linux-kernel - Re: [PATCH 0/8] make hugetlb put_page safe for all calling contexts

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Date:   Fri, 26 Mar 2021 09:42:36 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
CC:     Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Rientjes <rientjes@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        "Hillf Danton" <hdanton@...a.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/8] make hugetlb put_page safe for all calling contexts

Hi:
On 2021/3/25 8:28, Mike Kravetz wrote:
> This effort is the result a recent bug report [1].  In subsequent
> discussions [2], it was deemed necessary to properly fix the hugetlb

Many thanks for the effort. I have read the discussions and it is pretty long.
Maybe it would be helpful if you give a brief summary here?

> put_page path (free_huge_page).  This RFC provides a possible way to

trival: Not RFC here.

> 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()

trival: missing description of the Patches 3 ?

> - 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@google.com/
> [2] http://lkml.kernel.org/r/20210311021321.127500-1-mike.kravetz@oracle.com
> 
> 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(-)
>