[PATCH v3 3/6] inode: port __I_SYNC to var event

[Christian Brauner <brauner@xxxxxxxxxx>]

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

Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
 fs/fs-writeback.c | 45 +++++++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1a5006329f6f..d8bec3c1bb1f 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1386,12 +1386,13 @@ static void requeue_io(struct inode *inode, struct bdi_writeback *wb)
 
 static void inode_sync_complete(struct inode *inode)
 {
+	assert_spin_locked(&inode->i_lock);
+
 	inode->i_state &= ~I_SYNC;
 	/* If inode is clean an unused, put it into LRU now... */
 	inode_add_lru(inode);
-	/* Waiters must see I_SYNC cleared before being woken up */
-	smp_mb();
-	wake_up_bit(&inode->i_state, __I_SYNC);
+	/* Called with inode->i_lock which ensures memory ordering. */
+	inode_wake_up_bit(inode, __I_SYNC);
 }
 
 static bool inode_dirtied_after(struct inode *inode, unsigned long t)
@@ -1512,17 +1513,25 @@ static int write_inode(struct inode *inode, struct writeback_control *wbc)
  */
 void inode_wait_for_writeback(struct inode *inode)
 {
-	DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
-	wait_queue_head_t *wqh;
+	struct wait_bit_queue_entry wqe;
+	struct wait_queue_head *wq_head;
+
+	assert_spin_locked(&inode->i_lock);
+
+	if (!(inode->i_state & I_SYNC))
+		return;
 
-	lockdep_assert_held(&inode->i_lock);
-	wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
-	while (inode->i_state & I_SYNC) {
+	wq_head = inode_bit_waitqueue(&wqe, inode, __I_SYNC);
+	for (;;) {
+		prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE);
+		/* Checking I_SYNC with inode->i_lock guarantees memory ordering. */
+		if (!(inode->i_state & I_SYNC))
+			break;
 		spin_unlock(&inode->i_lock);
-		__wait_on_bit(wqh, &wq, bit_wait,
-			      TASK_UNINTERRUPTIBLE);
+		schedule();
 		spin_lock(&inode->i_lock);
 	}
+	finish_wait(wq_head, &wqe.wq_entry);
 }
 
 /*
@@ -1533,16 +1542,20 @@ void inode_wait_for_writeback(struct inode *inode)
 static void inode_sleep_on_writeback(struct inode *inode)
 	__releases(inode->i_lock)
 {
-	DEFINE_WAIT(wait);
-	wait_queue_head_t *wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
-	int sleep;
+	struct wait_bit_queue_entry wqe;
+	struct wait_queue_head *wq_head;
+	bool sleep;
+
+	assert_spin_locked(&inode->i_lock);
 
-	prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
-	sleep = inode->i_state & I_SYNC;
+	wq_head = inode_bit_waitqueue(&wqe, inode, __I_SYNC);
+	prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE);
+	/* Checking I_SYNC with inode->i_lock guarantees memory ordering. */
+	sleep = !!(inode->i_state & I_SYNC);
 	spin_unlock(&inode->i_lock);
 	if (sleep)
 		schedule();
-	finish_wait(wqh, &wait);
+	finish_wait(wq_head, &wqe.wq_entry);
 }
 
 /*

-- 
2.43.0