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x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH 3/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when unmapping To: Peter Xu , Mike Kravetz Cc: Gerald Schaefer , akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org References: <20220429220214.4cfc5539@thinkpad> <20220502160232.589a6111@thinkpad> <48a05075-a323-e7f1-9e99-6c0d106eb2cb@linux.alibaba.com> <20220503120343.6264e126@thinkpad> <927dfbf4-c899-b88a-4d58-36a637d611f9@oracle.com> From: Baolin Wang In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220509_182740_662187_AED3C253 X-CRM114-Status: GOOD ( 14.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/10/2022 12:41 AM, Peter Xu wrote: > On Fri, May 06, 2022 at 12:07:13PM -0700, Mike Kravetz wrote: >> On 5/3/22 03:03, Gerald Schaefer wrote: >>> On Tue, 3 May 2022 10:19:46 +0800 >>> Baolin Wang wrote: >>>> On 5/2/2022 10:02 PM, Gerald Schaefer wrote: > > [...] > >>>> Please see previous code, we'll use the original pte value to check if >>>> it is uffd-wp armed, and if need to mark it dirty though the hugetlbfs >>>> is set noop_dirty_folio(). >>>> >>>> pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); >>> >>> Uh, ok, that wouldn't work on s390, but we also don't have >>> CONFIG_PTE_MARKER_UFFD_WP / HAVE_ARCH_USERFAULTFD_WP set, so >>> I guess we will be fine (for now). >>> >>> Still, I find it a bit unsettling that pte_install_uffd_wp_if_needed() >>> would work on a potential hugetlb *pte, directly de-referencing it >>> instead of using huge_ptep_get(). >>> >>> The !pte_none(*pte) check at the beginning would be broken in the >>> hugetlb case for s390 (not sure about other archs, but I think s390 >>> might be the only exception strictly requiring huge_ptep_get() >>> for de-referencing hugetlb *pte pointers). > > We could have used is_vm_hugetlb_page(vma) within the helper so as to > properly use either generic pte or hugetlb version of pte fetching. We may > want to conditionally do set_[huge_]pte_at() too at the end. > > I could prepare a patch for that even if it's not really anything urgently > needed. I assume that won't need to block this patchset since we need the > pteval for pte_dirty() check anyway and uffd-wp definitely needs it too. OK. Thanks Peter. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel