Messages in this thread |  | | Date | Wed, 3 Sep 2025 14:01:46 +0530 | | Subject | Re: [PATCH] fs: quota: create dedicated workqueue for quota_release_work | | From | Shashank A P <> |
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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, "a_release_work, 1); >> + queue_delayed_work(quota_unbound_wq, "a_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 >>
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