[4/4] eliminate inode waitqueue hashtable

[William Lee Irwin III <wli@holomorphy.com>]

On Sat, Aug 28, 2004 at 02:23:37AM -0700, William Lee Irwin III wrote:
> Eliminate the bh waitqueue hashtable using bit_waitqueue() via
> wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
> with a bit.

Eliminate the inode waitqueue hashtable using bit_waitqueue() via
wait_on_bit() and wake_up_bit() to locate the waitqueue head associated
with a bit.

Index: mm1-2.6.9-rc1/fs/inode.c
===================================================================
--- mm1-2.6.9-rc1.orig/fs/inode.c	2004-08-26 15:04:02.000000000 -0700
+++ mm1-2.6.9-rc1/fs/inode.c	2004-08-27 22:15:43.602377440 -0700
@@ -1257,37 +1257,17 @@
 
 #endif
 
-/*
- * Hashed waitqueues for wait_on_inode().  The table is pretty small - the
- * kernel doesn't lock many inodes at the same time.
- */
-#define I_WAIT_TABLE_ORDER	3
-static struct i_wait_queue_head {
-	wait_queue_head_t wqh;
-} ____cacheline_aligned_in_smp i_wait_queue_heads[1<<I_WAIT_TABLE_ORDER];
+#define __I_LOCK	3
 
-/*
- * Return the address of the waitqueue_head to be used for this inode
- */
-static wait_queue_head_t *i_waitq_head(struct inode *inode)
+static int inode_wait(void *word)
 {
-	return &i_wait_queue_heads[hash_ptr(inode, I_WAIT_TABLE_ORDER)].wqh;
+	schedule();
+	return 0;
 }
 
 void __wait_on_inode(struct inode *inode)
 {
-	DECLARE_WAITQUEUE(wait, current);
-	wait_queue_head_t *wq = i_waitq_head(inode);
-
-	add_wait_queue(wq, &wait);
-repeat:
-	set_current_state(TASK_UNINTERRUPTIBLE);
-	if (inode->i_state & I_LOCK) {
-		schedule();
-		goto repeat;
-	}
-	remove_wait_queue(wq, &wait);
-	__set_current_state(TASK_RUNNING);
+	wait_on_bit(&inode->i_state, __I_LOCK, inode_wait, TASK_UNINTERRUPTIBLE);
 }
 
 /*
@@ -1305,27 +1285,23 @@
  */
 static void __wait_on_freeing_inode(struct inode *inode)
 {
-	DECLARE_WAITQUEUE(wait, current);
-	wait_queue_head_t *wq = i_waitq_head(inode);
+	wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_LOCK);
+	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);
 
-	add_wait_queue(wq, &wait);
-	set_current_state(TASK_UNINTERRUPTIBLE);
+	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
 	spin_unlock(&inode_lock);
 	schedule();
-	remove_wait_queue(wq, &wait);
+	finish_wait(wq, &wait.wait);
 	spin_lock(&inode_lock);
 }
 
 void wake_up_inode(struct inode *inode)
 {
-	wait_queue_head_t *wq = i_waitq_head(inode);
-
 	/*
 	 * Prevent speculative execution through spin_unlock(&inode_lock);
 	 */
 	smp_mb();
-	if (waitqueue_active(wq))
-		wake_up_all(wq);
+	wake_up_bit(&inode->i_state, __I_LOCK);
 }
 EXPORT_SYMBOL(wake_up_inode);
 
@@ -1361,11 +1337,6 @@
 
 void __init inode_init(unsigned long mempages)
 {
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(i_wait_queue_heads); i++)
-		init_waitqueue_head(&i_wait_queue_heads[i].wqh);
-
 	/* inode slab cache */
 	inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
 				0, SLAB_PANIC, init_once, NULL);