From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AC9A7EC4 for ; Wed, 11 Sep 2024 12:53:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726059241; cv=none; b=Oeid1gKxnbUTcVgcVikRliFIOABuzDCHfD8V/p6dV9w4Jq9LYIgYaKYsm180eKLSTkTqhVvHEZ5NtrRXPIu4qH9mOiHrRfsrPTJVXG3yiptxCvA8QVAI2E5cZAOPd/9RHTdmr/NlJ1YToq5WwrL7WqU7pJelOkX/7RkI+Fugawg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726059241; c=relaxed/simple; bh=14D//i72PG0G7UWjz8E2+D9dNoF5n7L+kd8QQ9Lwrms=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=llAn/HCcpeMGE/n6MUdpRcCFtMD01HnXJkMBllTV47BAXDabsXqursQaJmaAB1UmpY2ZSrHPjiC4JEcwvA0HjqCtDAOSNX93Du4x1sQdCwOM642lo4RpvCFuF2/sY0seUExkqMbhFtHOA0EZSm9m8FaWOdgDrW4h33OdU3qBkAk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 560CF1007; Wed, 11 Sep 2024 05:54:28 -0700 (PDT) Received: from [10.162.40.31] (e116581.arm.com [10.162.40.31]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 777F43F66E; Wed, 11 Sep 2024 05:53:50 -0700 (PDT) Message-ID: <8bc0e51b-0e9b-4eeb-997f-e2a0b1a0c0f8@arm.com> Date: Wed, 11 Sep 2024 18:23:47 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/2] mm: Abstract THP allocation To: David Hildenbrand , akpm@linux-foundation.org, willy@infradead.org, kirill.shutemov@linux.intel.com Cc: ryan.roberts@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com, apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org, baohua@kernel.org, jack@suse.cz, mark.rutland@arm.com, hughd@google.com, aneesh.kumar@kernel.org, yang@os.amperecomputing.com, peterx@redhat.com, ioworker0@gmail.com, jglisse@google.com, wangkefeng.wang@huawei.com, ziy@nvidia.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20240911065600.1002644-1-dev.jain@arm.com> <20240911065600.1002644-2-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/11/24 14:57, David Hildenbrand wrote: > On 11.09.24 08:55, Dev Jain wrote: >> In preparation for the second patch, abstract away the THP allocation >> logic present in the create_huge_pmd() path, which corresponds to the >> faulting case when no page is present. >> >> There should be no functional change as a result of applying >> this patch. >> > > [...] > >> + >> +static void map_pmd_thp(struct folio *folio, struct vm_fault *vmf, >> +            struct vm_area_struct *vma, unsigned long haddr) >> +{ >> +    pmd_t entry; >> + >> +    entry = mk_huge_pmd(&folio->page, vma->vm_page_prot); >> +    entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); >> +    folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE); >> +    folio_add_lru_vma(folio, vma); >> +    set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); >> +    update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); > > It's quite weird to see a mixture of haddr and vmf->address, and > likely this mixture is wrong or not not required. > > Looking at arc's update_mmu_cache_pmd() implementation, I cannot see > how passing in the unaligned address would do the right thing. But > maybe arc also doesn't trigger that code path ... who knows :) If I am reading correctly, arch/arc/mm/tlb.c: update_mmu_cache_pmd() calls update_mmu_cache_range() which is already expecting an unaligned address? But... > > > Staring at some other update_mmu_cache_pmd() users, it's quite > inconsistent. Primarily only do_huge_pmd_numa_page() and > __do_huge_pmd_anonymous_page() use the unaligned address. The others > seem to use the aligned address ... as one would expect when modifying > a PMD. Looking at riscv: update_mmu_cache_pmd()->update_mmu_cache()->update_mmu_cache_range(). The argument getting passed to local_flush_tlb_page() seems like, should expect an aligned address. > > > I suggest to change this function to *not* pass in the vmf, and rename > it to something like: > > static void folio_map_anon_pmd(struct folio *folio, struct > vm_area_struct *vma, pmd_t *pmd, unsigned long haddr) > > Then use haddr also to do the update_mmu_cache_pmd(). > >> +    add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); >> +    mm_inc_nr_ptes(vma->vm_mm); >> +} >> + >> +static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf) >> +{ >> +    struct vm_area_struct *vma = vmf->vma; >> +    struct folio *folio; >> +    pgtable_t pgtable; >> +    unsigned long haddr = vmf->address & HPAGE_PMD_MASK; >> +    vm_fault_t ret = 0; >> +    gfp_t gfp = vma_thp_gfp_mask(vma); > > Nit: While at it, try to use reverse christmas-tree where possible, > makes things more reasible. You could make haddr const. > > struct vm_area_struct *vma = vmf->vma; > unsigned long haddr = vmf->address & HPAGE_PMD_MASK; > gfp_t gfp = vma_thp_gfp_mask(vma); > struct folio *folio; > vm_fault_t ret = 0; > ... > >> + >> +    folio = pmd_thp_fault_alloc(gfp, vma, haddr, vmf->address); >> +    if (unlikely(!folio)) { >> +        ret = VM_FAULT_FALLBACK; >> +        goto release; >> +    } >> + >> +    pgtable = pte_alloc_one(vma->vm_mm); >> +    if (unlikely(!pgtable)) { >> +        ret = VM_FAULT_OOM; >> +        goto release; >> +    } >>         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); >> + > > Nit Unrelated change. > >>       if (unlikely(!pmd_none(*vmf->pmd))) { >>           goto unlock_release; > >