[PATCH 0/2] block: invalidate cached plug timestamp on context switch

[Usama Arif <usama.arif@linux.dev>]

The details for this are in patch 2. The main reason for this series
is to invalidate the cached timestamp on context switch. This was
done in sched_update_worker() only before which was resulting in
blk-iocost reading stale timestamps and throttling based on wrong
information.

Patch 1 is a prerequisite to create the invariant that
PF_BLOCK_TS set implies current->plug != NULL.

v2 -> v3:
  https://lore.kernel.org/all/20260612094042.3350401-1-usama.arif@linux.dev/
  - Add patch 1 to clear PF_BLOCK_TS in copy_process() so the
    invariant survives fork.
  - Drop the if (plug) NULL check inside blk_plug_invalidate_ts(),
    relying on the invariant established by patch 1. (Peter Zijlstra)

v1 -> v2:
  https://lore.kernel.org/all/20260611231428.345098-1-usama.arif@linux.dev/
  - Move the PF_BLOCK_TS check into blk_plug_invalidate_ts() and
    upgrade it to __always_inline (Peter Zijlstra).
  - Drop the tsk parameter; the helper only ever operates on current.
 
Usama Arif (2):
  kernel/fork: clear PF_BLOCK_TS in copy_process()
  block: invalidate cached plug timestamp after task switch

 include/linux/blkdev.h | 16 ++++++----------
 kernel/fork.c          |  1 +
 kernel/sched/core.c    | 12 ++++++++----
 3 files changed, 15 insertions(+), 14 deletions(-)

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2.53.0-Meta