Patchwork [1/4,v2] ext4: Use schedule_timeout_interruptible() for waiting in lazyinit thread

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Submitter Lukas Czerner
Date May 9, 2011, 3:57 p.m.
Message ID <1304956630-20384-1-git-send-email-lczerner@redhat.com>
Download mbox | patch
Permalink /patch/94786/
State Superseded
Headers show

Comments

Lukas Czerner - May 9, 2011, 3:57 p.m.
In order to make lazyinit eat approx. 10% of io bandwidth at max, we are
sleeping between zeroing each single inode table. For that purpose we
are using timer which wakes up thread when it expires. It is set via
add_timer() and this may cause troubles in the case that thread has been
woken up earlier and in next iteration we call add_timer() on still
running timer hence hitting BUG_ON in add_timer(). We could fix that by
using mod_timer() instead however we can use
schedule_timeout_interruptible() for waiting and hence simplifying
things a lot.

This commit exchange the old "waiting mechanism" with simple
schedule_timeout_interruptible(), setting the time to sleep. Hence we do
not longer need li_wait_daemon waiting queue and others, so get rid of
it.

This solves Red Hat bug 699708.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
---
[v2]: prevent sleepeng for a loong time when jiffies wraps
      (Thanks to Eric Sandeen)
 fs/ext4/ext4.h  |    4 ----
 fs/ext4/super.c |   31 ++++++-------------------------
 2 files changed, 6 insertions(+), 29 deletions(-)
Eric Sandeen - May 19, 2011, 7:30 p.m.
On 5/9/11 10:57 AM, Lukas Czerner wrote:
> In order to make lazyinit eat approx. 10% of io bandwidth at max, we are
> sleeping between zeroing each single inode table. For that purpose we
> are using timer which wakes up thread when it expires. It is set via
> add_timer() and this may cause troubles in the case that thread has been
> woken up earlier and in next iteration we call add_timer() on still
> running timer hence hitting BUG_ON in add_timer(). We could fix that by
> using mod_timer() instead however we can use
> schedule_timeout_interruptible() for waiting and hence simplifying
> things a lot.
> 
> This commit exchange the old "waiting mechanism" with simple
> schedule_timeout_interruptible(), setting the time to sleep. Hence we do
> not longer need li_wait_daemon waiting queue and others, so get rid of
> it.
> 
> This solves Red Hat bug 699708.
> 
> Signed-off-by: Lukas Czerner <lczerner@redhat.com>

Thanks Lukas - this looks good to me and takes care of the concern
about jiffies wrapping.

Reviewed-by: Eric Sandeen <sandeen@redhat.com>

> ---
> [v2]: prevent sleepeng for a loong time when jiffies wraps
>       (Thanks to Eric Sandeen)
>  fs/ext4/ext4.h  |    4 ----
>  fs/ext4/super.c |   31 ++++++-------------------------
>  2 files changed, 6 insertions(+), 29 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 4daaf2b..1e37c09 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1590,12 +1590,8 @@ void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
>   */
>  struct ext4_lazy_init {
>  	unsigned long		li_state;
> -
> -	wait_queue_head_t	li_wait_daemon;
>  	wait_queue_head_t	li_wait_task;
> -	struct timer_list	li_timer;
>  	struct task_struct	*li_task;
> -
>  	struct list_head	li_request_list;
>  	struct mutex		li_list_mtx;
>  };
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 8553dfb..f0e4c3a 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -2659,12 +2659,6 @@ static void print_daily_error_info(unsigned long arg)
>  	mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
>  }
>  
> -static void ext4_lazyinode_timeout(unsigned long data)
> -{
> -	struct task_struct *p = (struct task_struct *)data;
> -	wake_up_process(p);
> -}
> -
>  /* Find next suitable group and run ext4_init_inode_table */
>  static int ext4_run_li_request(struct ext4_li_request *elr)
>  {
> @@ -2712,7 +2706,7 @@ static int ext4_run_li_request(struct ext4_li_request *elr)
>  
>  /*
>   * Remove lr_request from the list_request and free the
> - * request tructure. Should be called with li_list_mtx held
> + * request structure. Should be called with li_list_mtx held
>   */
>  static void ext4_remove_li_request(struct ext4_li_request *elr)
>  {
> @@ -2756,14 +2750,10 @@ static int ext4_lazyinit_thread(void *arg)
>  	struct ext4_lazy_init *eli = (struct ext4_lazy_init *)arg;
>  	struct list_head *pos, *n;
>  	struct ext4_li_request *elr;
> -	unsigned long next_wakeup;
> -	DEFINE_WAIT(wait);
> +	unsigned long next_wakeup, cur;
>  
>  	BUG_ON(NULL == eli);
>  
> -	eli->li_timer.data = (unsigned long)current;
> -	eli->li_timer.function = ext4_lazyinode_timeout;
> -
>  	eli->li_task = current;
>  	wake_up(&eli->li_wait_task);
>  
> @@ -2797,19 +2787,15 @@ cont_thread:
>  		if (freezing(current))
>  			refrigerator();
>  
> -		if ((time_after_eq(jiffies, next_wakeup)) ||
> +		cur = jiffies;
> +		if ((time_after_eq(cur, next_wakeup)) ||
>  		    (MAX_JIFFY_OFFSET == next_wakeup)) {
>  			cond_resched();
>  			continue;
>  		}
>  
> -		eli->li_timer.expires = next_wakeup;
> -		add_timer(&eli->li_timer);
> -		prepare_to_wait(&eli->li_wait_daemon, &wait,
> -				TASK_INTERRUPTIBLE);
> -		if (time_before(jiffies, next_wakeup))
> -			schedule();
> -		finish_wait(&eli->li_wait_daemon, &wait);
> +		schedule_timeout_interruptible(next_wakeup - cur);
> +
>  		if (kthread_should_stop()) {
>  			ext4_clear_request_list();
>  			goto exit_thread;
> @@ -2833,12 +2819,10 @@ exit_thread:
>  		goto cont_thread;
>  	}
>  	mutex_unlock(&eli->li_list_mtx);
> -	del_timer_sync(&ext4_li_info->li_timer);
>  	eli->li_task = NULL;
>  	wake_up(&eli->li_wait_task);
>  
>  	kfree(ext4_li_info);
> -	ext4_lazyinit_task = NULL;
>  	ext4_li_info = NULL;
>  	mutex_unlock(&ext4_li_mtx);
>  
> @@ -2866,7 +2850,6 @@ static int ext4_run_lazyinit_thread(void)
>  	if (IS_ERR(ext4_lazyinit_task)) {
>  		int err = PTR_ERR(ext4_lazyinit_task);
>  		ext4_clear_request_list();
> -		del_timer_sync(&ext4_li_info->li_timer);
>  		kfree(ext4_li_info);
>  		ext4_li_info = NULL;
>  		printk(KERN_CRIT "EXT4: error %d creating inode table "
> @@ -2915,9 +2898,7 @@ static int ext4_li_info_new(void)
>  	INIT_LIST_HEAD(&eli->li_request_list);
>  	mutex_init(&eli->li_list_mtx);
>  
> -	init_waitqueue_head(&eli->li_wait_daemon);
>  	init_waitqueue_head(&eli->li_wait_task);
> -	init_timer(&eli->li_timer);
>  	eli->li_state |= EXT4_LAZYINIT_QUIT;
>  
>  	ext4_li_info = eli;

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Patch

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 4daaf2b..1e37c09 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1590,12 +1590,8 @@  void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
  */
 struct ext4_lazy_init {
 	unsigned long		li_state;
-
-	wait_queue_head_t	li_wait_daemon;
 	wait_queue_head_t	li_wait_task;
-	struct timer_list	li_timer;
 	struct task_struct	*li_task;
-
 	struct list_head	li_request_list;
 	struct mutex		li_list_mtx;
 };
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8553dfb..f0e4c3a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2659,12 +2659,6 @@  static void print_daily_error_info(unsigned long arg)
 	mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);  /* Once a day */
 }
 
-static void ext4_lazyinode_timeout(unsigned long data)
-{
-	struct task_struct *p = (struct task_struct *)data;
-	wake_up_process(p);
-}
-
 /* Find next suitable group and run ext4_init_inode_table */
 static int ext4_run_li_request(struct ext4_li_request *elr)
 {
@@ -2712,7 +2706,7 @@  static int ext4_run_li_request(struct ext4_li_request *elr)
 
 /*
  * Remove lr_request from the list_request and free the
- * request tructure. Should be called with li_list_mtx held
+ * request structure. Should be called with li_list_mtx held
  */
 static void ext4_remove_li_request(struct ext4_li_request *elr)
 {
@@ -2756,14 +2750,10 @@  static int ext4_lazyinit_thread(void *arg)
 	struct ext4_lazy_init *eli = (struct ext4_lazy_init *)arg;
 	struct list_head *pos, *n;
 	struct ext4_li_request *elr;
-	unsigned long next_wakeup;
-	DEFINE_WAIT(wait);
+	unsigned long next_wakeup, cur;
 
 	BUG_ON(NULL == eli);
 
-	eli->li_timer.data = (unsigned long)current;
-	eli->li_timer.function = ext4_lazyinode_timeout;
-
 	eli->li_task = current;
 	wake_up(&eli->li_wait_task);
 
@@ -2797,19 +2787,15 @@  cont_thread:
 		if (freezing(current))
 			refrigerator();
 
-		if ((time_after_eq(jiffies, next_wakeup)) ||
+		cur = jiffies;
+		if ((time_after_eq(cur, next_wakeup)) ||
 		    (MAX_JIFFY_OFFSET == next_wakeup)) {
 			cond_resched();
 			continue;
 		}
 
-		eli->li_timer.expires = next_wakeup;
-		add_timer(&eli->li_timer);
-		prepare_to_wait(&eli->li_wait_daemon, &wait,
-				TASK_INTERRUPTIBLE);
-		if (time_before(jiffies, next_wakeup))
-			schedule();
-		finish_wait(&eli->li_wait_daemon, &wait);
+		schedule_timeout_interruptible(next_wakeup - cur);
+
 		if (kthread_should_stop()) {
 			ext4_clear_request_list();
 			goto exit_thread;
@@ -2833,12 +2819,10 @@  exit_thread:
 		goto cont_thread;
 	}
 	mutex_unlock(&eli->li_list_mtx);
-	del_timer_sync(&ext4_li_info->li_timer);
 	eli->li_task = NULL;
 	wake_up(&eli->li_wait_task);
 
 	kfree(ext4_li_info);
-	ext4_lazyinit_task = NULL;
 	ext4_li_info = NULL;
 	mutex_unlock(&ext4_li_mtx);
 
@@ -2866,7 +2850,6 @@  static int ext4_run_lazyinit_thread(void)
 	if (IS_ERR(ext4_lazyinit_task)) {
 		int err = PTR_ERR(ext4_lazyinit_task);
 		ext4_clear_request_list();
-		del_timer_sync(&ext4_li_info->li_timer);
 		kfree(ext4_li_info);
 		ext4_li_info = NULL;
 		printk(KERN_CRIT "EXT4: error %d creating inode table "
@@ -2915,9 +2898,7 @@  static int ext4_li_info_new(void)
 	INIT_LIST_HEAD(&eli->li_request_list);
 	mutex_init(&eli->li_list_mtx);
 
-	init_waitqueue_head(&eli->li_wait_daemon);
 	init_waitqueue_head(&eli->li_wait_task);
-	init_timer(&eli->li_timer);
 	eli->li_state |= EXT4_LAZYINIT_QUIT;
 
 	ext4_li_info = eli;