Messages in this thread |  | | Date | Tue, 2 Sep 2025 15:47:18 +0200 | | From | Jan Kara <> | | Subject | Re: [PATCH] fs: quota: create dedicated workqueue for quota_release_work |
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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, "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 > -- Jan Kara <jack@suse.com> SUSE Labs, CR
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