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Commit 5318ce7d authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe
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bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy() 



Currently we waited for all cgwbs to get freed in cgwb_bdi_destroy()
which also means that writeback has been shutdown on them. Since this
wait is going away, directly shutdown writeback on cgwbs from
cgwb_bdi_destroy() to avoid live writeback structures after
bdi_unregister() has finished. To make that safe with concurrent
shutdown from cgwb_release_workfn(), we also have to make sure
wb_shutdown() returns only after the bdi_writeback structure is really
shutdown.

Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent e8cb72b3

include/linux/backing-dev-defs.h

+1 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ struct dentry; 
 */

enum wb_state {

	WB_registered,		/* bdi_register() was done */

	WB_shutting_down,	/* wb_shutdown() in progress */

	WB_writeback_running,	/* Writeback is in progress */

	WB_has_dirty_io,	/* Dirty inodes on ->b_{dirty|io|more_io} */

};

mm/backing-dev.c

+22 −0
Original line number Diff line number Diff line
@@ -356,8 +356,15 @@ static void wb_shutdown(struct bdi_writeback *wb) 
	spin_lock_bh(&wb->work_lock);

	if (!test_and_clear_bit(WB_registered, &wb->state)) {

		spin_unlock_bh(&wb->work_lock);

		/*

		 * Wait for wb shutdown to finish if someone else is just

		 * running wb_shutdown(). Otherwise we could proceed to wb /

		 * bdi destruction before wb_shutdown() is finished.

		 */

		wait_on_bit(&wb->state, WB_shutting_down, TASK_UNINTERRUPTIBLE);

		return;

	}

	set_bit(WB_shutting_down, &wb->state);

	spin_unlock_bh(&wb->work_lock);



	cgwb_remove_from_bdi_list(wb);
@@ -369,6 +376,12 @@ 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));

	/*

	 * Make sure bit gets cleared after shutdown is finished. Matches with

	 * the barrier provided by test_and_clear_bit() above.

	 */

	smp_wmb();

	clear_bit(WB_shutting_down, &wb->state);

}



static void wb_exit(struct bdi_writeback *wb)
@@ -699,12 +712,21 @@ static void cgwb_bdi_destroy(struct backing_dev_info *bdi) 
{

	struct radix_tree_iter iter;

	void **slot;

	struct bdi_writeback *wb;



	WARN_ON(test_bit(WB_registered, &bdi->wb.state));



	spin_lock_irq(&cgwb_lock);

	radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)

		cgwb_kill(*slot);



	while (!list_empty(&bdi->wb_list)) {

		wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,

				      bdi_node);

		spin_unlock_irq(&cgwb_lock);

		wb_shutdown(wb);

		spin_lock_irq(&cgwb_lock);

	}

	spin_unlock_irq(&cgwb_lock);



	/*