nilfs2: use unlocked_ioctl

Pekka Enberg suggested converting ->ioctl operations to use
->unlocked_ioctl to avoid BKL.

The conversion was verified to be safe, so I will take it on this
occasion.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/nilfs2/nilfs.h

@@ -242,7 +242,7 @@ extern void nilfs_set_link(struct inode *, struct nilfs_dir_entry *,
 extern int nilfs_sync_file(struct file *, struct dentry *, int);
 
 /* ioctl.c */
-int nilfs_ioctl(struct inode *, struct file *, unsigned int, unsigned long);
+long nilfs_ioctl(struct file *, unsigned int, unsigned long);
 int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *, void __user *);
 
 /* inode.c */