[PATCH v2] eventfd: use a generic helper instead of an open coded wait_event

[wenyang.linux@xxxxxxxxxxx]

From: Wen Yang <wenyang.linux@xxxxxxxxxxx>

Use wait_event_interruptible_locked_irq() in the eventfd_{write,read} to
avoid the longer, open coded equivalent.

Signed-off-by: Wen Yang <wenyang.linux@xxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Cc: Dan Carpenter <error27@xxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
v2:
- fix smatch warnings: eventfd_read() warn: inconsistent returns '&ctx->wqh.lock'.

 fs/eventfd.c | 41 +++++++----------------------------------
 1 file changed, 7 insertions(+), 34 deletions(-)

diff --git a/fs/eventfd.c b/fs/eventfd.c
index 249ca6c0b784..c5bda3df4a28 100644
--- a/fs/eventfd.c
+++ b/fs/eventfd.c
@@ -228,7 +228,6 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
 	struct file *file = iocb->ki_filp;
 	struct eventfd_ctx *ctx = file->private_data;
 	__u64 ucnt = 0;
-	DECLARE_WAITQUEUE(wait, current);
 
 	if (iov_iter_count(to) < sizeof(ucnt))
 		return -EINVAL;
@@ -239,23 +238,11 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
 			spin_unlock_irq(&ctx->wqh.lock);
 			return -EAGAIN;
 		}
-		__add_wait_queue(&ctx->wqh, &wait);
-		for (;;) {
-			set_current_state(TASK_INTERRUPTIBLE);
-			if (ctx->count)
-				break;
-			if (signal_pending(current)) {
-				__remove_wait_queue(&ctx->wqh, &wait);
-				__set_current_state(TASK_RUNNING);
-				spin_unlock_irq(&ctx->wqh.lock);
-				return -ERESTARTSYS;
-			}
+
+		if (wait_event_interruptible_locked_irq(ctx->wqh, ctx->count)) {
 			spin_unlock_irq(&ctx->wqh.lock);
-			schedule();
-			spin_lock_irq(&ctx->wqh.lock);
+			return -ERESTARTSYS;
 		}
-		__remove_wait_queue(&ctx->wqh, &wait);
-		__set_current_state(TASK_RUNNING);
 	}
 	eventfd_ctx_do_read(ctx, &ucnt);
 	current->in_eventfd = 1;
@@ -275,7 +262,6 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
 	struct eventfd_ctx *ctx = file->private_data;
 	ssize_t res;
 	__u64 ucnt;
-	DECLARE_WAITQUEUE(wait, current);
 
 	if (count < sizeof(ucnt))
 		return -EINVAL;
@@ -288,23 +274,10 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c
 	if (ULLONG_MAX - ctx->count > ucnt)
 		res = sizeof(ucnt);
 	else if (!(file->f_flags & O_NONBLOCK)) {
-		__add_wait_queue(&ctx->wqh, &wait);
-		for (res = 0;;) {
-			set_current_state(TASK_INTERRUPTIBLE);
-			if (ULLONG_MAX - ctx->count > ucnt) {
-				res = sizeof(ucnt);
-				break;
-			}
-			if (signal_pending(current)) {
-				res = -ERESTARTSYS;
-				break;
-			}
-			spin_unlock_irq(&ctx->wqh.lock);
-			schedule();
-			spin_lock_irq(&ctx->wqh.lock);
-		}
-		__remove_wait_queue(&ctx->wqh, &wait);
-		__set_current_state(TASK_RUNNING);
+		res = wait_event_interruptible_locked_irq(ctx->wqh,
+							  ULLONG_MAX - ctx->count > ucnt);
+		if (!res)
+			res = sizeof(ucnt);
 	}
 	if (likely(res > 0)) {
 		ctx->count += ucnt;
-- 
2.25.1