From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1A65C7618E for ; Fri, 21 Apr 2023 18:28:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233006AbjDUS2D (ORCPT ); Fri, 21 Apr 2023 14:28:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbjDUS2C (ORCPT ); Fri, 21 Apr 2023 14:28:02 -0400 Received: from out2-smtp.messagingengine.com (out2-smtp.messagingengine.com [66.111.4.26]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A0C519A1; Fri, 21 Apr 2023 11:28:00 -0700 (PDT) Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id A18465C00CA; Fri, 21 Apr 2023 14:27:56 -0400 (EDT) Received: from mailfrontend1 ([10.202.2.162]) by compute3.internal (MEProxy); Fri, 21 Apr 2023 14:27:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=devkernel.io; h= cc:cc:content-type:content-type:date:date:from:from:in-reply-to :in-reply-to:message-id:mime-version:references:reply-to:sender :subject:subject:to:to; s=fm1; t=1682101676; x=1682188076; bh=1x lLdlOEPewjSa9H68FV8Q5PO9B90Oygi7b4UAbYuQc=; b=P0wYN+pJ1GfvlJDlIK 3HaP8g8yxh54ko7FtDNoDaJ2UbAHZEH6f/Q++W6+apsYdWGtFEWE+VFQXClEsVG0 cNC/sNVd7/oMjY/xFtIAWOJvmZ7uXQ3mbJVWBHrrjEx3NEiwyXlrYfFrx4cv6pDx VHBa48YtKHzwfxpnI4JwohAAQtDQDSVVXx3QUmBAY7B+68+wZhG/dLvNn0OnsREa qjko2RCCZp7nO9MKyb0UCfHlnuT0PwJTFQfwhCSCs45y7Jxi3w6bnMbx8tbwVJ+3 //HYMjrxXN9VmmIBgsf8diCnZkCyjN3KiEiba50EMyFCX6mLalVggfzcTxbFQiYz Lytw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm3; t=1682101676; x=1682188076; bh=1xlLdlOEPewjS a9H68FV8Q5PO9B90Oygi7b4UAbYuQc=; b=YTbnAZJ3qUMiRj76RGU6xiJMr7F8Z AkF4d4qdl55apNKQF1ibg7v+FTxNs6LEJ9T/CbhXqMm/CMr0JUPsGdGAWF/cq1n4 hdoa6M0lt7boS8FLRptsOOIxImYCjFW8X9zq0pzlUlPuvbO8jWhlu7IAumUoDL66 qPBnyF2O0qu3+eKvQDofPbKIcJxXx7Vd0ivDUBvs9vBJAhlWOK1cWnup0gDjoYZS h8IXrSxl6vOW0PEIz+/bZERGinxio39/2lX8YmfR8N9mQat+4+V3G24GUH/f4JCM ZhJu46SbqRu3jmGtCF3l1bDmHnLHOFm9RUaS0AiHZtwdl0+ofXuNUEK5A== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrfedtgedguddvfecutefuodetggdotefrod ftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfgh necuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd enucfjughrpehffgfhvfevufffjgfkgggtsehttdertddtredtnecuhfhrohhmpefuthgv fhgrnhcutfhovghstghhuceoshhhrhesuggvvhhkvghrnhgvlhdrihhoqeenucggtffrrg htthgvrhhnpeevlefggffhheduiedtheejveehtdfhtedvhfeludetvdegieekgeeggfdu geeutdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpe hshhhrseguvghvkhgvrhhnvghlrdhioh X-ME-Proxy: Feedback-ID: i84614614:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Fri, 21 Apr 2023 14:27:54 -0400 (EDT) References: <20230418051342.1919757-1-shr@devkernel.io> <20230418152849.505124-1-david@redhat.com> <20230418152849.505124-4-david@redhat.com> <14d89518-0c11-7bfb-0c72-329a834ba1a1@redhat.com> User-agent: mu4e 1.10.1; emacs 28.2.50 From: Stefan Roesch To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Rik van Riel , Johannes Weiner , Michal Hocko , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Sven Schnelle , Shuah Khan Subject: Re: [PATCH v1 3/3] mm/ksm: move disabling KSM from s390/gmap code to KSM code Date: Fri, 21 Apr 2023 11:27:23 -0700 In-reply-to: <14d89518-0c11-7bfb-0c72-329a834ba1a1@redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org David Hildenbrand writes: > [...] > >>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c >>> index 0949811761e6..dfe905c7bd8e 100644 >>> --- a/arch/s390/mm/gmap.c >>> +++ b/arch/s390/mm/gmap.c >>> @@ -2585,30 +2585,12 @@ EXPORT_SYMBOL_GPL(s390_enable_sie); >>> >>> int gmap_mark_unmergeable(void) >>> { >>> - struct mm_struct *mm = current->mm; >>> - struct vm_area_struct *vma; >>> - unsigned long vm_flags; >>> - int ret; >>> - VMA_ITERATOR(vmi, mm, 0); >>> - >>> /* >>> * Make sure to disable KSM (if enabled for the whole process or >>> * individual VMAs). Note that nothing currently hinders user space >>> * from re-enabling it. >>> */ >>> - clear_bit(MMF_VM_MERGE_ANY, &mm->flags); >>> - >>> - for_each_vma(vmi, vma) { >>> - /* Copy vm_flags to avoid partial modifications in ksm_madvise */ >>> - vm_flags = vma->vm_flags; >>> - ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, >>> - MADV_UNMERGEABLE, &vm_flags); >>> - if (ret) >>> - return ret; >>> - vm_flags_reset(vma, vm_flags); >>> - } >>> - mm->def_flags &= ~VM_MERGEABLE; >>> >> > > Hi Stefan, > >> This clears the def_flags struct member, however, in ksm_disable() we >> clear the __flags struct member. Is this a problem? > > The patch description contains a comment regarding def_flags: "The existing > "mm->def_flags &= ~VM_MERGEABLE;" was essentially a NOP and can be dropped, > because def_flags should never include VM_MERGEABLE." > > We keep clearing the MADV_UNMERGEABLE flag from MADV_UNMERGEABLE. In the old > code, ksm_madvise() would have cleared it from local vm_flags and > vm_flags_reset() would have modified vma->vm_flags. Now we clear it directly via > vm_flags_clear(vma, VM_MERGEABLE); > > > Long story short, the mm->def_flags code as wrong and most probably copied from > thp_split_mm() where we do: > mm->def_flags |= VM_NOHUGEPAGE; > Which makes more sense. > > Thanks! Thanks for the explanation. Acked-by: Stefan Roesch