Checking RT patch for linux-2.6.23, I found,
- lock_list_first_entry() and lock_list_next_entry() were changed from
  'static inline'-ed function to 'global un-inlined'-ed function, and
  moved from lock_list.h to lock_list.c. They are not exported to kernel
  modules.
- lock_list_splice_init() was newly introduced, and it is not exported
  either.

Finally, you should,,,
- link aufs statically
- or, ask Ingo Molar to export them.


Index: fs/aufs/branch.c
===================================================================
RCS file: /cvsroot/aufs/aufs/fs/aufs/branch.c,v
retrieving revision 1.67
diff -u -p -r1.67 branch.c
--- fs/aufs/branch.c	5 Nov 2007 01:36:26 -0000	1.67
+++ fs/aufs/branch.c	14 Nov 2007 17:16:49 -0000
@@ -852,6 +852,7 @@ int br_mod(struct super_block *sb, struc
 		if (!br_writable(mod->perm)) {
 			/* rw --> ro, file might be mmapped */
 			struct file *file, *hf;
+			int idx;
 
 #if 1 // test here
 			DiMustNoWaiters(root);
@@ -863,7 +864,8 @@ int br_mod(struct super_block *sb, struc
 			 * since BKL (and sbinfo) is locked
 			 */
 			AuDebugOn(!kernel_locked());
-			list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
+			idx = au_rt_s_files_lock(sb);
+			au_rt_s_files_loop(file, sb) {
 				LKTRTrace("%.*s\n", AuDLNPair(file->f_dentry));
 				if (unlikely(!au_test_aufs_file(file)))
 					continue;
@@ -885,6 +887,7 @@ int br_mod(struct super_block *sb, struc
 				FiMustNoWaiters(file);
 				fi_read_unlock(file);
 			}
+			au_rt_s_files_unlock(sb, idx);
 
 			/* aufs_write_lock() calls ..._child() */
 			di_write_lock_child(root);
Index: fs/aufs/debug.c
===================================================================
RCS file: /cvsroot/aufs/aufs/fs/aufs/debug.c,v
retrieving revision 1.43
diff -u -p -r1.43 debug.c
--- fs/aufs/debug.c	12 Nov 2007 01:43:10 -0000	1.43
+++ fs/aufs/debug.c	14 Nov 2007 17:16:49 -0000
@@ -112,7 +112,7 @@ static int do_pri_inode(aufs_bindex_t bi
 	     ntfy,
 	     i_size_read(inode), (u64)inode->i_blocks,
 	     timespec_to_ns(&inode->i_ctime) & 0x0ffff,
-	     inode->i_mapping ? inode->i_mapping->nrpages : 0,
+	     inode->i_mapping ? au_mapping_nrpages(inode->i_mapping) : 0,
 	     inode->i_state, inode->i_flags, inode->i_generation,
 	     l ? ", wh " : "", l, n);
 	return 0;
Index: fs/aufs/misc.h
===================================================================
RCS file: /cvsroot/aufs/aufs/fs/aufs/misc.h,v
retrieving revision 1.38
diff -u -p -r1.38 misc.h
--- fs/aufs/misc.h	12 Nov 2007 01:40:06 -0000	1.38
+++ fs/aufs/misc.h	14 Nov 2007 17:16:49 -0000
@@ -29,6 +29,142 @@
 #include <linux/version.h>
 #include <linux/aufs_type.h>
 
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * support for RT patch (testing).
+ * it uses 'standard compat_rw_semaphore' instead of 'realtime rw_semaphore.'
+ * sigh, wrapper for wrapper...
+ */
+
+#ifndef CONFIG_PREEMPT_RT
+
+#define au_rw_semaphore		rw_semaphore
+#define au_init_rwsem		init_rwsem
+#define au_down_read		down_read
+#define au_down_read_nested	down_read_nested
+#define au_down_read_trylock	down_read_trylock
+#define au_up_read		up_read
+#define au_downgrade_write	downgrade_write
+#define au_down_write		down_write
+#define au_down_write_nested	down_write_nested
+#define au_down_write_trylock	down_write_trylock
+#define au_up_write		up_write
+
+static inline int au_rt_s_files_lock(struct super_block *sb)
+{
+	/* nothing */
+	return 0;
+}
+
+static inline void au_rt_s_files_unlock(struct super_block *sb, int idx)
+{
+	/* nothing */
+}
+
+#define au_rt_s_files_loop(pos, sb) \
+	list_for_each_entry(pos, &(sb)->s_files, f_u.fu_list)
+#define au_rt_s_files_loop_break(pos)	do {} while (0)
+
+static inline unsigned long au_mapping_nrpages(struct address_space *mapping)
+{
+	return mapping->nrpages;
+}
+
+#else /* CONFIG_PREEMPT_RT */
+
+#define au_rw_semaphore		compat_rw_semaphore
+#define au_init_rwsem		compat_init_rwsem
+#define au_down_read		compat_down_read
+#define au_down_read_nested	compat_down_read_nested
+#define au_down_read_trylock	compat_down_read_trylock
+#define au_up_read		compat_up_read
+#define au_downgrade_write	compat_downgrade_write
+#define au_down_write		compat_down_write
+#define au_down_write_nested	compat_down_write_nested
+#define au_down_write_trylock	compat_down_write_trylock
+#define au_up_write		compat_up_write
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 23)
+
+static inline int au_rt_s_files_lock(struct super_block *sb)
+{
+	int idx;
+	idx = qrcu_read_lock(&sb->s_qrcu);
+	percpu_list_fold(&sb->s_files);
+	return idx;
+}
+
+static inline void au_rt_s_files_unlock(struct super_block *sb, int idx)
+{
+	qrcu_read_unlock(&sb->s_qrcu, idx);
+}
+
+#define au_rt_s_files_loop(pos, sb) \
+	lock_list_for_each_entry(pos, percpu_list_head(&(sb)->s_files), \
+				 f_u.fu_llist)
+
+#define au_rt_s_files_loop_break(pos) \
+	lock_list_for_each_entry_stop(pos, f_u.fu_llist);
+
+static inline unsigned long au_mapping_nrpages(struct address_space *mapping)
+{
+	return mapping_nrpages(mapping);
+}
+
+#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 20)
+
+static inline int au_rt_s_files_lock(struct super_block *sb)
+{
+	//barrier_lock(&sb->s_barrier);
+	filevec_add_drain_all();
+	return 0;
+}
+
+static inline void au_rt_s_files_unlock(struct super_block *sb, int idx)
+{
+	//barrier_unlock(&sb->s_barrier);
+}
+
+#define au_rt_s_files_loop(pos, sb) \
+	lock_list_for_each_entry(pos, &(sb)->s_files, f_u.fu_llist)
+
+#define au_rt_s_files_loop_break(pos) \
+	lock_list_for_each_entry_stop(pos, f_u.fu_llist);
+
+static inline unsigned long au_mapping_nrpages(struct address_space *mapping)
+{
+	return mapping->nrpages;
+}
+
+#else
+
+static inline int au_rt_s_files_lock(struct super_block *sb)
+{
+	/* nothing */
+	return 0;
+}
+
+static inline void au_rt_s_files_unlock(struct super_block *sb, int idx)
+{
+	/* nothing */
+}
+
+#define au_rt_s_files_loop(pos, sb) \
+	list_for_each_entry(pos, &(sb)->s_files, f_u.fu_list)
+#define au_rt_s_files_loop_break(pos)	do {} while (0)
+
+static inline unsigned long au_mapping_nrpages(struct address_space *mapping)
+{
+	return mapping->nrpages;
+}
+
+#endif /* LINUX_VERSION_CODE */
+#endif /* CONFIG_PREEMPT_RT */
+
+/* ---------------------------------------------------------------------- */
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 18)
 #define I_MUTEX_QUOTA			0
 #define lockdep_off()			do {} while (0)
@@ -48,7 +184,7 @@ typedef unsigned int au_gen_t;
 /* ---------------------------------------------------------------------- */
 
 struct aufs_rwsem {
-	struct rw_semaphore	rwsem;
+	struct au_rw_semaphore	rwsem;
 #ifdef CONFIG_AUFS_DEBUG
 	atomic_t		rcnt;
 #endif
@@ -71,64 +207,64 @@ struct aufs_rwsem {
 static inline void rw_init_nolock(struct aufs_rwsem *rw)
 {
 	DbgRcntInit(rw);
-	init_rwsem(&rw->rwsem);
+	au_init_rwsem(&rw->rwsem);
 }
 
 static inline void rw_init_wlock(struct aufs_rwsem *rw)
 {
 	rw_init_nolock(rw);
-	down_write(&rw->rwsem);
+	au_down_write(&rw->rwsem);
 }
 
 static inline void rw_init_wlock_nested(struct aufs_rwsem *rw, unsigned int lsc)
 {
 	rw_init_nolock(rw);
-	down_write_nested(&rw->rwsem, lsc);
+	au_down_write_nested(&rw->rwsem, lsc);
 }
 
 static inline void rw_read_lock(struct aufs_rwsem *rw)
 {
-	down_read(&rw->rwsem);
+	au_down_read(&rw->rwsem);
 	DbgRcntInc(rw);
 }
 
 static inline void rw_read_lock_nested(struct aufs_rwsem *rw, unsigned int lsc)
 {
-	down_read_nested(&rw->rwsem, lsc);
+	au_down_read_nested(&rw->rwsem, lsc);
 	DbgRcntInc(rw);
 }
 
 static inline void rw_read_unlock(struct aufs_rwsem *rw)
 {
 	DbgRcntDec(rw);
-	up_read(&rw->rwsem);
+	au_up_read(&rw->rwsem);
 }
 
 static inline void rw_dgrade_lock(struct aufs_rwsem *rw)
 {
 	DbgRcntInc(rw);
-	downgrade_write(&rw->rwsem);
+	au_downgrade_write(&rw->rwsem);
 }
 
 static inline void rw_write_lock(struct aufs_rwsem *rw)
 {
-	down_write(&rw->rwsem);
+	au_down_write(&rw->rwsem);
 }
 
 static inline void rw_write_lock_nested(struct aufs_rwsem *rw, unsigned int lsc)
 {
-	down_write_nested(&rw->rwsem, lsc);
+	au_down_write_nested(&rw->rwsem, lsc);
 }
 
 static inline void rw_write_unlock(struct aufs_rwsem *rw)
 {
-	up_write(&rw->rwsem);
+	au_up_write(&rw->rwsem);
 }
 
 /* why is not _nested version defined */
 static inline int rw_read_trylock(struct aufs_rwsem *rw)
 {
-	int ret = down_read_trylock(&rw->rwsem);
+	int ret = au_down_read_trylock(&rw->rwsem);
 	if (ret)
 		DbgRcntInc(rw);
 	return ret;
@@ -136,7 +272,7 @@ static inline int rw_read_trylock(struct
 
 static inline int rw_write_trylock(struct aufs_rwsem *rw)
 {
-	return down_write_trylock(&rw->rwsem);
+	return au_down_write_trylock(&rw->rwsem);
 }
 
 #undef DbgRcntInit
@@ -145,7 +281,7 @@ static inline int rw_write_trylock(struc
 
 /* to debug easier, do not make them inlined functions */
 #define RwMustNoWaiters(rw)	AuDebugOn(!list_empty(&(rw)->rwsem.wait_list))
-#define RwMustAnyLock(rw)	AuDebugOn(down_write_trylock(&(rw)->rwsem))
+#define RwMustAnyLock(rw)	AuDebugOn(au_down_write_trylock(&(rw)->rwsem))
 #ifdef CONFIG_AUFS_DEBUG
 #define RwMustReadLock(rw) do { \
 	RwMustAnyLock(rw); \