inode: port __I_LRU_ISOLATING to var event

Port the __I_LRU_ISOLATING mechanism to use the new var event mechanism.

Link: https://lore.kernel.org/r/20240823-work-i_state-v3-5-5cd5fd207a57@kernel.orgReviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/inode.c

@@ -511,24 +511,35 @@ static void inode_unpin_lru_isolating(struct inode *inode)
 	spin_lock(&inode->i_lock);
 	WARN_ON(!(inode->i_state & I_LRU_ISOLATING));
 	inode->i_state &= ~I_LRU_ISOLATING;
-	smp_mb();
-	wake_up_bit(&inode->i_state, __I_LRU_ISOLATING);
+	/* Called with inode->i_lock which ensures memory ordering. */
+	inode_wake_up_bit(inode, __I_LRU_ISOLATING);
 	spin_unlock(&inode->i_lock);
 }
 
 static void inode_wait_for_lru_isolating(struct inode *inode)
 {
+	struct wait_bit_queue_entry wqe;
+	struct wait_queue_head *wq_head;
+
 	lockdep_assert_held(&inode->i_lock);
-	if (inode->i_state & I_LRU_ISOLATING) {
-		DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LRU_ISOLATING);
-		wait_queue_head_t *wqh;
+	if (!(inode->i_state & I_LRU_ISOLATING))
+		return;
 
-		wqh = bit_waitqueue(&inode->i_state, __I_LRU_ISOLATING);
+	wq_head = inode_bit_waitqueue(&wqe, inode, __I_LRU_ISOLATING);
+	for (;;) {
+		prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE);
+		/*
+		 * Checking I_LRU_ISOLATING with inode->i_lock guarantees
+		 * memory ordering.
+		 */
+		if (!(inode->i_state & I_LRU_ISOLATING))
+			break;
 		spin_unlock(&inode->i_lock);
-		__wait_on_bit(wqh, &wq, bit_wait, TASK_UNINTERRUPTIBLE);
+		schedule();
 		spin_lock(&inode->i_lock);
-		WARN_ON(inode->i_state & I_LRU_ISOLATING);
 	}
+	finish_wait(wq_head, &wqe.wq_entry);
+	WARN_ON(inode->i_state & I_LRU_ISOLATING);
 }
 
 /**