From: Andrea Arcangeli <aarcange@redhat.com>
To: Nadav Amit <nadav.amit@gmail.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Nadav Amit <namit@vmware.com>, Yu Zhao <yuzhao@google.com>,
Andy Lutomirski <luto@kernel.org>, Peter Xu <peterx@redhat.com>,
Pavel Emelyanov <xemul@openvz.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Minchan Kim <minchan@kernel.org>, Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH v2 2/2] fs/task_mmu: acquire mmap_lock for write on soft-dirty cleanup
Date: Tue, 5 Jan 2021 13:20:55 -0500 [thread overview]
Message-ID: <X/SuBxFfR+bncRhU@redhat.com> (raw)
In-Reply-To: <20201225092529.3228466-3-namit@vmware.com>
On Fri, Dec 25, 2020 at 01:25:29AM -0800, Nadav Amit wrote:
> Fixes: 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes tracking")
Targeting a backport down to 2013 when nothing could wrong in practice
with page_mapcount sounds backwards and unnecessarily risky.
In theory it was already broken and in theory
09854ba94c6aad7886996bfbee2530b3d8a7f4f4 is absolutely perfect and the
previous code of 2013 is completely wrong, but in practice the code
from 2013 worked perfectly until Aug 21 2020.
Since nothing at all could go wrong in soft dirty and uffd-wp until
09854ba94c6aad7886996bfbee2530b3d8a7f4f4, the Fixes need to target
that, definitely not a patch from 2013.
This means the backports will apply clean, they don't need a simple
solution but one that doesn't regress the performance of open source
virtual machines and open source products using clear_refs and uffd-wp
in general.
Thanks,
Andrea
next prev parent reply other threads:[~2021-01-05 18:22 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-25 9:25 [RFC PATCH v2 0/2] mm: fix races due to deferred TLB flushes Nadav Amit
2020-12-25 9:25 ` [RFC PATCH v2 1/2] mm/userfaultfd: fix memory corruption due to writeprotect Nadav Amit
2021-01-04 12:22 ` Peter Zijlstra
2021-01-04 19:24 ` Andrea Arcangeli
2021-01-04 19:35 ` Nadav Amit
2021-01-04 20:19 ` Andrea Arcangeli
2021-01-04 20:39 ` Nadav Amit
2021-01-04 21:01 ` Andrea Arcangeli
2021-01-04 21:26 ` Nadav Amit
2021-01-05 18:45 ` Andrea Arcangeli
2021-01-05 19:05 ` Nadav Amit
2021-01-05 19:45 ` Andrea Arcangeli
2021-01-05 20:06 ` Nadav Amit
2021-01-05 21:06 ` Andrea Arcangeli
2021-01-05 21:43 ` Peter Xu
2021-01-05 8:13 ` Peter Zijlstra
2021-01-05 8:52 ` Nadav Amit
2021-01-05 14:26 ` Peter Zijlstra
2021-01-05 8:58 ` Peter Zijlstra
2021-01-05 9:22 ` Nadav Amit
2021-01-05 17:58 ` Andrea Arcangeli
2021-01-05 15:08 ` Peter Xu
2021-01-05 18:08 ` Andrea Arcangeli
2021-01-05 18:41 ` Peter Xu
2021-01-05 18:55 ` Andrea Arcangeli
2021-01-05 19:07 ` Nadav Amit
2021-01-05 19:43 ` Peter Xu
2020-12-25 9:25 ` [RFC PATCH v2 2/2] fs/task_mmu: acquire mmap_lock for write on soft-dirty cleanup Nadav Amit
2021-01-05 15:08 ` Will Deacon
2021-01-05 18:20 ` Andrea Arcangeli [this message]
2021-01-05 19:26 ` Nadav Amit
2021-01-05 20:39 ` Andrea Arcangeli
2021-01-05 21:20 ` Yu Zhao
2021-01-05 21:22 ` Nadav Amit
2021-01-05 22:16 ` Will Deacon
2021-01-06 0:29 ` Andrea Arcangeli
2021-01-06 0:02 ` Andrea Arcangeli
2021-01-07 20:04 ` [PATCH 0/2] page_count can't be used to decide when wp_page_copy Andrea Arcangeli
2021-01-07 20:04 ` [PATCH 1/2] mm: proc: Invalidate TLB after clearing soft-dirty page state Andrea Arcangeli
2021-01-07 20:04 ` [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending Andrea Arcangeli
2021-01-07 20:17 ` Linus Torvalds
2021-01-07 20:25 ` Linus Torvalds
2021-01-07 20:58 ` Andrea Arcangeli
2021-01-07 21:29 ` Linus Torvalds
2021-01-07 21:53 ` John Hubbard
2021-01-07 22:00 ` Linus Torvalds
2021-01-07 22:14 ` John Hubbard
2021-01-07 22:20 ` Linus Torvalds
2021-01-07 22:24 ` Linus Torvalds
2021-01-07 22:37 ` John Hubbard
2021-01-15 11:27 ` Jan Kara
2021-01-07 22:31 ` Andrea Arcangeli
2021-01-07 22:42 ` Linus Torvalds
2021-01-07 22:51 ` Linus Torvalds
2021-01-07 23:48 ` Andrea Arcangeli
2021-01-08 0:25 ` Linus Torvalds
2021-01-08 12:48 ` Will Deacon
2021-01-08 16:14 ` Andrea Arcangeli
2021-01-08 17:39 ` Linus Torvalds
2021-01-08 17:53 ` Andrea Arcangeli
2021-01-08 19:25 ` Linus Torvalds
2021-01-09 0:12 ` Andrea Arcangeli
2021-01-08 17:30 ` Linus Torvalds
2021-01-07 23:28 ` Andrea Arcangeli
2021-01-07 21:36 ` kernel test robot
2021-01-07 20:25 ` [PATCH 0/2] page_count can't be used to decide when wp_page_copy Jason Gunthorpe
2021-01-07 20:32 ` Linus Torvalds
2021-01-07 21:05 ` Linus Torvalds
2021-01-07 22:02 ` Andrea Arcangeli
2021-01-07 22:17 ` Linus Torvalds
2021-01-07 22:56 ` Andrea Arcangeli
2021-01-09 19:32 ` Matthew Wilcox
2021-01-09 19:46 ` Linus Torvalds
2021-01-15 14:30 ` Jan Kara
2021-01-07 21:54 ` Andrea Arcangeli
2021-01-07 21:45 ` Andrea Arcangeli
2021-01-08 13:36 ` Jason Gunthorpe
2021-01-08 17:00 ` Andrea Arcangeli
2021-01-08 18:19 ` Jason Gunthorpe
2021-01-08 18:31 ` Andy Lutomirski
2021-01-08 18:38 ` Linus Torvalds
2021-01-08 23:34 ` Andrea Arcangeli
2021-01-09 19:03 ` Andy Lutomirski
2021-01-09 19:15 ` Linus Torvalds
2021-01-08 18:59 ` Linus Torvalds
2021-01-08 22:43 ` Andrea Arcangeli
2021-01-09 0:42 ` Jason Gunthorpe
2021-01-09 2:50 ` Andrea Arcangeli
2021-01-11 14:30 ` Jason Gunthorpe
2021-01-13 21:56 ` Jerome Glisse
2021-01-13 23:39 ` Jason Gunthorpe
2021-01-14 2:35 ` Jerome Glisse
[not found] ` <20210109034958.6928-1-hdanton@sina.com>
2021-01-11 14:39 ` Jason Gunthorpe
2021-01-05 21:55 ` [RFC PATCH v2 2/2] fs/task_mmu: acquire mmap_lock for write on soft-dirty cleanup Peter Xu
2021-03-02 22:13 ` [RFC PATCH v2 0/2] mm: fix races due to deferred TLB flushes Peter Xu
2021-03-02 22:14 ` Nadav Amit
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