fs/timerfd.c: make use of wait_event_interruptible_locked_irq()

This patch modifies the fs/timerfd.c to use the newly created
wait_event_interruptible_locked_irq() macro.  This replaces an open
code implementation with a single macro call.

Signed-off-by: Michal Nazarewicz <m.nazarewicz@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Author: Michal Nazarewicz

fs/timerfd.c

@@ -110,31 +110,14 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
 	struct timerfd_ctx *ctx = file->private_data;
 	ssize_t res;
 	u64 ticks = 0;
-	DECLARE_WAITQUEUE(wait, current);
 
 	if (count < sizeof(ticks))
 		return -EINVAL;
 	spin_lock_irq(&ctx->wqh.lock);
-	res = -EAGAIN;
-	if (!ctx->ticks && !(file->f_flags & O_NONBLOCK)) {
-		__add_wait_queue(&ctx->wqh, &wait);
-		for (res = 0;;) {
-			set_current_state(TASK_INTERRUPTIBLE);
-			if (ctx->ticks) {
-				res = 0;
-				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);
-	}
+	if (file->f_flags & O_NONBLOCK)
+		res = -EAGAIN;
+	else
+		res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
 	if (ctx->ticks) {
 		ticks = ctx->ticks;
 		if (ctx->expired && ctx->tintv.tv64) {