From: Peter Xu <peterx@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Jerome Glisse <jglisse@redhat.com>
Subject: Re: [PATCH 2/6] mm/userfaultfd: Fix uffd-wp special cases for fork()
Date: Tue, 25 May 2021 20:36:18 -0400 [thread overview]
Message-ID: <YK2YArvcaabj8GHi@t490s> (raw)
In-Reply-To: <20210525171558.3b223a89c16bdf002f3e83cf@linux-foundation.org>
On Tue, May 25, 2021 at 05:15:58PM -0700, Andrew Morton wrote:
> This run afoul of Alistair's "mm: Device exclusive memory access",
> https://lkml.kernel.org/r/20210524132725.12697-8-apopple@nvidia.com
>
> `vma' is now undeclared. I think this?
>
> --- a/mm/memory.c~mm-userfaultfd-fix-uffd-wp-special-cases-for-fork-fix
> +++ a/mm/memory.c
> @@ -850,8 +850,8 @@ copy_nonpresent_pte(struct mm_struct *ds
> * exclusive entries currently only support private writable
> * (ie. COW) mappings.
> */
> - VM_BUG_ON(!is_cow_mapping(vma->vm_flags));
> - if (try_restore_exclusive_pte(src_mm, src_pte, vma, addr))
> + VM_BUG_ON(!is_cow_mapping(dst_vma->vm_flags));
This one looks good, as both src_vma/dst_vma should have the same flags related
to is_cow.
> + if (try_restore_exclusive_pte(src_mm, src_pte, dst_vma, addr))
Should this be s/dst_vma/src_vma/ perhaps? Alistairs please correct me
otherwise, as it tries to restore the pte for src mm not dst (the child).
I haven't yet got time to look at the new series, planning to do it tomorrow
maybe.. but I see that it's already queued in -mm. Andrew, we do have chance
to go back if necessary, right?
I haven't looked at the rest, but I think try_restore_exclusive_pte() can at
least drop the *mm pointer as it's never used (even if we need, we've got
vma->vm_mm too)..
--
Peter Xu
next prev parent reply other threads:[~2021-05-26 0:36 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-28 22:50 [PATCH 0/6] mm/uffd: Misc fix for uffd-wp and one more test Peter Xu
2021-04-28 22:50 ` [PATCH 1/6] mm/thp: Simplify copying of huge zero page pmd when fork Peter Xu
2021-04-29 8:03 ` David Hildenbrand
2021-04-28 22:50 ` [PATCH 2/6] mm/userfaultfd: Fix uffd-wp special cases for fork() Peter Xu
2021-05-26 0:15 ` Andrew Morton
2021-05-26 0:36 ` Peter Xu [this message]
2021-05-26 3:04 ` Andrew Morton
2021-04-28 22:50 ` [PATCH 3/6] mm/userfaultfd: Fix a few thp pmd missing uffd-wp bit Peter Xu
2021-04-28 22:50 ` [PATCH 4/6] mm/userfaultfd: Fail uffd-wp registeration if not supported Peter Xu
2021-04-28 22:50 ` [PATCH 5/6] mm/pagemap: Export uffd-wp protection information Peter Xu
2021-04-28 22:50 ` [PATCH 6/6] userfaultfd/selftests: Add pagemap uffd-wp test Peter Xu
2021-05-07 16:05 ` [PATCH 0/6] mm/uffd: Misc fix for uffd-wp and one more test Peter Xu
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