In the initialization of zswap, about 18MB memory will be allocated for       
zswap_pool. Since not all users use zswap, the memory may be wasted. Save  
the memory for these users by delaying the initialization of zswap to         
first enablement.                                                             

v3->v4: Revert three patches to replace previous patch[1-2] suggested by
Vitaly.
v2->v3: Fix frontswap_ops NULL reported by Nathan and add init for online
swap device in backend register.
v1->v2: Change init_zswap to zswap_init suggested by Andrew.

Liu Shixin (6):
  Revert "frontswap: remove support for multiple ops"
  Revert "mm: mark swap_lock and swap_active_head static"
  Revert "frontswap: simplify frontswap_register_ops"
  mm/zswap: replace zswap_init_{started/failed} with zswap_init_state
  mm/zswap: delay the initializaton of zswap until the first enablement
  mm/zswap: skip confusing print info

 include/linux/frontswap.h |  3 +-
 include/linux/swapfile.h  |  2 +
 mm/frontswap.c            | 91 +++++++++++++++++++++++++++++++++------
 mm/swapfile.c             |  4 +-
 mm/zswap.c                | 85 +++++++++++++++++++++++++-----------
 5 files changed, 145 insertions(+), 40 deletions(-)

-- 
2.25.1