bdi: avoid oops on device removal
After commit 839a8e8660b6 ("writeback: replace custom worker pool
implementation with unbound workqueue") when device is removed while we
are writing to it we crash in bdi_writeback_workfn() ->
set_worker_desc() because bdi->dev is NULL.
This can happen because even though bdi_unregister() cancels all pending
flushing work, nothing really prevents new ones from being queued from
balance_dirty_pages() or other places.
Fix the problem by clearing BDI_registered bit in bdi_unregister() and
checking it before scheduling of any flushing work.
Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Derek Basehore <dbasehore@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 6788fe0c..a163159 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -89,16 +89,29 @@
#define CREATE_TRACE_POINTS
#include <trace/events/writeback.h>
+static void bdi_wakeup_thread(struct backing_dev_info *bdi)
+{
+ spin_lock_bh(&bdi->wb_lock);
+ if (test_bit(BDI_registered, &bdi->state))
+ mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+ spin_unlock_bh(&bdi->wb_lock);
+}
+
static void bdi_queue_work(struct backing_dev_info *bdi,
struct wb_writeback_work *work)
{
trace_writeback_queue(bdi, work);
spin_lock_bh(&bdi->wb_lock);
+ if (!test_bit(BDI_registered, &bdi->state)) {
+ if (work->done)
+ complete(work->done);
+ goto out_unlock;
+ }
list_add_tail(&work->list, &bdi->work_list);
- spin_unlock_bh(&bdi->wb_lock);
-
mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+out_unlock:
+ spin_unlock_bh(&bdi->wb_lock);
}
static void
@@ -114,7 +127,7 @@
work = kzalloc(sizeof(*work), GFP_ATOMIC);
if (!work) {
trace_writeback_nowork(bdi);
- mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+ bdi_wakeup_thread(bdi);
return;
}
@@ -161,7 +174,7 @@
* writeback as soon as there is no other work to do.
*/
trace_writeback_wake_background(bdi);
- mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+ bdi_wakeup_thread(bdi);
}
/*
@@ -1017,7 +1030,7 @@
current->flags |= PF_SWAPWRITE;
if (likely(!current_is_workqueue_rescuer() ||
- list_empty(&bdi->bdi_list))) {
+ !test_bit(BDI_registered, &bdi->state))) {
/*
* The normal path. Keep writing back @bdi until its
* work_list is empty. Note that this path is also taken