[XFS] fix instant oops with tracing enabled

We can only read inode->i_count if the inode is actually there and not a
NULL pointer. This was introduced in one of the recent sync patches.

SGI-PV: 988255

SGI-Modid: xfs-linux-melb:xfs-kern:32315a
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

fs/xfs/linux-2.6/xfs_vnode.c

@@ -92,7 +92,7 @@ static inline int xfs_icount(struct xfs_inode *ip)
 {
 	struct inode *inode = VFS_I(ip);
 
-	if (!inode)
+	if (inode)
 		return atomic_read(&inode->i_count);
 	return -1;
 }