From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A14033F383; Thu, 6 Aug 2026 16:45:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786034742; cv=none; b=H/HBL2AT317tt+YlsleQ30O8jfhzAsNvU+6gHlA9TsIjzJd2j7u0mSRLatqJXel/PqSuIVm4BITsW3B7wDkV/okWuy+4YcTnMhVTTWAYw9zqZZsCpz9drWD60sgC1rS2NJmS6wXnlvYhV0Wr9EK0W/qV+4t/Lcu0RWnM9LTw334= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786034742; c=relaxed/simple; bh=wcH9/Cw3vGVBCHbi3z6CbaQXHFcSW7QVMk0gQotEFlk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oQKF5wb18Qt0vcBQAuZTpJtntZCv+ZQB7LQjtviSRu25oEH9lC4xcCXb5AZRbQWJ3EcqLaf8sTk714scNohrkWIWW/H22s7F3c7mmPbqHEOYICEfDpDsU3Fhx6gmw2koE6igsHxEVhSKTVjlgMsZr2NnXxHX5B/bIK4/BbVAldc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KXiUMrsM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KXiUMrsM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A80651F00A3A; Thu, 6 Aug 2026 16:45:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786034738; bh=VrdYoYmL+T5FlaJX6gRMCUi3wWSvcdyxUT0pa5jmJHw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=KXiUMrsM5jdndCIntJReZr0x2HnPjsWH60xKSgXTjnftr76RGmt+1g7fcXDDLukjK bPCbcxzZ0jtr2cnnns6XD/kH1hWiM3agXfL6gkzrLYK7edFKbHKn8OrWZGgLwUdj8R l+OA/n2RUUhf2TbUWue/FxpqOejOL0q9srpQXixktHk1yXx8SMYZCa/CFmzOx7qovu RnabFQ8CofvqZ+0Ru1X+sA+iTaadt5Vo50/XAkzI3Z8GoEtid05wqQs7dM8WKwWZKQ 7HqDX1M+9u8v97tat8XcM3cdX4VC40nizoaJoahol3Uuj+LsJy5GSfx0uDXz66GMrh qpb25E6/i+gaQ== Message-ID: <857ed4fb-7f99-410f-be1a-59ada04d06a8@kernel.org> Date: Thu, 6 Aug 2026 18:45:33 +0200 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] mm/huge_memory: let special huge VMAs bypass the THP policy check To: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= , "Lorenzo Stoakes (ARM)" Cc: Andrew Morton , linux-mm@kvack.org, Peter Xu , Alex Williamson , Jason Gunthorpe , Zi Yan , stable@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260805055544.1568534-1-clg@redhat.com> <0bd6d355-e6d9-4f5a-b101-9a041c2a2436@kernel.org> <2a7686ee-56ab-439a-90fd-ad3c10e4c336@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit >> >> +static bool file_vma_honors_thp_toggles(struct vm_area_struct *vma,> +        >> enum tva_type type) >> +{ >> +    const bool forced_collapse = type == TVA_FORCED_COLLAPSE; >> + >> +    if (forced_collapse) >> +        return false; >> +    /* Huge PFN mappings allocate no folios so the policy doesn't apply. */ > > So, may be rename the routine to file_vma_thp_policy_applies() ? Also a possibility. I'll let Lorenzo handle this. > >> +    return !(vma_test(vma, VMA_PFNMAP_BIT) && vma->vm_ops->huge_fault); >> +} >> + >> +static bool vma_thp_toggles_enabled(struct vm_area_struct *vma, > > This routine could use the same 'file_vma_' prefix. It's true even for non-file vmas. > >> +        vm_flags_t vm_flags) >> +{ >> +    /* THP=always? */ >> +    if (hugepage_global_always()) >> +        return true; >> +    /* THP=madvise and actually advised? */ >> +    return hugepage_global_enabled() && vm_flags & VM_HUGEPAGE; > > I would add extra parentheses around 'vm_flags & VM_HUGEPAGE' It's even required and the compiler might complain :) > >> +} >> + >> +static bool file_vma_forces_order_0(struct vm_area_struct *vma, >> +        vm_flags_t vm_flags, enum tva_type type) >> +{ >> +    const bool in_pf = type == TVA_PAGEFAULT; >> +    const bool smaps = type == TVA_SMAPS; >> + >> +    /* >> +     * Enforce THP collapse requirements as necessary. Anonymous vmas >> +     * were already handled in thp_vma_allowable_orders(). >> +     */ >> + >> +    if (file_vma_honors_thp_toggles(vma, type) && >> +        !vma_thp_toggles_enabled(vma, vm_flags)) >> +        return true; >> + >> +    /* >> +     * Trust that ->huge_fault() handlers know what they are doing >> +     * in fault path. >> +     */ >> +    if (((in_pf || smaps)) && vma->vm_ops->huge_fault) > > and there remove the extra parentheses. Agreed, that was already there in existing code. Anyhow, it was mostly for inspiration for Lorenzo. I should start spelling out more clearly in the future that this is just a quick prototype, because recently people assumed that some quick stuff I post inline would be complete or even tested :) -- Cheers, David