* [PATCH] mm: Make logic in bdi_forker_thread() straight
@ 2011-09-02 11:26 Jan Kara
2011-09-02 11:30 ` Jan Kara
0 siblings, 1 reply; 2+ messages in thread
From: Jan Kara @ 2011-09-02 11:26 UTC (permalink / raw)
To: Jens Axboe
Cc: LKML, linux-mm, Jan Kara, Andrew Morton, Wu Fengguang, consul.kautuk
The logic in bdi_forker_thread() is unnecessarily convoluted by setting task
state there and back or calling schedule_timeout() in TASK_RUNNING state. Also
clearing of BDI_pending bit is placed at the and of global loop and cases of a
switch which mustn't reach it must call 'continue' instead of 'break' which is
non-intuitive and thus asking for trouble. So make the logic more obvious.
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Wu Fengguang <fengguang.wu@intel.com>
CC: consul.kautuk@gmail.com
Signed-off-by: Jan Kara <jack@suse.cz>
---
mm/backing-dev.c | 37 ++++++++++++++++++++-----------------
1 files changed, 20 insertions(+), 17 deletions(-)
Jens, would you merge this patch?
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index d6edf8d..fc441d7 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -359,6 +359,17 @@ static unsigned long bdi_longest_inactive(void)
return max(5UL * 60 * HZ, interval);
}
+/*
+ * Clear pending bit and wakeup anybody waiting for flusher thread startup
+ * or teardown.
+ */
+static void bdi_clear_pending(struct backing_dev *bdi)
+{
+ clear_bit(BDI_pending, &bdi->state);
+ smp_mb__after_clear_bit();
+ wake_up_bit(&bdi->state, BDI_pending);
+}
+
static int bdi_forker_thread(void *ptr)
{
struct bdi_writeback *me = ptr;
@@ -390,8 +401,6 @@ static int bdi_forker_thread(void *ptr)
}
spin_lock_bh(&bdi_lock);
- set_current_state(TASK_INTERRUPTIBLE);
-
list_for_each_entry(bdi, &bdi_list, bdi_list) {
bool have_dirty_io;
@@ -441,13 +450,8 @@ static int bdi_forker_thread(void *ptr)
}
spin_unlock_bh(&bdi_lock);
- /* Keep working if default bdi still has things to do */
- if (!list_empty(&me->bdi->work_list))
- __set_current_state(TASK_RUNNING);
-
switch (action) {
case FORK_THREAD:
- __set_current_state(TASK_RUNNING);
task = kthread_create(bdi_writeback_thread, &bdi->wb,
"flush-%s", dev_name(bdi->dev));
if (IS_ERR(task)) {
@@ -469,14 +473,21 @@ static int bdi_forker_thread(void *ptr)
spin_unlock_bh(&bdi->wb_lock);
wake_up_process(task);
}
+ bdi_clear_pending(bdi);
break;
case KILL_THREAD:
- __set_current_state(TASK_RUNNING);
kthread_stop(task);
+ bdi_clear_pending(bdi);
break;
case NO_ACTION:
+ /* Keep working if default bdi still has things to do */
+ if (!list_empty(&me->bdi->work_list)) {
+ try_to_freeze();
+ break;
+ }
+ set_current_state(TASK_INTERRUPTIBLE);
if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
/*
* There are no dirty data. The only thing we
@@ -489,16 +500,8 @@ static int bdi_forker_thread(void *ptr)
else
schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
try_to_freeze();
- /* Back to the main loop */
- continue;
+ break;
}
-
- /*
- * Clear pending bit and wakeup anybody waiting to tear us down.
- */
- clear_bit(BDI_pending, &bdi->state);
- smp_mb__after_clear_bit();
- wake_up_bit(&bdi->state, BDI_pending);
}
return 0;
--
1.7.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [PATCH] mm: Make logic in bdi_forker_thread() straight
2011-09-02 11:26 [PATCH] mm: Make logic in bdi_forker_thread() straight Jan Kara
@ 2011-09-02 11:30 ` Jan Kara
0 siblings, 0 replies; 2+ messages in thread
From: Jan Kara @ 2011-09-02 11:30 UTC (permalink / raw)
To: Jens Axboe
Cc: LKML, linux-mm, Jan Kara, Andrew Morton, Wu Fengguang, consul.kautuk
On Fri 02-09-11 13:26:08, Jan Kara wrote:
> The logic in bdi_forker_thread() is unnecessarily convoluted by setting task
> state there and back or calling schedule_timeout() in TASK_RUNNING state. Also
> clearing of BDI_pending bit is placed at the and of global loop and cases of a
> switch which mustn't reach it must call 'continue' instead of 'break' which is
> non-intuitive and thus asking for trouble. So make the logic more obvious.
>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Wu Fengguang <fengguang.wu@intel.com>
> CC: consul.kautuk@gmail.com
> Signed-off-by: Jan Kara <jack@suse.cz>
Argh, this patch is missing one fix I forgot to commit --amend to it. I'm
sending v2 in a minute. Sorry for the noise.
Honza
> ---
> mm/backing-dev.c | 37 ++++++++++++++++++++-----------------
> 1 files changed, 20 insertions(+), 17 deletions(-)
>
> Jens, would you merge this patch?
>
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index d6edf8d..fc441d7 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -359,6 +359,17 @@ static unsigned long bdi_longest_inactive(void)
> return max(5UL * 60 * HZ, interval);
> }
>
> +/*
> + * Clear pending bit and wakeup anybody waiting for flusher thread startup
> + * or teardown.
> + */
> +static void bdi_clear_pending(struct backing_dev *bdi)
> +{
> + clear_bit(BDI_pending, &bdi->state);
> + smp_mb__after_clear_bit();
> + wake_up_bit(&bdi->state, BDI_pending);
> +}
> +
> static int bdi_forker_thread(void *ptr)
> {
> struct bdi_writeback *me = ptr;
> @@ -390,8 +401,6 @@ static int bdi_forker_thread(void *ptr)
> }
>
> spin_lock_bh(&bdi_lock);
> - set_current_state(TASK_INTERRUPTIBLE);
> -
> list_for_each_entry(bdi, &bdi_list, bdi_list) {
> bool have_dirty_io;
>
> @@ -441,13 +450,8 @@ static int bdi_forker_thread(void *ptr)
> }
> spin_unlock_bh(&bdi_lock);
>
> - /* Keep working if default bdi still has things to do */
> - if (!list_empty(&me->bdi->work_list))
> - __set_current_state(TASK_RUNNING);
> -
> switch (action) {
> case FORK_THREAD:
> - __set_current_state(TASK_RUNNING);
> task = kthread_create(bdi_writeback_thread, &bdi->wb,
> "flush-%s", dev_name(bdi->dev));
> if (IS_ERR(task)) {
> @@ -469,14 +473,21 @@ static int bdi_forker_thread(void *ptr)
> spin_unlock_bh(&bdi->wb_lock);
> wake_up_process(task);
> }
> + bdi_clear_pending(bdi);
> break;
>
> case KILL_THREAD:
> - __set_current_state(TASK_RUNNING);
> kthread_stop(task);
> + bdi_clear_pending(bdi);
> break;
>
> case NO_ACTION:
> + /* Keep working if default bdi still has things to do */
> + if (!list_empty(&me->bdi->work_list)) {
> + try_to_freeze();
> + break;
> + }
> + set_current_state(TASK_INTERRUPTIBLE);
> if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
> /*
> * There are no dirty data. The only thing we
> @@ -489,16 +500,8 @@ static int bdi_forker_thread(void *ptr)
> else
> schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
> try_to_freeze();
> - /* Back to the main loop */
> - continue;
> + break;
> }
> -
> - /*
> - * Clear pending bit and wakeup anybody waiting to tear us down.
> - */
> - clear_bit(BDI_pending, &bdi->state);
> - smp_mb__after_clear_bit();
> - wake_up_bit(&bdi->state, BDI_pending);
> }
>
> return 0;
> --
> 1.7.1
>
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2011-09-02 11:30 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-09-02 11:26 [PATCH] mm: Make logic in bdi_forker_thread() straight Jan Kara
2011-09-02 11:30 ` Jan Kara
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox