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[70.31.27.79]) by smtp.gmail.com with ESMTPSA id i22-20020ac871d6000000b003431446588fsm17123qtp.5.2022.10.28.16.20.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Oct 2022 16:20:42 -0700 (PDT) Date: Fri, 28 Oct 2022 19:20:40 -0400 From: Peter Xu To: Mike Kravetz Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Naoya Horiguchi , David Hildenbrand , Axel Rasmussen , Mina Almasry , Rik van Riel , Vlastimil Babka , Matthew Wilcox , Andrew Morton , Wei Chen , stable@vger.kernel.org Subject: Re: [PATCH v2] hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing Message-ID: References: <20221023025047.470646-1-mike.kravetz@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Oct 28, 2022 at 02:17:01PM -0700, Mike Kravetz wrote: > On 10/28/22 12:13, Peter Xu wrote: > > On Fri, Oct 28, 2022 at 08:23:25AM -0700, Mike Kravetz wrote: > > > On 10/26/22 21:12, Peter Xu wrote: > > > > On Wed, Oct 26, 2022 at 04:54:01PM -0700, Mike Kravetz wrote: > > > > > On 10/26/22 17:42, Peter Xu wrote: > > > diff --git a/mm/madvise.c b/mm/madvise.c > > > index c7105ec6d08c..d8b4d7e56939 100644 > > > --- a/mm/madvise.c > > > +++ b/mm/madvise.c > > > @@ -790,7 +790,10 @@ static int madvise_free_single_vma(struct vm_area_struct *vma, > > > static long madvise_dontneed_single_vma(struct vm_area_struct *vma, > > > unsigned long start, unsigned long end) > > > { > > > - zap_page_range(vma, start, end - start); > > > + if (!is_vm_hugetlb_page(vma)) > > > + zap_page_range(vma, start, end - start); > > > + else > > > + clear_hugetlb_page_range(vma, start, end); > > > > With the new ZAP_FLAG_UNMAP flag, clear_hugetlb_page_range() can be dropped > > completely? As zap_page_range() won't be with ZAP_FLAG_UNMAP so we can > > identify things? > > > > IIUC that's the major reason why I thought the zap flag could be helpful.. > > Argh. I went to drop clear_hugetlb_page_range() but there is one issue. > In zap_page_range() the MMU_NOTIFY_CLEAR notifier is certainly called. > However, we really need to have a 'adjust_range_if_pmd_sharing_possible' > call in there because the 'range' may be part of a shared pmd. :( > > I think we need to either have a separate routine like clear_hugetlb_page_range > that sets up the appropriate range, or special case hugetlb in zap_page_range. > What do you think? > I think clear_hugetlb_page_range is the least bad of the two options. How about special case hugetlb as you mentioned? If I'm not wrong, it should be 3 lines change: ---8<--- diff --git a/mm/memory.c b/mm/memory.c index c5599a9279b1..0a1632e44571 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1706,11 +1706,13 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start, lru_add_drain(); mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, start, start + size); + if (is_vm_hugetlb_page(vma)) + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); tlb_gather_mmu(&tlb, vma->vm_mm); update_hiwater_rss(vma->vm_mm); mmu_notifier_invalidate_range_start(&range); do { - unmap_single_vma(&tlb, vma, start, range.end, NULL); + unmap_single_vma(&tlb, vma, start, start + size, NULL); } while ((vma = mas_find(&mas, end - 1)) != NULL); mmu_notifier_invalidate_range_end(&range); tlb_finish_mmu(&tlb); ---8<--- As zap_page_range() is already vma-oriented anyway. But maybe I missed something important? -- Peter Xu