[PATCH v2 0/2] mm/ksm: clean up scan_get_next_rmap_item() initialization

["Xu Xin (vivo)" <xu.xin@linux.dev>]

Currently, scan_get_next_rmap_item() has grown quite large and complex.
When introducing new features, such as the only-merge-zero-page mode we
are currently working on, we don't want to add more complexity to it
and don't want to touch rmap_item structures to avoid unnecessary overhead,
so we need to extract some common logic.

With these changes, the entry of scan_get_next_rmap_item() becomes much
cleaner and easier to follow, instead of being cluttered with unrelated
boilerplate such as stale stable_node pruning and cycle initialization.

Let's start by cleaning up these two parts at the beginning (where I think
abstraction is necessary), and we can continue cleaning up further if
needed later.

Changes in v2:
- Rename scan_begin_new_cycle() to scan_should_start_new_cycle() and keep
  it simple (David).
- Keep lru_add_drain_all() in scan_get_next_rmap_item() (David).
- Use scoped_guard(spinlock, &ksm_mmlist_lock) in scan_get_first_mm()
  (Lorenzo).
- Collect Reviewed-by and Acked-by tags from v1.

Xu Xin (vivo) (2):
  mm/ksm: extract helper functions for scan cycle cleanup
  mm/ksm: add initialization helpers for scan_get_next_rmap_item()

 mm/ksm.c | 98 +++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 62 insertions(+), 36 deletions(-)

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2.34.1