drain_all_stock() can leave FLUSHING_CACHED_CHARGE set after the
work is dropped.  It sets the bit before checking isolation and
schedule_drain_work() checks isolation and queues in a separate RCU
critical section, so housekeeping_update()'s synchronize_rcu() can
race the second check.

drain_local_stock() only clears the bit for work that ran, so the bit
remains set and the stock is never drained again.

Patch 1 extracts the stock drain predicates into helpers.

Patch 2 reorganizes the drain_all_stock() loop, reducing nesting,
splitting out local vs remote cpu handling, and skipping everything
on isolated cpus, which solves the stuck FLUSHING_CACHED_CHARGE flag.

Link: https://sashiko.dev/#/patchset/20260827124211.3b94b103@fangorn

Rik van Riel (2):
  mm/memcontrol: extract stock drain predicates into helpers
  mm/memcontrol: fix stuck FLUSHING_CACHED_CHARGE bit on isolated cpus

 mm/memcontrol.c | 61 ++++++++++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 26 deletions(-)

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2.55.0