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[PATCH] fs: quota: create dedicated workqueue for quota_release_work

Shashank A P posted 1 patch 5 months, 1 week ago 
fs/quota/dquot.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
[PATCH] fs: quota: create dedicated workqueue for quota_release_work
Posted by Shashank A P 5 months, 1 week ago 
There is a kernel panic due to WARN_ONCE when panic_on_warn is set.

This issue occurs when writeback is triggered due to sync call for an
opened file(ie, writeback reason is WB_REASON_SYNC). When f2fs balance
is needed at sync path, flush for quota_release_work is triggered.
By default quota_release_work is queued to "events_unbound" queue which
does not have WQ_MEM_RECLAIM flag. During f2fs balance "writeback"
workqueue tries to flush quota_release_work causing kernel panic due to
MEM_RECLAIM flag mismatch errors.

This patch creates dedicated workqueue with WQ_MEM_RECLAIM flag
for work quota_release_work.

------------[ cut here ]------------
WARNING: CPU: 4 PID: 14867 at kernel/workqueue.c:3721 check_flush_dependency+0x13c/0x148
Call trace:
 check_flush_dependency+0x13c/0x148
 __flush_work+0xd0/0x398
 flush_delayed_work+0x44/0x5c
 dquot_writeback_dquots+0x54/0x318
 f2fs_do_quota_sync+0xb8/0x1a8
 f2fs_write_checkpoint+0x3cc/0x99c
 f2fs_gc+0x190/0x750
 f2fs_balance_fs+0x110/0x168
 f2fs_write_single_data_page+0x474/0x7dc
 f2fs_write_data_pages+0x7d0/0xd0c
 do_writepages+0xe0/0x2f4
 __writeback_single_inode+0x44/0x4ac
 writeback_sb_inodes+0x30c/0x538
 wb_writeback+0xf4/0x440
 wb_workfn+0x128/0x5d4
 process_scheduled_works+0x1c4/0x45c
 worker_thread+0x32c/0x3e8
 kthread+0x11c/0x1b0
 ret_from_fork+0x10/0x20
Kernel panic - not syncing: kernel: panic_on_warn set ...

Fixes: ac6f420291b3 ("quota: flush quota_release_work upon quota writeback")
CC: stable@vger.kernel.org
Signed-off-by: Shashank A P <shashank.ap@samsung.com>
---
 fs/quota/dquot.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index df4a9b348769..d0f83a0c42df 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -162,6 +162,9 @@ static struct quota_module_name module_names[] = INIT_QUOTA_MODULE_NAMES;
 /* SLAB cache for dquot structures */
 static struct kmem_cache *dquot_cachep;
 
+/* workqueue for work quota_release_work*/
+struct workqueue_struct *quota_unbound_wq;
+
 void register_quota_format(struct quota_format_type *fmt)
 {
 	spin_lock(&dq_list_lock);
@@ -881,7 +884,7 @@ void dqput(struct dquot *dquot)
 	put_releasing_dquots(dquot);
 	atomic_dec(&dquot->dq_count);
 	spin_unlock(&dq_list_lock);
-	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
+	queue_delayed_work(quota_unbound_wq, &quota_release_work, 1);
 }
 EXPORT_SYMBOL(dqput);
 
@@ -3041,6 +3044,11 @@ static int __init dquot_init(void)
 
 	shrinker_register(dqcache_shrinker);
 
+	quota_unbound_wq = alloc_workqueue("quota_events_unbound",
+					   WQ_UNBOUND | WQ_MEM_RECLAIM, WQ_MAX_ACTIVE);
+	if (!quota_unbound_wq)
+		panic("Cannot create quota_unbound_wq\n");
+
 	return 0;
 }
 fs_initcall(dquot_init);
-- 
2.34.1
Re: [PATCH] fs: quota: create dedicated workqueue for quota_release_work
Posted by Jan Kara 5 months, 1 week ago 
On Mon 01-09-25 14:59:00, Shashank A P wrote:
> There is a kernel panic due to WARN_ONCE when panic_on_warn is set.
> 
> This issue occurs when writeback is triggered due to sync call for an
> opened file(ie, writeback reason is WB_REASON_SYNC). When f2fs balance
> is needed at sync path, flush for quota_release_work is triggered.
> By default quota_release_work is queued to "events_unbound" queue which
> does not have WQ_MEM_RECLAIM flag. During f2fs balance "writeback"
> workqueue tries to flush quota_release_work causing kernel panic due to
> MEM_RECLAIM flag mismatch errors.
> 
> This patch creates dedicated workqueue with WQ_MEM_RECLAIM flag
> for work quota_release_work.
> 
> ------------[ cut here ]------------
> WARNING: CPU: 4 PID: 14867 at kernel/workqueue.c:3721 check_flush_dependency+0x13c/0x148
> Call trace:
>  check_flush_dependency+0x13c/0x148
>  __flush_work+0xd0/0x398
>  flush_delayed_work+0x44/0x5c
>  dquot_writeback_dquots+0x54/0x318
>  f2fs_do_quota_sync+0xb8/0x1a8
>  f2fs_write_checkpoint+0x3cc/0x99c
>  f2fs_gc+0x190/0x750
>  f2fs_balance_fs+0x110/0x168
>  f2fs_write_single_data_page+0x474/0x7dc
>  f2fs_write_data_pages+0x7d0/0xd0c
>  do_writepages+0xe0/0x2f4
>  __writeback_single_inode+0x44/0x4ac
>  writeback_sb_inodes+0x30c/0x538
>  wb_writeback+0xf4/0x440
>  wb_workfn+0x128/0x5d4
>  process_scheduled_works+0x1c4/0x45c
>  worker_thread+0x32c/0x3e8
>  kthread+0x11c/0x1b0
>  ret_from_fork+0x10/0x20
> Kernel panic - not syncing: kernel: panic_on_warn set ...
> 
> Fixes: ac6f420291b3 ("quota: flush quota_release_work upon quota writeback")
> CC: stable@vger.kernel.org
> Signed-off-by: Shashank A P <shashank.ap@samsung.com>

Thanks. It seems a bit unfortunate that we have to create a separate
workqueue just for this but I don't see a different easy solution. So I've
added your patch to my tree.

								Honza

> ---
>  fs/quota/dquot.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index df4a9b348769..d0f83a0c42df 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -162,6 +162,9 @@ static struct quota_module_name module_names[] = INIT_QUOTA_MODULE_NAMES;
>  /* SLAB cache for dquot structures */
>  static struct kmem_cache *dquot_cachep;
>  
> +/* workqueue for work quota_release_work*/
> +struct workqueue_struct *quota_unbound_wq;
> +
>  void register_quota_format(struct quota_format_type *fmt)
>  {
>  	spin_lock(&dq_list_lock);
> @@ -881,7 +884,7 @@ void dqput(struct dquot *dquot)
>  	put_releasing_dquots(dquot);
>  	atomic_dec(&dquot->dq_count);
>  	spin_unlock(&dq_list_lock);
> -	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
> +	queue_delayed_work(quota_unbound_wq, &quota_release_work, 1);
>  }
>  EXPORT_SYMBOL(dqput);
>  
> @@ -3041,6 +3044,11 @@ static int __init dquot_init(void)
>  
>  	shrinker_register(dqcache_shrinker);
>  
> +	quota_unbound_wq = alloc_workqueue("quota_events_unbound",
> +					   WQ_UNBOUND | WQ_MEM_RECLAIM, WQ_MAX_ACTIVE);
> +	if (!quota_unbound_wq)
> +		panic("Cannot create quota_unbound_wq\n");
> +
>  	return 0;
>  }
>  fs_initcall(dquot_init);
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR
Re: [PATCH] fs: quota: create dedicated workqueue for quota_release_work
Posted by Shashank A P 5 months, 1 week ago 
On 9/2/2025 7:17 PM, Jan Kara wrote:
> On Mon 01-09-25 14:59:00, Shashank A P wrote:
>> There is a kernel panic due to WARN_ONCE when panic_on_warn is set.
>>
>> This issue occurs when writeback is triggered due to sync call for an
>> opened file(ie, writeback reason is WB_REASON_SYNC). When f2fs balance
>> is needed at sync path, flush for quota_release_work is triggered.
>> By default quota_release_work is queued to "events_unbound" queue which
>> does not have WQ_MEM_RECLAIM flag. During f2fs balance "writeback"
>> workqueue tries to flush quota_release_work causing kernel panic due to
>> MEM_RECLAIM flag mismatch errors.
>>
>> This patch creates dedicated workqueue with WQ_MEM_RECLAIM flag
>> for work quota_release_work.
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 4 PID: 14867 at kernel/workqueue.c:3721 check_flush_dependency+0x13c/0x148
>> Call trace:
>>   check_flush_dependency+0x13c/0x148
>>   __flush_work+0xd0/0x398
>>   flush_delayed_work+0x44/0x5c
>>   dquot_writeback_dquots+0x54/0x318
>>   f2fs_do_quota_sync+0xb8/0x1a8
>>   f2fs_write_checkpoint+0x3cc/0x99c
>>   f2fs_gc+0x190/0x750
>>   f2fs_balance_fs+0x110/0x168
>>   f2fs_write_single_data_page+0x474/0x7dc
>>   f2fs_write_data_pages+0x7d0/0xd0c
>>   do_writepages+0xe0/0x2f4
>>   __writeback_single_inode+0x44/0x4ac
>>   writeback_sb_inodes+0x30c/0x538
>>   wb_writeback+0xf4/0x440
>>   wb_workfn+0x128/0x5d4
>>   process_scheduled_works+0x1c4/0x45c
>>   worker_thread+0x32c/0x3e8
>>   kthread+0x11c/0x1b0
>>   ret_from_fork+0x10/0x20
>> Kernel panic - not syncing: kernel: panic_on_warn set ...
>>
>> Fixes: ac6f420291b3 ("quota: flush quota_release_work upon quota writeback")
>> CC: stable@vger.kernel.org
>> Signed-off-by: Shashank A P <shashank.ap@samsung.com>
> Thanks. It seems a bit unfortunate that we have to create a separate
> workqueue just for this but I don't see a different easy solution. So I've
> added your patch to my tree.
>
> 								Honza

Hi Jan Kara,
Thanks for your comments.

We've got a below kernel warning from kernel test 
robot(lkp@intel.com)that related to the changes, and we need your 
suggestions to resolve this warning as its merged already in your tree.

Should we post a new patch version to fix this warning, or can you 
please incorporate the fix while applying it to linux-next?


sparse warnings: (new ones prefixed by >>)
 >> fs/quota/dquot.c:166:25: sparse: sparse: symbol 'quota_unbound_wq' 
was not declared. Should it be static?

https://lore.kernel.org/all/202509031153.0ACADDn6-lkp@intel.com/

Thanks,
Shashank

>
>> ---
>>   fs/quota/dquot.c | 10 +++++++++-
>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
>> index df4a9b348769..d0f83a0c42df 100644
>> --- a/fs/quota/dquot.c
>> +++ b/fs/quota/dquot.c
>> @@ -162,6 +162,9 @@ static struct quota_module_name module_names[] = INIT_QUOTA_MODULE_NAMES;
>>   /* SLAB cache for dquot structures */
>>   static struct kmem_cache *dquot_cachep;
>>   
>> +/* workqueue for work quota_release_work*/
>> +struct workqueue_struct *quota_unbound_wq;
>> +
>>   void register_quota_format(struct quota_format_type *fmt)
>>   {
>>   	spin_lock(&dq_list_lock);
>> @@ -881,7 +884,7 @@ void dqput(struct dquot *dquot)
>>   	put_releasing_dquots(dquot);
>>   	atomic_dec(&dquot->dq_count);
>>   	spin_unlock(&dq_list_lock);
>> -	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
>> +	queue_delayed_work(quota_unbound_wq, &quota_release_work, 1);
>>   }
>>   EXPORT_SYMBOL(dqput);
>>   
>> @@ -3041,6 +3044,11 @@ static int __init dquot_init(void)
>>   
>>   	shrinker_register(dqcache_shrinker);
>>   
>> +	quota_unbound_wq = alloc_workqueue("quota_events_unbound",
>> +					   WQ_UNBOUND | WQ_MEM_RECLAIM, WQ_MAX_ACTIVE);
>> +	if (!quota_unbound_wq)
>> +		panic("Cannot create quota_unbound_wq\n");
>> +
>>   	return 0;
>>   }
>>   fs_initcall(dquot_init);
>> -- 
>> 2.34.1
>>
Re: [PATCH] fs: quota: create dedicated workqueue for quota_release_work
Posted by Jan Kara 5 months, 1 week ago 
On Wed 03-09-25 14:01:46, Shashank A P wrote:
> On 9/2/2025 7:17 PM, Jan Kara wrote:
> > On Mon 01-09-25 14:59:00, Shashank A P wrote:
> >> There is a kernel panic due to WARN_ONCE when panic_on_warn is set.
> >>
> >> This issue occurs when writeback is triggered due to sync call for an
> >> opened file(ie, writeback reason is WB_REASON_SYNC). When f2fs balance
> >> is needed at sync path, flush for quota_release_work is triggered.
> >> By default quota_release_work is queued to "events_unbound" queue which
> >> does not have WQ_MEM_RECLAIM flag. During f2fs balance "writeback"
> >> workqueue tries to flush quota_release_work causing kernel panic due to
> >> MEM_RECLAIM flag mismatch errors.
> >>
> >> This patch creates dedicated workqueue with WQ_MEM_RECLAIM flag
> >> for work quota_release_work.
> >>
> >> ------------[ cut here ]------------
> >> WARNING: CPU: 4 PID: 14867 at kernel/workqueue.c:3721 check_flush_dependency+0x13c/0x148
> >> Call trace:
> >>   check_flush_dependency+0x13c/0x148
> >>   __flush_work+0xd0/0x398
> >>   flush_delayed_work+0x44/0x5c
> >>   dquot_writeback_dquots+0x54/0x318
> >>   f2fs_do_quota_sync+0xb8/0x1a8
> >>   f2fs_write_checkpoint+0x3cc/0x99c
> >>   f2fs_gc+0x190/0x750
> >>   f2fs_balance_fs+0x110/0x168
> >>   f2fs_write_single_data_page+0x474/0x7dc
> >>   f2fs_write_data_pages+0x7d0/0xd0c
> >>   do_writepages+0xe0/0x2f4
> >>   __writeback_single_inode+0x44/0x4ac
> >>   writeback_sb_inodes+0x30c/0x538
> >>   wb_writeback+0xf4/0x440
> >>   wb_workfn+0x128/0x5d4
> >>   process_scheduled_works+0x1c4/0x45c
> >>   worker_thread+0x32c/0x3e8
> >>   kthread+0x11c/0x1b0
> >>   ret_from_fork+0x10/0x20
> >> Kernel panic - not syncing: kernel: panic_on_warn set ...
> >>
> >> Fixes: ac6f420291b3 ("quota: flush quota_release_work upon quota writeback")
> >> CC: stable@vger.kernel.org
> >> Signed-off-by: Shashank A P <shashank.ap@samsung.com>
> > Thanks. It seems a bit unfortunate that we have to create a separate
> > workqueue just for this but I don't see a different easy solution. So I've
> > added your patch to my tree.
> >
> > 								Honza
> 
> Hi Jan Kara,
> Thanks for your comments.
> 
> We've got a below kernel warning from kernel test 
> robot(lkp@intel.com)that related to the changes, and we need your 
> suggestions to resolve this warning as its merged already in your tree.
> 
> Should we post a new patch version to fix this warning, or can you 
> please incorporate the fix while applying it to linux-next?
> 
> 
> sparse warnings: (new ones prefixed by >>)
>  >> fs/quota/dquot.c:166:25: sparse: sparse: symbol 'quota_unbound_wq' 
> was not declared. Should it be static?
> 
> https://lore.kernel.org/all/202509031153.0ACADDn6-lkp@intel.com/

Thanks for noticing. Somehow I didn't get this notification. Anyway, I've
fixed up the commit in my tree to declare quota_unbound_wq as static.

								Honza

> >> ---
> >>   fs/quota/dquot.c | 10 +++++++++-
> >>   1 file changed, 9 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> >> index df4a9b348769..d0f83a0c42df 100644
> >> --- a/fs/quota/dquot.c
> >> +++ b/fs/quota/dquot.c
> >> @@ -162,6 +162,9 @@ static struct quota_module_name module_names[] = INIT_QUOTA_MODULE_NAMES;
> >>   /* SLAB cache for dquot structures */
> >>   static struct kmem_cache *dquot_cachep;
> >>   
> >> +/* workqueue for work quota_release_work*/
> >> +struct workqueue_struct *quota_unbound_wq;
> >> +
> >>   void register_quota_format(struct quota_format_type *fmt)
> >>   {
> >>   	spin_lock(&dq_list_lock);
> >> @@ -881,7 +884,7 @@ void dqput(struct dquot *dquot)
> >>   	put_releasing_dquots(dquot);
> >>   	atomic_dec(&dquot->dq_count);
> >>   	spin_unlock(&dq_list_lock);
> >> -	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
> >> +	queue_delayed_work(quota_unbound_wq, &quota_release_work, 1);
> >>   }
> >>   EXPORT_SYMBOL(dqput);
> >>   
> >> @@ -3041,6 +3044,11 @@ static int __init dquot_init(void)
> >>   
> >>   	shrinker_register(dqcache_shrinker);
> >>   
> >> +	quota_unbound_wq = alloc_workqueue("quota_events_unbound",
> >> +					   WQ_UNBOUND | WQ_MEM_RECLAIM, WQ_MAX_ACTIVE);
> >> +	if (!quota_unbound_wq)
> >> +		panic("Cannot create quota_unbound_wq\n");
> >> +
> >>   	return 0;
> >>   }
> >>   fs_initcall(dquot_init);
> >> -- 
> >> 2.34.1
> >>
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Patchew 2.1-devel-b67e4c2

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