• Boaz Harrosh's avatar
    exofs: ios: Move to a per inode components & device-table · 9e9db456
    Boaz Harrosh authored
    Exofs raid engine was saving on memory space by having a single layout-info,
    single pid, and a single device-table, global to the filesystem. Then passing
    a credential and object_id info at the io_state level, private for each
    inode. It would also devise this contraption of rotating the device table
    view for each inode->ino to spread out the device usage.
    
    This is not compatible with the pnfs-objects standard, demanding that
    each inode can have it's own layout-info, device-table, and each object
    component it's own pid, oid and creds.
    
    So: Bring exofs raid engine to be usable for generic pnfs-objects use by:
    
    * Define an exofs_comp structure that holds obj_id and credential info.
    
    * Break up exofs_layout struct to an exofs_components structure that holds a
      possible array of exofs_comp and the array of devices + the size of the
      arrays.
    
    * Add a "comps" parameter to get_io_state() that specifies the ids creds
      and device array to use for each IO.
    
      This enables to keep the layout global, but the device-table view, creds
      and IDs at the inode level. It only adds two 64bit to each inode, since
      some of these members already existed in another form.
    
    * ios raid engine now access layout-info and comps-info through the passed
      pointers. Everything is pre-prepared by caller for generic access of
      these structures and arrays.
    
    At the exofs Level:
    
    * Super block holds an exofs_components struct that holds the device
      array, previously in layout. The devices there are in device-table
      order. The device-array is twice bigger and repeats the device-table
      twice so now each inode's device array can point to a random device
      and have a round-robin view of the table, making it compatible to
      previous exofs versions.
    
    * Each inode has an exofs_components struct that is initialized at
      load time, with it's own view of the device table IDs and creds.
      When doing IO this gets passed to the io_state together with the
      layout.
    
    While preforming this change. Bugs where found where credentials with the
    wrong IDs where used to access the different SB objects (super.c). As well
    as some dead code. It was never noticed because the target we use does not
    check the credentials.
    Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
    9e9db456
super.c 27.5 KB