From: Michal Hocko <mhocko@suse.com>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
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>
Subject: Re: [RFC PATCH 1/8] hugetlb: add per-hstate mutex to synchronize user adjustments
Date: Mon, 22 Mar 2021 14:59:03 +0100 [thread overview]
Message-ID: <YFiipzEs0wuL/Qdl@dhcp22.suse.cz> (raw)
In-Reply-To: <20210319224209.150047-2-mike.kravetz@oracle.com>
On Fri 19-03-21 15:42:02, Mike Kravetz wrote:
> The number of hugetlb pages can be adjusted by writing to the
> sysps/proc files nr_hugepages, nr_hugepages_mempolicy or
> nr_overcommit_hugepages. There is nothing to prevent two
> concurrent modifications via these files. The underlying routine
> set_max_huge_pages() makes assumptions that only one occurrence is
> running at a time. Specifically, alloc_pool_huge_page uses a
> hstate specific variable without any synchronization.
From the above it is not really clear whether the unsynchronized nature
of set_max_huge_pages is really a problem or a mere annoynce. I suspect
the later because counters are properly synchronized with the
hugetlb_lock. It would be great to clarify that.
> Add a mutex to the hstate and use it to only allow one hugetlb
> page adjustment at a time.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
> include/linux/hugetlb.h | 1 +
> mm/hugetlb.c | 5 +++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index cccd1aab69dd..f42d44050548 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -555,6 +555,7 @@ HPAGEFLAG(Freed, freed)
> #define HSTATE_NAME_LEN 32
> /* Defines one hugetlb page size */
> struct hstate {
> + struct mutex mutex;
> int next_nid_to_alloc;
> int next_nid_to_free;
> unsigned int order;
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 5b1ab1f427c5..d5be25f910e8 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2601,6 +2601,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> else
> return -ENOMEM;
>
> + /* mutex prevents concurrent adjustments for the same hstate */
> + mutex_lock(&h->mutex);
> spin_lock(&hugetlb_lock);
>
> /*
> @@ -2633,6 +2635,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
> if (count > persistent_huge_pages(h)) {
> spin_unlock(&hugetlb_lock);
> + mutex_unlock(&h->mutex);
> NODEMASK_FREE(node_alloc_noretry);
> return -EINVAL;
> }
> @@ -2707,6 +2710,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid,
> out:
> h->max_huge_pages = persistent_huge_pages(h);
> spin_unlock(&hugetlb_lock);
> + mutex_unlock(&h->mutex);
>
> NODEMASK_FREE(node_alloc_noretry);
>
> @@ -3194,6 +3198,7 @@ void __init hugetlb_add_hstate(unsigned int order)
> BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
> BUG_ON(order == 0);
> h = &hstates[hugetlb_max_hstate++];
> + mutex_init(&h->mutex);
> h->order = order;
> h->mask = ~(huge_page_size(h) - 1);
> for (i = 0; i < MAX_NUMNODES; ++i)
> --
> 2.30.2
>
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-03-22 13:59 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 22:42 [RFC PATCH 0/8] make hugetlb put_page safe for all calling contexts Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 1/8] hugetlb: add per-hstate mutex to synchronize user adjustments Mike Kravetz
2021-03-22 13:59 ` Michal Hocko [this message]
2021-03-22 16:57 ` Mike Kravetz
2021-03-23 7:48 ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 2/8] hugetlb: recompute min_count when dropping hugetlb_lock Mike Kravetz
2021-03-22 14:07 ` Michal Hocko
2021-03-22 23:07 ` Mike Kravetz
2021-03-23 7:50 ` Michal Hocko
2021-03-23 8:01 ` Peter Zijlstra
2021-03-23 8:14 ` Michal Hocko
2021-03-23 23:18 ` Mike Kravetz
2021-03-24 8:36 ` Michal Hocko
2021-03-24 16:43 ` Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 3/8] hugetlb: create remove_hugetlb_page() to separate functionality Mike Kravetz
2021-03-22 14:15 ` Michal Hocko
2021-03-22 17:01 ` Mike Kravetz
2021-03-19 22:42 ` [RFC PATCH 4/8] hugetlb: call update_and_free_page without hugetlb_lock Mike Kravetz
2021-03-22 14:19 ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 5/8] hugetlb: change free_pool_huge_page to remove_pool_huge_page Mike Kravetz
2021-03-22 14:31 ` Michal Hocko
2021-03-22 23:28 ` Mike Kravetz
2021-03-23 7:57 ` Michal Hocko
2021-03-24 1:03 ` Mike Kravetz
2021-03-24 8:40 ` Michal Hocko
2021-03-24 16:38 ` Mike Kravetz
2021-03-24 16:50 ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 6/8] hugetlb: make free_huge_page irq safe Mike Kravetz
2021-03-21 19:55 ` Mike Kravetz
2021-03-22 13:36 ` [hugetlb] cd190f60f9: BUG:sleeping_function_called_from_invalid_context_at_mm/hugetlb.c kernel test robot
2021-03-22 14:35 ` [RFC PATCH 6/8] hugetlb: make free_huge_page irq safe Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 7/8] hugetlb: add update_and_free_page_no_sleep for irq context Mike Kravetz
2021-03-20 1:18 ` Hillf Danton
2021-03-25 0:26 ` Mike Kravetz
2021-03-22 8:41 ` Peter Zijlstra
2021-03-22 17:42 ` Mike Kravetz
2021-03-22 18:10 ` Roman Gushchin
2021-03-23 18:51 ` Mike Kravetz
2021-03-23 19:07 ` Roman Gushchin
2021-03-24 8:43 ` Michal Hocko
2021-03-24 16:53 ` Mike Kravetz
2021-03-22 20:43 ` Peter Zijlstra
2021-03-22 14:42 ` Michal Hocko
2021-03-22 14:46 ` Michal Hocko
2021-03-19 22:42 ` [RFC PATCH 8/8] hugetlb: track hugetlb pages allocated via cma_alloc Mike Kravetz
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