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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-735af82d2b8sm494958a34.3.2025.05.29.21.52.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 May 2025 21:52:43 -0700 (PDT) Date: Thu, 29 May 2025 21:52:31 -0700 (PDT) From: Hugh Dickins To: Roman Gushchin cc: Andrew Morton , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Jann Horn , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Hugh Dickins Subject: Re: [PATCH v6] mmu_gather: move tlb flush for VM_PFNMAP/VM_MIXEDMAP vmas into free_pgtables() In-Reply-To: <20250522012838.163876-1-roman.gushchin@linux.dev> Message-ID: <9fc25829-fb3f-8a13-94d0-786127bf12ce@google.com> References: <20250522012838.163876-1-roman.gushchin@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Thu, 22 May 2025, Roman Gushchin wrote: > Commit b67fbebd4cf9 ("mmu_gather: Force tlb-flush VM_PFNMAP vmas") > added a forced tlbflush to tlb_vma_end(), which is required to avoid a > race between munmap() and unmap_mapping_range(). However it added some > overhead to other paths where tlb_vma_end() is used, but vmas are not > removed, e.g. madvise(MADV_DONTNEED). > > Fix this by moving the tlb flush out of tlb_end_vma() into new > tlb_flush_vmas() called from free_pgtables(), somewhat similar to the > stable version of the original commit: > commit 895428ee124a ("mm: Force TLB flush for PFNMAP mappings before > unlink_file_vma()"). > > Note, that if tlb->fullmm is set, no flush is required, as the whole > mm is about to be destroyed. > > Signed-off-by: Roman Gushchin > Cc: Jann Horn > Cc: Peter Zijlstra > Cc: Will Deacon > Cc: "Aneesh Kumar K.V" > Cc: Andrew Morton > Cc: Nick Piggin > Cc: Hugh Dickins > Cc: linux-arch@vger.kernel.org > Cc: linux-mm@kvack.org > > --- > v6: > - tlb->vma_pfn is initialized in __tlb_gather_mmu() and > is never cleared (by Jann H) Acked-by: Hugh Dickins