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Message-Id: <20240205191843.4009640-1-leitao@debian.org>
Date: Mon, 5 Feb 2024 11:18:40 -0800
From: Breno Leitao <leitao@...ian.org>
To: mike.kravetz@...cle.com,
linux-mm@...ck.org,
akpm@...ux-foundation.org,
muchun.song@...ux.dev
Cc: lstoakes@...il.com,
willy@...radead.org,
hannes@...xchg.org,
mhocko@...nel.org,
roman.gushchin@...ux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/2] mm/hugetlb: Restore the reservation
This is a fix for a case where a backing huge page could stolen after
madvise(MADV_DONTNEED).
A full reproducer is in selftest. See
https://lore.kernel.org/all/20240105155419.1939484-1-leitao@debian.org/
v1:
* https://lore.kernel.org/all/20240117171058.2192286-1-leitao@debian.org/
v2:
* In version 1, there was a lockdep dependency detected by syzbot.
* https://lore.kernel.org/all/00000000000050a2fb060fdc478c@google.com/
* The lockdep dependency was caused because `vma_add_reservation()` was
called with the pte lock. This is fixed now by deferring the
vma_add_reservation() to after the spinlock.
* Version 2 fixes the problem above by setting the restore_reserve bit
inside the ptl, but, calling vma_add_reservation() later, after the
lock is released.
* Reported by a test done by Ryan Roberts.
In order to test this patch, I instrumented the kernel with LOCKDEP and
KASAN, and run the following tests, without any regression:
* The self test that reproduces the problem
* All mm hugetlb selftests
SUMMARY: PASS=9 SKIP=0 FAIL=0
* All libhugetlbfs tests
PASS: 0 86
FAIL: 0 0
Breno Leitao (2):
mm/hugetlb: Restore the reservation if needed
selftests/mm: run_vmtests.sh: add hugetlb_madv_vs_map
mm/hugetlb.c | 25 +++++++++++++++++++++++
tools/testing/selftests/mm/run_vmtests.sh | 1 +
2 files changed, 26 insertions(+)
--
2.34.1
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