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* [PATCH] nbd: make the config put is called before the notifying the waiter
@ 2020-10-14  2:45 xiubli
  2020-10-14 17:33 ` Josef Bacik
  2020-10-14 18:30 ` Jens Axboe
  0 siblings, 2 replies; 3+ messages in thread
From: xiubli @ 2020-10-14  2:45 UTC (permalink / raw)
  To: josef, axboe; +Cc: linux-block, nbd, Xiubo Li

From: Xiubo Li <xiubli@redhat.com>

There has one race case for ceph's rbd-nbd tool. When do mapping
it may fail with EBUSY from ioctl(nbd, NBD_DO_IT), but actually
the nbd device has already unmaped.

It dues to if just after the wake_up(), the recv_work() is scheduled
out and defers calling the nbd_config_put(), though the map process
has exited the "nbd->recv_task" is not cleared.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 drivers/block/nbd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index edf8b632e3d2..f46e26c9d9b3 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -801,9 +801,9 @@ static void recv_work(struct work_struct *work)
 		if (likely(!blk_should_fake_timeout(rq->q)))
 			blk_mq_complete_request(rq);
 	}
+	nbd_config_put(nbd);
 	atomic_dec(&config->recv_threads);
 	wake_up(&config->recv_wq);
-	nbd_config_put(nbd);
 	kfree(args);
 }
 
-- 
2.18.4


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] nbd: make the config put is called before the notifying the waiter
  2020-10-14  2:45 [PATCH] nbd: make the config put is called before the notifying the waiter xiubli
@ 2020-10-14 17:33 ` Josef Bacik
  2020-10-14 18:30 ` Jens Axboe
  1 sibling, 0 replies; 3+ messages in thread
From: Josef Bacik @ 2020-10-14 17:33 UTC (permalink / raw)
  To: xiubli, axboe; +Cc: linux-block, nbd

On 10/13/20 10:45 PM, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> There has one race case for ceph's rbd-nbd tool. When do mapping
> it may fail with EBUSY from ioctl(nbd, NBD_DO_IT), but actually
> the nbd device has already unmaped.
> 
> It dues to if just after the wake_up(), the recv_work() is scheduled
> out and defers calling the nbd_config_put(), though the map process
> has exited the "nbd->recv_task" is not cleared.
> 
> Signed-off-by: Xiubo Li <xiubli@redhat.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] nbd: make the config put is called before the notifying the waiter
  2020-10-14  2:45 [PATCH] nbd: make the config put is called before the notifying the waiter xiubli
  2020-10-14 17:33 ` Josef Bacik
@ 2020-10-14 18:30 ` Jens Axboe
  1 sibling, 0 replies; 3+ messages in thread
From: Jens Axboe @ 2020-10-14 18:30 UTC (permalink / raw)
  To: xiubli, josef; +Cc: linux-block, nbd

On 10/13/20 8:45 PM, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> There has one race case for ceph's rbd-nbd tool. When do mapping
> it may fail with EBUSY from ioctl(nbd, NBD_DO_IT), but actually
> the nbd device has already unmaped.
> 
> It dues to if just after the wake_up(), the recv_work() is scheduled
> out and defers calling the nbd_config_put(), though the map process
> has exited the "nbd->recv_task" is not cleared.

Applied, thanks.

-- 
Jens Axboe


^ permalink raw reply	[flat|nested] 3+ messages in thread

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2020-10-14  2:45 [PATCH] nbd: make the config put is called before the notifying the waiter xiubli
2020-10-14 17:33 ` Josef Bacik
2020-10-14 18:30 ` Jens Axboe

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