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 54AF3C4332F for ; Tue, 22 Mar 2022 21:46:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236435AbiCVVrf (ORCPT ); Tue, 22 Mar 2022 17:47:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230347AbiCVVr3 (ORCPT ); Tue, 22 Mar 2022 17:47:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0647F5F8C1; Tue, 22 Mar 2022 14:46:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 99B86615B1; Tue, 22 Mar 2022 21:46:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED3C8C340EE; Tue, 22 Mar 2022 21:45:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1647985560; bh=vksHlh41Yl8TntR4WEXfMzLzqp4dQjqNQcVeZWBmRXI=; h=Date:To:From:In-Reply-To:Subject:From; b=kBzVph6uHpG5u7ts3Lowr6XsitPhMfna0Tw9PvqqB5J8umZ/w7LKMaAQE46N5cw4B c5P5IW7TtpPd1ltOob5kQcKROBkO5AI0+IYlZp4a/dOP1qXhfc35exp4VTrDxJJy7g unis9W2tc8uU0g3+xvOPHfGIglVgVM8VdrGpwscc= Date: Tue, 22 Mar 2022 14:45:59 -0700 To: vbabka@suse.cz, stable@vger.kernel.org, oleg@redhat.com, Liam.Howlett@oracle.com, hughd@google.com, akpm@linux-foundation.org, patches@lists.linux.dev, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220322143803.04a5e59a07e48284f196a2f9@linux-foundation.org> Subject: [patch 147/227] mempolicy: mbind_range() set_policy() after vma_merge() Message-Id: <20220322214559.ED3C8C340EE@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Hugh Dickins Subject: mempolicy: mbind_range() set_policy() after vma_merge() v2.6.34 commit 9d8cebd4bcd7 ("mm: fix mbind vma merge problem") introduced vma_merge() to mbind_range(); but unlike madvise, mlock and mprotect, it put a "continue" to next vma where its precedents go to update flags on current vma before advancing: that left vma with the wrong setting in the infamous vma_merge() case 8. v3.10 commit 1444f92c8498 ("mm: merging memory blocks resets mempolicy") tried to fix that in vma_adjust(), without fully understanding the issue. v3.11 commit 3964acd0dbec ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction") reverted that, and went about the fix in the right way, but chose to optimize out an unnecessary mpol_dup() with a prior mpol_equal() test. But on tmpfs, that also pessimized out the vital call to its ->set_policy(), leaving the new mbind unenforced. The user visible effect was that the pages got allocated on the local node (happened to be 0), after the mbind() caller had specifically asked for them to be allocated on node 1. There was not any page migration involved in the case reported: the pages simply got allocated on the wrong node. Just delete that optimization now (though it could be made conditional on vma not having a set_policy). Also remove the "next" variable: it turned out to be blameless, but also pointless. Link: https://lkml.kernel.org/r/319e4db9-64ae-4bca-92f0-ade85d342ff@google.com Fixes: 3964acd0dbec ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction") Signed-off-by: Hugh Dickins Acked-by: Oleg Nesterov Reviewed-by: Liam R. Howlett Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- mm/mempolicy.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) --- a/mm/mempolicy.c~mempolicy-mbind_range-set_policy-after-vma_merge +++ a/mm/mempolicy.c @@ -786,7 +786,6 @@ static int vma_replace_policy(struct vm_ static int mbind_range(struct mm_struct *mm, unsigned long start, unsigned long end, struct mempolicy *new_pol) { - struct vm_area_struct *next; struct vm_area_struct *prev; struct vm_area_struct *vma; int err = 0; @@ -801,8 +800,7 @@ static int mbind_range(struct mm_struct if (start > vma->vm_start) prev = vma; - for (; vma && vma->vm_start < end; prev = vma, vma = next) { - next = vma->vm_next; + for (; vma && vma->vm_start < end; prev = vma, vma = vma->vm_next) { vmstart = max(start, vma->vm_start); vmend = min(end, vma->vm_end); @@ -817,10 +815,6 @@ static int mbind_range(struct mm_struct anon_vma_name(vma)); if (prev) { vma = prev; - next = vma->vm_next; - if (mpol_equal(vma_policy(vma), new_pol)) - continue; - /* vma_merge() joined vma && vma->next, case 8 */ goto replace; } if (vma->vm_start != vmstart) { _