From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Yang Shi <shy828301@gmail.com>,
Wang Yugui <wangyugui@e16-tech.com>,
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>,
Peter Xu <peterx@redhat.com>, Jan Kara <jack@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/7] mm/thp: fix vma_address() if virtual address below file offset
Date: Fri, 4 Jun 2021 18:53:22 +0300 [thread overview]
Message-ID: <20210604155322.vl6wcen4fmngg27r@box.shutemov.name> (raw)
In-Reply-To: <alpine.LSU.2.11.2106031436390.11704@eggly.anvils>
On Thu, Jun 03, 2021 at 02:40:30PM -0700, Hugh Dickins wrote:
> Running certain tests with a DEBUG_VM kernel would crash within hours,
> on the total_mapcount BUG() in split_huge_page_to_list(), while trying
> to free up some memory by punching a hole in a shmem huge page: split's
> try_to_unmap() was unable to find all the mappings of the page (which,
> on a !DEBUG_VM kernel, would then keep the huge page pinned in memory).
>
> When that BUG() was changed to a WARN(), it would later crash on the
> VM_BUG_ON_VMA(end < vma->vm_start || start >= vma->vm_end, vma) in
> mm/internal.h:vma_address(), used by rmap_walk_file() for try_to_unmap().
>
> vma_address() is usually correct, but there's a wraparound case when the
> vm_start address is unusually low, but vm_pgoff not so low: vma_address()
> chooses max(start, vma->vm_start), but that decides on the wrong address,
> because start has become almost ULONG_MAX.
>
> Rewrite vma_address() to be more careful about vm_pgoff; move the
> VM_BUG_ON_VMA() out of it, returning -EFAULT for errors, so that it can
> be safely used from page_mapped_in_vma() and page_address_in_vma() too.
>
> Add vma_address_end() to apply similar care to end address calculation,
> in page_vma_mapped_walk() and page_mkclean_one() and try_to_unmap_one();
> though it raises a question of whether callers would do better to supply
> pvmw->end to page_vma_mapped_walk() - I chose not, for a smaller patch.
>
> An irritation is that their apparent generality breaks down on KSM pages,
> which cannot be located by the page->index that page_to_pgoff() uses: as
> 4b0ece6fa016 ("mm: migrate: fix remove_migration_pte() for ksm pages")
> once discovered. I dithered over the best thing to do about that, and
> have ended up with a VM_BUG_ON_PAGE(PageKsm) in both vma_address() and
> vma_address_end(); though the only place in danger of using it on them
> was try_to_unmap_one().
>
> Sidenote: vma_address() and vma_address_end() now use compound_nr() on
> a head page, instead of thp_size(): to make the right calculation on a
> hugetlbfs page, whether or not THPs are configured. try_to_unmap() is
> used on hugetlbfs pages, but perhaps the wrong calculation never mattered.
>
> Fixes: a8fa41ad2f6f ("mm, rmap: check all VMAs that PTE-mapped THP can be part of")
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: <stable@vger.kernel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2021-06-04 15:53 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
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 [this message]
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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