block: add blk_io_schedule() for avoiding task hung in sync dio

Sync dio could be big, or may take long time in discard or in case of
IO failure.

We have prevented task hung in submit_bio_wait() and blk_execute_rq(),
so apply the same trick for prevent task hung from happening in sync dio.

Add helper of blk_io_schedule() and use io_schedule_timeout() to prevent
task hung warning.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Cc: Salman Qazi <sqazi@google.com>
Cc: Jesse Barnes <jsbarnes@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/block_dev.c

@@ -255,7 +255,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
 			break;
 		if (!(iocb->ki_flags & IOCB_HIPRI) ||
 		    !blk_poll(bdev_get_queue(bdev), qc, true))
-			io_schedule();
+			blk_io_schedule();
 	}
 	__set_current_state(TASK_RUNNING);
 
@@ -449,7 +449,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
 
 		if (!(iocb->ki_flags & IOCB_HIPRI) ||
 		    !blk_poll(bdev_get_queue(bdev), qc, true))
-			io_schedule();
+			blk_io_schedule();
 	}
 	__set_current_state(TASK_RUNNING);
 

fs/direct-io.c

@@ -500,7 +500,7 @@ static struct bio *dio_await_one(struct dio *dio)
 		spin_unlock_irqrestore(&dio->bio_lock, flags);
 		if (!(dio->iocb->ki_flags & IOCB_HIPRI) ||
 		    !blk_poll(dio->bio_disk->queue, dio->bio_cookie, true))
-			io_schedule();
+			blk_io_schedule();
 		/* wake up sets us TASK_RUNNING */
 		spin_lock_irqsave(&dio->bio_lock, flags);
 		dio->waiter = NULL;

fs/iomap/direct-io.c

@@ -561,7 +561,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 			    !dio->submit.last_queue ||
 			    !blk_poll(dio->submit.last_queue,
 					 dio->submit.cookie, true))
-				io_schedule();
+				blk_io_schedule();
 		}
 		__set_current_state(TASK_RUNNING);
 	}

include/linux/blkdev.h

@@ -27,6 +27,7 @@
 #include <linux/percpu-refcount.h>
 #include <linux/scatterlist.h>
 #include <linux/blkzoned.h>
+#include <linux/sched/sysctl.h>
 
 struct module;
 struct scsi_ioctl_command;
@@ -1827,4 +1828,15 @@ static inline void blk_wake_io_task(struct task_struct *waiter)
 		wake_up_process(waiter);
 }
 
+static inline void blk_io_schedule(void)
+{
+	/* Prevent hang_check timer from firing at us during very long I/O */
+	unsigned long timeout = sysctl_hung_task_timeout_secs * HZ / 2;
+
+	if (timeout)
+		io_schedule_timeout(timeout);
+	else
+		io_schedule();
+}
+
 #endif