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