bfs: fix bitmap size argument to find_first_zero_bit()

The usage of find_first_zero_bit() in bfs_create() is wrong for two
reasons.

The bitmap size argument to find_first_zero_bit() is info->si_lasti but
the correct bitmap size is info->si_lasti + 1 as info->si_lasti is the
last valid index in info->si_imap bitmap.

Another problem is that it is impossible to detect that info->si_imap
bitmap is full because there is an off-by-one bug in the return value
check for find_first_zero_bit().  If no zero bits exist in info->si_imap,
find_first_zero_bit() returns info->si_lasti.  But the check can't catch
it due to the off-by-one.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: "Tigran A. Aivazian" <tigran@aivazian.fsnet.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/bfs/dir.c

@@ -97,7 +97,7 @@ static int bfs_create(struct inode *dir, struct dentry *dentry, int mode,
 	if (!inode)
 		return -ENOSPC;
 	mutex_lock(&info->bfs_lock);
-	ino = find_first_zero_bit(info->si_imap, info->si_lasti);
+	ino = find_first_zero_bit(info->si_imap, info->si_lasti + 1);
 	if (ino > info->si_lasti) {
 		mutex_unlock(&info->bfs_lock);
 		iput(inode);