reiserfs: fix inode mutex - reiserfs lock misordering

reiserfs_unpack() locks the inode mutex with reiserfs_mutex_lock_safe()
to protect against reiserfs lock dependency.  However this protection
requires to have the reiserfs lock to be locked.

This is the case if reiserfs_unpack() is called by reiserfs_ioctl but
not from reiserfs_quota_on() when it tries to unpack tails of quota
files.

Fix the ordering of the two locks in reiserfs_unpack() to fix this
issue.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reported-by: Markus Gapp <markus.gapp@gmx.net>
Reported-by: Jan Kara <jack@suse.cz>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: <stable@kernel.org>		[2.6.36.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/ioctl.c

@@ -183,12 +183,11 @@ int reiserfs_unpack(struct inode *inode, struct file *filp)
 		return 0;
 	}
 
-	/* we need to make sure nobody is changing the file size beneath
-	 ** us
-	 */
-	reiserfs_mutex_lock_safe(&inode->i_mutex, inode->i_sb);
 	depth = reiserfs_write_lock_once(inode->i_sb);
 
+	/* we need to make sure nobody is changing the file size beneath us */
+	reiserfs_mutex_lock_safe(&inode->i_mutex, inode->i_sb);
+
 	write_from = inode->i_size & (blocksize - 1);
 	/* if we are on a block boundary, we are already unpacked.  */
 	if (write_from == 0) {