• Dave Chinner's avatar
    dax: don't abuse get_block mapping for endio callbacks · e842f290
    Dave Chinner authored
    dax_fault() currently relies on the get_block callback to attach an
    io completion callback to the mapping buffer head so that it can
    run unwritten extent conversion after zeroing allocated blocks.
    
    Instead of this hack, pass the conversion callback directly into
    dax_fault() similar to the get_block callback. When the filesystem
    allocates unwritten extents, it will set the buffer_unwritten()
    flag, and hence the dax_fault code can call the completion function
    in the contexts where it is necessary without overloading the
    mapping buffer head.
    
    Note: The changes to ext4 to use this interface are suspect at best.
    In fact, the way ext4 did this end_io assignment in the first place
    looks suspect because it only set a completion callback when there
    wasn't already some other write() call taking place on the same
    inode. The ext4 end_io code looks rather intricate and fragile with
    all it's reference counting and passing to different contexts for
    modification via inode private pointers that aren't protected by
    locks...
    Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
    Acked-by: default avatarJan Kara <jack@suse.cz>
    Signed-off-by: default avatarDave Chinner <david@fromorbit.com>
    e842f290
file.c 16.5 KB