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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1726059212; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qwPPrKU8Uil+7y00DTh07NRnFAl2kBDmcElf/wXciSw=; b=MWSh61Yiu2W+bx8y1sRTw1QozgZLAoGAn8XnxUo0S6R2NEMZHq5jBfEhygYOv/G33sXl1y PHnzUWS7alkBdObojuagus5JpBBj/tKzgGDse8/bLRgahZNR+xR1OIis2EFlGKGpVGX92w 06uvzEOC4rcRBUq1rvTU75bP5ZwCL1E= 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 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 X-Rspam-User: X-Rspamd-Queue-Id: 02D762000C X-Rspamd-Server: rspam01 X-Stat-Signature: ficdjiwm6qbe6eoiigd8z7ewps348f1q X-HE-Tag: 1726059239-683571 X-HE-Meta: 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 V/3YUDJl 2AhknetaSNiBg5C9/h3iTzOsQ+OXSoOFO5fhRXptXFj7D5Jvog4pU0XfITM2zfkhN0kSm7+X8tKS+hl+2qIx7nwpOif/EX5FUHqB6AodfQpyP3NICLznDHs+AlLpcGWyLoqzNqTtTXvgJsY+qvSv7p6md2aiXy5lbfQ8sRnlRGKBFJz8= 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: List-Subscribe: List-Unsubscribe: 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; > >