hostfs: store inode in dentry after mkdir if possible.

After handling a mkdir, get the inode for the name and use
d_splice_alias() to store the correct dentry in the dcache.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20250227013949.536172-3-neilb@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/hostfs/hostfs_kern.c

@@ -682,14 +682,22 @@ static int hostfs_symlink(struct mnt_idmap *idmap, struct inode *ino,
 static struct dentry *hostfs_mkdir(struct mnt_idmap *idmap, struct inode *ino,
 				   struct dentry *dentry, umode_t mode)
 {
+	struct inode *inode;
 	char *file;
 	int err;
 
 	if ((file = dentry_name(dentry)) == NULL)
 		return ERR_PTR(-ENOMEM);
 	err = do_mkdir(file, mode);
+	if (err) {
+		dentry = ERR_PTR(err);
+	} else {
+		inode = hostfs_iget(dentry->d_sb, file);
+		d_drop(dentry);
+		dentry = d_splice_alias(inode, dentry);
+	}
 	__putname(file);
-	return ERR_PTR(err);
+	return dentry;
 }
 
 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)