Commit 0ed35fa4 authored by Yu Kuai's avatar Yu Kuai Committed by Li Lingfeng
Browse files

block: add a switch to enable hungtask check for io 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAAQ73



--------------------------------

Because slow io or io timeout handler can take a long time, hungtask check
is forbidden in order to prevent false positive warnings. However, this
also cause kenel to be silence if io really hang.

It's quite complicated to distinguish if io is slow or hanged, this
patch add a switch to enable hungtask check, the switch is enabled by
default, and can be turn off by:

1) disable config BLK_IO_HUNG_TASK_CHECK
2) add blk_core.io_hung_task_check=0 to boot cmd
3) echo 0 > /sys/module/blk_core/parameters/io_hung_task_check

Noted that user has to be careful to use this with hungtask panic
enabeld, since there could be false positive hungtask warnings.

Signed-off-by: default avatarYu Kuai <yukuai3@huawei.com>

Fixes: 4b197769 ("block: Prevent hang_check firing during long I/O")
Fixes: e6249cdd ("block: add blk_io_schedule() for avoiding task hung in sync dio")
Fixes: de6a78b6 ("block: Prevent hung_check firing during long sync IO")
Signed-off-by: default avatarLi Lingfeng <lilingfeng3@huawei.com>
parent 83ed2eb1

block/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -266,6 +266,15 @@ config BLK_DEV_WRITE_MOUNTED_DUMP 
	  Enabling this to dump info when opening mounted block devices

	  for write or trying to mount write opened block devices.



config BLK_IO_HUNG_TASK_CHECK

	bool "Enable io hung task check"

	depends on DETECT_HUNG_TASK

	default y

	help

	  Enabling this lets the block layer detect hungtask for io, noted

	  if this is set, hungtask will complain about slow io even if such

	  io is not hanged. Be careful to enable hungtask panic in this case.



source "block/partitions/Kconfig"



config BLK_MQ_PCI

block/bio.c

+1 −1
Original line number Diff line number Diff line
@@ -1375,7 +1375,7 @@ int submit_bio_wait(struct bio *bio) 
	submit_bio(bio);



	/* Prevent hang_check timer from firing at us during very long I/O */

	hang_check = sysctl_hung_task_timeout_secs;

	hang_check = sysctl_hung_task_timeout_secs && !io_hung_task_check;

	if (hang_check)

		while (!wait_for_completion_io_timeout(&done,

					hang_check * (HZ/2)))

block/blk-core.c

+12 −1
Original line number Diff line number Diff line
@@ -86,6 +86,17 @@ static int __init precise_iostat_setup(char *str) 
}

__setup("precise_iostat=", precise_iostat_setup);



/*

 * Noted if this is set, hungtask will complain about slow io even if such io is

 * not hanged. Be careful to enable hungtask panic in this case.

 */

#ifdef CONFIG_BLK_IO_HUNG_TASK_CHECK

bool io_hung_task_check = true;

#else

bool io_hung_task_check;

#endif

module_param_named(io_hung_task_check, io_hung_task_check, bool, 0644);



/**

 * blk_queue_flag_set - atomically set a queue flag

 * @flag: flag to be set
@@ -1205,7 +1216,7 @@ 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)

	if (timeout && !io_hung_task_check)

		io_schedule_timeout(timeout);

	else

		io_schedule();

block/blk-mq.c

+1 −1
Original line number Diff line number Diff line
@@ -1420,7 +1420,7 @@ blk_status_t blk_execute_rq(struct request *rq, bool at_head) 
		 * Prevent hang_check timer from firing at us during very long

		 * I/O

		 */

		unsigned long hang_check = sysctl_hung_task_timeout_secs;

		unsigned long hang_check = sysctl_hung_task_timeout_secs && !io_hung_task_check;



		if (hang_check)

			while (!wait_for_completion_io_timeout(&wait.done,

block/blk.h

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ struct elevator_type; 
#define BLK_MAX_TIMEOUT		(5 * HZ)



extern struct dentry *blk_debugfs_root;

extern bool io_hung_task_check;



struct blk_flush_queue {

	spinlock_t		mq_flush_lock;