• David Sterba's avatar
    btrfs: drop bio_set_dev where not needed · 1a418027
    David Sterba authored
    
    
    bio_set_dev sets a bdev to a bio and is not only setting a pointer bug
    also changing some state bits if there was a different bdev set before.
    This is one thing that's not needed.
    
    Another thing is that setting a bdev at bio allocation time is too early
    and actually does not work with plain redundancy profiles, where each
    time we submit a bio to a device, the bdev is set correctly.
    
    In many places the bio bdev is set to latest_bdev that seems to serve as
    a stub pointer "just to put something to bio". But we don't have to do
    that.
    
    Where do we know which bdev to set:
    
    * for regular IO: submit_stripe_bio that's called by btrfs_map_bio
    
    * repair IO: repair_io_failure, read or write from specific device
    
    * super block write (using buffer_heads but uses raw bdev) and barriers
    
    * scrub: this does not use all regular IO paths as it needs to reach all
      copies, verify and fixup eventually, and for that all bdev management
      is independent
    
    * raid56: rbio_add_io_page, for the RMW write
    
    * integrity-checker: does it's own low-level block tracking
    
    Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
    1a418027