init_wait_bit_key() initializes the key field in an already 
allocated wait bit structure, useful for async wait bit support.
Also separate out the wait bit test to a common routine which
can be used by different kinds of wakeup callbacks.

Signed-off-by: Suparna Bhattacharya <suparna@in.ibm.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
---

 linux-2.6.20-rc3-root/include/linux/wait.h |   26 ++++++++++++++++++++++++++
 linux-2.6.20-rc3-root/kernel/wait.c        |   11 ++---------
 2 files changed, 28 insertions(+), 9 deletions(-)

diff -puN include/linux/wait.h~init-wait-bit-key include/linux/wait.h
--- linux-2.6.20-rc3/include/linux/wait.h~init-wait-bit-key	2007-01-10 09:40:19.000000000 +0530
+++ linux-2.6.20-rc3-root/include/linux/wait.h	2007-01-10 09:40:19.000000000 +0530
@@ -108,6 +108,17 @@ static inline int waitqueue_active(wait_
 	return !list_empty(&q->task_list);
 }
 
+static inline int test_wait_bit_key(wait_queue_t *wait,
+				struct wait_bit_key *key)
+{
+	struct wait_bit_queue *wait_bit
+		= container_of(wait, struct wait_bit_queue, wait);
+
+	return (wait_bit->key.flags == key->flags &&
+			wait_bit->key.bit_nr == key->bit_nr &&
+			!test_bit(key->bit_nr, key->flags));
+}
+
 /*
  * Used to distinguish between sync and async io wait context:
  * sync i/o typically specifies a NULL wait queue entry or a wait
@@ -416,6 +427,21 @@ int wake_bit_function(wait_queue_t *wait
 		INIT_LIST_HEAD(&(wait)->task_list);			\
 	} while (0)
 
+static inline void init_wait_bit_key(struct wait_bit_queue *waitbit,
+					void *word, int bit)
+{
+	waitbit->key.flags = word;
+	waitbit->key.bit_nr = bit;
+}
+
+static inline void init_wait_bit_task(struct wait_bit_queue *waitbit,
+					struct task_struct *tsk)
+{
+	waitbit->wait.private = tsk;
+	waitbit->wait.func = wake_bit_function;
+	INIT_LIST_HEAD(&waitbit->wait.task_list);
+}
+
 /**
  * wait_on_bit - wait for a bit to be cleared
  * @word: the word being waited on, a kernel virtual address
diff -puN kernel/wait.c~init-wait-bit-key kernel/wait.c
--- linux-2.6.20-rc3/kernel/wait.c~init-wait-bit-key	2007-01-10 09:40:19.000000000 +0530
+++ linux-2.6.20-rc3-root/kernel/wait.c	2007-01-10 09:40:19.000000000 +0530
@@ -139,16 +139,9 @@ EXPORT_SYMBOL(autoremove_wake_function);
 
 int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
 {
-	struct wait_bit_key *key = arg;
-	struct wait_bit_queue *wait_bit
-		= container_of(wait, struct wait_bit_queue, wait);
-
-	if (wait_bit->key.flags != key->flags ||
-			wait_bit->key.bit_nr != key->bit_nr ||
-			test_bit(key->bit_nr, key->flags))
+	if (!test_wait_bit_key(wait, arg))
 		return 0;
-	else
-		return autoremove_wake_function(wait, mode, sync, key);
+	return autoremove_wake_function(wait, mode, sync, arg);
 }
 EXPORT_SYMBOL(wake_bit_function);
 
_