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Mon, 09 Jan 2023 12:54:27 -0800 (PST) Date: Mon, 9 Jan 2023 12:53:13 -0800 In-Reply-To: <20230109205336.3665937-1-surenb@google.com> Mime-Version: 1.0 References: <20230109205336.3665937-1-surenb@google.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog Message-ID: <20230109205336.3665937-19-surenb@google.com> Subject: [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page From: Suren Baghdasaryan To: akpm@linux-foundation.org Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: michel@lespinasse.org, joelaf@google.com, songliubraving@fb.com, mhocko@suse.com, leewalsh@google.com, david@redhat.com, peterz@infradead.org, bigeasy@linutronix.de, peterx@redhat.com, dhowells@redhat.com, linux-mm@kvack.org, edumazet@google.com, jglisse@google.com, punit.agrawal@bytedance.com, arjunroy@google.com, dave@stgolabs.net, minchan@google.com, x86@kernel.org, hughd@google.com, willy@infradead.org, gurua@google.com, laurent.dufour@fr.ibm.com, linux-arm-kernel@lists.infradead.org, rientjes@google.com, axelrasmussen@google.com, kernel-team@android.com, soheil@google.com, paulmck@kernel.org, jannh@google.com, liam.howlett@oracle.com, shakeelb@google.com, luto@kernel.org, gthelen@google.com, ldufour@linux.ibm.com, surenb@google.com, vbabka@suse.cz, posk@google.com, lstoakes@gmail.com, peterjung1337@gmail.com, linuxppc-dev@lists.ozlabs.org, kent.overstreet@linux.dev, hughlynch@google.com, linux-kernel@vger.kernel.org, hannes@cmpxchg.org, tatashin@google.com, mgorman@techsingu larity.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Protect VMA from concurrent page fault handler while collapsing a huge page. Page fault handler needs a stable PMD to use PTL and relies on per-VMA lock to prevent concurrent PMD changes. pmdp_collapse_flush(), set_huge_pmd() and collapse_and_free_pmd() can modify a PMD, which will not be detected by a page fault handler without proper locking. Signed-off-by: Suren Baghdasaryan --- mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5376246a3052..d8d0647f0c2c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1032,6 +1032,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address, if (result != SCAN_SUCCEED) goto out_up_write; + vma_write_lock(vma); anon_vma_lock_write(vma->anon_vma); mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, @@ -1503,6 +1504,9 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, goto drop_hpage; } + /* Lock the vma before taking i_mmap and page table locks */ + vma_write_lock(vma); + /* * We need to lock the mapping so that from here on, only GUP-fast and * hardware page walks can access the parts of the page tables that @@ -1690,6 +1694,7 @@ static int retract_page_tables(struct address_space *mapping, pgoff_t pgoff, result = SCAN_PTE_UFFD_WP; goto unlock_next; } + vma_write_lock(vma); collapse_and_free_pmd(mm, vma, addr, pmd); if (!cc->is_khugepaged && is_target) result = set_huge_pmd(vma, addr, pmd, hpage); -- 2.39.0