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 C6032186E24 for ; Wed, 11 Sep 2024 12:55:48 +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=1726059350; cv=none; b=tCiuUUcglHBs7O0jSb01vJUHjs2GP3ZmcyAOBf5eO5z4zJNZNV0wlkjlYyEuG6yEbZZoX71xJFIp4LfeMWjUKTbrZ3oE814KA19Z468GjU5P9KlmOPrXTUkXqKv6CLXw8tOrLM3r0+vn64+O4kOxWIMZQ4Rue4VrHUT4BWyeqgM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726059350; c=relaxed/simple; bh=CVbBSshLzANXCgTPqq0L+TtE6iP2AsyUqYxsji9HqiA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BFokb1BYKIVrvoRMho51rHI8nuOjpK11Y9Bzm5LDr0HmCKE9KEFDelAvx2JP1mDorpFSrhMGgmrOutXYIPjhXNc9Kx9KW0252nE9WKU9KzsSpYI+UDz923QW/55vEFV87oKN4wNkkQjuaWOlyOOHmvZ2DfTfRxCCH4ORqmjgNZ4= 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 8E3A91007; Wed, 11 Sep 2024 05:56:17 -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 BD6BF3F66E; Wed, 11 Sep 2024 05:55:39 -0700 (PDT) Message-ID: <4b981fae-0f40-4338-990f-839a39c3c190@arm.com> Date: Wed, 11 Sep 2024 18:25:36 +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> <552e9b77-c1ea-4a60-8434-e360ca692f1f@arm.com> <18271c5b-d190-448a-b513-34c20de1dcd2@redhat.com> Content-Language: en-US From: Dev Jain In-Reply-To: <18271c5b-d190-448a-b513-34c20de1dcd2@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/11/24 18:05, David Hildenbrand wrote: > [...] > >>> >>>> + >>>> +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 :) >>> >>> >>> 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. >>> >>> >>> 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(). >> >> The code I changed, already was passing vmf->address to >> update_mmu_cache_pmd(). >> I did not change any of the haddr and vmf->address semantics, so really >> can't comment >> on this. > > I'm not saying that you changed it. I say, "we touch it we fix it" :). > We could do that in a separate cleanup patch upfront. Sure. > >> I agree with the name change; vmf will be required for >> set_pmd_at(vmf->pmd), so I should >> just pass 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; >> >> Okay. >>> ... >>> >>>> + >>>> +    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. >> >> Are you asking me to align this line with the below line? > > No, just pointing out that you add a newline in a code section you > don't really touch. Sometimes that's deliberate, sometimes not (e.g., > going back and forth while reworking the code and accidentally leaving > that in). We try to avoid such unrelated changes because it adds noise > to the patches. > > If it was deliberate, feel free to leave it in. Ah, I accidentally inserted that new line. Will revert that.