Damien, > Introduce zone write locking to avoid write request reordering with > zoned block devices. This is achieved using a finer selection of the > next request to dispatch: > 1) Any non-write request is always allowed to proceed. > 2) Any write to a conventional zone is always allowed to proceed. > 3) For a write to a sequential zone, the zone lock is first checked. > a) If the zone is not locked, the write is allowed to proceed after > its target zone is locked. > b) If the zone is locked, the write request is skipped and the next > request in the dispatch queue tested (back to step 1). > > For a write request that has locked its target zone, the zone is > unlocked either when the request completes and the method > deadline_request_completed() is called, or when the request is requeued > using the method deadline_add_request(). > > Requests targeting a locked zone are always left in the scheduler queue > to preserve the initial write order. If no write request can be > dispatched, allow reads to be dispatched even if the write batch is not > done. > > If the device used is not a zoned block device, or if zoned block device > support is disabled, this patch does not modify deadline behavior. Reviewed-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> -- Martin K. Petersen Oracle Linux Engineering
