ublk: fix infinite loop in ublk server teardown#725
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If a ublk server starts recovering devices but dies before issuing fetch commands for all IOs, cancellation of the fetch commands that were successfully issued may never complete. This is because the per-IO canceled flag can remain set even after the fetch for that IO has been submitted - the per-IO canceled flags for all IOs in a queue are reset together only once all IOs for that queue have been fetched. So if a nonempty proper subset of the IOs for a queue are fetched when the ublk server dies, the IOs in that subset will never successfully be canceled, as their canceled flags remain set, and this prevents ublk_cancel_cmd from actually calling io_uring_cmd_done on the commands, despite the fact that they are outstanding. Fix this by resetting the per-IO cancel flags immediately when each IO is fetched instead of waiting for all IOs for the queue (which may never happen). Signed-off-by: Uday Shankar <ushankar@purestorage.com> Fixes: 728cbac ("ublk: move device reset into ublk_ch_release()") Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: zhang, the-essence-of-life <zhangweize9@gmail.com>
Before the fix, teardown of a ublk server that was attempting to recover a device, but died when it had submitted a nonempty proper subset of the fetch commands to any queue would loop forever. Add a test to verify that, after the fix, teardown completes. This is done by: - Adding a new argument to the fault_inject target that causes it die after fetching a nonempty proper subset of the IOs to a queue - Using that argument in a new test while trying to recover an already-created device - Attempting to delete the ublk device at the end of the test; this hangs forever if teardown from the fault-injected ublk server never completed. It was manually verified that the test passes with the fix and hangs without it. Signed-off-by: Uday Shankar <ushankar@purestorage.com> Reviewed-by: Ming Lei <ming.lei@redhat.com>
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Pull request for series with
subject: ublk: fix infinite loop in ublk server teardown
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1077214