reiserfs: shrink superblock if no xattrs

This makes in-core superblock fit into one cacheline here.

Before:
    struct dentry *            xattr_root;           /*   124     4 */
    /* --- cacheline 1 boundary (128 bytes) --- */
    struct rw_semaphore        xattr_dir_sem;        /*   128    12 */
    int                        j_errno;              /*   140     4 */
    }; /* size: 144, cachelines: 2 */
       /* sum members: 142, holes: 1, sum holes: 2 */
       /* last cacheline: 16 bytes */

After:
    int                        j_errno;              /*   124     4 */
    /* --- cacheline 1 boundary (128 bytes) --- */
    }; /* size: 128, cachelines: 1 */
       /* sum members: 126, holes: 1, sum holes: 2 */

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: <reiserfs-dev@namesys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/reiserfs_fs_sb.h b/include/linux/reiserfs_fs_sb.h
index 3a28742..1e5488e 100644
--- a/include/linux/reiserfs_fs_sb.h
+++ b/include/linux/reiserfs_fs_sb.h
@@ -401,9 +401,10 @@
 	int reserved_blocks;	/* amount of blocks reserved for further allocations */
 	spinlock_t bitmap_lock;	/* this lock on now only used to protect reserved_blocks variable */
 	struct dentry *priv_root;	/* root of /.reiserfs_priv */
+#ifdef CONFIG_REISERFS_FS_XATTR
 	struct dentry *xattr_root;	/* root of /.reiserfs_priv/.xa */
 	struct rw_semaphore xattr_dir_sem;
-
+#endif
 	int j_errno;
 #ifdef CONFIG_QUOTA
 	char *s_qf_names[MAXQUOTAS];