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bdi: Shutdown writeback on all cgwbs in cgwb_bdi_destroy()

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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: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jan Kara 2017-03-23 01:36:57 +01:00 committed by Jens Axboe
parent e8cb72b322
commit 5318ce7d46
2 changed files with 23 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/linux/backing-dev-defs.h
View file

@ -21,6 +21,7 @@ struct dentry;
*/ */
enum wb_state { enum wb_state {
WB_registered, /* bdi_register() was done */ WB_registered, /* bdi_register() was done */
WB_shutting_down, /* wb_shutdown() in progress */
WB_writeback_running, /* Writeback is in progress */ WB_writeback_running, /* Writeback is in progress */
WB_has_dirty_io, /* Dirty inodes on ->b_{dirty|io|more_io} */ WB_has_dirty_io, /* Dirty inodes on ->b_{dirty|io|more_io} */
}; };

22
mm/backing-dev.c
View file

@ -356,8 +356,15 @@ static void wb_shutdown(struct bdi_writeback *wb)
spin_lock_bh(&wb->work_lock); spin_lock_bh(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) { if (!test_and_clear_bit(WB_registered, &wb->state)) {
spin_unlock_bh(&wb->work_lock); 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; return;
} }
set_bit(WB_shutting_down, &wb->state);
spin_unlock_bh(&wb->work_lock); spin_unlock_bh(&wb->work_lock);
cgwb_remove_from_bdi_list(wb); 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); mod_delayed_work(bdi_wq, &wb->dwork, 0);
flush_delayed_work(&wb->dwork); flush_delayed_work(&wb->dwork);
WARN_ON(!list_empty(&wb->work_list)); 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) 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; struct radix_tree_iter iter;
void **slot; void **slot;
struct bdi_writeback *wb;
WARN_ON(test_bit(WB_registered, &bdi->wb.state)); WARN_ON(test_bit(WB_registered, &bdi->wb.state));
spin_lock_irq(&cgwb_lock); spin_lock_irq(&cgwb_lock);
radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0) radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
cgwb_kill(*slot); 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); spin_unlock_irq(&cgwb_lock);
/* /*