• Damien Le Moal's avatar
    deadline-iosched: Introduce zone locking support · 8dc8146f
    Damien Le Moal authored
    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.
    Signed-off-by: default avatarDamien Le Moal <damien.lemoal@wdc.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Reviewed-by: Martin K. Petersen's avatarMartin K. Petersen <martin.petersen@oracle.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    8dc8146f
deadline-iosched.c 13.2 KB