[PATCH] inode: remove __I_DIO_WAKEUP

[Christian Brauner <brauner@xxxxxxxxxx>]

Afaict, we can just rely on inode->i_dio_count for waiting instead of
this awkward indirection through __I_DIO_WAKEUP. This survives LTP dio
and xfstests dio tests.

Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
---
 fs/inode.c         | 23 +++++++++++------------
 fs/netfs/locking.c | 18 +++---------------
 include/linux/fs.h |  9 ++++-----
 3 files changed, 18 insertions(+), 32 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 7a4e27606fca..46bf05d826db 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2465,18 +2465,12 @@ EXPORT_SYMBOL(inode_owner_or_capable);
 /*
  * Direct i/o helper functions
  */
-static void __inode_dio_wait(struct inode *inode)
+bool inode_dio_finished(const struct inode *inode)
 {
-	wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
-	DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
-
-	do {
-		prepare_to_wait(wq, &q.wq_entry, TASK_UNINTERRUPTIBLE);
-		if (atomic_read(&inode->i_dio_count))
-			schedule();
-	} while (atomic_read(&inode->i_dio_count));
-	finish_wait(wq, &q.wq_entry);
+	smp_mb__before_atomic();
+	return atomic_read(&inode->i_dio_count) == 0;
 }
+EXPORT_SYMBOL(inode_dio_finished);
 
 /**
  * inode_dio_wait - wait for outstanding DIO requests to finish
@@ -2490,11 +2484,16 @@ static void __inode_dio_wait(struct inode *inode)
  */
 void inode_dio_wait(struct inode *inode)
 {
-	if (atomic_read(&inode->i_dio_count))
-		__inode_dio_wait(inode);
+	wait_var_event(&inode->i_dio_count, inode_dio_finished);
 }
 EXPORT_SYMBOL(inode_dio_wait);
 
+void inode_dio_wait_interruptible(struct inode *inode)
+{
+	wait_var_event_interruptible(&inode->i_dio_count, inode_dio_finished);
+}
+EXPORT_SYMBOL(inode_dio_wait_interruptible);
+
 /*
  * inode_set_flags - atomically set some inode flags
  *
diff --git a/fs/netfs/locking.c b/fs/netfs/locking.c
index 75dc52a49b3a..c2cfdda85230 100644
--- a/fs/netfs/locking.c
+++ b/fs/netfs/locking.c
@@ -21,23 +21,11 @@
  */
 static int inode_dio_wait_interruptible(struct inode *inode)
 {
-	if (!atomic_read(&inode->i_dio_count))
+	if (inode_dio_finished(inode))
 		return 0;
 
-	wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
-	DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
-
-	for (;;) {
-		prepare_to_wait(wq, &q.wq_entry, TASK_INTERRUPTIBLE);
-		if (!atomic_read(&inode->i_dio_count))
-			break;
-		if (signal_pending(current))
-			break;
-		schedule();
-	}
-	finish_wait(wq, &q.wq_entry);
-
-	return atomic_read(&inode->i_dio_count) ? -ERESTARTSYS : 0;
+	inode_dio_wait_interruptible(inode);
+	return !inode_dio_finished(inode) ? -ERESTARTSYS : 0;
 }
 
 /* Call with exclusively locked inode->i_rwsem */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b6f2e2a1e513..f744cd918259 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2380,8 +2380,6 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
  *
  * I_REFERENCED		Marks the inode as recently references on the LRU list.
  *
- * I_DIO_WAKEUP		Never set.  Only used as a key for wait_on_bit().
- *
  * I_WB_SWITCH		Cgroup bdi_writeback switching in progress.  Used to
  *			synchronize competing switching instances and to tell
  *			wb stat updates to grab the i_pages lock.  See
@@ -2413,8 +2411,6 @@ static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
 #define __I_SYNC		7
 #define I_SYNC			(1 << __I_SYNC)
 #define I_REFERENCED		(1 << 8)
-#define __I_DIO_WAKEUP		9
-#define I_DIO_WAKEUP		(1 << __I_DIO_WAKEUP)
 #define I_LINKABLE		(1 << 10)
 #define I_DIRTY_TIME		(1 << 11)
 #define I_WB_SWITCH		(1 << 13)
@@ -3230,6 +3226,7 @@ static inline ssize_t blockdev_direct_IO(struct kiocb *iocb,
 #endif
 
 void inode_dio_wait(struct inode *inode);
+void inode_dio_wait_interruptible(struct inode *inode);
 
 /**
  * inode_dio_begin - signal start of a direct I/O requests
@@ -3241,6 +3238,7 @@ void inode_dio_wait(struct inode *inode);
 static inline void inode_dio_begin(struct inode *inode)
 {
 	atomic_inc(&inode->i_dio_count);
+	smp_mb__after_atomic();
 }
 
 /**
@@ -3252,8 +3250,9 @@ static inline void inode_dio_begin(struct inode *inode)
  */
 static inline void inode_dio_end(struct inode *inode)
 {
+	smp_mb__before_atomic();
 	if (atomic_dec_and_test(&inode->i_dio_count))
-		wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+		wake_up_var(&inode->i_dio_count);
 }
 
 extern void inode_set_flags(struct inode *inode, unsigned int flags,

---
base-commit: 5570f04d0bb1a34ebcb27caac76c797a7c9e36c9
change-id: 20240816-vfs-misc-dio-5cb07eaae155