On Wed, Jun 13, 2012 at 08:59:46AM +0800, Fengguang Wu wrote:
>On Wed, Jun 13, 2012 at 08:52:53AM +0800, Wanpeng Li wrote:
>> From: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
>>
>> I use several dd processes to write a slow SD card
>> dd if=/dev/sda1 of=/dev/sdc4 bs=1M count=4000
>> and several sync commands(maybe > 10),dmesg show this:
>>
>> [ 366.888741] INFO: task sync:3518 blocked for more than 120 seconds.
>> [ 366.888742] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> [ 366.888746] sync D 00000201 0 3518 3462 0x00000000
>
>> Too many similar messages flood the logs. So I use a present method to
>> fix this issue.
>> ------------------------------------------
>> Author: Mark Lord <kernel@xxxxxxxxxxxx>
>> Date: Fri Sep 24 09:51:13 2010 -0400
>>
>> block: Prevent hang_check firing during long I/O
>> ------------------------------------------
>>
>> Signed-off-by: Wanpeng Li <liwp.linux@xxxxxxxxx>
>
>Yeah that's also what I'd like to do. So you've tested it?
Not yet, I will test it today.
>
>> ---
>> fs/fs-writeback.c | 8 +++++++-
>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
>> index f2d0109..5d403a1 100644
>> --- a/fs/fs-writeback.c
>> +++ b/fs/fs-writeback.c
>> @@ -1300,6 +1300,7 @@ void writeback_inodes_sb_nr(struct super_block *sb,
>> enum wb_reason reason)
>> {
>> DECLARE_COMPLETION_ONSTACK(done);
>> + unsigned long hangcheck;
>> struct wb_writeback_work work = {
>> .sb = sb,
>> .sync_mode = WB_SYNC_NONE,
>> @@ -1311,7 +1312,12 @@ void writeback_inodes_sb_nr(struct super_block *sb,
>>
>> WARN_ON(!rwsem_is_locked(&sb->s_umount));
>> bdi_queue_work(sb->s_bdi, &work);
>> - wait_for_completion(&done);
>> + hangcheck = sysctl_hung_task_timeout_secs;
>> + if (hangcheck)
>
>The hangcheck variable looks redundant.
if sysctl_hung_task_timeout_secs is equal to ZERO, it means infinite
timeout -- no checking done. So I think wait_for_completion_timeout
makes no sense this time.
Regards,
Wanpeng Li
>
>> + while (!wait_for_completion_timeout(&done, HZ/2))
>> + ;
>> + else
>> + wait_for_completion(&done);
>> }
>> EXPORT_SYMBOL(writeback_inodes_sb_nr);
>>
>> --
>> 1.7.9.5
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