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(p200300cbc706fb00f5c324b23d039d52.dip0.t-ipconnect.de. [2003:cb:c706:fb00:f5c3:24b2:3d03:9d52]) by smtp.gmail.com with ESMTPSA id g6-20020a05600c4ec600b003a3199c243bsm14398006wmq.0.2022.08.05.11.22.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Aug 2022 11:22:47 -0700 (PDT) Message-ID: Date: Fri, 5 Aug 2022 20:22:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v1 1/2] mm/hugetlb: fix hugetlb not supporting write-notify Content-Language: en-US To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mike Kravetz , Muchun Song , Peter Feiner , "Kirill A . Shutemov" , stable@vger.kernel.org References: <20220805110329.80540-1-david@redhat.com> <20220805110329.80540-2-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05.08.22 20:14, Peter Xu wrote: > On Fri, Aug 05, 2022 at 01:03:28PM +0200, David Hildenbrand wrote: >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 61e6135c54ef..462a6b0344ac 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -1683,6 +1683,13 @@ int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot) >> if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) >> return 0; >> >> + /* >> + * Hugetlb does not require/support writenotify; especially, it does not >> + * support softdirty tracking. >> + */ >> + if (is_vm_hugetlb_page(vma)) >> + return 0; > > I'm kind of confused here.. you seems to be fixing up soft-dirty for > hugetlb but here it's explicitly forbidden. > > Could you explain a bit more on why this patch is needed if (assume > there'll be a working) patch 2 being provided? I want something simple to backport. And even with patch #2 in place, as long as we don't support softdirty tracking, it doesn't make sense to enable it here as of now. -- Thanks, David / dhildenb