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[209.132.183.28]) by mx.google.com with ESMTPS id k127si52851862qkc.355.2019.08.08.09.33.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Aug 2019 09:33:07 -0700 (PDT) Received-SPF: pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleg@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=oleg@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6CD3BCF22; Thu, 8 Aug 2019 16:33:06 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.136]) by smtp.corp.redhat.com (Postfix) with SMTP id A42CE19C69; Thu, 8 Aug 2019 16:33:04 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 8 Aug 2019 18:33:06 +0200 (CEST) Date: Thu, 8 Aug 2019 18:33:03 +0200 From: Oleg Nesterov To: Song Liu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, matthew.wilcox@oracle.com, kirill.shutemov@linux.intel.com, kernel-team@fb.com, william.kucharski@oracle.com, srikar@linux.vnet.ibm.com Subject: Re: [PATCH v12 5/6] khugepaged: enable collapse pmd for pte-mapped THP Message-ID: <20190808163303.GB7934@redhat.com> References: <20190807233729.3899352-1-songliubraving@fb.com> <20190807233729.3899352-6-songliubraving@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190807233729.3899352-6-songliubraving@fb.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Thu, 08 Aug 2019 16:33:06 +0000 (UTC) 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 08/07, Song Liu wrote: > > +void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) > +{ > + unsigned long haddr = addr & HPAGE_PMD_MASK; > + struct vm_area_struct *vma = find_vma(mm, haddr); > + struct page *hpage = NULL; > + pmd_t *pmd, _pmd; > + spinlock_t *ptl; > + int count = 0; > + int i; > + > + if (!vma || !vma->vm_file || > + vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) > + return; > + > + /* > + * This vm_flags may not have VM_HUGEPAGE if the page was not > + * collapsed by this mm. But we can still collapse if the page is > + * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() > + * will not fail the vma for missing VM_HUGEPAGE > + */ > + if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) > + return; > + > + pmd = mm_find_pmd(mm, haddr); OK, I do not see anything really wrong... a couple of questions below. > + for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { > + pte_t *pte = pte_offset_map(pmd, addr); > + struct page *page; > + > + if (pte_none(*pte)) > + continue; > + > + page = vm_normal_page(vma, addr, *pte); > + > + if (!page || !PageCompound(page)) > + return; > + > + if (!hpage) { > + hpage = compound_head(page); OK, > + if (hpage->mapping != vma->vm_file->f_mapping) > + return; is it really possible? May be WARN_ON(hpage->mapping != vm_file->f_mapping) makes more sense ? > + if (hpage + i != page) > + return; ditto. Oleg.