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

From: Mike Kravetz <mike.kravetz@oracle.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Michal Hocko <mhocko@suse.com>,
	Shakeel Butt <shakeelb@google.com>,
	Oscar Salvador <osalvador@suse.de>,
	David Hildenbrand <david@redhat.com>,
	Muchun Song <songmuchun@bytedance.com>,
	David Rientjes <rientjes@google.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
	"Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
	Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
	Mina Almasry <almasrymina@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Kravetz <mike.kravetz@oracle.com>
Subject: [RFC PATCH 0/8] make hugetlb put_page safe for all calling contexts
Date: Fri, 19 Mar 2021 15:42:01 -0700	[thread overview]
Message-ID: <20210319224209.150047-1-mike.kravetz@oracle.com> (raw)

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.  At a high level, this series does:
- Patches 1 & 2 are cleanups/fixes to existing code in the areas to be
  modified.
- Patches 3, 4 & 5 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.  In addition, the known
  long hold time in hugetlb_cgroup_css_offline still needs to be
  addressed (suggestions welcome).
- Patch 6 makes hugetlb_lock and subpool lock IRQ safe.  It also reverts
  the code which defers calls to a workqueue if !in_task.
- Patch 7 adds code to defer freeing of pages to a workqueue if the freeing
  routines could possibly sleep.
- Patch 8 adds a flag to gigantic pages allocated from CMA so that we
  only defer freeing those pages.

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

Mike Kravetz (8):
  hugetlb: add per-hstate mutex to synchronize user adjustments
  hugetlb: recompute min_count when dropping hugetlb_lock
  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 update_and_free_page_no_sleep for irq context
  hugetlb: track hugetlb pages allocated via cma_alloc

 include/linux/hugetlb.h |  20 +-
 mm/hugetlb.c            | 450 +++++++++++++++++++++++++---------------
 mm/hugetlb_cgroup.c     |  10 +-
 3 files changed, 310 insertions(+), 170 deletions(-)

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2.30.2