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 16B3EC6FD1C for ; Fri, 24 Mar 2023 11:15:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231357AbjCXLPe (ORCPT ); Fri, 24 Mar 2023 07:15:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34826 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbjCXLPc (ORCPT ); Fri, 24 Mar 2023 07:15:32 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED82225962 for ; Fri, 24 Mar 2023 04:15:26 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id A0A0433777; Fri, 24 Mar 2023 11:15:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1679656525; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type; bh=i2iOJQ2cBwIeRh7jfmFtt3V7v9mVqIjDAe9mWv1x44U=; b=tYtBHkKnJMFuKvkIoLLY6nYBE0BzCtmtYZO6wi3h/nh4JoqIHotdlkNH5HZBtW7J/2XDX+ l/38tbjS4b68QIN/okh7YS+rbPoTrsH82Y8NsCz9j+qCuHlByZydrvbUjAE3oHv3qBNshC 3nT/DkhKWh4ddxa2laQSu1E5ugFrIJs= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 7E614133E5; Fri, 24 Mar 2023 11:15:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 3hIbHU2GHWS3XAAAMHmgww (envelope-from ); Fri, 24 Mar 2023 11:15:25 +0000 Date: Fri, 24 Mar 2023 12:15:24 +0100 From: Michal Hocko To: Linus Torvalds , Naresh Kamboju , Joel Fernandes , "Kirill A. Shutemov" Cc: Andrew Morton , linux-mm@kvack.org, LKML Subject: WARN_ON in move_normal_pmd Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, our QA is regularly hitting [ 544.198822][T20518] WARNING: CPU: 1 PID: 20518 at ../mm/mremap.c:255 move_pgt_entry+0x4c6/0x510 triggered by thp01 LTP test. This has been brought up in the past and resulted in f81fdd0c4ab7 ("mm: document warning in move_normal_pmd() and make it warn only once"). While it is good that the underlying problem is understood, it doesn't seem there is enough interest to fix it properly. Which is fair but I am wondering whether the WARN_ON gives us anything here. Our QA process collects all unexpected side effects of tests and a WARN* in the log is certainly one of those. This trigger bugs which are mostly ignored as there is no upstream fix for them. This alone is nothing really critical but there are workloads which do run with panic on warn configured and this issue would put the system down which is unnecessary IMHO. Would it be sufficient to replace the WARN_ON_ONCE by pr_warn_once? Thanks! -- Michal Hocko SUSE Labs