[PATCH v5 0/5] Delay the initializaton of zswap

[Liu Shixin <liushixin2@huawei.com>]

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.                                                             

v4->v5: Rebase on next-20220913, the previous first patch is superseded
by patch ("frontswap: don't call ->init if no ops are registered").
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 (5):
  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/swapfile.h |  2 ++
 mm/frontswap.c           | 42 ++++++++++++++++++++++
 mm/swapfile.c            |  4 +--
 mm/zswap.c               | 77 ++++++++++++++++++++++++++++++----------
 4 files changed, 104 insertions(+), 21 deletions(-)

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2.25.1