[PATCH v4 0/7] zram idle page writeback

[Minchan Kim]

Inherently, swap device has many idle pages which are rare touched since
it was allocated. It is never problem if we use storage device as swap.
However, it's just waste for zram-swap.

This patchset supports zram idle page writeback feature.

* Admin can define what is idle page "no access since X time ago"
* Admin can define when zram should writeback them
* Admin can define when zram should stop writeback to prevent wearout

Detail is on each patch's description.

Below first two patches are -stable material so it could go first
separately with others in this series.

  zram: fix lockdep warning of free block handling
  zram: fix double free backing device

* from v3
  - add more words in changelog - akpm
  - clarification writeback limit - akpm
  - fix 4k unit of bd_stat - akpm
  - change writeback_limit interface - minchan
  - add reviewed-by - sergey, joey

* from v2
  - use strscpy instead of strlcpy - Joey Pabalinas
  - remove irqlock for bitmap op - akpm
  - don't use page as stat unit - akpm

* from v1
  - add fix dobule free backing device - minchan
  - change writeback/idle interface - minchan 
  - remove direct incompressible page writeback - sergey

Minchan Kim (7):
  zram: fix lockdep warning of free block handling
  zram: fix double free backing device
  zram: refactoring flags and writeback stuff
  zram: introduce ZRAM_IDLE flag
  zram: support idle/huge page writeback
  zram: add bd_stat statistics
  zram: writeback throttle

 Documentation/ABI/testing/sysfs-block-zram |  32 ++
 Documentation/blockdev/zram.txt            |  80 +++-
 drivers/block/zram/Kconfig                 |   5 +-
 drivers/block/zram/zram_drv.c              | 502 +++++++++++++++------
 drivers/block/zram/zram_drv.h              |  19 +-
 5 files changed, 476 insertions(+), 162 deletions(-)

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2.20.0.rc1.387.gf8505762e3-goog