Re: [PATCH] bdi: Fix another oops in wb_workfn()
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Date: 2018-06-13 11:51:59
Also in:
linux-fsdevel, lkml
Possibly related (same subject, not in this thread)
- 2018-06-22 · Re: [PATCH] bdi: Fix another oops in wb_workfn() · Jens Axboe <axboe@kernel.dk>
- 2018-06-22 · Re: [PATCH] bdi: Fix another oops in wb_workfn() · Jan Kara <jack@suse.cz>
- 2018-06-19 · Re: [PATCH] bdi: Fix another oops in wb_workfn() · Jan Kara <jack@suse.cz>
- 2018-06-18 · Re: [PATCH] bdi: Fix another oops in wb_workfn() · Tejun Heo <tj@kernel.org>
- 2018-06-18 · Re: [PATCH] bdi: Fix another oops in wb_workfn() · Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Tetsuo Handa wrote:
quoted hunk ↗ jump to hunk
Or, toggling a dedicated flag using test_and_change_bit(): include/linux/backing-dev-defs.h | 1 + mm/backing-dev.c | 8 +++++++- 2 files changed, 8 insertions(+), 1 deletion(-)diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h index 0bd432a..93ff83c 100644 --- a/include/linux/backing-dev-defs.h +++ b/include/linux/backing-dev-defs.h@@ -26,6 +26,7 @@ enum wb_state { WB_writeback_running, /* Writeback is in progress */ WB_has_dirty_io, /* Dirty inodes on ->b_{dirty|io|more_io} */ WB_start_all, /* nr_pages == 0 (all) work pending */ + WB_postpone_kfree, /* cgwb_bdi_unregister() will access later */ }; enum wb_congested_state {diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 347cc83..422d7a7 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c@@ -516,7 +516,10 @@ static void cgwb_release_workfn(struct work_struct *work) fprop_local_destroy_percpu(&wb->memcg_completions); percpu_ref_exit(&wb->refcnt); wb_exit(wb); - kfree_rcu(wb, rcu); + spin_lock_irq(&cgwb_lock); + if (!test_and_change_bit(WB_postpone_kfree, &wb->state)) + kfree_rcu(wb, rcu); + spin_unlock_irq(&cgwb_lock); } static void cgwb_release(struct percpu_ref *refcnt)@@ -721,9 +724,12 @@ static void cgwb_bdi_unregister(struct backing_dev_info *bdi) while (!list_empty(&bdi->wb_list)) { wb = list_first_entry(&bdi->wb_list, struct bdi_writeback, bdi_node); + set_bit(WB_postpone_kfree, &wb->state); spin_unlock_irq(&cgwb_lock); wb_shutdown(wb); spin_lock_irq(&cgwb_lock); + if (!test_and_change_bit(WB_postpone_kfree, &wb->state)) + kfree_rcu(wb, rcu); } spin_unlock_irq(&cgwb_lock); }
Forgot to include below change, but isn't this approach the simplest?
@@ -370,7 +370,6 @@ static void wb_shutdown(struct bdi_writeback *wb) set_bit(WB_shutting_down, &wb->state); spin_unlock_bh(&wb->work_lock); - cgwb_remove_from_bdi_list(wb); /* * Drain work list and shutdown the delayed_work. !WB_registered * tells wb_workfn() that @wb is dying and its work_list needs to
@@ -379,6 +378,7 @@ static void wb_shutdown(struct bdi_writeback *wb) mod_delayed_work(bdi_wq, &wb->dwork, 0); flush_delayed_work(&wb->dwork); WARN_ON(!list_empty(&wb->work_list)); + cgwb_remove_from_bdi_list(wb); /* * Make sure bit gets cleared after shutdown is finished. Matches with * the barrier provided by test_and_clear_bit() above.
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