[v2] writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

[PATCH V2] writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

Posted by Huacai Chen 5 days, 6 hours ago

Recent changes of fs-writeback cause such warnings if DETECT_HUNG_TASK
is not enabled:

INFO: The task sync:1342 has been waiting for writeback completion for more than 1 seconds.

The reason is sysctl_hung_task_timeout_secs is 0 when DETECT_HUNG_TASK
is not enabled, then it causes the warning message even if the writeback
lasts for only one second.

So guard the wakeup and logging with "#ifdef CONFIG_DETECT_HUNG_TASK",
so as to eliminate the warning messages.

Fixes: 1888635532fb ("writeback: Wake up waiting tasks when finishing the writeback of a chunk.")
Fixes: d6e621590764 ("writeback: Add logging for slow writeback (exceeds sysctl_hung_task_timeout_secs)")
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
V2: Disable wakeup and logging for !DETECT_HUNG_TASK.

 fs/fs-writeback.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5444fc706ac7..bfe469fff97c 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -198,13 +198,15 @@ static void wb_queue_work(struct bdi_writeback *wb,
 
 static bool wb_wait_for_completion_cb(struct wb_completion *done)
 {
+#ifdef CONFIG_DETECT_HUNG_TASK
 	unsigned long waited_secs = (jiffies - done->wait_start) / HZ;
 
-	done->progress_stamp = jiffies;
 	if (waited_secs > sysctl_hung_task_timeout_secs)
 		pr_info("INFO: The task %s:%d has been waiting for writeback "
 			"completion for more than %lu seconds.",
 			current->comm, current->pid, waited_secs);
+#endif
+	done->progress_stamp = jiffies;
 
 	return !atomic_read(&done->cnt);
 }
@@ -2029,11 +2031,13 @@ static long writeback_sb_inodes(struct super_block *sb,
 		 */
 		__writeback_single_inode(inode, &wbc);
 
+#ifdef CONFIG_DETECT_HUNG_TASK
 		/* Report progress to inform the hung task detector of the progress. */
 		if (work->done && work->done->progress_stamp &&
 		   (jiffies - work->done->progress_stamp) > HZ *
 		   sysctl_hung_task_timeout_secs / 2)
 			wake_up_all(work->done->waitq);
+#endif
 
 		wbc_detach_inode(&wbc);
 		work->nr_pages -= write_chunk - wbc.nr_to_write;
-- 
2.47.3

Re: [PATCH V2] writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

Posted by Jan Kara 5 days, 3 hours ago

On Tue 03-02-26 14:30:23, Huacai Chen wrote:
> Recent changes of fs-writeback cause such warnings if DETECT_HUNG_TASK
> is not enabled:
> 
> INFO: The task sync:1342 has been waiting for writeback completion for more than 1 seconds.
> 
> The reason is sysctl_hung_task_timeout_secs is 0 when DETECT_HUNG_TASK
> is not enabled, then it causes the warning message even if the writeback
> lasts for only one second.
> 
> So guard the wakeup and logging with "#ifdef CONFIG_DETECT_HUNG_TASK",
> so as to eliminate the warning messages.
> 
> Fixes: 1888635532fb ("writeback: Wake up waiting tasks when finishing the writeback of a chunk.")
> Fixes: d6e621590764 ("writeback: Add logging for slow writeback (exceeds sysctl_hung_task_timeout_secs)")
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Thanks! Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
> V2: Disable wakeup and logging for !DETECT_HUNG_TASK.
> 
>  fs/fs-writeback.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 5444fc706ac7..bfe469fff97c 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -198,13 +198,15 @@ static void wb_queue_work(struct bdi_writeback *wb,
>  
>  static bool wb_wait_for_completion_cb(struct wb_completion *done)
>  {
> +#ifdef CONFIG_DETECT_HUNG_TASK
>  	unsigned long waited_secs = (jiffies - done->wait_start) / HZ;
>  
> -	done->progress_stamp = jiffies;
>  	if (waited_secs > sysctl_hung_task_timeout_secs)
>  		pr_info("INFO: The task %s:%d has been waiting for writeback "
>  			"completion for more than %lu seconds.",
>  			current->comm, current->pid, waited_secs);
> +#endif
> +	done->progress_stamp = jiffies;
>  
>  	return !atomic_read(&done->cnt);
>  }
> @@ -2029,11 +2031,13 @@ static long writeback_sb_inodes(struct super_block *sb,
>  		 */
>  		__writeback_single_inode(inode, &wbc);
>  
> +#ifdef CONFIG_DETECT_HUNG_TASK
>  		/* Report progress to inform the hung task detector of the progress. */
>  		if (work->done && work->done->progress_stamp &&
>  		   (jiffies - work->done->progress_stamp) > HZ *
>  		   sysctl_hung_task_timeout_secs / 2)
>  			wake_up_all(work->done->waitq);
> +#endif
>  
>  		wbc_detach_inode(&wbc);
>  		work->nr_pages -= write_chunk - wbc.nr_to_write;
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH V2] writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK

Posted by Huacai Chen 5 days, 3 hours ago

On Tue, Feb 3, 2026 at 5:08 PM Jan Kara <jack@suse.cz> wrote:
>
> On Tue 03-02-26 14:30:23, Huacai Chen wrote:
> > Recent changes of fs-writeback cause such warnings if DETECT_HUNG_TASK
> > is not enabled:
> >
> > INFO: The task sync:1342 has been waiting for writeback completion for more than 1 seconds.
> >
> > The reason is sysctl_hung_task_timeout_secs is 0 when DETECT_HUNG_TASK
> > is not enabled, then it causes the warning message even if the writeback
> > lasts for only one second.
> >
> > So guard the wakeup and logging with "#ifdef CONFIG_DETECT_HUNG_TASK",
> > so as to eliminate the warning messages.
> >
> > Fixes: 1888635532fb ("writeback: Wake up waiting tasks when finishing the writeback of a chunk.")
> > Fixes: d6e621590764 ("writeback: Add logging for slow writeback (exceeds sysctl_hung_task_timeout_secs)")
> > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
>
> Thanks! Looks good to me. Feel free to add:
>
> Reviewed-by: Jan Kara <jack@suse.cz>
Thanks, but don't apply because I found that
sysctl_hung_task_timeout_secs can also be 0 for DETECT_HUNG_TASK.
Please wait for V3.

Huacai

>
>                                                                 Honza
>
> > ---
> > V2: Disable wakeup and logging for !DETECT_HUNG_TASK.
> >
> >  fs/fs-writeback.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> > index 5444fc706ac7..bfe469fff97c 100644
> > --- a/fs/fs-writeback.c
> > +++ b/fs/fs-writeback.c
> > @@ -198,13 +198,15 @@ static void wb_queue_work(struct bdi_writeback *wb,
> >
> >  static bool wb_wait_for_completion_cb(struct wb_completion *done)
> >  {
> > +#ifdef CONFIG_DETECT_HUNG_TASK
> >       unsigned long waited_secs = (jiffies - done->wait_start) / HZ;
> >
> > -     done->progress_stamp = jiffies;
> >       if (waited_secs > sysctl_hung_task_timeout_secs)
> >               pr_info("INFO: The task %s:%d has been waiting for writeback "
> >                       "completion for more than %lu seconds.",
> >                       current->comm, current->pid, waited_secs);
> > +#endif
> > +     done->progress_stamp = jiffies;
> >
> >       return !atomic_read(&done->cnt);
> >  }
> > @@ -2029,11 +2031,13 @@ static long writeback_sb_inodes(struct super_block *sb,
> >                */
> >               __writeback_single_inode(inode, &wbc);
> >
> > +#ifdef CONFIG_DETECT_HUNG_TASK
> >               /* Report progress to inform the hung task detector of the progress. */
> >               if (work->done && work->done->progress_stamp &&
> >                  (jiffies - work->done->progress_stamp) > HZ *
> >                  sysctl_hung_task_timeout_secs / 2)
> >                       wake_up_all(work->done->waitq);
> > +#endif
> >
> >               wbc_detach_inode(&wbc);
> >               work->nr_pages -= write_chunk - wbc.nr_to_write;
> > --
> > 2.47.3
> >
> --
> Jan Kara <jack@suse.com>
> SUSE Labs, CR