From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 888A3A94A for ; Mon, 28 Apr 2025 08:21:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745828483; cv=none; b=jXZkrFVpeyXj03OQTUy7R9Sk38lyP17ED88WNHWbobX8auABewA50VKYJMl+MDF4csFqlLUBimJlVfHY+DQKfuwSm07tlynXoHbjP0Khh69peYgSyHdxsMuTz66u0gFTqSKJ10THevWyC1PH9B2gv8LPz6UL7TCjPVyIbJ4wYIE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745828483; c=relaxed/simple; bh=kOLotEy9ifmJEWGdDzcouKa7Zx459L0qksnA3q6JbrE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cuzP/ZsVoMMAn4EkoMSEZkCxh6J6lQYmHg3kz6nSxgklP4dvPlFESKxB3yrJdd9bOWtdgKoDCtuSU6B+R3vM9TryVoibd4oQ3vBcw5+geve65BYeAehc4J1ttqOh9r8fPb8qE6A4LZM6aOxO33S2MoiLp0uYkvVpf+U8r2cnoc4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=XYVo26ud; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=d3v3SQli; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b=XYVo26ud; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b=d3v3SQli; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="XYVo26ud"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="d3v3SQli"; dkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de header.b="XYVo26ud"; dkim=permerror (0-bit key) header.d=suse.de header.i=@suse.de header.b="d3v3SQli" Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 9276E21255; Mon, 28 Apr 2025 08:21:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1745828473; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jxPebaF3kiPUYQxRXvMQDBE+nUkuHfTh3XZdTAcceoM=; b=XYVo26udBArxSDxNmH1e+qCq9YxbyiMSToMVRJVyfKRsJDudCs5LsRbffQ3h3f2TT22gGg YGnEHkei2UNjLRnjWGMliOxe9skvsRR/+yD8Q1vtxrg5ucbTKIBU3PFEmKXNbEQRZU8BGO ZwEg8yPqdrisue2+liPFDROEJ0JVVNU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1745828473; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jxPebaF3kiPUYQxRXvMQDBE+nUkuHfTh3XZdTAcceoM=; b=d3v3SQlinbqSrlP9NEetTR2ykulmJF4pJtrgBkoeFhDjmvM7hj3wPuqThTYs/370pnu3o3 OzlWw5p0vIhnTvBw== Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=XYVo26ud; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=d3v3SQli DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1745828473; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jxPebaF3kiPUYQxRXvMQDBE+nUkuHfTh3XZdTAcceoM=; b=XYVo26udBArxSDxNmH1e+qCq9YxbyiMSToMVRJVyfKRsJDudCs5LsRbffQ3h3f2TT22gGg YGnEHkei2UNjLRnjWGMliOxe9skvsRR/+yD8Q1vtxrg5ucbTKIBU3PFEmKXNbEQRZU8BGO ZwEg8yPqdrisue2+liPFDROEJ0JVVNU= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1745828473; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=jxPebaF3kiPUYQxRXvMQDBE+nUkuHfTh3XZdTAcceoM=; b=d3v3SQlinbqSrlP9NEetTR2ykulmJF4pJtrgBkoeFhDjmvM7hj3wPuqThTYs/370pnu3o3 OzlWw5p0vIhnTvBw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 439551336F; Mon, 28 Apr 2025 08:21:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id AcHsDXk6D2gafgAAD6G6ig (envelope-from ); Mon, 28 Apr 2025 08:21:13 +0000 Date: Mon, 28 Apr 2025 10:21:11 +0200 From: Oscar Salvador To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , David Hildenbrand , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memory: fix mapcount / refcount sanity check for mTHP reuse Message-ID: References: <20250425074325.61833-1-ryncsn@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250425074325.61833-1-ryncsn@gmail.com> X-Rspamd-Queue-Id: 9276E21255 X-Spam-Score: -4.51 X-Rspamd-Action: no action X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCPT_COUNT_FIVE(0.00)[5]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:email,suse.de:dkim]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: On Fri, Apr 25, 2025 at 03:43:25PM +0800, Kairui Song wrote: > From: Kairui Song > > The following WARNING was triggered during swap stress test with > mTHP enabled: ... > The WARN_ON here is simply incorrect. The refcount here must be at least > the mapcount, not the opposite. Each mapcount must have a corresponding > refcount, but the refcount may increase if other components grab the > folio, which is acceptable. Meanwhile, having a mapcount larger than > refcount is a real problem. > > So fix the WARN_ON condition. > > Fixes: 1da190f4d0a6 ("mm: Copy-on-Write (COW) reuse support for PTE-mapped THP") > Reported-by: Kairui Song > Closes: https://lore.kernel.org/all/CAMgjq7D+ea3eg9gRCVvRnto3Sv3_H3WVhupX4e=k8T5QAfBHbw@mail.gmail.com/ > Suggested-by: David Hildenbrand > Signed-off-by: Kairui Song Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE Labs