[PATCH 0/8] make hugetlb put_page safe for all calling contexts

[Mike Kravetz]

This effort is the result a recent bug report [1].  In subsequent
discussions [2], it was deemed necessary to properly fix the hugetlb
put_page path (free_huge_page).  This RFC provides a possible way to
address the issue.  Comments are welcome/encouraged as several attempts
at this have been made in the past.

This series is based on v5.12-rc3-mmotm-2021-03-17-22-24.  At a high
level, the series provides:
- Patches 1 & 2 from Roman Gushchin provide cma_release_nowait()
- Patches 4, 5 & 6 are aimed at reducing lock hold times.  To be clear
  the goal is to eliminate single lock hold times of a long duration.
  Overall lock hold time is not addressed.
- Patch 7 makes hugetlb_lock and subpool lock IRQ safe.  It also reverts
  the code which defers calls to a workqueue if !in_task.
- Patch 8 adds some lockdep_assert_held() calls

[1] https://lore.kernel.org/linux-mm/000000000000f1c03b05bc43aadc@xxxxxxxxxx/
[2] http://lkml.kernel.org/r/20210311021321.127500-1-mike.kravetz@xxxxxxxxxx

RFC -> v1
- Add Roman's cma_release_nowait() patches.  This eliminated the need
  to do a workqueue handoff in hugetlb code.
- Use Michal's suggestion to batch pages for freeing.  This eliminated
  the need to recalculate loop control variables when dropping the lock.
- Added lockdep_assert_held() calls
- Rebased to v5.12-rc3-mmotm-2021-03-17-22-24

Mike Kravetz (6):
  hugetlb: add per-hstate mutex to synchronize user adjustments
  hugetlb: create remove_hugetlb_page() to separate functionality
  hugetlb: call update_and_free_page without hugetlb_lock
  hugetlb: change free_pool_huge_page to remove_pool_huge_page
  hugetlb: make free_huge_page irq safe
  hugetlb: add lockdep_assert_held() calls for hugetlb_lock

Roman Gushchin (2):
  mm: cma: introduce cma_release_nowait()
  mm: hugetlb: don't drop hugetlb_lock around cma_release() call

 include/linux/cma.h     |   2 +
 include/linux/hugetlb.h |   1 +
 mm/cma.c                |  93 +++++++++++
 mm/cma.h                |   5 +
 mm/hugetlb.c            | 354 +++++++++++++++++++++-------------------
 mm/hugetlb_cgroup.c     |   8 +-
 6 files changed, 294 insertions(+), 169 deletions(-)

-- 
2.30.2