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From:   Peter Xu <peterx@redhat.com>
To:     linux-kernel@vger.kernel.org, linux-mm@kvack.org
Cc:     peterx@redhat.com, Jason Gunthorpe <jgg@ziepe.ca>,
        John Hubbard <jhubbard@nvidia.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@lst.de>, Yang Shi <shy828301@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Kirill Shutemov <kirill@shutemov.name>,
        Hugh Dickins <hughd@google.com>, Jann Horn <jannh@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>, Jan Kara <jack@suse.cz>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Leon Romanovsky <leonro@nvidia.com>
Subject: [PATCH v2 0/4] mm: Break COW for pinned pages during fork()
Date:   Fri, 25 Sep 2020 18:25:56 -0400
Message-Id: <20200925222600.6832-1-peterx@redhat.com>
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Due to the rebase to latest rc6, the major pte copy patch changed a lot.  S=
o=0D
maybe not that useful to write a changelog any more.  However all the comme=
nts=0D
should be addressed as long as discussed in previous thread.  Please shoot =
if I=0D
missed anything important.=0D
=0D
This series is majorly inspired by the previous discussion on the list [1],=
=0D
starting from the report from Jason on the rdma test failure.  Linus propos=
ed=0D
the solution, which seems to be a very nice approach to avoid the breakage =
of=0D
userspace apps that didn't use MADV_DONTFORK properly before.  More informa=
tion=0D
can be found in that thread too.=0D
=0D
I tested it myself with fork() after vfio pinning a bunch of device pages, =
and=0D
I verified that the new copy pte logic worked as expected at least in the m=
ost=0D
general path.  However I didn't test thp case yet because afaict vfio does =
not=0D
support thp backed dma pages.  Luckily, the pmd/pud thp patch is much more=
=0D
straightforward than the pte one, so hopefully it can be directly verified =
by=0D
some code review plus some more heavy-weight rdma tests.=0D
=0D
Patch 1:      Introduce mm.has_pinned=0D
Patch 2:      Preparation patch=0D
Patch 3:      Early cow solution for pte copy for pinned pages=0D
Patch 4:      Same as above, but for thp (pmd/pud).=0D
=0D
Hugetlbfs fix is still missing, but as planned, that's not urgent so we can=
=0D
work upon.  Comments greatly welcomed.=0D
=0D
[1] https://lore.kernel.org/lkml/20200914143829.GA1424636@nvidia.com/=0D
=0D
Thanks.=0D
=0D
Peter Xu (4):=0D
  mm: Introduce mm_struct.has_pinned=0D
  mm/fork: Pass new vma pointer into copy_page_range()=0D
  mm: Do early cow for pinned pages during fork() for ptes=0D
  mm/thp: Split huge pmds/puds if they're pinned when fork()=0D
=0D
 include/linux/mm.h       |   2 +-=0D
 include/linux/mm_types.h |  10 +++=0D
 kernel/fork.c            |   3 +-=0D
 mm/gup.c                 |   6 ++=0D
 mm/huge_memory.c         |  28 ++++++=0D
 mm/memory.c              | 186 ++++++++++++++++++++++++++++++++++-----=0D
 6 files changed, 212 insertions(+), 23 deletions(-)=0D
=0D
-- =0D
2.26.2=0D
=0D