From: Muchun Song <songmuchun@bytedance.com>
To: mike.kravetz@oracle.com, akpm@linux-foundation.org
Cc: n-horiguchi@ah.jp.nec.com, ak@linux.intel.com, mhocko@suse.cz,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Muchun Song <songmuchun@bytedance.com>,
stable@vger.kernel.org
Subject: [PATCH v4 3/6] mm: hugetlb: fix a race between freeing and dissolving the page
Date: Wed, 13 Jan 2021 13:22:06 +0800 [thread overview]
Message-ID: <20210113052209.75531-4-songmuchun@bytedance.com> (raw)
In-Reply-To: <20210113052209.75531-1-songmuchun@bytedance.com>
There is a race condition between __free_huge_page()
and dissolve_free_huge_page().
CPU0: CPU1:
// page_count(page) == 1
put_page(page)
__free_huge_page(page)
dissolve_free_huge_page(page)
spin_lock(&hugetlb_lock)
// PageHuge(page) && !page_count(page)
update_and_free_page(page)
// page is freed to the buddy
spin_unlock(&hugetlb_lock)
spin_lock(&hugetlb_lock)
clear_page_huge_active(page)
enqueue_huge_page(page)
// It is wrong, the page is already freed
spin_unlock(&hugetlb_lock)
The race windows is between put_page() and dissolve_free_huge_page().
We should make sure that the page is already on the free list
when it is dissolved.
Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: stable@vger.kernel.org
---
mm/hugetlb.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4741d60f8955..4a9011e12175 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -79,6 +79,21 @@ DEFINE_SPINLOCK(hugetlb_lock);
static int num_fault_mutexes;
struct mutex *hugetlb_fault_mutex_table ____cacheline_aligned_in_smp;
+static inline bool PageHugeFreed(struct page *head)
+{
+ return page_private(head + 4) == -1UL;
+}
+
+static inline void SetPageHugeFreed(struct page *head)
+{
+ set_page_private(head + 4, -1UL);
+}
+
+static inline void ClearPageHugeFreed(struct page *head)
+{
+ set_page_private(head + 4, 0);
+}
+
/* Forward declaration */
static int hugetlb_acct_memory(struct hstate *h, long delta);
@@ -1028,6 +1043,7 @@ static void enqueue_huge_page(struct hstate *h, struct page *page)
list_move(&page->lru, &h->hugepage_freelists[nid]);
h->free_huge_pages++;
h->free_huge_pages_node[nid]++;
+ SetPageHugeFreed(page);
}
static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
@@ -1044,6 +1060,7 @@ static struct page *dequeue_huge_page_node_exact(struct hstate *h, int nid)
list_move(&page->lru, &h->hugepage_activelist);
set_page_refcounted(page);
+ ClearPageHugeFreed(page);
h->free_huge_pages--;
h->free_huge_pages_node[nid]--;
return page;
@@ -1504,6 +1521,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
spin_lock(&hugetlb_lock);
h->nr_huge_pages++;
h->nr_huge_pages_node[nid]++;
+ ClearPageHugeFreed(page);
spin_unlock(&hugetlb_lock);
}
@@ -1770,6 +1788,14 @@ int dissolve_free_huge_page(struct page *page)
int nid = page_to_nid(head);
if (h->free_huge_pages - h->resv_huge_pages == 0)
goto out;
+
+ /*
+ * We should make sure that the page is already on the free list
+ * when it is dissolved.
+ */
+ if (unlikely(!PageHugeFreed(head)))
+ goto out;
+
/*
* Move PageHWPoison flag from head page to the raw error page,
* which makes any subpages rather than the error page reusable.
--
2.11.0
next prev parent reply other threads:[~2021-01-13 5:25 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-13 5:22 [PATCH v4 0/6] Fix some bugs about HugeTLB code Muchun Song
2021-01-13 5:22 ` [PATCH v4 1/6] mm: migrate: do not migrate HugeTLB page whose refcount is one Muchun Song
2021-01-13 10:30 ` David Hildenbrand
2021-01-13 10:57 ` Oscar Salvador
2021-01-13 11:03 ` [External] " Muchun Song
2021-01-13 5:22 ` [PATCH v4 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page Muchun Song
2021-01-13 11:00 ` Oscar Salvador
2021-01-13 5:22 ` Muchun Song [this message]
2021-01-13 9:31 ` [PATCH v4 3/6] mm: hugetlb: fix a race between freeing and dissolving the page Michal Hocko
2021-01-13 5:22 ` [PATCH v4 4/6] mm: hugetlb: retry dissolve page when hitting race Muchun Song
2021-01-13 9:33 ` Michal Hocko
2021-01-13 10:14 ` [External] " Muchun Song
2021-01-13 10:38 ` Michal Hocko
2021-01-13 11:11 ` Muchun Song
2021-01-13 11:14 ` Oscar Salvador
2021-01-13 11:20 ` Muchun Song
2021-01-13 12:03 ` Michal Hocko
2021-01-13 11:22 ` Michal Hocko
2021-01-13 12:15 ` Muchun Song
2021-01-13 5:22 ` [PATCH v4 5/6] mm: hugetlb: fix a race between isolating and freeing page Muchun Song
2021-01-13 5:22 ` [PATCH v4 6/6] mm: hugetlb: remove VM_BUG_ON_PAGE from page_huge_active Muchun Song
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