Fix concurrent resilvers initiated at same time
For draid vdevs it was possible to initiate both the
sequential and healing resilver at same time.
This fixes the following two scenarios.
- There's a window where a sequential rebuild can
be started via ZED even if a healing resilver has been
scheduled.
- This is fixed by adding additional check in
spa_vdev_attach() for any scheduled resilver and return
appropriate error code when a resilver is already in
progress.
- It was possible for zpool clear to start a healing
resilver when it wasn't needed at all. This occurs because
during a vdev_open() the device is presumed to be healthy not
until the device is validated by vdev_validate() and it's set
unavailable. However, by this point an async resilver will
have already been requested if the DTL isn't empty.
- This is fixed by cancelling the SPA_ASYNC_RESILVER
request immediately at the end of vdev_reopen() when a resilver
is unneeded.
Finally, added a testcase in ZTS for verification.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Dipak Ghosh <dipak.ghosh@hpe.com>
Signed-off-by: Akash B <akash-b@hpe.com>
Closes #14881
Closes #14892