From: Peter Xu <peterx@redhat.com>
To: linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: Rik van Riel <riel@surriel.com>,
Muchun Song <songmuchun@bytedance.com>,
Andrew Morton <akpm@linux-foundation.org>,
peterx@redhat.com, James Houghton <jthoughton@google.com>,
Nadav Amit <nadav.amit@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
David Hildenbrand <david@redhat.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: [PATCH RFC v2 08/12] mm/hugetlb: Use hugetlb walker lock in follow_hugetlb_page()
Date: Thu, 17 Nov 2022 20:10:21 -0500 [thread overview]
Message-ID: <20221118011025.2178986-9-peterx@redhat.com> (raw)
In-Reply-To: <20221118011025.2178986-1-peterx@redhat.com>
Hugetlb walker lock makes sure the pte_t* won't go away from under us.
Some trick is used to release the walker lock slightly earlier when we
found present pte.
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/hugetlb.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index fc49e3ca8acd..e81af6a46c59 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6280,6 +6280,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
break;
}
+ hugetlb_walker_lock();
/*
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
@@ -6304,6 +6305,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
!hugetlbfs_pagecache_present(h, vma, vaddr)) {
if (pte)
spin_unlock(ptl);
+ hugetlb_walker_unlock();
remainder = 0;
break;
}
@@ -6325,6 +6327,8 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (pte)
spin_unlock(ptl);
+ hugetlb_walker_unlock();
+
if (flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
else if (unshare)
@@ -6367,6 +6371,15 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
continue;
}
+ /*
+ * When reach here, it means the pteval is not absent, so
+ * anyone who wants to free and invalidate the pgtable page
+ * (aka, pte*) should need to first unmap the entries which
+ * relies on the pgtable lock. Since we're holding it,
+ * we're safe even without the walker lock anymore.
+ */
+ hugetlb_walker_unlock();
+
pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT;
page = pte_page(huge_ptep_get(pte));
--
2.37.3
next prev parent reply other threads:[~2022-11-18 1:13 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-18 1:10 [PATCH RFC v2 00/12] mm/hugetlb: Make huge_pte_offset() thread-safe for pmd unshare Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 01/12] mm/hugetlb: Let vma_offset_start() to return start Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 02/12] mm/hugetlb: Move swap entry handling into vma lock for fault Peter Xu
2022-11-18 1:35 ` Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 03/12] mm/hugetlb: Don't wait for migration entry during follow page Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 04/12] mm/hugetlb: Add pgtable walker lock Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 05/12] mm/hugetlb: Make userfaultfd_huge_must_wait() safe to pmd unshare Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 06/12] mm/hugetlb: Protect huge_pmd_share() with walker lock Peter Xu
2022-11-18 1:17 ` Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 07/12] mm/hugetlb: Use hugetlb walker lock in hugetlb_follow_page_mask() Peter Xu
2022-11-18 1:10 ` Peter Xu [this message]
2022-11-18 1:10 ` [PATCH RFC v2 09/12] mm/hugetlb: Use hugetlb walker lock in hugetlb_vma_maps_page() Peter Xu
2022-11-18 1:10 ` [PATCH RFC v2 10/12] mm/hugetlb: Use hugetlb walker lock in walk_hugetlb_range() Peter Xu
2022-11-18 1:11 ` [PATCH RFC v2 11/12] mm/hugetlb: Use hugetlb walker lock in page_vma_mapped_walk() Peter Xu
2022-11-18 1:11 ` [PATCH RFC v2 12/12] mm/hugetlb: Introduce hugetlb_walk() Peter Xu
2022-11-23 9:40 ` [PATCH RFC v2 00/12] mm/hugetlb: Make huge_pte_offset() thread-safe for pmd unshare David Hildenbrand
2022-11-23 15:09 ` Peter Xu
2022-11-23 18:21 ` Mike Kravetz
2022-11-23 18:56 ` Peter Xu
2022-11-23 19:31 ` David Hildenbrand
2022-11-25 9:43 ` David Hildenbrand
2022-11-25 13:55 ` Peter Xu
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