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?
> ---
> 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.
> + 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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