linux-kernel - [PATCH 4/9] Use wait_var_event() instead of I_DIO

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Message-ID: <20240819053605.11706-5-neilb@suse.de>
Date: Mon, 19 Aug 2024 15:20:38 +1000
From: NeilBrown <neilb@...e.de>
To: Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH 4/9] Use wait_var_event() instead of I_DIO_WAKEUP

inode_dio_wait() is essentially an open-coded version of
wait_var_event().  Similarly inode_dio_wait_interruptible() is an
open-coded version of wait_var_event_interruptible().

If we switch to waiting on the var, instead of an imaginary bit, the
code is more transparent, is shorter, and we can discard I_DIO_WAKEUP.

Signed-off-by: NeilBrown <neilb@...e.de>
---
 fs/inode.c         | 16 ++--------------
 fs/netfs/locking.c | 19 ++-----------------
 include/linux/fs.h |  7 +------
 3 files changed, 5 insertions(+), 37 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 86670941884b..91bb2f80fa03 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2467,18 +2467,6 @@ EXPORT_SYMBOL(inode_owner_or_capable);
 /*
  * Direct i/o helper functions
  */
-static void __inode_dio_wait(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);
-}
 
 /**
  * inode_dio_wait - wait for outstanding DIO requests to finish
@@ -2492,8 +2480,8 @@ 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,
+		       atomic_read(&inode->i_dio_count) == 0);
 }
 EXPORT_SYMBOL(inode_dio_wait);
 
diff --git a/fs/netfs/locking.c b/fs/netfs/locking.c
index 75dc52a49b3a..c171a0a48ed0 100644
--- a/fs/netfs/locking.c
+++ b/fs/netfs/locking.c
@@ -21,23 +21,8 @@
  */
 static int inode_dio_wait_interruptible(struct inode *inode)
 {
-	if (!atomic_read(&inode->i_dio_count))
-		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;
+	return wait_var_event_interruptible(&inode->i_dio_count,
+					    !atomic_read(&inode->i_dio_count));
 }
 
 /* Call with exclusively locked inode->i_rwsem */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index fd34b5755c0b..fc1b68134cbf 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2372,8 +2372,6 @@ 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
@@ -2405,8 +2403,6 @@ 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)
@@ -3237,8 +3233,7 @@ static inline void inode_dio_begin(struct inode *inode)
  */
 static inline void inode_dio_end(struct inode *inode)
 {
-	if (atomic_dec_and_test(&inode->i_dio_count))
-		wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
+	atomic_dec_and_wake_up_var(&inode->i_dio_count);
 }
 
 extern void inode_set_flags(struct inode *inode, unsigned int flags,
-- 
2.44.0