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[70.31.27.79]) by smtp.gmail.com with ESMTPSA id m17-20020ae9e711000000b006e42a8e9f9bsm2788884qka.121.2022.11.02.12.24.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Nov 2022 12:24:07 -0700 (PDT) Date: Wed, 2 Nov 2022 15:24:05 -0400 From: Peter Xu To: Mike Kravetz Cc: Nadav Amit , Linux-MM , kernel list , Naoya Horiguchi , David Hildenbrand , Axel Rasmussen , Mina Almasry , Rik van Riel , Vlastimil Babka , Matthew Wilcox , Andrew Morton , Wei Chen , "# 5 . 10+" , Linus Torvalds Subject: Re: [PATCH v2] hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing Message-ID: References: <7048D2B5-5FA5-4F72-8FDC-A02411CFD71D@gmail.com> <3232338E-77BB-42A8-9A25-5A4AD61FD4B2@gmail.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 Sun, Oct 30, 2022 at 06:44:10PM -0700, Mike Kravetz wrote: > On 10/30/22 11:52, Nadav Amit wrote: > > On Oct 30, 2022, at 11:43 AM, Peter Xu wrote: > > > > > The loop comes from 7e027b14d53e ("vm: simplify unmap_vmas() calling > > > convention", 2012-05-06), where zap_page_range() was used to replace a call > > > to unmap_vmas() because the patch wanted to eliminate the zap details > > > pointer for unmap_vmas(), which makes sense. > > > > > > I didn't check the old code, but from what I can tell (and also as Mike > > > pointed out) I don't think zap_page_range() in the lastest code base is > > > ever used on multi-vma at all. Otherwise the mmu notifier is already > > > broken - see mmu_notifier_range_init() where the vma pointer is also part > > > of the notification. > > > > > > Perhaps we should just remove the loop? > > > > There is already zap_page_range_single() that does exactly that. Just need > > to export it. > > I was thinking that zap_page_range() should perform a notification call for > each vma within the loop. Something like this? I'm boldly guessing what Nadav suggested was using zap_page_range_single() and export it for MADV_DONTNEED. Hopefully that's also the easiest for stable? For the long term, I really think we should just get rid of the loop.. > > @@ -1704,15 +1704,21 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start, > MA_STATE(mas, mt, vma->vm_end, vma->vm_end); > > lru_add_drain(); > - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, > - start, start + size); > 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); > + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, > + vma->vm_mm, > + max(start, vma->vm_start), > + min(start + size, vma->vm_end)); > + if (is_vm_hugetlb_page(vma)) > + adjust_range_if_pmd_sharing_possible(vma, > + &range.start, > + &range.end); > + mmu_notifier_invalidate_range_start(&range); > + unmap_single_vma(&tlb, vma, start, start + size, NULL); > + mmu_notifier_invalidate_range_end(&range); > } while ((vma = mas_find(&mas, end - 1)) != NULL); > - mmu_notifier_invalidate_range_end(&range); > tlb_finish_mmu(&tlb); > } > > > One thing to keep in mind is that this patch is a fix that must be > backported to stable. Therefore, I do not think we want to add too > many changes out of the direct scope of the fix. > > We can always change things like this in follow up patches. > -- > Mike Kravetz > -- Peter Xu