfs_rpc_ops {
 	int	(*link)    (struct inode *, struct inode *, const struct qstr *);
 	int	(*symlink) (struct inode *, struct dentry *, struct folio *,
 			    unsigned int, struct iattr *);
-	int	(*mkdir)   (struct inode *, struct dentry *, struct iattr *);
+	struct dentry *(*mkdir)   (struct inode *, struct dentry *, struct iattr *);
 	int	(*rmdir)   (struct inode *, const struct qstr *);
 	int	(*readdir) (struct nfs_readdir_arg *, struct nfs_readdir_res *);
 	int	(*mknod)   (struct inode *, struct dentry *, struct iattr *,