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The purpose of > this feature is to ensure that we keep the gendisk for intermittent path > failures. > > The delayed removal works on a timer - when all paths are gone, a timer is > kicked off; once the timer expires and no paths have returned, the gendisk > is removed. > > When all paths are gone and the gendisk is still present, all reads and > writes to the disk are queued. If a path returns before the timer > expiration, the timer canceled and the queued IO is submitted; > otherwise they fail when the timer expires. > > This testcase covers two scenarios in separate parts: > a. test that IOs submitted after all paths are removed (and do not return) > fail > b. test that IOs submitted between all paths removed and a path > returning succeed > > During the period of the timer being active, it must be ensured that the > nvme-core module is not removed. Otherwise the driver may not be present > to handle the timeout expiry. The kernel ensures this by taking a > reference to the module. Ideally, we would try to remove the module during > this test to prove that this is not possible (and the kernel behaves as > expected), but that module will probably not be removable anyway due to > many references. To test this feature, check that the refcount of the > nvme-core module is incremented when the delayed timer is active. > > Reviewed-by: Chaitanya Kulkarni > Reviewed-by: Nilay Shroff > Signed-off-by: John Garry I applied this patch. Thanks!