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    dm: implement REQ_FLUSH/FUA support for bio-based dm · d87f4c14
    Tejun Heo 提交于
    This patch converts bio-based dm to support REQ_FLUSH/FUA instead of
    now deprecated REQ_HARDBARRIER.
    
    * -EOPNOTSUPP handling logic dropped.
    
    * Preflush is handled as before but postflush is dropped and replaced
      with passing down REQ_FUA to member request_queues.  This replaces
      one array wide cache flush w/ member specific FUA writes.
    
    * __split_and_process_bio() now calls __clone_and_map_flush() directly
      for flushes and guarantees all FLUSH bio's going to targets are zero
    `  length.
    
    * It's now guaranteed that all FLUSH bio's which are passed onto dm
      targets are zero length.  bio_empty_barrier() tests are replaced
      with REQ_FLUSH tests.
    
    * Empty WRITE_BARRIERs are replaced with WRITE_FLUSHes.
    
    * Dropped unlikely() around REQ_FLUSH tests.  Flushes are not unlikely
      enough to be marked with unlikely().
    
    * Block layer now filters out REQ_FLUSH/FUA bio's if the request_queue
      doesn't support cache flushing.  Advertise REQ_FLUSH | REQ_FUA
      capability.
    
    * Request based dm isn't converted yet.  dm_init_request_based_queue()
      resets flush support to 0 for now.  To avoid disturbing request
      based dm code, dm->flush_error is added for bio based dm while
      requested based dm continues to use dm->barrier_error.
    
    Lightly tested linear, stripe, raid1, snap and crypt targets.  Please
    proceed with caution as I'm not familiar with the code base.
    Signed-off-by: NTejun Heo <tj@kernel.org>
    Cc: dm-devel@redhat.com
    Cc: Christoph Hellwig <hch@lst.de>
    Signed-off-by: NJens Axboe <jaxboe@fusionio.com>
    d87f4c14
dm-snap-persistent.c 20.7 KB