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# Paging

In the course of Maksym's [[translator/tmpfs]] work:

IRC, freenode, #hurd, 2011-10-24:

    <mcsim> I've compared the way pagers are handled in ext2fs and found out
      that for every file new pager is created when occurs reading or writing
      to this file. Is it necessary? And can one pager handle several memory
      objects?
    <antrik> mcsim: yes, this in necessary. one pager port corresponds to one
      memory object
    <antrik> mcsim: note that a pager, from the kernel's point of view, is
      essentially just the port used to communicated with the process
      responsible for paging the object. how your process manages multiple
      pager ports is up to you
    <mcsim> so, how can I attach those pager_* functions, which are declared
      now in pager-stubs.c to new pager?
    <mcsim> or is it done automatically with all pagers, which I create, If
      only I'm not using default one?
    <antrik> I'm not sure how libpager works; but I suspect it's based on
      libports. you probably need a port class for the pager ports, and add the
      port for each new pager your create to that class
    <antrik> (of course you also need to add it to some port bucket. if you use
      a single dispatcher for everything, this would be the default bucket; if
      you want a separate thread for pager handling, you'd have to create an
      extra bucket for the pagers)

This is the `diskfs_get_filemap` function that a `libdiskfs` client has to
provide; used in `libdiskfs/rdwr-internal.c:_diskfs_rdwr_internal`, which in
turn is used by the [[interface/io_read]]/[[interface/io_write]] RPCs.