[PATCH V2] block: add blk_io_schedule() for avoiding task hung in sync dio

[Ming Lei <ming.lei@xxxxxxxxxx>]

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.

Cc: Salman Qazi <sqazi@xxxxxxxxxx>
Cc: Jesse Barnes <jsbarnes@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
V2:
	- drop helper of blk_default_io_timeout()


 fs/block_dev.c         |  4 ++--
 fs/direct-io.c         |  2 +-
 fs/iomap/direct-io.c   |  2 +-
 include/linux/blkdev.h | 12 ++++++++++++
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 5eb30a474f6d..3b396f8c967c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -256,7 +256,7 @@ __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);
 
@@ -450,7 +450,7 @@ __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);
 
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 00b4d15bb811..6d5370eac2a8 100644
--- a/fs/direct-io.c
+++ b/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;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 20dde5aadcdd..fd3bd06fabb6 100644
--- a/fs/iomap/direct-io.c
+++ b/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);
 	}
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f00bd4042295..222eb5f32279 100644
--- a/include/linux/blkdev.h
+++ b/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
-- 
2.25.2