From: Peter Xu <peterx@redhat.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Yang Shi <shy828301@gmail.com>,
Wang Yugui <wangyugui@e16-tech.com>,
Matthew Wilcox <willy@infradead.org>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Alistair Popple <apopple@nvidia.com>,
Ralph Campbell <rcampbell@nvidia.com>, Zi Yan <ziy@nvidia.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Minchan Kim <minchan@kernel.org>, Jue Wang <juew@google.com>,
Jan Kara <jack@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/7] mm/thp: try_to_unmap() use TTU_SYNC for safe DEBUG_VM splitting
Date: Thu, 3 Jun 2021 17:48:46 -0400 [thread overview]
Message-ID: <YLlOPoP/rIRMm2U5@t490s> (raw)
In-Reply-To: <alpine.LSU.2.11.2106011405510.2148@eggly.anvils>
On Tue, Jun 01, 2021 at 02:07:53PM -0700, Hugh Dickins wrote:
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index 2cf01d933f13..b45d22738b45 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -212,6 +212,14 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
> pvmw->ptl = NULL;
> }
> } else if (!pmd_present(pmde)) {
> + /*
> + * If PVMW_SYNC, take and drop THP pmd lock so that we
> + * cannot return prematurely, while zap_huge_pmd() has
> + * cleared *pmd but not decremented compound_mapcount().
> + */
> + if ((pvmw->flags & PVMW_SYNC) &&
> + PageTransCompound(pvmw->page))
> + spin_unlock(pmd_lock(mm, pvmw->pmd));
> return false;
> }
> if (!map_pte(pvmw))
Sorry if I missed something important, but I'm totally confused on how this
unlock is pairing with another lock()..
And.. isn't PVMW_SYNC only meaningful for pte-level only (as I didn't see a
reference of it outside map_pte)?
--
Peter Xu
next prev parent reply other threads:[~2021-06-03 21:49 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-01 21:03 [PATCH 0/7] mm/thp: fix THP splitting unmap BUGs and related Hugh Dickins
2021-06-01 21:05 ` [PATCH 1/7] mm/thp: fix __split_huge_pmd_locked() on shmem migration entry Hugh Dickins
2021-06-03 21:26 ` Yang Shi
2021-06-04 2:22 ` Hugh Dickins
2021-06-04 18:03 ` Yang Shi
2021-06-04 21:52 ` Hugh Dickins
2021-06-04 15:34 ` Kirill A. Shutemov
2021-06-04 21:29 ` Hugh Dickins
2021-06-01 21:07 ` [PATCH 2/7] mm/thp: try_to_unmap() use TTU_SYNC for safe DEBUG_VM splitting Hugh Dickins
2021-06-02 1:59 ` Alistair Popple
2021-06-03 21:45 ` Yang Shi
2021-06-04 2:45 ` Hugh Dickins
2021-06-04 18:24 ` Yang Shi
2021-06-03 21:48 ` Peter Xu [this message]
2021-06-04 2:54 ` Hugh Dickins
2021-06-04 14:48 ` Peter Xu
2021-06-04 22:26 ` Hugh Dickins
2021-06-04 15:47 ` Kirill A. Shutemov
2021-06-01 21:09 ` [PATCH 3/7] mm/thp: fix vma_address() if virtual address below file offset Hugh Dickins
2021-06-01 21:30 ` Matthew Wilcox
2021-06-03 21:36 ` Hugh Dickins
2021-06-03 21:40 ` [PATCH v2 " Hugh Dickins
2021-06-04 15:53 ` Kirill A. Shutemov
2021-06-04 17:36 ` Matthew Wilcox
2021-06-04 22:35 ` Hugh Dickins
2021-06-01 21:11 ` [PATCH 4/7] mm/thp: fix page_address_in_vma() on file THP tails Hugh Dickins
2021-06-01 21:32 ` Matthew Wilcox
2021-06-03 22:06 ` Yang Shi
2021-06-04 15:54 ` Kirill A. Shutemov
2021-06-01 21:13 ` [PATCH 5/7] mm/thp: fix page_vma_mapped_walk() if huge page mapped by ptes Hugh Dickins
2021-06-04 16:24 ` Kirill A. Shutemov
2021-06-04 17:42 ` Matthew Wilcox
2021-06-04 22:56 ` Hugh Dickins
2021-06-01 21:15 ` [PATCH 6/7] mm/thp: unmap_mapping_page() to fix THP truncate_cleanup_page() Hugh Dickins
2021-06-04 16:39 ` Kirill A. Shutemov
2021-06-04 23:07 ` Hugh Dickins
2021-06-01 21:17 ` [PATCH 7/7] mm/thp: remap_page() is only needed on anonymous THP Hugh Dickins
2021-06-03 22:09 ` Yang Shi
2021-06-04 16:41 ` Kirill A. Shutemov
2021-06-02 2:07 ` [PATCH 0/7] mm/thp: fix THP splitting unmap BUGs and related Alistair Popple
2021-06-03 22:21 ` Hugh Dickins
2021-06-03 23:03 ` Andrew Morton
2021-06-03 22:26 ` [PATCH 6.1/7] mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split Hugh Dickins
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