From: Matthew Wilcox <willy@infradead.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Suren Baghdasaryan <surenb@google.com>,
Qi Zheng <zhengqi.arch@bytedance.com>,
Yang Shi <shy828301@gmail.com>,
Mel Gorman <mgorman@techsingularity.net>,
Peter Xu <peterx@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Will Deacon <will@kernel.org>, Yu Zhao <yuzhao@google.com>,
Alistair Popple <apopple@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>,
Ira Weiny <ira.weiny@intel.com>,
Steven Price <steven.price@arm.com>,
SeongJae Park <sj@kernel.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Zack Rusin <zackr@vmware.com>, Jason Gunthorpe <jgg@ziepe.ca>,
Axel Rasmussen <axelrasmussen@google.com>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>,
Christoph Hellwig <hch@infradead.org>, Song Liu <song@kernel.org>,
Thomas Hellstrom <thomas.hellstrom@linux.intel.com>,
Russell King <linux@armlinux.org.uk>,
"David S. Miller" <davem@davemloft.net>,
Michael Ellerman <mpe@ellerman.id.au>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Christian Borntraeger <borntraeger@linux.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Jann Horn <jannh@google.com>,
linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 05/12] powerpc: add pte_free_defer() for pgtables sharing page
Date: Mon, 29 May 2023 15:02:02 +0100 [thread overview]
Message-ID: <ZHSwWgLWaEd+zi/g@casper.infradead.org> (raw)
In-Reply-To: <28eb289f-ea2c-8eb9-63bb-9f7d7b9ccc11@google.com>
On Sun, May 28, 2023 at 11:20:21PM -0700, Hugh Dickins wrote:
> +void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
> +{
> + struct page *page;
> +
> + page = virt_to_page(pgtable);
> + call_rcu(&page->rcu_head, pte_free_now);
> +}
This can't be safe (on ppc). IIRC you might have up to 16x4k page
tables sharing one 64kB page. So if you have two page tables from the
same page being defer-freed simultaneously, you'll reuse the rcu_head
and I cannot imagine things go well from that point.
I have no idea how to solve this problem.
next prev parent reply other threads:[~2023-05-29 14:03 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 6:11 [PATCH 00/12] mm: free retracted page table by RCU Hugh Dickins
2023-05-29 6:14 ` [PATCH 01/12] mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s Hugh Dickins
2023-05-31 17:06 ` Jann Horn
2023-05-29 6:16 ` [PATCH 02/12] mm/pgtable: add PAE safety to __pte_offset_map() Hugh Dickins
2023-05-29 13:56 ` Matthew Wilcox
2023-05-29 6:17 ` [PATCH 03/12] arm: adjust_pte() use pte_offset_map_nolock() Hugh Dickins
2023-05-29 6:18 ` [PATCH 04/12] powerpc: assert_pte_locked() " Hugh Dickins
2023-05-29 6:20 ` [PATCH 05/12] powerpc: add pte_free_defer() for pgtables sharing page Hugh Dickins
2023-05-29 14:02 ` Matthew Wilcox [this message]
2023-05-29 14:36 ` Hugh Dickins
[not found] ` <ZHn6n5eVTsr4Wl8x@ziepe.ca>
[not found] ` <4df4909f-f5dd-6f94-9792-8f2949f542b3@google.com>
[not found] ` <ZH95oobIqN0WO5MK@ziepe.ca>
[not found] ` <ZH+DAxLhIYpTlIFc@x1n>
[not found] ` <ZH+EMp9RuEVOjVNb@ziepe.ca>
2023-06-07 3:49 ` Hugh Dickins
2023-05-29 6:21 ` [PATCH 06/12] sparc: " Hugh Dickins
2023-05-29 6:22 ` [PATCH 07/12] s390: add pte_free_defer(), with use of mmdrop_async() Hugh Dickins
[not found] ` <175ebec8-761-c3f-2d98-6c3bd87161c8@google.com>
2023-06-06 19:40 ` Gerald Schaefer
2023-06-08 3:35 ` Hugh Dickins
2023-06-08 13:58 ` Jason Gunthorpe
2023-06-08 15:47 ` Gerald Schaefer
[not found] ` <ZH99cLKeALvUCIH8@ziepe.ca>
2023-06-08 2:46 ` Hugh Dickins
2023-05-29 6:23 ` [PATCH 08/12] mm/pgtable: add pte_free_defer() for pgtable as page Hugh Dickins
2023-05-29 6:25 ` [PATCH 09/12] mm/khugepaged: retract_page_tables() without mmap or vma lock Hugh Dickins
2023-05-29 23:26 ` Peter Xu
2023-05-31 0:38 ` Hugh Dickins
2023-05-31 15:34 ` Jann Horn
2023-05-29 6:26 ` [PATCH 10/12] mm/khugepaged: collapse_pte_mapped_thp() with mmap_read_lock() Hugh Dickins
2023-05-31 17:25 ` Jann Horn
2023-05-29 6:28 ` [PATCH 11/12] mm/khugepaged: delete khugepaged_collapse_pte_mapped_thps() Hugh Dickins
2023-05-29 6:30 ` [PATCH 12/12] mm: delete mmap_write_trylock() and vma_try_start_write() Hugh Dickins
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