linux-kernel - [PATCH v2 0/2] mm/uffd: Fix vma merge/split

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Date:   Wed, 17 May 2023 15:09:14 -0400
From:   Peter Xu <peterx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Mike Rapoport <rppt@...nel.org>, peterx@...hat.com,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH v2 0/2] mm/uffd: Fix vma merge/split

v2:
- Added r-bs for Lorenzo and Liam
- Reworded patch 1's commit message [Lorenzo]

This series contains two patches that fix vma merge/split for userfaultfd
on two separate issues.  The patchset is based on akpm/mm-hotfixes-unstable
with 2f628010799e reverted (where patch 1 should be used to replace it
which seems to be the plan we reached).

Patch 1 fixes a regression since 6.1+ due to something we overlooked when
converting to maple tree apis.  The plan is we use patch 1 to replace the
commit "2f628010799e (mm: userfaultfd: avoid passing an invalid range to
vma_merge())" in mm-hostfixes-unstable tree if possible, so as to bring
uffd vma operations back aligned with the rest code again.

Patch 2 fixes a long standing issue that vma can be left unmerged even if
we can for either uffd register or unregister.

Many thanks to Lorenzo on either noticing this issue from the assert
movement patch, looking at this problem, and also provided a reproducer on
the unmerged vma issue [1].

Please have a look, thanks.

[1] https://gist.github.com/lorenzo-stoakes/a11a10f5f479e7a977fc456331266e0e

Peter Xu (2):
  mm/uffd: Fix vma operation where start addr cuts part of vma
  mm/uffd: Allow vma to merge as much as possible

 fs/userfaultfd.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

-- 
2.39.1