From: David Hildenbrand <david@redhat.com>
To: Peter Xu <peterx@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc: James Houghton <jthoughton@google.com>,
Jann Horn <jannh@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Rik van Riel <riel@surriel.com>,
Nadav Amit <nadav.amit@gmail.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Muchun Song <songmuchun@bytedance.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH 09/10] mm/hugetlb: Make page_vma_mapped_walk() safe to pmd unshare
Date: Wed, 30 Nov 2022 17:18:45 +0100 [thread overview]
Message-ID: <65a3a912-3534-6718-2c55-e0d4b5246f1e@redhat.com> (raw)
In-Reply-To: <20221129193526.3588187-10-peterx@redhat.com>
On 29.11.22 20:35, Peter Xu wrote:
> Since page_vma_mapped_walk() walks the pgtable, it needs the vma lock
> to make sure the pgtable page will not be freed concurrently.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> include/linux/rmap.h | 4 ++++
> mm/page_vma_mapped.c | 5 ++++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> index bd3504d11b15..a50d18bb86aa 100644
> --- a/include/linux/rmap.h
> +++ b/include/linux/rmap.h
> @@ -13,6 +13,7 @@
> #include <linux/highmem.h>
> #include <linux/pagemap.h>
> #include <linux/memremap.h>
> +#include <linux/hugetlb.h>
>
> /*
> * The anon_vma heads a list of private "related" vmas, to scan if
> @@ -408,6 +409,9 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw)
> pte_unmap(pvmw->pte);
> if (pvmw->ptl)
> spin_unlock(pvmw->ptl);
> + /* This needs to be after unlock of the spinlock */
> + if (is_vm_hugetlb_page(pvmw->vma))
> + hugetlb_vma_unlock_read(pvmw->vma);
> }
>
> bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw);
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index 93e13fc17d3c..f94ec78b54ff 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -169,10 +169,13 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
> if (pvmw->pte)
> return not_found(pvmw);
>
> + hugetlb_vma_lock_read(vma);
> /* when pud is not present, pte will be NULL */
> pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
> - if (!pvmw->pte)
> + if (!pvmw->pte) {
> + hugetlb_vma_unlock_read(vma);
> return false;
> + }
>
> pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
> if (!check_pte(pvmw))
Looking at code like mm/damon/paddr.c:__damon_pa_mkold() and reading
the doc of page_vma_mapped_walk(), this might be broken.
Can't we get page_vma_mapped_walk() called multiple times? Wouldn't we
have to remember that we already took the lock to not lock twice, and to
see if we really have to unlock in page_vma_mapped_walk_done() ?
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2022-11-30 16:19 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-29 19:35 [PATCH 00/10] mm/hugetlb: Make huge_pte_offset() thread-safe for pmd unshare Peter Xu
2022-11-29 19:35 ` [PATCH 01/10] mm/hugetlb: Let vma_offset_start() to return start Peter Xu
2022-11-30 10:11 ` David Hildenbrand
2022-11-29 19:35 ` [PATCH 02/10] mm/hugetlb: Don't wait for migration entry during follow page Peter Xu
2022-11-30 4:37 ` Mike Kravetz
2022-11-30 10:15 ` David Hildenbrand
2022-11-29 19:35 ` [PATCH 03/10] mm/hugetlb: Document huge_pte_offset usage Peter Xu
2022-11-30 4:55 ` Mike Kravetz
2022-11-30 15:58 ` Peter Xu
2022-12-05 21:47 ` Mike Kravetz
2022-11-30 10:21 ` David Hildenbrand
2022-11-30 10:24 ` David Hildenbrand
2022-11-30 16:09 ` Peter Xu
2022-11-30 16:11 ` David Hildenbrand
2022-11-30 16:25 ` Peter Xu
2022-11-30 16:31 ` David Hildenbrand
2022-11-29 19:35 ` [PATCH 04/10] mm/hugetlb: Move swap entry handling into vma lock when faulted Peter Xu
2022-12-05 22:14 ` Mike Kravetz
2022-12-05 23:36 ` Peter Xu
2022-11-29 19:35 ` [PATCH 05/10] mm/hugetlb: Make userfaultfd_huge_must_wait() safe to pmd unshare Peter Xu
2022-11-30 16:08 ` David Hildenbrand
2022-12-05 22:23 ` Mike Kravetz
2022-11-29 19:35 ` [PATCH 06/10] mm/hugetlb: Make hugetlb_follow_page_mask() " Peter Xu
2022-11-30 16:09 ` David Hildenbrand
2022-12-05 22:29 ` Mike Kravetz
2022-11-29 19:35 ` [PATCH 07/10] mm/hugetlb: Make follow_hugetlb_page() " Peter Xu
2022-11-30 16:09 ` David Hildenbrand
2022-12-05 22:45 ` Mike Kravetz
2022-11-29 19:35 ` [PATCH 08/10] mm/hugetlb: Make walk_hugetlb_range() " Peter Xu
2022-11-30 16:11 ` David Hildenbrand
2022-12-05 23:33 ` Mike Kravetz
2022-12-05 23:52 ` John Hubbard
2022-12-06 16:45 ` Peter Xu
2022-12-06 18:50 ` Mike Kravetz
2022-12-06 21:03 ` John Hubbard
2022-12-06 21:51 ` Peter Xu
2022-12-06 22:31 ` John Hubbard
2022-12-07 0:07 ` Peter Xu
2022-12-07 2:38 ` John Hubbard
2022-12-07 14:58 ` Peter Xu
2022-11-29 19:35 ` [PATCH 09/10] mm/hugetlb: Make page_vma_mapped_walk() " Peter Xu
2022-11-30 16:18 ` David Hildenbrand [this message]
2022-11-30 16:32 ` Peter Xu
2022-11-30 16:39 ` David Hildenbrand
2022-12-05 23:52 ` Mike Kravetz
2022-12-06 17:10 ` Mike Kravetz
2022-12-06 17:39 ` Peter Xu
2022-12-06 17:43 ` Peter Xu
2022-12-06 19:58 ` Mike Kravetz
2022-11-29 19:35 ` [PATCH 10/10] mm/hugetlb: Introduce hugetlb_walk() Peter Xu
2022-11-30 5:18 ` Eric Biggers
2022-11-30 15:37 ` Peter Xu
2022-12-06 0:21 ` Mike Kravetz
2022-11-29 20:49 ` [PATCH 00/10] mm/hugetlb: Make huge_pte_offset() thread-safe for pmd unshare Andrew Morton
2022-11-29 21:19 ` Peter Xu
2022-11-29 21:26 ` Andrew Morton
2022-11-29 20:51 ` Andrew Morton
2022-11-29 21:36 ` Peter Xu
2022-11-30 9:46 ` David Hildenbrand
2022-11-30 16:23 ` Peter Xu
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