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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 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=eM33psnG; spf=pass (imf15.hostedemail.com: domain of peterx@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666999250; a=rsa-sha256; cv=none; b=aIRlzXXODyC4nUcNLKvR8/tDvIsFhV76y+33/7Ig6A1nYNsi/XGv1jA97XHzVuu7Ka0qy3 AxRiUfDn7ASoRJId5k4BdItcLzlcDlhbHjv7MKdlTHJFPBglz88wY8jRCg3kyMHrn3FjAT HlJJsfElOPoj93eMuKwMBx9nXlHMvVw= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666999250; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=oYIHvTeMwIb+K7W2HGaQbire9czNW42U37FGK9GoxFo=; b=f6CicGGZ3wEN+B/zePENXwLVLS7EnW7ZcAdoyCa4uVISbEgS1uNBlVZJJVKWAr+nXgLXth MgONKAa2ASAAP3Ip129pkw6S4EqfiUABIPf7nVLLMtiyzAF7rhtZJTxprD93zrBwwhlUWT j7XybE/7vZTnuJdP0x2o8hw6oygk6Zw= X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=eM33psnG; spf=pass (imf15.hostedemail.com: domain of peterx@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam07 X-Stat-Signature: b5a7xwm6skeqkpirpq5bzumo3fc91hwt X-Rspamd-Queue-Id: 11E01A0004 X-HE-Tag: 1666999247-105484 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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